Top Banner
1 Doug Harper B.Eng Civil and Structural Engineering School of Civil Engineering & Geosciences, Newcastle University 2011 Alternative Methods of Stabilisation for Unfired Mud Bricks
88
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Page 1: Mud Brick Construction

1

08 Fall

Doug Harper

B.Eng Civil and Structural Engineering

School of Civil Engineering & Geosciences, Newcastle University

2011

Alternative Methods of Stabilisation for Unfired Mud Bricks

Page 2: Mud Brick Construction

2

Executive Summary

Mud brick construction dates back, in various forms, for several thousand years.

Recently, Interlocking Compressed Soil Blocks (ICSB) have emerged as a viable,

sustainable and affordable construction material, suitable for the provision of low cost

housing in the developing world. However, questions have been raised as to their long

term durability and susceptibility to water damage. Traditionally, unfired mud bricks

have been stabilised with cement to overcome these short comings but the use of

cement reduces the environmental differential between unfired bricks and fired ones.

This report investigates the use of Ground Granulated Blast furnace Slag (GGBS) and

Pulverised Fly Ash (PFA) as alternatives to cement for the stabilisation of ICSB.

Sample bricks were constructed using varying concentrations of PC, PFA and GGBS

and the sample’s compressive strength and Initial rate of Water Absorption (IRA)

compared. Simultaneously, a sustainability study was undertaken to contrast the three

materials in terms of ease of manufacture, financial cost and implications to health.

The PC stabilised bricks displayed the highest compressive strength (4.3-6.0 kN/mm2)

followed by the PFA bricks (0.75-0.98 kN/mm2) and then the GGBS samples (0.12-0.17

kN/mm2). Only two of the samples, both stabilised with PC, had compressive strengths

acceptable under UK Building Regulations. All of the tested samples had an IRA of

less than 0.13 kg/m2/min, significantly below accepted limits. The report concludes that

whilst GGBS and PFA are alternative stabilisers for ICSB they do not perform as well

as PC in the proportions tested. The sustainability study concludes that GGBS is more

sustainable (though the limitations of any definition of sustainability are acknowledged)

than PC and PFA. This is contrary to previously published information that would

define both GGBS and PFA as more environmentally sound. The use of GGBS and

PFA in ICSB ultimately depends on two factors: whether the observed engineering

properties are sufficient for the requirement and whether the alternative stabilisers are

available.

Page 3: Mud Brick Construction

3

Table of Contents

List of Figures: ......................................................................................................................... 6

List of Tables: ........................................................................................................................... 7

1.0 Introduction ................................................................................................................. 8

2.0 Aims and Objectives ............................................................................................... 10

3.0 Literature Review ................................................................................................... 11

3.1 Background ......................................................................................................................... 12

3.1.1 Mud and Earth Construction............................................................................................. 12

3.1.2 Interlocking Compressed Stabilised Blocks ............................................................... 16

3.2 A Review of Potential Stabilisers for Unfired Masonry Bricks ......................... 20

3.3 A Comparative Study of the Selected Stabilisers ................................................... 22

3.4 Testing Procedures for the Mechanical Properties of Masonry ...................... 24

3.4.1 Compressive Strength Testing of Masonry ................................................................. 24

3.4.2 Shrinkage Testing of ICSB .................................................................................................. 25

3.4.3 Absorption Testing of Masonry ....................................................................................... 26

3.5 Key Points from the Literature Review .................................................................... 26

4.0 Proposed Method Statement ............................................................................... 28

4.0.1 Research .................................................................................................................................... 28

4.0.2 Preliminary Experiments ................................................................................................... 28

4.0.3 Laboratory Experiments .................................................................................................... 29

4.0.4 Sustainability Study .............................................................................................................. 30

4.1 Timeline ............................................................................................................................... 31

5.0 Method Statement .................................................................................................. 33

5.1 Constructing the Mud Bricks ........................................................................................ 33

5.1.1 Equipment Required ............................................................................................................ 33

5.1.2 Health and Safety ................................................................................................................... 34

5.1.3 Procedure ................................................................................................................................. 34

5.2 Shrinkage Testing ............................................................................................................. 38

5.2.1 Equipment Required ............................................................................................................ 38

5.2.2 Health and Safety ................................................................................................................... 39

Page 4: Mud Brick Construction

4

5.3.3 Procedure ................................................................................................................................. 39

5.3 Absorption Testing .......................................................................................................... 40

5.3.1 Equipment Required ............................................................................................................ 40

5.3.2 Health and Safety ................................................................................................................... 40

5.3.3 Procedure ................................................................................................................................. 40

5.4 Compressive Strength Testing ........................................................................ 41

5.4.1 Equipment Required ............................................................................................................ 41

5.4.2 Health and Safety ................................................................................................................... 41

5.4.3 Procedure ................................................................................................................................. 42

6.1 Preliminary Experimental Results ............................................................................. 43

6.0 Results ......................................................................................................................... 43

6.2 Main Laboratory Experimental Results .................................................................... 44

6.2.1 Shrinkage Testing .................................................................................................................. 44

6.2.2 Sample Appearance and Texture .................................................................................... 44

6.2.3 Absorption Testing ............................................................................................................... 44

6.2.4 Compressive Strength Testing .................................................................... 46

7.0 Sustainability Study ................................................................................................ 49

7.1 Ease of Manufacture ........................................................................................................ 50

7.2 Financial Cost ..................................................................................................................... 51

7.3 Health Implications.......................................................................................................... 53

7.3.1 GGBS (CEMEX, 2008) ........................................................................................................... 53

7.3.2 PC (US Department of Health and Human Services, 1995) .................................. 53

7.3.3 PFA (Scotash, 2005) ............................................................................................................. 54

7.4 Quantitative Ecopoints Analysis ................................................................................. 54

8.0 Discussion ................................................................................................................ 56

8.1 Preliminary Experiments .............................................................................................. 56

8.2 Sustainability Study ......................................................................................................... 57

8.2.1 Defining Sustainability ........................................................................................................ 57

8.2.2 Ease of Manufacture ............................................................................................................. 58

8.2.3 Financial Cost .......................................................................................................................... 59

8.2.4 Health Implications .............................................................................................................. 59

8.2.5 Overall Sustainability ........................................................................................................... 60

8.3 Laboratory Experiments ................................................................................................ 61

8.3.1 Shrinkage Testing .................................................................................................................. 61

Page 5: Mud Brick Construction

5

8.3.2 Manufacturing Procedure .................................................................................................. 62

8.3.3 Absorption Testing ............................................................................................................... 63

8.3.4 Compressive Strength Testing ......................................................................................... 64

8.3.5 Application of ICSB Technology ...................................................................................... 66

8.3.6 Limitations to the Research .............................................................................................. 67

9.0 Conclusions ............................................................................................................. 69

10.0 Recommendations for Future Research ......................................................... 71

References: ............................................................................................................................ 73

Appendices ............................................................................................................................ 77

Appendix 1 - Project Management Statement ..................................................................... 78

Appendix 2 – Risk Assessment for Laboratory Work ....................................................... 80

Appendix 3 – Ecopoints PFA....................................................................................................... 81

Appendix 4 – Ecopoints GGBS .................................................................................................... 82

Appendix 5 – Samples of Raw Data for the Compressive Strength Testing .............. 83

Page 6: Mud Brick Construction

6

List of Figures:

Figure 1 - Examples of Earthen Architecture in India (Source: www.banasura.com )

...................................................................................... Error! Bookmark not defined.

Figure 2 - Example of a Modern Earthen Structure in Riyadh, Saudi Arabia (Source:

www.rael-sanfratello.com) .......................................................................................... 14

Figure 3 - Rammed Earth Construction Underway in India (Source:

www.banasura.com) ................................................................................................... 14

Figure 4 - Makiga Press (Source: www.makiga-engineering.com) ............................. 17

Figure 5 - Examples of Interlocking Blocks (Source: www.goodearthtrust.org.uk) ....... 17

Figure 6 - Proposed Project Timeline .......................................................................... 32

Figure 7 - Raw Materials for Soil Mix .......................................................................... 36

Figure 8 - Mixed Homogenous Soil ............................................................................. 36

Figure 9 - Empty Brick Moulds .................................................................................... 37

Figure 10 - Completed Bricks in Moulds (L-R, stabilised with PC, GGBS, PFA,

shrinkage test) ............................................................................................................ 37

Figure 11 - Bricks and Shrinkage Test Left for Curing ................................................. 38

Figure 12 - Shrinkage Testing Mould .......................................................................... 39

Figure 13 - The Experimental Setup for the Absorption Testing .................................. 41

Figure 14 – The Experimental Set-up for the Compressive Strength Testing .............. 42

Figure 15 - Compressive Strength of the Bricks Tested at 'Get Sheltered' .................. 43

Figure 16 – The Appearance of the Bricks after Curing (Top: GGBS, Btm Left: PC, Btm

Right: PFA) ................................................................................................................. 44

Figure 17 - The Initial Rate of Water Absorption for the Samples ................................ 45

Figure 18 - A Comparison of the Compressive Strength of the Samples ..................... 46

Figure 19 - Stress-Strain Curves for the PC Stabilised Bricks ..................................... 47

Figure 20 - Stress-Strain Curves for the PFA Stabilised Bricks ................................... 47

Figure 21 - Stress-Strain Curves for the GGBS Stabilised Bricks ................................ 47

Figure 22 - The Appearance of a Selection of Samples after Compressive Strength

Testing ........................................................................................................................ 48

Figure 23 - Interrelationship between the Spheres of Sustainability (Source: Tanguay,

et al. 2009).................................................................................................................. 49

Page 7: Mud Brick Construction

7

List of Tables:

Table 1 - Types of Earth Construction Methods (adapted from UN HABITAT 2009). .. 15

Table 2 - Comparison of Interlocking Blocks to its Alternatives (Source: UN Human

Settlements Programme) ............................................................................................ 19

Table 3 - Comparison of the Energy Costs of GGBS, PFA and PC (Sources: Oti, 2008

& 2009, Reddy, 2004 & 2001, Ash Solutions Ltd, 2009) ............................................. 22

Table 4 - Engineering Parameters and Performance of Unfired Clay Bricks and

Mainstream Bricks (Source: Oti, 2009) ....................................................................... 24

Table 5 - Raw Material Quantities for Mud Brick Construction .................................... 35

Table 6 - Compressive Strength Testing of the Bricks Tested at 'Get Sheltered' ......... 43

Table 7 - Absorption Testing Results .......................................................................... 45

Table 8 - Compressive Strength Results ..................................................................... 46

Table 9 - A Comparison of the Costs of Fired Bricks and ICSB (adapted from Smith,

2010) .......................................................................................................................... 52

Table 10 – A Comparison of Estimated Stabiliser Cost in Ugandan Shillings and Cost

per ICSB ..................................................................................................................... 53

Table 11 - An Overall Comparison of the Sustainability of the Stabilisers ................... 60

Page 8: Mud Brick Construction

8

1.0 Introduction

Mud brick construction is not a new technology and dates back, in various forms, for

several thousand years. Recently it has been utilised and investigated as a possible

form of sustainable construction in the developing, and the developed, world.

There has been a large amount of interest and subsequent research into the use of

interlocking mud bricks as an economical and environmentally sound method of

satisfying the housing demand in many countries, particularly those of sub-Saharan

Africa and the Middle East.

Mud bricks perform considerably better, in environmental terms, than fired bricks. They

have significantly less embodied energy, contribute fewer CO2 emissions and help to

promote the local economy and local labour. At first glance they appear to be an ideal

candidate for an economically viable sustainable construction material. However, the

major drawback of unfired mud bricks is that they tend to be less durable than their

fired counterparts and are more susceptible to water damage. Traditionally, unfired

mud bricks have been stabilised with cement to overcome these short comings but the

use of cement reduces the environmental differential between unfired bricks and fired

ones. Research into alternative stabilisers is both relevant and necessary to ensure

unfired mud bricks remain a competitive alternative to modern construction methods.

This project, which is conducted in association with Engineers Without Borders (EWB),

will look at two alternatives to cement for stabilizing unfired mud bricks. Ground

Granulated Blast-furnace Slag (GGBS) and Pulverized Fly Ash (PFA) have been

selected as the alternative stabilisers. These are both by-products of existing industry

(steel production and coal fired power stations respectively) and are considered to be

more sustainable than Portland Cement (PC). They are also used as cement

alternatives in soil stabilisation in the UK and around the developed world. Specific

research into their use in earthen construction is lacking.

This research project focuses on two main areas; the structural integrity of bricks made

with the alternative stabilisers and the potential sustainability of the stabilisers in the

developing world.

Page 9: Mud Brick Construction

9

The structural integrity will be measured by 3 tests; compressive strength, shrinkage

and absorption. These tests will be performed on hand made mud bricks prepared in

the laboratory.

Sustainability will be assessed by the availability of GGBS and PFA in Uganda and

Tanzania, the relative costs of these products compared to PC and by looking at any

potential hazards associated with adopting these stabilisers.

Page 10: Mud Brick Construction

10

2.0 Aims and Objectives

The aim of this individual research project is to investigate sustainable alternatives to

cement for the stabilisation of unfired mud bricks.

To achieve the aim, the following objectives will apply:

Undertake a literature review to establish the current position of research

relating to the topic.

Identify two alternatives to cement for mud brick stabilisation.

Compare the alternatives to cement for cost, ease of manufacture and

embodied energy.

Investigate mud bricks made with the alternative stabilisers and compare them,

quantitatively, to cement stabilised bricks for three mechanical properties:

o Compressive strength.

o Absorption.

o Shrinkage.

Summarize whether the cement alternatives are a viable engineering

alternative.

Investigate the availability of the alternative stabilisers in the developing world

using Uganda and Tanzania as benchmarks.

Analyze whether the alternatives will be viable in the developing world.

Investigate whether there would be any social implications to the use of cement

alternatives in the developing world.

Recommend future research.

Page 11: Mud Brick Construction

11

3.0 Literature Review

Construction with earth or clay has been around for thousands of years. In the 1970’s

it was estimated that there were more than 80 million earthen dwellings in India without

considering significant numbers in Africa and China (Norton, 1997). It may be

conservative to suggest that over two billion of the worlds’ population live in buildings

primarily made from earth or clay.

Additionally, UN-HABITAT estimates that 3 billion people lack decent housing. With a

continually growing global population, this figure is likely only to rise. In Uganda, for

example, demand exists for 1.6 million new homes each year; this is met by a supply of

a mere 100,000. Building new homes on such a scale requires large amounts of

construction materials. Traditional building methods such as fired masonry or concrete

are environmentally damaging on many fronts – deforestation occurs to provide

firewood, concrete involves large amounts of embodied energy etc (The Good Earth

Trust, 2008).

In contrast to traditional fired masonry, building with unfired mud or clay bricks reduces

the cost of construction and the environmental impact. Importantly it also promotes

local business and employment. As a potential construction material it seems to tick all

the sustainability boxes and has great potential in the developing world.

The Good Earth Trust aims to promote the use of Interlocking Compressed Stabilised

Blocks (ICSB) in the developing world with an eventual aspiration to transform the

market so that people will opt for this technology rather than fired bricks:

„…to do this we take a multi-pronged approach through awareness raising, advocacy,

technical and business training, capacity building, research & development of the

technologies, and the provision of information and guidance. In our advocacy work we

target the government to ensure they are aware of the technology and include it in

building codes, technical specifications, and policy. We also advocate to Agencies,

NGOs, and the private sector to adopt these technologies in the projects and work they

do. In selected areas, we engage directly with local communities to implement practical

projects to understand what is needed to promote the adoption of the technology at

community levels.‟ (The Good Earth Trust, 2008)

Page 12: Mud Brick Construction

12

This project aims to research alternative stabilisers for compressed earth blocks. To

do so, further information on current ICSB technology is required. This information will

be presented, via a literature review, in 4 parts:

1. Background.

2. A review of potential stabilisers for unfired masonry bricks.

3. Comparative study of embodied energy, cost and manufacture of selected

stabilisers.

4. Testing procedures for the mechanical properties of masonry.

3.1 Background

3.1.1 Mud and Earth Construction

Although mud and earth construction has been around for thousands of years it is

important to ask whether it is still relevant today. Hadjri et al. (2007) interviewed ten

residents of earthen buildings about five key points: durability, affordability, living

conditions, aesthetics and their general performance compared to a ‘modern’ house.

Their findings are as follows:

1. Durability – Half of the residents indicated that their dwelling was durable, with

a lifespan of more than 20 years. The other half reported a lifespan of just 10

years with regular maintenance required. The latter category reported the

major factors in lack of durability were water and/or termite damage.

2. Affordability – All residents agreed that earthen dwellings were affordable

when compared to modern dwellings.

3. Living Conditions – 8 out of 10 interviewees stated that their homes offered

very comfortable living conditions with excellent thermal properties; cool in

summer and warm in winter. The other two were less impressed. However, it

should be noted that the two who complained about conditions lived in buildings

roofed with corrugated iron resulting in excessive heat transmission.

Page 13: Mud Brick Construction

13

4. Aesthetics – Four interviewees appreciated the appearance of earthen

architecture, two were indifferent but four found the appearance less pleasing

compared to ‘modern’ dwellings.

5. General Preference – 70% of residents stated that they would not live in an

earthen home if they had the financial resources to do otherwise. This was

mainly due to the fact that earthen dwellings were associated with poverty and

a lower social class.

These results show that there are still issues with the perceptions of earthen

architecture in the developing world (Hadjri, et al., 2007) and that any drive to promote

earthen architecture as a realistic alternative to ‘modern’ building materials must be

combined with an educational programme.

Earthen architecture, however, has changed considerably in recent years with better

understanding and increased use. The current trend for sustainable living combined

with greater understanding of the thermal benefits, safety and potential durability of

earth has led to substantial advances in the quality and appearance of mud and clay

based buildings (Burroughs, 2009). Some examples of earthen architecture, old and

new, are shown in Figs 1 to 3 These examples show that with the correct materials,

dedication and imagination, earth structures can be as impressive as more modern

construction methods.

Figure 1 - Examples of Earthen Architecture in India (Source: www.banasura.com)

Page 14: Mud Brick Construction

14

Figure 2 - Example of a Modern Earthen Structure in Riyadh, Saudi Arabia (Source: www.rael-sanfratello.com)

Figure 3 - Rammed Earth Construction Underway in India (Source: www.banasura.com)

Page 15: Mud Brick Construction

15

There are six predominant methods of earthen construction; these are summarized in

Table 1:

Table 1 - Types of Earth Construction Methods (adapted from UN HABITAT 2009).

1 Compressed Earth Block These are construction blocks made from a mixture of soil and a stabilizing agent compressed by different types of manual or motor driven press machines. ICSB are a variation of this.

2 Adobe Blocks These are similar to compressed earth blocks and often considered their precursor. Adobe blocks are usually made of a compacted mixture of clay and straw but are less uniform in size and shape than compressed earth blocks.

3 Cob In cob construction a mix of clay, sand and straw is made, then moulded and compressed into flowing forms to make walls and roofs.

4 Rammed Earth This involves the making of a mould into which the soil, inclusive of a weatherproofing agent, is compacted and left to dry. Subsequently the mould is removed and the earthen form remains.

5 Earth Sheltering This refers to the use of earth on the structure of a building. It includes earth berming, in-hill construction and underground construction.

6 Wattle and Daub This consists of a wooden or bamboo frame laid vertically and horizontally reinforced on which earthen daub is packed.

This project will focus solely on compressed earth blocks and their modern evolution;

the interlocking compressed stabilised block (ICSB).

Page 16: Mud Brick Construction

16

3.1.2 Interlocking Compressed Stabilised Blocks

In the past the traditional method of making blocks from compacting earth used

wooden moulds (similar to Adobe in Table 3-1). The blocks were then either wood-

fired or left to dry in the sun. In recent years the development of mechanical presses

has superseded the more primitive technology in most areas of the world (Norton,

1997).

In the 1950’s the Chilean engineer Raul Ramirez created the CINVA-RAM press at the

Inter American Housing Centre in Columbia. Methods of producing earth blocks have

continually developed since and there are now a diverse range of both manual and

motor driven presses catering for all scales of production.

The CINVA-RAM and similar machines provided a cost effective and more

environmentally friendly method of construction. However, skilled labourers were still

required to construct the blocks and significant amounts of cement and mortar were

required. To counter this, the Human Settlements Division of the Asian Institute of

Technology and the Thailand Institute of Scientific and Technological Research worked

together to modify the CINVA-RAM to produce interlocking blocks. These interlocking

blocks reduced the need for cement and for skilled tradesmen. As a result the cost of

construction was considerably reduced and the structural stability improved (UN

Human Settlements Programme, 2009). An example of a modern variation of the

CINVA-RAM, a Makiga press, is shown in Fig 4. Interlocking blocks have developed in

complexity since their early forerunners and now double interlocking and curved blocks

are available.

Page 17: Mud Brick Construction

17

Figure 4 - Makiga Press (Source: www.makiga-engineering.com)

An example of double interlocking blocks is shown in Fig 5; the interlocking fins on the

top and side of the blocks are easily identifiable. Also clear from this Figure is the high

quality outward appearance of the constructed blocks.

Figure 5 - Examples of Interlocking Blocks (Source: www.goodearthtrust.org.uk)

There are many advantages of interlocking blocks including environmental

considerations, ease of use and quality of performance. Table 3-2 compares an

interlocking block to some of the alternatives over a range of properties (source: (UN

Human Settlements Programme, 2009).

Page 18: Mud Brick Construction

18

Additional advantages of ICSB include:

1. Health – Curved blocks can be used to build water tanks, latrines and septic

tanks. These basic facilities are lacking in many areas of the developing world

and their provision can dramatically reduce disease.

2. Environment – ICSB are an environmentally sound alternative to traditional

fired blocks. In Uganda, for example, the firing of traditional masonry has led to

vast deforestation and destruction of wetlands (UN Human Settlements

Programme, 2009).

3. Ease of Use – ICSB machines are comparatively easy to use and maintain.

Construction using the blocks also requires less skill than traditional masonry.

4. Economics – ICSB construction is cheaper than traditional methods. Raw

materials can usually be sourced in the area of construction and the stabilised

blocks are weatherproof and require no further rendering.

5. Structural – ICSB technology compares favourably with traditional methods of

construction (Norton, 1997).

Page 19: Mud Brick Construction

19

Table 2 - Comparison of Interlocking Blocks to its Alternatives (Source: UN Human Settlements

Programme)

Page 20: Mud Brick Construction

20

3.2 A Review of Potential Stabilisers for Unfired Masonry Bricks

Browne (2005) tested handmade bricks and found they typically display strengths of 2

N/mm2 compared to machined bricks that provide strengths of more than 4 N/mm2.

This shows that handmade bricks satisfy the strength required for simple structures, for

example single storey shelters, and machined bricks (made with a Makiga ram for

example) are suitable for more complicated buildings.

However, the biggest drawback with mud block construction is the concerns over its

durability. Earthen structures are considered to last, on average, approximately 20%

less time than similar structures built by more traditional methods (Norton, 1997).

Traditionally cement or lime is added to stabilize the block and improve its’ durability

but some research has been done into chemical admixtures (Vinod, et al., 2010). This

research was inconclusive but chemicals can be discounted for use in the developed

world due to cost, difficulty of supply and the potential cost of training tradesmen.

The problem with cement stabilisation is that ICSB technology is promoted as an

environmentally friendly construction material. The addition of a cement stabiliser

lessens the embodied energy differential between ICSB and traditional fired blocks. It

is, therefore, important to investigate alternatives to cement.

Previous researchers, including Davis (2003) and Longland (1985), have suggested

lime as a suitable alternative, especially in clayey soils. Lime production is less

intensive than cement production but more lime is required to deliver similar results

(Sivapullaiah, et al., 2000). Lime as a stabiliser will not be investigated further in this

research project other than as an additive to activate the pozzolanic reaction.

Soil stabilisers are used in a variety of contexts including structural (ICSB),

geotechnical (pavement design) and geo-environmental (soil stabilisation), Jegendan

et al. (2010) investigated the use of cement blends for soil stabilisation and suggested

the following as possible alternatives to cement:

1. Ground Granulated Blast-furnace Slag (GGBS) – This is a by product of the

steel industry which occurs when iron ore is separated from the remaining slag.

This slag is tapped off and rapidly quenched in water to promote its

Page 21: Mud Brick Construction

21

cementitious properties. GGBS is used throughout the UK and approx 2 million

tonnes are used per annum (Jegendan, et al., 2010). It is commonly used as

an additive in cement mixes and lime can used to activate the reaction rather

than PC. Better durability is expected with higher GGBS content but it also

slows the curing time (Oti, et al., 2009).

2. Pulverised Fly Ash (PFA) – Fly ash is a by product from coal fired power

stations and over 6 million tonnes are produced annually in the UK (Jegendan,

et al., 2010). Of this, approximately 3.5 tonnes are used in the construction

industry. Coal is ground into a fine dust prior to combustion and it is the finer

ash which is cementitious. PFA requires water and a source of alkali, usually

calcium hydroxide, to stabilize soil, an application for which it has been used for

many years. The benefits of using PFA in terms of enhanced durability and

sustainability have been well documented in other applications including

pavement stabilisation (Sear, 2007), (Shafique, et al., 2004) and (Jegendan, et

al., 2010).

3. Cement Kiln Dust (CKD) – This is a by-product of cement manufacture quality

control. CKD is collected from cement kiln exhaust gasses and consists of

particles of clinker, unreacted calcined raw materials, and fuel ash. The

generation of CKD is environmentally questionable as it is related to cement

manufacture with its associated high embodied energy. However, although

CKD production is reducing due to improved processes a large amount is still

disposed of in landfill. Studies have shown that CKD is a useful soil stabiliser

and can also be used as an alkali activator for GGBS ((Jegendan, et al., 2010).

Other soil stabilisers suggested include reactive magnesia and zeolite though these

have been discounted due to high prices and expected problems of availability in the

developed world.

Coutand et al. (2006) investigated the use of Sewage Sludge Ash (SSA) as an

admixture in mortars. However, they concluded that SSA had a fundamentally different

chemical composition when compared to PFA which made it less suitable as a

stabiliser. This was mainly due to the low content of silica in SSA which meant its

pozzolanic activity was limited. SSA does not meet the European standards as a

Page 22: Mud Brick Construction

22

mineral admixture but could be used as a low grade pozzolan (Coutand, et al., 2006).

It will not be considered further in this project.

3.3 A Comparative Study of the Selected Stabilisers

Housing construction methods in the developed and the developing world need to fulfil

a variety of criteria. These include; energy consumed in the manufacturing processes,

problems associated with long distance transportation, consumption of raw materials

and natural resources, recycling, the impact on the environment and long term

sustainability (Reddy, 2004). It is unrealistic to consider all these factors in a

comparison of stabilisers. Some prioritization is necessary and this review will

concentrate on energy consumed in the manufacturing process (embodied energy),

cost of transportation and financial cost. When considered together these factors will

indicate the environmental impact and give some suggestion as to the long term

sustainability of each stabiliser.

Oti et al. (2009) found that the embodied energy and carbon dioxide emissions of fired

bricks are 4186 MJ/t and 202 Kg CO2/t respectively and comparatively, Portland

Cement (PC) stabilised unfired bricks have an embodied energy of 1025 MJ/t and

emissions of 125 Kg CO2/t. Clearly, in terms of energy, unfired bricks, even when

stabilised with PC, are a much better material for long term sustainability.

This project aims to investigate alternative stabilisers to PC for ICSB technology and

will focus on the use of GGBS and PFA. Table 3 compares these potential stabilisers

with PC in terms of energy costs during manufacture and construction.

Table 3 - Comparison of the Energy Costs of GGBS, PFA and PC (Sources: Oti, 2008 & 2009, Reddy,

2004 & 2001, Ash Solutions Ltd, 2009)

Ser Stabiliser Embodied Energy (MJ/t)

CO2 Emissions During Manufacture

(per t)

Energy in Transportation for

100km (MJ/t)

1 Portland Cement

5000 1000 kg 100

2 GGBS 1300 70 kg 100*

3 PFA 900 800 kg 400

4 No stabiliser 525 25 kg - *- No values were found in current literature for transportation costs of GGBS but it was assumed they would be very

similar to PC.

Page 23: Mud Brick Construction

23

Table 3 shows that GGBS and PFA are competitive with PC in terms of energy cost.

However, bricks with no stabiliser are the most environmentally appealing.

Unfortunately a lack of stabiliser means the brick is susceptible to water damage and

has poor durability when compared to a stabilised brick making it unviable (Oti, et al.,

2009).

In the UK GGBS and PFA retail for about the same price and making concrete with

these admixtures rather than PC is no more expensive (Vincent, 2010). This should be

similar across the world as both GGBS and PFA are by products of existing industry.

However, it should be noted that in previous studies GGBS has replaced up to 70% of

PC compared to 40% for PFA and can be more durable (Vincent, 2010). Therefore,

GGBS may deliver greater financial savings when looking at whole life cycle costs.

In conclusion, when considering embodied energy, transportation costs and financial

cost we can list the potential stabilisers in descending order of preference as follows:

GGBS, PFA, PC.

There is no literature investigating the use of PFA as a sustainable stabiliser for mud

brick construction, however, some initial research has been conducted into the use of

GGBS. Studies into the compressive strength of unfired bricks stabilised with

GGBS/PC mixtures realized results of 2.7-5 N/mm2 in the laboratory and 3.4-7.4 on an

industrial scale. These results are within the range specified by UK building

regulations (5 – 8 N/mm2) but at the lower end (Oti, et al., 2009).

Table 4 (source: Oti, 2009) illustrates some of the engineering parameters and

performance of unfired clay bricks stabilised with PC / lime and GGBS mixes with

mainstream bricks. Due to the early nature of the research there is no published

information on the complete range of engineering properties.

Page 24: Mud Brick Construction

24

Table 4 - Engineering Parameters and Performance of Unfired Clay Bricks and Mainstream Bricks

(Source: Oti, 2009)

Ser Parameter Fired Clay Sun Baked PC Stabilised Unfired Brick

GGBS/PC Mix Stabilised

Unfired Brick

1 Firing X - - -

2 Stabiliser Content

- - 8 – 12% PC 1.5 % Lime, 5% GGBS

3 Design Application

Internal / external walls

Internal walls Internal / external walls

Internal / external walls

4 Robustness / Durability

Frost resistant Susceptible to water damage

Dependant on stabiliser

Robust and durable with

activated GGBS blend

5 Cost High Low High Low

6 Use of PC - - x -

7 Breathability No No Impeded by PC Yes

This research further reinforces the idea that GGBS is an ideal replacement stabiliser

for PC.

3.4 Testing Procedures for the Mechanical Properties of Masonry

For this project three engineering properties have been selected to investigate the

strength and durability of the blocks stabilised with the cement alternatives:

1. Compressive strength.

2. Shrinkage.

3. Absorption.

Each of these properties will be tested by the European standards or the equivalent

accepted standard for ICSB technology.

3.4.1 Compressive Strength Testing of Masonry

The European standard for the compressive strength of clay masonry units is BS EN

772-1:2010 (though this draft has yet to be approved it varies little from the 2000

version).

The standard specifies a number of different conditioning procedures: air dry, oven dry,

conditioning to 6% moisture content and conditioning by immersion. Previous research

Page 25: Mud Brick Construction

25

suggests that immersing unfired bricks is unnecessary as if the bricks are handled

correctly and the building is properly detailed it is unlikely that bricks will be immersed

whilst in use (Heath, et al., 2009).

For this project, and to simulate most closely the conditions likely to be found in

Uganda and Tanzania, air drying the samples will be used. To achieve this in line with

the European standard, samples must be stored at room temperature (>15oC) at a

relative humidity of approximately 60% for 14 days before testing.

The compressive strength is determined using a compressive strength testing machine.

This machine must have an error of less than 2% (BSI, 2010). Further details of the

testing machine are as follows:

“The testing machine shall have adequate capacity to crush all the test specimens, but

the scale used shall be such that the failure load on the specimen exceeds one-fifth of

the full scale reading. The machine shall be provided with a load-pacer or equivalent

means to enable the load to be applied at the rate given in 8.2. The testing machine

shall be equipped with 2 steel-bearing platens. The stiffness of the platens and the

manner of load transfer shall be such that the deflection of the platen surfaces at failure

load shall be less than 0.1 mm measured over 250 mm. The platens shall either be

through hardened or the faces case hardened. The testing faces shall have a Vickers

hardness of at least 600 HV when tested in accordance with EN ISO 6507-1.”

(BSI, 2010)

The European standard states that the minimum number of samples to be tested is six.

However, this is for industrial scale production and is unrealistic for handmade bricks

constructed to compare stabilisers.

3.4.2 Shrinkage Testing of ICSB

UN HABITAT recognizes that the laboratory testing of ICBS technology is not always

viable, particularly in the developing world. Instead it recommends a number of ICSB

specific tests to determine whether a site, and more importantly its soil, is suitable for

the creation of unfired mud bricks (UN Human Settlements Programme, 2009).

These tests include a sedimentation test and a shrinkage test. Only the shrinkage test

will be considered in this project. This test is important to ensure that ICSB will not

Page 26: Mud Brick Construction

26

shrink so much during curing as to prove difficult to work with during subsequent

construction. Another drawback to significant shrinkage is the appearance of cracks

which can decrease durability, increase water absorption and have an adverse affect

on appearance. Shrinkage can be controlled with stabilisers. Depending on the soil

type and the shrinkage observed during initial testing the amount of stabiliser will vary.

Typically, when using PC, ratios of 5% are used but this can increase to 10% with

higher levels of clay (Browne, 2009).

3.4.3 Absorption Testing of Masonry

The European standard for absorption testing of clay masonry units is BS EN 772-

11:2010.

The principle of absorption testing is to immerse a face of the masonry unit in water for

a set period and determine the increase in mass. For clay masonry units the bed face

is the one that is tested (BSI, 2010).

3.5 Key Points from the Literature Review

The following key points have been drawn out from the literature review:

Various forms of earthen construction have been used for thousands of years.

A stigma is still attached to earthen construction in the developing world where

it is associated with poverty and low social standing. Therefore, an educational

programme will need to run concurrently to any concerted ICSB drive promoting

it as a viable, modern and sustainable construction material.

ICSB technology has numerous advantages over rival earthen construction

methods notably in strength, appearance and ease of use.

Ground Granulated Blast-furnace Slag (GGBS) and Pulverized Fly Ash (PFA)

are potential alternatives to Portland Cement (PC) as stabilisers for ICSB

technology.

GGBS and PFA are both favourable to PC in terms of embodied energy and

CO2 emissions. They also represent no significant additional financial cost.

Page 27: Mud Brick Construction

27

GGBS is the preferred stabiliser according to current research. However, there

is a lack of current research into the engineering properties of unfired bricks

stabilised with PFA.

BS EN 772-1:2010 gives the procedure for compressive strength testing of clay

masonry units.

UN HABITAT provides a range of tests to ensure the suitability of sites for

ICSB. The shrinkage test is useful to determine the amount of stabiliser and

the suitability of the local soil.

BS EN 772-11:2010 gives the procedure for absorption testing of clay masonry

units.

Page 28: Mud Brick Construction

28

4.0 Proposed Method Statement

In order to achieve the aim of this research project each of the objectives outlined

above will be taken in turn. To simplify the methodology it has been divided into a

number of Sections; research, preliminary experiments, laboratory experiments and a

sustainability study.

4.0.1 Research

The first three objectives are driven largely by the literature review and studying

published professional research. The outcome of the literature review is summarized

in paragraph 3.5 but most importantly GGBS and PFA have been selected as the

stabilisers to investigate.

Further research is required into a manufacturer of GGBS and PFA who will be willing

to support the project.

4.0.2 Preliminary Experiments

Get Sheltered, an EWB workshop designed to discuss various aspects of sustainable

construction in the developing world, is to be held at Newcastle University on the 20

Nov 10. This workshop will include a session on mud bricks during which ICSB

technology will be introduced to the participants by the researcher before a number of

mud bricks, some stabilised with lime or PC, will be made.

It is proposed that Get Sheltered be used as a set of preliminary experiments for the

project. The following outcomes are expected:

Familiarization with hand-made mud brick construction techniques.

Construction of moulds suitable for the main laboratory experiments testing

compressive strength and absorption.

Familiarization with compressive strength testing procedures for masonry units.

Page 29: Mud Brick Construction

29

Production of reference data for hand-made bricks stabilised with PC, lime and

no stabiliser (these will be included in the Results Section of this project).

4.0.3 Laboratory Experiments

Laboratory experiments will be used to determine the engineering properties of mud

bricks stabilised with PC, GGBS and PFA.

The following points will remain extant:

Bricks will be hand made by the researcher and no press will be used.

Three bricks with each stabiliser will be made. The amount of stabiliser in each

brick will vary in order to test the extremes of expected optimum stabiliser

content (e.g. 5-10% for PC).

Moulds will be constructed to ensure all hand-made bricks are of the same

dimensions.

The bricks will be used for both compressive testing and for absorption testing.

The absorption test will be conducted first and there will be seven days between

the two tests to allow the bricks to dry out.

The curing period before testing will be 30 days.

Compressive strength will be tested to EN 772-1 by the procedure detailed

below:

1. Clean the bedding surface to ensure even contact is maintained.

2. Measure the width and length of the loaded area and calculate the loaded

area.

3. Align the specimen in the testing machine without using any extra packing.

4. Apply loading at a rate of 0.05 N/mm2/s (the approved rate for masonry with

a strength <10N/mm2).

5. Record the maximum load.

6. Calculate the strength of the specimen by dividing the maximum load by the

loaded area and express to the nearest 0.1 N/mm2

Shrinkage will be measured by the procedure detailed below:

Page 30: Mud Brick Construction

30

1. Construct a wooden box with internal dimensions of 40mm x 40mm x

600mm.

2. Grease the box and insert the clay / sand mix to be tested.

3. Compact the mix well.

4. Leave to cure in the shade for at least 7 days.

5. Measure the amount of shrinkage and calculate as a percentage of the

initial dimensions. This value can be used to compare the shrinkage of soil

mixes.

Absorption will be measured using the procedure detailed below:

1. Measure the dimensions of the test face and determine the gross area.

2. Measure the dry weight of the specimen.

3. Immerse the specimen in water up to a depth of 5mm (+/-1mm) for 24 hours

(BSI, 2003).

4. Measure the new weight of the specimen.

5. Calculate the initial rate of water absorption using the formula in BS EN

772-11:2010 Section 8.3.

Results for the bricks stabilised with PC, GGBS and PFA will be compared to

each other both quantitatively and graphically.

4.0.4 Sustainability Study

This part of the project will fulfil the objectives concerned with the sustainability,

availability and potential implications of using the proposed stabilisers in the developing

world. Geographically, it will use Tanzania and Uganda as it is benchmarks.

The price and availability of GGBS and PFA will be initially sought from The Good

Earth Trust who have ongoing projects in those countries. A comparative study of the

health and social implications will be undertaken using existing published information.

The sustainability study is likely to be a relatively small part of the final project.

Page 31: Mud Brick Construction

31

4.1 Timeline

The key milestones for this project were the PIR submission date (3 Dec 10) and the

Project submission date (20 May 11).

All laboratory testing will take place during the period Jan – Mar 11 and a Gantt chart

showing the proposed timeline for the project is at Fig 1 (shaded tasks are ones that

were completed by 3 Dec 10).

Page 32: Mud Brick Construction

32

Figure 6 - Proposed Project Timeline

Page 33: Mud Brick Construction

33

5.0 Method Statement

The points in the Proposed Method Statement remain extant throughout this section

and technical details of the compressive strength, absorption and shrinkage tests can

be found in that section. The experimental steps are detailed in chronological order

and a table detailing the exact timeline of the project is at Appendix 1.

5.1 Constructing the Mud Bricks

Mud bricks are, by their very nature, simple to construct. They require only three raw

materials; soil, water and a stabiliser, in varying proportions. Production of mud bricks,

particularly in the developing world, is done by unskilled labourers. This means that

the measuring and mixing of the materials is usually approximated and is at best

measured using crude units such as ‘bags of sand’ or ‘wheelbarrows full’ (UN Human

Settlements Programme, 2009). This is one of the main advantages of this form of

construction. The percentage of stabiliser used usually varies depending on the soil

type but is typically between 5 and 20% with the higher proportions being applicable to

clayey soils (Browne, 2009).

The method detailed below was adapted from that used at the ‘Get Sheltered’

workshop in Nov 10. This was, in turn, learnt from another EWB workshop hosted by

Paul Jaquin, an individual who has done considerable research into earthen

construction. It is noted that the method is not incredibly detailed but this recreates

well the circumstances expected on a typical earthen construction site.

5.1.1 Equipment Required

The following equipment and materials were required to construct the bricks:

60 Kg sand (coarse Leyton sand).

36 Kg pea shingle.

8 Kg powered clay (whole white e china clay).

5 Kg PC.

5 Kg GGBS.

5 Kg PFA.

5 Kg lime.

Page 34: Mud Brick Construction

34

Safety footwear.

Heavy duty balance (up to 20 kg, 0.1 Kg accuracy).

Accurate balance (up to 2.5 Kg, 0.001 Kg accuracy)

Shovel.

Mixing tray for sand/clay.

Wheelbarrow.

PPE for lime (goggles, masks, gloves, lab coats).

Moulds for bricks (pre-made, as used at ‘Get Sheltered’).

Oil for lining moulds.

Water source.

Trowel.

Permanent marker.

5.1.2 Health and Safety

In addition to the existing safety rules of the laboratory a project specific risk

assessment was completed prior to the laboratory sessions. The format used was

standard for the Newcastle University Geotechnical Laboratories and is reproduced at

Appendix 2.

The main risk was from using lime and this was mitigated by the wearing of correct

PPE (lab coat, safety glasses, safety footwear and a mask).

5.1.3 Procedure

In line with the Section 4.0 nine bricks were made in total, three with each stabiliser.

For this project, stabiliser percentages of 10%, 15%, and 20% were used to provide a

range of a data as outlined in Section 4.0. These values were chosen as the

homogeneous soil that was used had high clay content. Normality of the stabiliser

content across all 3 stabilisers also allows ease of comparison and consistency of

results. The use of differing stabiliser quantities is considered further in Section 8.0.

In concrete preparation, and in other uses of GGBS as a cement replacement material,

the established practice is to replace PC on a 1:1 basis (ACI Committee, 1987). PFA

Page 35: Mud Brick Construction

35

is different from GGBS because it contains little calcium and therefore is unable to

react cementitiously unless there is lime from another source present. In common

construction practice PFA would not completely replace PC but would rather replace

up to 60%. However, in order to keep as many variables as possible constant PFA

replaced 100% of the PC during this research. For each PFA stabilised brick the PC

was replaced with the same volume of Lime/PFA in a ratio 1:2 (Caltrone, 2010).

Table 5 shows the quantities of each raw material required for the mud bricks

constructed for this project. Each brick was given an identifier to make reporting the

results more concise. These comprised of the letters A - I and are shown in Table 5.

Table 5 - Raw Material Quantities for Mud Brick Construction

Type of

Stabiliser Raw Material

% Stabiliser

10% 15% 20%

PC

Soil (+/- 0.1 kg)

A

9.0

B

8.5

C

8.0

Water (+/- 10ml) 1000 1100 1150

PC (+/- 0.01 kg) 1.0 1.5 2.0

PFA

Soil (+/- 0.1 kg)

D

9.0

E

8.5

F

8.0

Water (+/- 10ml) 1100 1250 1350

PFA (+/- 0.01kg) 0.67 1.0 1.33

Lime (+/- 0.01kg) 0.33 0.50 0.67

GGBS

Soil (+/- 0.1 kg)

G

9.0

H

8.5

I

8.0

Water (+/- 10 ml) 1000 1200 1050

GGBS (+/- 0.01 kg) 1.0 1.5 2.0

The bricks were constructed using the following method:

1. A manufactured soil mix was used for all bricks (and the shrinkage testing).

This mix was made by the researcher and was used to ensure that the only

variables changed during the research were the type and quantity of stabiliser.

By creating a homogeneous soil in the laboratory results can be more easily

and more accurately compared. The proportions chosen for the soil mix gave a

clay content of just under 8%; this is similar to the typical soil type in much of

Uganda [Mwebeze, 2007]. The soil was made as follows, in two batches:

a. 60 Kg of sand was weighed.

Page 36: Mud Brick Construction

36

b. 36 Kg of pea shingle was weighed.

c. 8 Kg of dry clay was weighed.

d. The raw materials were mixed together on a mixing tray. Fig 7

shows the raw materials and Fig 8 shows the mixed soil.

Figure 7 - Raw Materials for Soil Mix

Figure 8 - Mixed Homogenous Soil

2. The moulds used for the bricks were previously constructed using 5mm

plywood and were of the dimensions 145mm (w) x 300 mm (l) x 110 mm (d).

These dimensions were chosen as a suitable size to represent ICSB technology

which typically requires 35 bricks to cover 1m2, giving a profile surface area of

0.028m2, compared with 0.033m2 for the bricks manufactured during this project

Page 37: Mud Brick Construction

37

[Smith, 2010]. These were lined with mould oil (to prevent the brick from

sticking to the mould) prior to brick construction. Fig 9 shows the empty

moulds.

Figure 9 - Empty Brick Moulds

3. The raw materials were mixed in the required proportions for each sample.

4. One brick with each proportion of materials from Table 5 was constructed,

compacted well and levelled. Fig 10 shows the completed bricks in the moulds.

Figure 10 - Completed Bricks in Moulds (L-R, stabilised with PC, GGBS, PFA, shrinkage test)

5. The moulds for each brick were clearly marked.

6. The moulds were left to cure for 28 days prior to absorption testing. For the

initial curing period they were left loosely covered with plastic, as shown in Fig

11, for 7 days (The Good Earth Trust, 2008). This was to create a humid

Page 38: Mud Brick Construction

38

environment which would prevent the clay from setting before the cementitious

reaction was complete. After 7 days several holes were made in the plastic to

allow the evaporated water to escape. The plastic was kept in place to increase

the temperature and help recreate the humid conditions expected in the

developing world.

Figure 11 - Bricks and Shrinkage Test Left for Curing

No replicates of the bricks were made as this would have placed unnecessary time

constraints on the project. The sample size selected is the minimum size to allow a

comparison to be made between the different stabilisers.

5.2 Shrinkage Testing

The shrinkage testing was conducted at the same time as the curing of the mud bricks.

5.2.1 Equipment Required

The following equipment was required:

Safety boots.

Soil mix as made in Section 5.1.

Mould.

Trowel.

Page 39: Mud Brick Construction

39

5.2.2 Health and Safety

As this experiment was carried out at the same time as the construction of the mud

bricks in Section 5.1 the same risk assessment was used (reproduced at Appendix 2).

5.3.3 Procedure

The following procedure was followed:

1. In order to achieve a mould similar to the one detailed in the UN HABITAT

guide one of the internal batons was removed from a spare mud brick mould

constructed for ‘Get Sheltered’. This left a rectangular mould of dimensions 615

mm (l) x 145 mm (w) x 110 mm (d). The mould is shown in Fig 12.

Figure 12 - Shrinkage Testing Mould

2. The mould was filled with 20kg of the soil mix, rehydrated with 2000 ml of water.

No stabiliser was added.

3. The soil was compacted and levelled off before being left to cure in the same

conditions as the mud bricks for 14 days.

4. The shrinkage was calculated as per the method outlined in Section 4.0.3.

Page 40: Mud Brick Construction

40

5.3 Absorption Testing

The absorption testing was undertaken over a 24 hour period 28 days after the bricks

were constructed. It was conducted in line with the Proposed Method Statement,

specifically Section 4.0.3.

5.3.1 Equipment Required

The following equipment was required:

Metal trays x 2.

Water source.

PPE.

5.3.2 Health and Safety

No additional Risk Assessment was required because of the basic nature of the test.

5.3.3 Procedure

As stated, the proposed method was adhered to. Additional details are as follows:

1. The bricks were exposed to water (depth = 5mm) for a period of 24 hours. Fig

13 shows the experimental setup.

Page 41: Mud Brick Construction

41

Figure 13 - The Experimental Setup for the Absorption Testing

2. The water was topped up once during this period.

3. The Initial Rate of Water Absorption was calculated in line with BS EN 772:2010

Section 8.2.

5.4 Compressive Strength Testing

5.4.1 Equipment Required

The following equipment was required:

Compressive strength testing machine (as specified in the Section 4.0).

Brick samples, as prepared above.

Wood packing.

5.4.2 Health and Safety

The Risk Assessment at Appendix 2 was used for this procedure. No additional

controls were required.

Page 42: Mud Brick Construction

42

5.4.3 Procedure

The procedure used was as detailed in the Section 4.0. The only variation was the use

of wooden packing to distribute the load over the surface of the brick. This was

necessary due to the design of the machine. Fig 14 shows the experimental set up.

Figure 14 – The Experimental Set-up for the Compressive Strength Testing

The bricks were tested sequentially, on the same day. This meant that all the bricks

benefited from the same curing time.

Page 43: Mud Brick Construction

43

6.1 Preliminary Experimental Results

The experiments conducted at ‘Get Sheltered’ proved to be less extensive than at first

hoped. Nevertheless a range of mud bricks were constructed using the same method

as for those in the main laboratory experiments allowing familiarisation with the

procedure. Some previously constructed bricks, which had cured for 28 days, were

tested for their compressive strength. These bricks were stabilised with lime or PC and

one contained no stabiliser. A fired brick (from Uganda) and a regular house brick, as

used in masonry construction in the UK, were also tested. The results of the

compressive strength testing are shown in Table 6.1 and Figure 15.

Table 6 - Compressive Strength Testing of the Bricks Tested at 'Get Sheltered'

Ser Brick

1 2 3 4 5 Parameter

1 Description Lime stab PC stab No stab Fired brick House brick

2 Failure load (N) 40196 17427 51617 62352 249376

3 Area (mm2) 41300 41300 41300 29000 22360

4 Compressive Strength

(N/mm2)

0.97 0.42 1.25 2.15 11.2

Figure 15 - Compressive Strength of the Bricks Tested at 'Get Sheltered'

0

2

4

6

8

10

12

Lime stab PC stab No stab Fired brick House brick

Co

mp

ress

ive

Str

en

gth

(N

/m

m2

)

Type of Brick

6.0 Results

Page 44: Mud Brick Construction

44

6.2 Main Laboratory Experimental Results

6.2.1 Shrinkage Testing

The shrinkage test produced no shrinkage after the prescribed period. Even after

extending the test to 28 days, the observed shrinkage was still negligible.

6.2.2 Sample Appearance and Texture

Fig 16 shows the appearance of the samples once they had been removed from the

moulds. The PFA and PC stabilised samples (A-F) presented as expected with a

dense, hard texture. In contrast, samples G-I were very delicate, crumbling on touch

and with obvious surface cracking.

Figure 16 – The Appearance of the Bricks after Curing (Top: GGBS, Btm Left: PC, Btm Right: PFA)

6.2.3 Absorption Testing

The formula used to calculate the Initial Rate of Water Absorption is taken from BS EN

771-11:2010:

Where:

Page 45: Mud Brick Construction

45

Cws = Initial Rate of Water Absorption (kg/m2/min)

The results of the absorption testing are shown in Table 7 and Figure 17.

Table 7 - Absorption Testing Results

Sample Stabiliser %

Mass before

absorption test

(g)

Mass after

absorption test

(g)

Change in mass

(g)

Initial rate of

Water

Absorption

(kg/m2/min)

A

PC

10 10240 10450 210 0.033524904

B 15 10340 10430 90 0.014367816

C 20 10560 10620 60 0.009578544

D

PFA

10 9550 10040 490 0.078224777

E 15 9480 10030 550 0.087803321

F 20 9360 10090 730 0.116538953

G

GGBS

10 9580 10040 460 0.073435504

H 15 9470 10260 790 0.126117497

I 20 9070 9700 630 0.100574713

Figure 17 - The Initial Rate of Water Absorption for the Samples

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

A B C D E F G H I

Init

ial

Ra

te o

f W

ate

r A

bso

rpti

on

(k

g/

m2/

min

)

Sample

Page 46: Mud Brick Construction

46

6.2.4 Compressive Strength Testing

Sample raw data for the compressive strength testing is reproduced at Appendix 5.

Table 8 and Fig 18 compare the compressive strength of the various samples using all

the raw data recorded. Figs 19 – 21 show stress-strain curves for the bricks made with

the three stabilisers. Fig 22 shows the appearance of a selection of the bricks at the

conclusion of the test.

Table 8 - Compressive Strength Results

Sample Stabiliser % Ultimate Load (kN)

Area (mm2)

Compressive Strength (N/mm

2)

A PC 10 187.751 43500 4.316114943

B 15 247.544 43500 5.690666667

C 20 262.501 43500 6.034505747

D PFA 10 32.519 43500 0.747563218

E 15 33.331 43500 0.766229885

F 20 42.703 43500 0.981678161

G GGBS 10 5.011 43500 0.115195402

H 15 6.277 43500 0.144298851

I 20 7.407 43500 0.170275862

Figure 18 - A Comparison of the Compressive Strength of the Samples

0

1

2

3

4

5

6

7

A B C D E F G H I

Co

mp

ress

ive

Str

en

gth

(N

/m

m2)

Sample

Page 47: Mud Brick Construction

47

Figure 19 - Stress-Strain Curves for the PC Stabilised Bricks

Figure 20 - Stress-Strain Curves for the PFA Stabilised Bricks

Figure 21 - Stress-Strain Curves for the GGBS Stabilised Bricks

0

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0 0.05 0.1 0.15 0.2

Str

ess

(k

n/

mm

2)

Strain

10% Stabilizer

15% Stabilizer

20% Stabilizer

0

0.0002

0.0004

0.0006

0.0008

0.001

0.0012

0 0.05 0.1 0.15

Str

ess

(k

N/

mm

2)

Strain

10% Stabilizer

15% Stabilizer

20% Stabilizer

0

0.00002

0.00004

0.00006

0.00008

0.0001

0.00012

0.00014

0.00016

0.00018

0 0.02 0.04 0.06 0.08 0.1

Str

ess

(k

N/

mm

2)

Strain

10% Stabilizer

15% Stabilizer

20% Stabilizer

Page 48: Mud Brick Construction

48

GGB S:

S:

PF A:

A:

PC:

Figure 22 - The Appearance of a Selection of Samples after Compressive Strength Testing

Page 49: Mud Brick Construction

49

7.0 Sustainability Study

More than 20 years since the Brundtland Commission brought sustainable

development to international prominence the issue still arouses much debate as to how

it should be defined, interpreted and assessed. Proponents of the theory have

designed earnest procedures for the measuring and reporting of it. Others, more

sceptical to the concept are of the opinion that the World Commission for Environment

and Development (WCED) definition is ‘an idea so vague that everyone can agree to it’

(Lindsay, 2001). They assert that sustainable development is an oxymoron and that

neo liberal discourse on the subject focuses almost solely on the economic rather than

any social or environmental aspects (Davidson, 2010).

However, there is broad consensus that the concept is multi dimensional, advocating a

complicated, and often subjective, interrelationship between social, environmental and

economic factors (as shown in Fig 23). Many definitions exist but most typically

suggest some responsibility to current and future generations as well as an

appreciation that the natural environment is not an infinite resource to be continually

degraded (Walton, et al., 2005). Perhaps the most commonly quoted definition is that

proposed by the WCED:

„…development that meets the need of the present without compromising the ability of

future generations to meet their own needs.‟

(World Commission on Environment and Development, 1987)

Figure 23 - Interrelationship between the Spheres of Sustainability (Source: Tanguay, et al. 2009)

Page 50: Mud Brick Construction

50

One method of measuring sustainability and one that is popular with a number of public

administrators is the use of Sustainable Development Indicators (SDIs). However, the

sheer number of SDIs and the lack of common interpretation of their meaning means

that their use is still problematic (Tanguay, et al., 2009).

In the context of this report this presents difficulty in determining exactly how to define

sustainability and how to compare the different stabilisers.

To counter this difficulty the report will broadly endorse the WCED definition and

investigate the proposed alternative stabilisers, GGBS, PFA and PC, across four

areas:

Ease of Manufacture (environmental, economic, and social).

Financial cost (economic).

Health implications (social, environmental).

Quantitative eco-points analysis (environmental).

Whilst it is acknowledged that this approach has its limitations, so do the alternatives

and this method will at least provide both quantitative and qualitative results for

discussion.

7.1 Ease of Manufacture

PFA and GGBS are both by products of existing industry. Details of their manufacture

are contained in Section 3.2 above.

PC is not a by-product. Instead its manufacture consists of a tightly controlled

combination of calcium, silica, aluminium, iron and small amounts of other materials.

Gypsum is added at the final grinding stage in order to regulate the setting time.

Two methods of production exist for PC; wet and dry. In both methods the raw

materials (calcium carbonate and silica) are mixed together and fed into large rotating

kiln cylinders. These are heated to approx 1450oC to create the conditions necessary

for the chemical reactions to take place. A substance called clinker is produced,

Page 51: Mud Brick Construction

51

cooled and then ground with gypsum to produce cement powder (Portland Cement

Association, 2011).

The cement manufacturing procedure is extremely energy intensive and the

environmental implications of producing PC, in comparison to PFA and GGBS, have

already been stated in Table 3.

7.2 Financial Cost

The financial cost of ICSB technology varies, depending on a number of factors

primarily the availability of quality material on site, the transportation costs and the

amount of mortar used. A financial estimate for 1 m2 of ICSB wall compared to 1 m2 of

fired brick wall is shown in Table 9. In this table it should be noted that marram is a

grass traditionally added as a further stabiliser/aggregate. The discrepancy in mortar

requirements between fired bricks and ICSB is due to the ‘fins’ designed into the ICSB

blocks, these reduce the need for mortar. However, more labour is required for the

ICSB blocks as they are usually made locally (or even on site) rather than being

delivered from a manufacturing plant.

Page 52: Mud Brick Construction

52

Table 9 - A Comparison of the Costs of Fired Bricks and ICSB (adapted from Smith, 2010)

Per 100 Bricks Per 400 Bricks Per Brick

Fired Bricks

Blocks:

Purchase cost 15000 150

Mortar:

Coarse sand (3 wheelbarrows) 6300 63

Fine sand (2 wheelbarrows) 6000 60

PC (25 kg) 28000 280

Labour:

1 x mason (per day) 10000 25

0.5 x labourer (per day) 2500 6

Total (Ugandan Shillings / m2

(50 bricks))

29213

ICSB

Blocks:

Marram (6 wheelbarrows) 8400 84

PC (25 kg) 28000 280

Mortar:

Coarse sand (3 wheelbarrows) 6300 16

Fine sand (2 wheelbarrows) 6000 15

PC (25 kg) 28000 70

Labour:

1 x mason (per day) 10000 25

3.5 x labourers (per day) 17500 44

Total (Ugandan Shillings / m2

(35 bricks))

18690

Table 9 shows that ICSB technology is financially more viable than fired bricks but this

table was based on mud bricks that had been stabilised with PC. Unfortunately, finding

prices for GGBS and PFA in Uganda or Tanzania proved unsuccessful. However, a

model has been developed to adjust the costs proposed for PC stabilised blocks to

give a proposed cost for blocks stabilised with GGBS and PFA.

Prices for PC, GGBS and PFA in the UK were found ([A1 Building Supplies, 2011],

[Benny Industries, Unknown], [ValueUK, 2011], [The Building Lime Company, 2011]).

These are presented in Table 10. By comparing the UK PC price to the Ugandan PC

price a multiplication factor of 7197.94 can be applied to all prices to give an

Page 53: Mud Brick Construction

53

approximate Ugandan price, assuming availability. Table 10 also compares the price,

in Ugandan Shillings, of producing 1 x ICSB with the various stabilisers using the

variables detailed in Table 9.

Table 10 – A Comparison of Estimated Stabiliser Cost in Ugandan Shillings and Cost per ICSB

PC GGBS PFA / Lime

UK Price (GBP per 25 kg) 3.89 6.00 3.78 (PFA)

9.97 (Lime)

= 5.84

Ugandan Price (Ugandan Shillings per 25 kg) 28000 43187 42036

Total cost of producing 1 x ICSB (Ugandan

Shillings)

18690 24005 23602.25

7.3 Health Implications

7.3.1 GGBS (CEMEX, 2008)

For use as a stabiliser or concrete admix GGBS is supplied as a fine powder or dust.

As with all dusts it can irritate the eyes, skin, respiratory system or gastro-intestinal

tract. When mixed with water the resulting solution can be alkali. Current industry

practice in the UK is that appropriate protective clothing should be worn to minimize

contact with the skin and eyes. The substance is stable in normal conditions and,

provided reasonable care is taken, is not hazardous in the quantities that would be

used for ICSB stabilisation.

7.3.2 PC (US Department of Health and Human Services, 1995)

PC is also used in powered form, comprising a grey, fine, odourless powder. The

health risks associated with the substance are similar to GGBS, notably that the dust

can cause eye irritation and prolonged or repeated contact with the skin can cause

dermatitis. Protective clothing (boots and gloves) should be worn when handling

cement but the use of a respirator is unnecessary unless heavy exposure is

anticipated.

Page 54: Mud Brick Construction

54

7.3.3 PFA (Scotash, 2005)

PFA also presents as a grey, odourless dust. However the health risks associated with

it are markedly lower than either GGBS or PC. It is still recommended to wear

protective clothing but there is no clinical evidence of skin inflammation, respiratory

problems (unless excessive amounts have been inhaled) or issues associated with

ingestion.

However, it should be noted that PFA requires lime to initiate the cementitious reaction

and this has health and safety implications of its own (CEMEX, 2007). Lime can burn

skin in the presence of water and there is risk of serious damage to the eyes.

Protective clothing must be worn at all times, including eye protection and face masks.

It should also be noted that the reaction between water and lime is highly exothermic.

7.4 Quantitative Ecopoints Analysis

The environmental impacts of construction are hard to analyse as they impact on a

number of different areas, for example water resource quality and climate change.

Comparing directly different situations is unhelpful and inaccurate as it involves

subjective judgement on the scope of influence and their relative importance. For

example is a mineral extraction programme that significantly impacts water quality but

has very little effect on climate change a better or worse construction practice than an

industry with the reverse environmental implications?

To enable greater accuracy in such assessments BRE (formerly the Building Research

Establishment) have developed Eco-points.

The parameters that Eco-points consider include climate change, fossil fuel depletion,

freight transport, toxicity and waste disposal. BRE have then attempted to normalize

the environmental impact of these activities by comparing them to a norm. This norm

has been taken as the average impact of a UK citizen, calculated by dividing the total

UK impact by the population of the UK. The system has also, in consultation with

industry experts and stakeholders, assigned a weighting to each environmental impact

(BRE, 2009). The result is a single figure score for the environmental impact of a

material where the higher the number, the higher the impact.

Page 55: Mud Brick Construction

55

The Eco-point summaries for PFA and GGBS are reproduced in Appendices 3 and 4.

The Eco-point summary for PC was not available but several articles and papers detail

the score at around 4.1 ([A1 Building Supplies, 2011] [Portland Cement Association,

2011]). This is largely due to the huge amounts of embodied energy involved in the

production of cement compared to the other two substances which are merely by-

products of existing industry. To summarise, the Eco-point scores are as follows:

GGBS: 0.35 Eco-points.

PFA: 0.066 Eco-points.

PC: Approx 4 Eco-points.

Page 56: Mud Brick Construction

56

8.0 Discussion

8.1 Preliminary Experiments

The results from the preliminary experiments were not as expected. The compressive

strength of all the unfired bricks was disappointingly low (0.42-1.25 N/mm2) and short

of the 5-8 N/mm2 required by current Eurocode, and UK Building Regulation, standards

(Oti, et al., 2009). Another notable observation is that the unfired brick without a

stabiliser performed recorded the highest compressive strength during testing. There

are a number of potential reasons for this:

1. Unknown Provenance. The manufacture of the bricks took place at an

external location and by unknown individuals. This means there is plenty of

scope for inaccuracy, both in terms of the manufacturing procedure and the

materials used. For example, substandard or badly stored lime may have been

used and this could have affected the results. Other factors, which remain

unknown, that could have affected the performance of the bricks include the

manner of storage, the curing period and how they have been treated since

manufacture (e.g. have they been dropped, have they been exposed to water

etc).

2. Appropriate Ratios of Materials. The mix of materials that was used for the

production of the bricks in the preliminary experiment is also unknown.

Although there were estimates of a uniform addition of 20% of stabiliser across

the bricks this has not been confirmed. This makes any comparison with the

results from the main laboratory experiments virtually worthless and also casts

doubt on the appropriateness of the mix proportions.

3. Uneven Loading on the Bedding Plane. The tested bricks were particularly

coarse. The nature of the compressive strength testing machine means that

the application of the load is, therefore, uneven (because a point load is

transferred across the bedding plane by a piece of additional material and there

is no cushioning between the two to mitigate for uneven surfaces). Even with a

piece of soft wooden packing to try and lessen the effects there were still raised

Page 57: Mud Brick Construction

57

points on the bedding plane which will have taken the brunt of the load. This

source of error could potentially be reduced by testing one of the surfaces that

were in contact with the mould (and, therefore, smoother). However, EN 772-1

states that the bedding plane to be loaded is the one that should be tested.

Testing the brick on its side, for example, would give skewed results because it

would be testing the compressive strength in a plane not loaded in usual use.

The most obvious way to provide a more level bedding surface is to use a

mould that contains the brick on all surfaces. Testing of ICSB that has been

produced in a press will probably sidestep this potential source of inaccuracy as

the bricks will be more uniform.

The preliminary experiments were still a worthwhile exercise. The results show that the

compressive strength of both the fired brick and the house brick (2.15 N/mm2 and 11.2

N/mm2 respectively) are superior to the unfired bricks. This confirms that although

unfired mud bricks are an adequate solution for affordable housing they are not as

efficient at carrying load as more traditional methods of construction. Another positive

outcome from the preliminary experiments was the hands-on experience of making

mud bricks. This proved invaluable when conducting the main laboratory experiments

as a manufacturing method was already known and had been practiced.

8.2 Sustainability Study

8.2.1 Defining Sustainability

The first paragraphs of Section 7.0 alluded to the problems with attempting to define

sustainability and outlined the areas which would be considered in the context of this

report. For clarity these are reproduced below:

Ease of Manufacture (environmental, economic, and social).

Financial cost (economic).

Health implications (social, environmental).

Quantitative eco-points analysis (environmental).

Page 58: Mud Brick Construction

58

The decision to use these four areas was based on the fact that they would produce

both qualitative and quantitative results for comparison. Each of these areas will be

discussed in turn.

8.2.2 Ease of Manufacture

If it is assumed that a product or service is ‘more sustainable’ if its manufacturing

process is least harmful to the environment then it is apparent that PFA and GGBS are

inherently ‘more sustainable’ products than PC. As PFA and GGBS are by-products of

existing industry so their production contributes no more environmental damage than

the primary industry. Indeed, the environmental damage caused by the production of

these stabilisers has already been compared in Section 3.3. However, this is a fairly

simplistic overview and the environmental considerations, and the longevity, of the

primary industry must be taken into account.

Coal fired power stations, the industry behind the production of PFA, have a limited

lifespan as the global reserves of coal are finite. However, as recently as 2009 the UK

government announced plans for 4 new plants before 2020. There are natural

concerns about this apparent pursuance of ‘dirty’ technology and questions raised as

to the merit of investing in existing technology rather than pursuing greener energy

options such as nuclear power and renewable energy. However, since it is reasonable

to assert that ‘green’ technology in the developing world is likely to lag behind that of

the developed world then it is also reasonable to assume that coal fired power stations

will continue to be used in the areas where ICSB technology is most likely to be

employed. This claim is reinforced by the fact that there are currently plans in place to

build a new 200MW coal powered plant in Tanzania. Therefore, whilst it is certainly not

a solution that will be applicable forever, PFA will be produced for the foreseeable

future though the rate of production may slow if power stations continue to improve

efficiency. The use of PFA will also help to reduce the environmental impact of coal

fired power stations by committing less waste to landfill and creating worthwhile

products out of a greater percentage of raw materials.

GGBS is a by-product of the steel manufacturing process and the demand for steel is

increasing. Attempts are being made to streamline industry processes and make them

more sustainable, particularly regarding the recycling of steel. However, it is

reasonable to deduce that steel, and by inference GGBS, production will continue for

Page 59: Mud Brick Construction

59

the foreseeable future. Steel is a key industry in Uganda with Sembule Steel providing

steel products to more than 10 countries in East and Central Africa [USGS, 2006].

This alludes to the possibility of GGBS production in the area. The sustainability of

GGBS, in terms of ease of manufacturing, can therefore be placed on a par with PFA.

If the primary industry for both materials persists then they will continue to be, at least

theoretically, available.

It is widely known, and reported, that cement production is an extremely energy

intensive manufacturing process that cannot claim to have good environmental

credentials. However, the cement industry is suggesting reformist agendas to

modernize production and improve the reputation of the industry. There is strong

scepticism about these reforms, however, as the cement producers are disadvantaged

by basic chemistry. The chemical reaction that produces cement releases large

amounts of CO2 and about 60% of the CO2 emissions from manufacture are from this

reaction. To minimize emissions the cement industry is attempting to reduce the fuel

input in production. However, if demand for concrete continues to rise faster than the

emissions are reduced then the negative environmental effect of cement manufacture

will continue to worsen. For this reason, and in terms of ease of manufacture, PC is

the least sustainable stabiliser tested in this project.

8.2.3 Financial Cost

The financial cost of the stabilisers is easier to compare as there is quantitative data

available from the model detailed in Section 7.2. If it is assumed that ‘more sustainable’

in a financial context is defined as lower cost then the relative ranking of the stabilisers

would be: PC (18690 UGS per ICSB), GGBS (23602.25 UGS per ICSB) then PFA

(24005 UGS per ICSB).

8.2.4 Health Implications

There is no major difference in the potential stabilisers in terms of health implications.

However, PFA requires lime to initiate the cementitious reaction and this is a potentially

hazardous material.

Page 60: Mud Brick Construction

60

In a social context it can be assumed that ‘more sustainable’ means least hazardous.

As a result the stabilisers can be ranked in the following order: PC and GGBS are

equal followed by PFA.

8.2.5 Overall Sustainability

This project is attempting to rank the proposed stabilisers in terms of their overall

sustainability and the problems with this approach have been made clear. It is

incredibly difficult, not to mention subjective, to compare such different substances

over such a diverse range of factors. However, Table 11 and the preceding

paragraphs, attempt to do that. Table 11 shows the stabilisers ranked according to

three of the four key areas considered above. It ranks each stabiliser against each

area allocating a 1 (green) for the most sustainable and a 3 (red) for the least. The

final column shows an overall sustainability ‘score’ according to the research carried

out for this project and the criteria discussed in Sections 8.2.2 to 8.2.4. This score was

calculated by adding together the individual scores for each key area.

Table 11 - An Overall Comparison of the Sustainability of the Stabilisers

Stabiliser Ease of

Manufacture

Financial Cost Health

Implications

Total

PC 3 1 1 5

PFA 1 3 3* 7

GGBS 1 2 1 4

*Although PFA is considerably less harmful than either GGBS or PC the requirement for lime makes it the least

‘sustainable’ option.

Table 11 shows that, according to the sustainability study in Section 7.0, GGBS is the

most sustainable followed by PC and then PFA. This is at odds with the eco-points

scores which rank the stabilisers in the following order: PFA, GGBS and then PC.

Since the eco-points system and the sustainability study in this report are effectively

trying to achieve the same result (although the eco-point system considers many more

factors) this is a surprising outcome. 2 possible reasons for this discrepancy will be

considered here. The first is that the eco-point system is based on the energy

consumption of a typical UK resident. This report has attempted to rate the

Page 61: Mud Brick Construction

61

sustainability of the stabilisers from a Ugandan and Tanzanian perspective. The

financial cost for example, which has been calculated in UGS, has had a significant

impact on the overall sustainability score achieved from this research. The second,

and perhaps more considerable, reason for the discrepancy is one of the fundamental

drawbacks of the concept of sustainability; subjectivity. Any author or authority can,

intentionally or otherwise, skew the results of such a subjective idea. Whilst every

intention can be made to be as neutral as possible there is always a vested interest by

the compiler of any research. This may vary from a desire to produce the best possible

report, thesis or article to providing evidence in support of the claims of a financial

backer. It is not being proposed that all measures of sustainability have inherent

intentional inaccuracy but it would be naïve to take all published data simply at face

value.

A final point to note from the sustainability study is that this entire report has been

conducted under the assumption that PFA and GGBS are available in the developing

world. Whilst it has been proved that the industry that produces these by-products

exist in Uganda and Tanzania, and are likely to do so for the foreseeable future, there

has been no definitive evidence found that PFA and/or GGBS are refined, marketed

and sold in those countries. If these substances are not available, or need to be

imported from further afield, then any environmental and financial advantage will be

negated. Conversely, questions can be asked if the products aren’t available in the

developing world yet the industry that produces them exists. It is worth further

investigation to see if the economic, commercial and social conditions exist to make

their sale worthwhile.

8.3 Laboratory Experiments

8.3.1 Shrinkage Testing

The shrinkage testing returned a result of zero shrinkage, despite increasing the curing

time to allow the soil to dry further. There are several possible reasons for this

unexpected result:

1. The Use of an Artificial Homogeneous Soil. As described in Section 5.0

an artificial homogeneous soil was used for the construction of all the bricks.

Page 62: Mud Brick Construction

62

Although this allowed more accurate comparison of the various samples it

also meant that the soil was devoid of the differences (e.g. void ratios and

variable water content) that would influence the shrinkage of a natural

material.

2. Inappropriate Curing Conditions. The shrinkage mould was left to cure at

room temperature (approx 20OC) and normal humidity. This may not have

provided the ideal curing conditions for shrinkage to occur. The effect of

this, however, is likely to be minimal because the curing time was extended

when no shrinkage was observed initially.

3. Lack of Hydration. The shrinkage testing mix was hydrated with 2000ml of

water. This was estimated from the amount of water required to hydrate the

bricks and may not have been sufficient to properly hydrate the soil to

obtain any significant shrinkage.

Although the shrinkage testing produced disappointing results the reason for

undertaking the test should be reiterated. The test has been adapted from the UN

HABITAT test for calculating the required amount of stabiliser. Since this project

intended to investigate the use of alternative stabilisers in mud bricks, the percentage

of stabiliser was likely to be varied. Therefore, the utility of the test in this instance is

fairly limited. No shrinkage would suggest that a low proportion of stabiliser is required

as one of the key roles of the stabiliser is to prevent shrinkage. Even the 10% bricks,

the lowest tested percentage of stabiliser, should, therefore, not have been affected by

shrinkage during the project. In practical application the amount of stabiliser tends to

be around 10% (Browne, 2009). This published data, and the negligible shrinkage,

gives additional credence to the stabiliser percentages chosen for the main laboratory

experiments.

8.3.2 Manufacturing Procedure

The manufacturing procedure is a potential source of inaccuracy in the Method

Statement. As previously stated, the procedure used was adapted from a technique

taught at EWB workshops. However, an element of judgement was required when

calculating mix proportions and curing times. Although previous research and standard

Page 63: Mud Brick Construction

63

procedures were consulted to shape the method used in this project (notably UN

HABITAT and Oti, 2009) there is no professional standard for this type of brick

manufacture.

Other sources of inaccuracy in the manufacturing procedure include the mixing

technique (which could be improved by the use of a mechanical mixing device), the

source of the materials (which was taken on trust from the laboratory technicians) and

the curing conditions (which, although designed to simulate a practical environment,

were subject to the vagaries of the laboratory).

8.3.3 Absorption Testing

The Initial Rate of water Absorption (IRA) ranged from 0.01 Kg/m2/min for the 20% PC

brick (sample C) to 0.13 Kg/m2/min for the 15% GGBS brick (sample H).

The PC bricks (samples A-C) performed as expected and the IRA decreased with

increased proportions of stabiliser. This is not surprising as higher cement content will

decrease the porosity of the material and cement is a water resistant material when

cured.

Conversely, the PFA bricks (samples D-E) performed contrary to expectation because

the IRA increased with increased stabiliser content. This is probably due to the

presence of excess lime in the PFA bricks which would not have been fully hydrated

during the cementitious reaction. The excess lime would then absorb the water during

the absorption testing adversely affecting the IRA results.

The results from the GGBS bricks (samples G-I) are unreliable. There is no pattern to

the IRA as the 15% brick (sample H, 0.13 Kg/m2/min) exceeds both the 10% brick

(sample G, 0.07 Kg/m2/min) and the 20% brick (sample I, Kg/m2/min). There is no

obvious explanation for these results and, when combined with the disappointing

compressive strength results discussed in Section 8.3.4, the conclusion must be that

the manufacture of the GGBS bricks was in some way unsatisfactory. This is

discussed in further detail in Sections 8.3.2 and 8.3.4.

The results from all the samples, however, are positive. The IRA of a brick has a

significant effect on the eventual overall strength of a masonry wall. For example, if the

Page 64: Mud Brick Construction

64

IRA of a brick rises from 2 Kg/m2/min to 4 Kg/m2/min then the strength of the wall will

be reduced by 50%. Bricks with large IRA values will draw moisture from the mortar

and reduce its effectiveness. (Whilst it is appreciated that one of the appeals of ICSB

technology is the reduced reliance on mortar there is still a need for some). Bricks with

an IRA of greater than 2 Kg/m2/min are considered difficult to lay with traditional

mortars. All of the samples tested in this research have displayed IRAs of significantly

less than 2 Kg/m2/min and, therefore, would be acceptable in traditional construction

[Claybricks and Tiles Sdn, 1998-2007].

There is one important aspect of the absorption testing method that should be

considered and potentially adapted for future research. BS EN 772-11:2010 Section

8.3 details the absorption testing procedure that was followed during this research.

That document states that the sample should be submerged in water up to a depth of

5mm (+/- 1mm) for 24 hours. It makes no mention of whether the water level should be

topped up during that 24 hour period. When using samples as permeable as unfired

bricks this becomes a noteworthy omission. If the water was to be kept at a constant

level throughout the 24 hour period then it is likely that the IRA results would be very

different (indeed, the GGBS bricks would probably have been unusable for further

testing had this been the case). As mentioned in Section 5.0 the water, in this

absorption test, was topped up once during the 24 hour period and this may have

affected the results for the PFA and GGBS bricks. Careful consideration should be

given to this, and to the proportion of lime in the PFA mix, if the research is to be

repeated. Further discussion on the applicability of the Eurocodes to this type of

construction material is contained in Section 8.3.5.

8.3.4 Compressive Strength Testing

The compressive strength of the bricks varied from 0.12 N/mm2 for the 10% GGBS

brick (sample G) to 6.03 N/mm2 for the 20% PC brick (sample C). The mean

compressive strength for all the samples was 2.11 N/mm2 which is below the desired

minimum of 5 N/mm2 required for UK building regulations. This is not unexpected,

however, as previous research into similar bricks yielded compressive strengths of 2.7

– 7.4 N/mm2 (Oti, et al., 2009). These are also below the required building regulation

standards. The results from this project, however, were still significantly below the

published findings.

Page 65: Mud Brick Construction

65

Specifically, and surprisingly, the GGBS stabilised bricks (samples G-I) performed least

well with a compressive strength range of 0.12 – 0.17 N/mm2. However, increased

percentages of stabiliser improved the performance of the bricks as expected.

Previous research had been conducted into GGBS stabilised unfired bricks by Oti and

they performed much better in his work (2.7 – 5 N/mm2).

The PFA bricks (samples D-F) produced a compressive strength range of 0.75 – 0.98

N/mm2 with a slightly anomalous result for the 15% brick (sample E, 0.77 N/mm2)

which should have been higher when compared to the 10% brick (sample D, 0.75

N/mm2). The compressive strength results were all below 1 N/mm2 which is lower than

expected.

The PC bricks (samples A-C) exhibited the highest compressive strength by a large

margin. This is not an unexpected result and reinforces the selection of PC as the

preferred stabiliser in current ICSB practice. Samples A-C produced a compressive

strength range of 4.32-6.03 N/mm2 though the value for C is estimated as it exceeded

the load capacity of the testing machine. These results also increased with the

stabiliser content. Samples B and C (15% and 20% PC stabiliser respectively)

displayed compressive strengths over 5.0 N/mm2 and would thus be acceptable to UK

building regulations.

There are several factors pertaining to the compressive strength testing that should be

considered further:

1. Uneven Bedding Planes. The same issues discussed in Section 8.1 are

applicable to the main laboratory experiments. The same suggestions

should be followed to mitigate them.

2. Materials Provenance. The GGBS bricks (samples G-I) produced

surprising results across both areas of interest. A question must, therefore,

be raised as to the quality, and the provenance, of the raw material.

Published research by Oti has realized much improved results (see above).

Whist the surprisingly poor results in this research may be attributable to

inappropriate material storage or handling it is important to remember the

eventual practical application of ICSB technology. Construction sites, and

construction workers, across the world are unlikely to favour GGBS to PC if

Page 66: Mud Brick Construction

66

the change involves complicated handling or storage implications.

Alternatively, the results could be due to another reason, perhaps

inaccurate manufacture (but this should have affected the other stabilisers

as well because all of the sample were made in the same way) or

unsuitable mix proportions.

3. Machine Reliability. The machine used to test the compressive strength

was modern and complied with all the requirements stated in EN 772-1.

Therefore, machine reliability can be discarded as the reason for the low

compressive strength results.

4. Subsequent Testing on the same Samples. Both the absorption test and

the compressive strength testing were carried out on the same samples.

This may have influenced the results, particularly for the bricks that showed

a higher rate of IRA (i.e. the GGBS bricks). Excess water in the bricks may

have reduced their strength. Although this is a valid source of potential

error it should be remembered that one of the concerns surrounding the use

of unfired bricks is their susceptibility to water damage If it proved the case

that the compressive strength was considerably reduced by the previous

absorption testing then it doesn’t breed confidence in the use of GGBS

bricks in a practical environment

8.3.5 Application of ICSB Technology

In summary, the results of the engineering property testing indicate that whilst all of the

bricks performed adequately in terms of IRA, the vast majority were not sufficiently

strong in terms of compressive strength to be considered as a construction material

according to UK Building Regulations. However, it is important to define exactly what

the requirements are for ICSB technology. The primary use, certainly in the developing

world, is to provide affordable housing and for low scale construction projects. Even

the diverse projects discussed in Section 3.0 all share a fairly limited ambition in terms

of construction scope. Therefore, it may not be essential for ICSB to satisfy the

requirements of construction materials that are used in more complex developments.

If the application of ICSB technology in the developing world is limited to small scale

projects then the loads that would be expected to act on the structure would be

Page 67: Mud Brick Construction

67

considerably less than, for example, a 2 storey house in the UK. Design could be

undertaken without recourse to snow loads, which would further lessen the expected

forces. The primary loads are likely to be the dead weight of the structure and wind

loading. In this situation a compressive strength of less than 1 kN/mm2 may be

adequate though it is still unlikely that the GGBS blocks produced for this research

would be of any considerable utility due to their brittle nature.

There is a strong argument for the creation of a specific standard for this type of

technology. This standard could contain substantial information relating to the use of

ICSB technology including:

Manufacturing guidance.

Typical mix proportions for different shrinkage results.

Testing procedures.

Minimum required engineering properties.

Curing procedures.

Although the UN HABITAT guide gives some of the information listed above it is not

presented in a scientific way nor is it comprehensive. Research into a new

professional standard is recommended in Section 10.0.

8.3.6 Limitations to the Research

Several limitations to the research conducted during this project have been alluded to

throughout this report. The major limitations are summarized below and should be

given due consideration if the research is to be repeated:

1. Manufacturing Process. ICSB is made using a press in the practical

environment. The bricks tested in these experiments were hand-made and,

despite best intentions, will not have been compressed as well as those made

in a press. This is likely to have negatively affected both the IRA and

compressive strength results.

Page 68: Mud Brick Construction

68

2. Sample Size. The sample size was necessarily small due to time and labour

constraints. A larger variety of samples would have meant anomalous results

had less credence.

3. Whole Life Analysis. The manufactured bricks were only tested in the short

term and the long term durability has not been addressed.

Page 69: Mud Brick Construction

69

9.0 Conclusions

The following conclusions can be drawn from this research:

Current research on alternative stabilisers for unfired mud bricks is fairly limited.

Some published data is available for bricks stabilised with Ground Granulated

Blast furnace Slag (GGBS) but none is available for Pulverised Fly Ash (PFA).

However, the use of these substances as admixtures in other applications is

well documented.

PFA and GGBS were identified as potential alternatives to PC for unfired mud

brick stabilisation.

GGBS was assessed as ‘more sustainable’ than PC in terms of cost, ease of

manufacture. embodied energy and health implications. PFA fared worse than

both the alternatives, mainly due to the requirement for lime to facilitate the

cementitious reaction.

Bricks manufactured with the alternative stabilisers, at a range of proportions,

were compared across three mechanical properties:

o Compressive Strength. The PC stabilised bricks performed

considerably better than either the GGBS or PFA stabilised bricks. Only

the PC bricks exhibited a compressive strength greater than 1 N/mm2.

o Absorption. All of the bricks tested had an acceptable Initial Rate of

Water Abortion (IRA) according to current standards.

o Shrinkage. The soil used in these experiments displayed zero

shrinkage after 14 days curing.

The PFA and GGBS stabilised bricks tested were not a viable engineering

alternative according to UK Building Regulations. However, the PFA bricks

may be adequate depending on their practical application.

The availability of the alternative stabilisers in the developing world remains

unknown.

Page 70: Mud Brick Construction

70

PFA and GGBS are viable admixtures in the developing world since their

primary industries will exist for the foreseeable future.

There are no known social implications to the use of PFA or GGBS in the

developing world.

Page 71: Mud Brick Construction

71

10.0 Recommendations for Future Research

The following list outlines some recommended topics for further research. This is not

an exhaustive list and there are many more variables that could be adjusted or

amended. The topics detailed here are those which have become obvious avenues of

exploration after the research undertaken during this project; there are countless others

involving mud bricks in general and other sustainable construction materials.

1. More Extensive Testing. Due to time constraints the sample size considered

in this report was very small. Indeed, it was the smallest possible sample size

that allows useful comparison. There is scope to increase the number of bricks

tested, the variations in mix composition, the number of stabilisers tested and

different curing conditions.

2. Repeat Research with GGBS. Due to the disappointing results obtained for

the GGBS stabilised bricks it would be useful to repeat the experiments with

greater emphasis on the provenance of the materials, the mix proportions and

the curing method.

3. Long Term Durability. Research into unfired mud bricks is partially justified by

the concerns surrounding their long term durability and susceptibility to water

damage. This has not been addressed in this project. There is considerable

value in undertaking research to compare the long term durability of bricks

stabilised with alternatives to PC, ideally in a location which is likely to use the

technology (e.g. Uganda). Cross referencing the results of these experiments

with research into the absorption rates of bricks stabilised with PC alternatives

could give useful clues as to what, chemically, is affecting the durability.

4. Chemical Changes. Detailed research into the chemical reactions that take

place during cementation would be useful. There has been some research

already undertaken in this area but there is still scope to clarify the chemistry

that occurs when using alternative stabilisers. The results may drive a

consistent approach to mix compositions that could be implemented in a

practical environment.

Page 72: Mud Brick Construction

72

5. Testing on Bricks made with a Press. Perhaps the most limiting factor in this

research, and others, is that the bricks tested were hand-made and not made

using a Magika press (or similar). This is likely to have an effect on the

uniformity of the shape, the chemical structure and, ultimately, on the

performance of the bricks. This research could be combined with that

suggested in Part 1 of this Section as using a press is likely to speed up the

manufacture of the bricks so a larger sample could be used.

6. Appropriate Manufacturing Standard. Section 8.3 highlights some of the

shortcomings that manifest themselves as a result of applying Eurocode

standards to technology that doesn’t require such rigorous testing and

application. The development of a specific manufacturing standard for ICSB

technology could be a useful step forward. In an ideal world this could then be

applied to all ICSB building and help to standardize practices. Unfortunately

this is unlikely to happen, at least in the short to medium term, due to the

conditions, and locations, where ICSB is likely to be considered an option.

However, there is still value in such a standard.

7. Availability. The availability of the alternative stabilisers was discussed in

8.2.5. There are 2 distinct research possibilities in this area. Firstly, in-country

research to assess the availability of the stabilisers and secondly a cost-benefit

analysis into the feasibility of sourcing and distributing them if they aren’t

currently available.

Page 73: Mud Brick Construction

73

References:

A1 Building Supplies. (2011). Retrieved 03 14, 2011, from A1 Building Supplies

Limited: http://www.a1building.co.uk/index.php?osCsid=0fpg0kb115v4gqs4j75r7grcr0

ACI Committee. (1987). Ground Granulated Blast Furnace Slag as an Admixture. 87a

(226) . ACI.

Ash Solutions Ltd. (2009). Fly Ash BSEN 450 Product Information. Retrieved Nov 10,

2010, from Aggregate.com: www.aggregate.com/Documents/TDS/fly-ash-techdata.pdf

Benny Industries. (Unknown). How to Buy Fly Ash. Retrieved 03 14, 2011, from Fly

Ash Bricks Information: http://flyashbricksinfo.com/flyash-brick-machine-price-

quotation.html

BRE. (2009). Ecopoints: A Single Score Environmental Assessment. Glasgow: BRE.

Browne, G. (2009). Stabilised Interlocking Rammed Earth Blocks. Southampton:

Southampton Solent University.

BSI. (2003). BS EN 771-1:2003. Specifications of Masonry Units . Brussels: BSI

Group.

BSI. (2010, Jun 29). BS EN 772-1:2010. Part 1 - Determination of Compressive

Strength . London: BSI Group.

BSI. (2010). BS EN 772-11:2010. Part 11: Determination of water absorption of

aggregate concrete, autoclaved aerated concrete, . Brussels: BSI Group.

Burroughs, S. (2009). Relationships Between the Strength and Demsity of Rammed

Earth. Construction Materials (CM3).

Caltrone, G. (2010). Fly Ash Addition in Clayey Materials to Improve the Quality of

Solid Bricks. Retrieved January 31, 2011, from Constructionz: www.constructionz.com

Page 74: Mud Brick Construction

74

CEMEX. (2008). Ground Granulated Blast Furnace Slag Material Safety Datasheet.

Rugby: CEMEX UK.

CEMEX. (2007). Hydrated Lime - Material Safety Datasheet. Rugby: CEMEX.

Claybricks and Tiles Sdn. (1998-2007). The Basics of Bricks. Retrieved 05 02, 2011,

from Clay Bricks: http://www.claybricks.com/more_info/basic-of-bricks.html

Coutand, M., Cyr, M., & Clastres, P. (2006). Use of Sewage Sludge Ash as Mineral

Admixture in Mortars. Construction Materials , 159 (CM4), 153-162.

Davidson, K. (2010). Reporting Systems for Sustainability: What are they Measuring?

2011.

Hadjri, K., Osmani, M., Baiche, B., & Chifunds, C. (2007). Attitudes Towards Earth

Building for Zambian Housing Provision. Engineering Sustainability , 160 (ES3), 141-

169.

Heath, A., Walker, P., Fourie, C., & Lawrence, M. (2009). Compressive Strength of

Extruded Unfired Clay Masonry Units. Constructions Materials 162 , 105-112.

Jegendan, S., Liska, M., Osman, A., & Aj-Tabbaa, A. (2010). Sustainable Binders for

Soil Stabilisation. Ground Improvement , 163 (G11), 53-61.

Lindsay, G. (2001, May). The Holy Grail of Sustainable Development. Retrieved Feb

14, 2011, from Indiana University: http://www.indiana.edu/

Mwebeze, S. (2007). Uganda. Retrieved 03 14, 2011, from Grasslands and Pastural

Crops:

http://www.fao.org/ag/AGP/AGPC/doc/Counprof/uganda.htm#2.%20SOILS%20AND%

20TOPOGRAPHY

Norton, J. (1997). Building With Earth. London: Intermediate Technology Publications.

Oti, J. E., Kinuthua, J., & Bai, J. (2009). Compressive Strength and Microstructural

Analysis of Unfired Clay Masonry Bricks. Engineering Geology , 109, 230-249.

Page 75: Mud Brick Construction

75

Oti, J. E., Kinuthua, J., & Bai, J. (2009). Unfired Clay Bricks: From Laboratory to

Industrial Production. Engineering Sustainability , 229-237.

Oti, J. E., Kinuthua, J., & Bai, J. (2008). Using Slag for Unfired Clay Masonry Bricks.

Construction Materials , 147-155.

Portland Cement Association. (2011). How Portland Cement is Made. (PCA) Retrieved

02 25, 2011, from Cement and Concrete Basics:

http://www.cement.org/basics/howmade.asp

Reddy, B. V., & Kumar, P. (2001). Embodied Energy of Common and Alternative

Building Materials and Technologies. Energy and Buildings , 129-137.

Reddy, V. (2004). Sustainable Building Technologies. Current Science , 899-907.

Scotash. (2005). Health and Safety Information - Pulverised Fly Ash. Kincardine:

Scotash.

Shafique, S. B., Edil, T., Benson, C., & Senol, A. (2004). Incorporating a Fly-ash

Stabiliser Layer into Pavement Design. Geotechnical Engineering , 157 (GE4), 239-

249.

Sivapullaiah, P. V., Sridharan, A., & Bhaskar, K. (2000). Role of Amount and Type of

Clay in the Lime Stabilisation of Soils. Ground Improvement , 4, 37-45.

Smith, E. (2010). Interlocking Stabilised Soil Blocks: Appropriate Technology that

Doesn't Cost the Earth. 88 (15/16).

Tanguay, G., Rajaonson, J., & Lefebvre, J.-F. (2009). Measuring the Sustainability of

Cities: An Analysis of the Use of Local Indicators. 10.

The Building Lime Company. (2011). Price List. Retrieved 03 14, 2011, from The

Building Lime Company: http://www.buildinglime.co.uk/price.html

Page 76: Mud Brick Construction

76

The Good Earth Trust. (2008). What We Do. Retrieved October 2010, from Good Earth

Trust: http://www.goodearthtrust.org.uk/index.html

UN Human Settlements Programme. (2009). Interlocking Stabilised Soil Blocks.

Nairobi: UN Habitat.

US Department of Health and Human Services. (1995). Occupational Health and

Safety Guidance for Portland Cement. US Government.

USGS. (2006). 2006 Minerals Yearbook Uganda. US Department for the Interior.

ValueUK. (2011). Portland Cement 25kg Bags. Retrieved 03 14, 2011, from

ValueMEDIA: http://www.valuemedia.co.uk/popprods.htm?Product=566897

Vincent, T. H. (2010). Mastering Different Fields of Civil Engineering Works. Retrieved

Nov 15, 2010, from Civil Engineering Portal: http://www.engineeringcivil.com/which-of-

the-following-cement-replacement-material-is-better-pfa-or-ggbs.html

Vinod, J. S., Indraratna, B., & Mahamud, A. (2010). Stabilisation of an Erodible Soil

Using a Chemical Admixture. Ground Improvement , 163 (GI1), 43-51.

Walton, J. S., El-Haram, M., Castillo, N., Horner, M., & Price, A. (2005). Integrated

Assessment of Urban Sustainability. 158 (ES2).

World Commission on Environment and Development. (1987). Our Common Future.

Oxford: Oxford Press.

Page 77: Mud Brick Construction

77

Appendices

Appendix 1 - Project Management Statement ......... Error! Bookmark not defined.8

Appendix 2 – Risk Assessment for Laboratory Work ......................................... 80

Appendix 3 – Ecopoints PFA ................................................................................ 81

Appendix 4 – Ecopoints GGBS ............................................................................ 82

Appendix 5 – Samples of Raw Data for the Compressive Strength Testing…..83

Page 78: Mud Brick Construction

78

Appendix 1 - Project Management Statement

The following table summarises the main activities conducted each week during the

course of the project. It should be read in conjunction with the Project Timeline in

Section 4.0. There were no major alterations to the conduct of the project throughout

its duration.

Week Commencing Activities Completed

28 Jun 10 Initial project meeting with Claire Furlong.

Jun – Sep 10 Background research conducted.

Literature review started.

27 Sep 10 Memorandum Of Understanding (MOU) received from

Engineers Without Borders (EWB).

11 Oct 10 Paul Jaquin (PJ) appointed as EWB liaison.

25 Oct 10 Return to NCL, project meeting with Charlotte Paterson (CP)

and Chandra Vemury (CV).

8 Nov 10 Project meeting with CP and CV.

Aims/objectives agreed.

PIR compiled.

15 Nov 10 Draft PIR submitted to CP and CV.

‘Get Sheltered’ workshop.

22 Nov 10 Proposed Method Statement compiled.

29 Nov 10 PIR submitted.

13 Dec 10 Get Sheltered results written up and analysed.

PIR returned.

Feedback from Paul Joaquin (PJ) received.

10 Jan 11 Project meeting with CP and CV.

PIR feedback discussed.

PJ feedback discussed.

Project timeline agreed.

31 Jan 11 Mix composition researched.

Sustainability study started.

Bursary awarded by EWB.

Page 79: Mud Brick Construction

79

7 Feb 11 Method statement for brick construction completed.

Lab sessions booked / raw materials arranged.

Project meeting with CP and CV.

Method statement discussed and improvements suggested.

14 Feb 11 Risk Assessment compiled.

Mud brick preparation and shrinkage testing started completed.

Methodology improved.

21 Feb 11 Curing method adapted.

Sustainability study continued (ease of manufacture and health

implications).

Methodology completed for mud brick construction and

shrinkage testing.

28 Feb 11 Project meeting with CP and CV.

Methodology and sustainability study drafts discussed.

Sustainability study continued.

Shrinkage testing complete.

14 Mar 11 Sustainability study continued, financial cost model designed.

Compressive strength testing booked.

Absorption testing conducted.

Absorption and shrinkage testing results compiled.

21 Mar 11 Compressive Strength testing undertaken completed.

28 Mar 11 Results compiled and presented.

Project meeting with CP and CV.

25 Apr 11 Style and content of results presentation amended.

Discussion, conclusions and recommendations for future

research started.

2 May 11 Discussion, conclusions and recommendations continued.

9 May 11 Discussion, conclusions and recommendations completed.

Draft copy complete.

Editing started.

16 May 11 Project completed and handed in.

Page 80: Mud Brick Construction

80

Appendix 2 – Risk Assessment for Laboratory Work

Risk Assessment

For

Newcastle University

CEGs

Geotechnical

Engineering

Laboratory

Assessment

Undertaken

Date: 14 Feb 11

Name: D Harper

Signed: [Original

signed]

Supervisory Review

Date: 16 Feb 11

Name: S Patterson

Signed: [Original

signed]

Assessment

Review

Date: N/A

Hazard People at Risk Existing Controls

Information Location

Controls Needed

Mixed hazards of non related

experiments

All Do not touch non related

experiments or equipment

Slips, trips and falls All Proceed with caution in the

lab.

No running.

Any liquid spillage reported

and cleaned up.

Heavy masses around lab All Care taken to employ correct

handling techniques.

Safety footwear to be worn at

all time.

Hazards associated with lime Researcher PPE worn when handling lime

(goggles, lab coats, masks.

safety footwear).

Shattering of samples during

compressive strength testing.

All Eye protection to be worn

during testing.

Hazards associated with OPC Researcher PPE to be worn (as above).

NB. All existing Risk Assessments relating to the Geotechnical laboratory

remain extant.

Page 81: Mud Brick Construction

81

Appendix 3 – Ecopoints PFA

Page 82: Mud Brick Construction

82

Appendix 4 – Ecopoints GGBS

Page 83: Mud Brick Construction

83

Appendix 5 – Samples of Raw Data for the Compressive Strength Testing

The following tables show selected raw data from the compressive strength testing.

PC 10% PC 15% PC 20%

Compressive extension

Strain Compressive

load Stress

Compressive extension

Strain Compressive

load Stress

Compressive extension

Strain Compressive

load Stress

(mm)

(kN) (kN/mm2) (mm)

(kN) (kN/mm2) (mm)

(kN) (kN/mm2)

0 0 0.01 2.3E-07 0 0 0.008 1.84E-07 0 0 0.007 1.61E-07

0.5 0.004545 0.087 0.000002 0.5 0.004545 0.12 2.76E-06 0.5 0.004545 0.104 2.39E-06

1 0.009091 0.463 1.06E-05 1 0.009091 0.717 1.65E-05 1 0.009091 0.476 1.09E-05

1.5 0.013636 2.609 6E-05 1.5 0.013636 1.83 4.21E-05 1.5 0.013636 0.998 2.29E-05

2 0.018182 6.624 0.000152 2 0.018182 3.49 8.02E-05 2 0.018182 1.73 3.98E-05

2.5 0.022727 15.505 0.000356 2.5 0.022727 5.475 0.000126 2.5 0.022727 3.444 7.92E-05

3 0.027273 32.925 0.000757 3 0.027273 7.822 0.00018 3 0.027273 6.372 0.000146

3.5 0.031818 59.336 0.001364 3.5 0.031818 10.596 0.000244 3.5 0.031818 11.365 0.000261

4 0.036364 89.964 0.002068 4 0.036364 13.708 0.000315 4 0.036364 20.574 0.000473

4.5 0.040909 118.033 0.002713 4.5 0.040909 17.381 0.0004 4.5 0.040909 35.471 0.000815

5 0.045455 144.202 0.003315 5 0.045455 21.897 0.000503 5 0.045455 57.308 0.001317

5.5 0.05 164.97 0.003792 5.5 0.05 27.243 0.000626 5.5 0.05 86.041 0.001978

6 0.054545 177.027 0.00407 6 0.054545 33.588 0.000772 6 0.054545 115.226 0.002649

6.5 0.059091 182.817 0.004203 6.5 0.059091 41.629 0.000957 6.5 0.059091 142.606 0.003278

7 0.063636 186.192 0.00428 7 0.063636 55.026 0.001265 7 0.063636 167.36 0.003847

7.5 0.068182 186.85 0.004295 7.5 0.068182 75.524 0.001736 7.5 0.068182 185.306 0.00426

8 0.072727 186.486 0.004287 8 0.072727 96.898 0.002228 8 0.072727 195.407 0.004492

Page 84: Mud Brick Construction

84

8.5 0.077273 184.853 0.004249 8.5 0.077273 116.117 0.002669 8.5 0.077273 204.197 0.004694

9 0.081818 182.43 0.004194 9 0.081818 135.197 0.003108 9 0.081818 212.43 0.004883

9.5 0.086364 181.227 0.004166 9.5 0.086364 154.178 0.003544 9.5 0.086364 220.945 0.005079

10 0.090909 178.901 0.004113 10 0.090909 171.173 0.003935 10 0.090909 229.456 0.005275

10.5 0.095455 173.8 0.003995 10.5 0.095455 185.471 0.004264 10.5 0.095455 237.869 0.005468

11 0.1 196.809 0.004524 11 0.1 246.398 0.005664

12 0.109091 215.178 0.004947

12.5 0.113636 222.341 0.005111

13 0.118182 228.311 0.005249

13.5 0.122727 232.854 0.005353

Page 85: Mud Brick Construction

85

PFA 10% PFA 15% PFA 20%

Compressive extension

Strain Compressive

load Stress

Compressive extension

Strain Compressive

load Stress

Compressive extension

Strain Compressive

load Stress

(mm) (kN) (kN/mm2) (mm) (kN) (kN/mm2) (mm) (kN) (kN/mm2)

0 0 0.009 2.07E-07 0 0 0.008 1.84E-07 0 0 0.008 1.84E-07

0.5 0.004545 0.043 9.89E-07 0.5 0.004545 0.054 1.24E-06 0.5 0.004545 0.184 4.23E-06

1 0.009091 0.293 6.74E-06 1 0.009091 0.351 8.07E-06 1 0.009091 0.26 5.98E-06

1.5 0.013636 1.099 2.53E-05 1.5 0.013636 0.851 1.96E-05 1.5 0.013636 0.477 1.1E-05

2 0.018182 2.595 5.97E-05 2 0.018182 1.55 3.56E-05 2 0.018182 0.732 1.68E-05

2.5 0.022727 4.378 0.000101 2.5 0.022727 2.238 5.14E-05 2.5 0.022727 1.088 2.5E-05

3 0.027273 7.902 0.000182 3 0.027273 3.786 8.7E-05 3 0.027273 1.486 3.42E-05

3.5 0.031818 12.767 0.000293 3.5 0.031818 7.207 0.000166 3.5 0.031818 2.011 4.62E-05

4 0.036364 17.536 0.000403 4 0.036364 12.039 0.000277 4 0.036364 3.053 7.02E-05

4.5 0.040909 21.5 0.000494 4.5 0.040909 17.814 0.00041 4.5 0.040909 4.718 0.000108

5 0.045455 24.389 0.000561 5 0.045455 22.901 0.000526 5 0.045455 7.552 0.000174

5.5 0.05 26.983 0.00062 5.5 0.05 26.54 0.00061 5.5 0.05 11.403 0.000262

6 0.054545 29.181 0.000671 6 0.054545 28.978 0.000666 6 0.054545 15.519 0.000357

6.5 0.059091 30.848 0.000709 6.5 0.059091 30.549 0.000702 6.5 0.059091 18.639 0.000428

7 0.063636 31.879 0.000733 7 0.063636 31.766 0.00073 7 0.063636 23.508 0.00054

7.5 0.068182 32.425 0.000745 7.5 0.068182 32.579 0.000749 7.5 0.068182 28.572 0.000657

8 0.072727 32.261 0.000742 8 0.072727 33.115 0.000761 8 0.072727 33.106 0.000761

8.5 0.077273 30.7 0.000706 8.5 0.077273 33.305 0.000766 8.5 0.077273 37.052 0.000852

9 0.081818 27.86 0.00064 9 0.081818 32.567 0.000749 9 0.081818 40.224 0.000925

9.5 0.086364 30.176 0.000694 9.5 0.086364 41.302 0.000949

Page 86: Mud Brick Construction

86

10 0.090909 27.699 0.000637 10 0.090909 42.579 0.000979

10.5 0.095455 39.546 0.000909

11 0.1 38.801 0.000892

Page 87: Mud Brick Construction

87

GGBS 10% GGBS 15% GGBS 20%

Compressive extension

Strain Compressive

load Stress

Compressive extension

Strain Compressive

load Stress

Compressive extension

Strain Compressive

load Stress

(mm) (kN) (kN/mm2) (mm) (kN) (kN/mm2) (mm) (kN) (kN/mm2)

0 0 0.013 2.99E-07 0 0 0.003 6.9E-08 0 0 0.008 1.84E-07

0.5 0.004545 0.091 2.09E-06 0.5 0.004545 0.266 6.11E-06 0.5 0.004545 0.118 2.71E-06

1 0.009091 0.196 4.51E-06 1 0.009091 0.688 1.58E-05 1 0.009091 0.329 7.56E-06

1.5 0.013636 0.056 1.29E-06 1.5 0.013636 1.17 2.69E-05 1.5 0.013636 0.692 1.59E-05

2 0.018182 0.184 4.23E-06 2 0.018182 1.863 4.28E-05 2 0.018182 1.14 2.62E-05

2.5 0.022727 0.435 0.00001 2.5 0.022727 2.813 6.47E-05 2.5 0.022727 1.823 4.19E-05

3 0.027273 0.531 1.22E-05 3 0.027273 3.849 8.85E-05 3 0.027273 2.86 6.57E-05

3.5 0.031818 0.62 1.43E-05 3.5 0.031818 4.772 0.00011 3.5 0.031818 4 9.2E-05

4 0.036364 0.626 1.44E-05 4 0.036364 5.557 0.000128 4 0.036364 5.057 0.000116

4.5 0.040909 0.677 1.56E-05 4.5 0.040909 6.04 0.000139 4.5 0.040909 6.08 0.00014

5 0.045455 1.001 2.3E-05 5 0.045455 6.254 0.000144 5 0.045455 6.875 0.000158

5.5 0.05 1.395 3.21E-05 5.5 0.05 6.215 0.000143 5.5 0.05 7.327 0.000168

6 0.054545 2.104 4.84E-05 6 0.054545 5.876 0.000135 6 0.054545 7.314 0.000168

6.5 0.059091 3.055 7.02E-05 6.5 0.059091 6.961 0.00016

7 0.063636 3.887 8.94E-05

7.5 0.068182 4.606 0.000106

8 0.072727 4.922 0.000113

8.5 0.077273 4.989 0.000115

9 0.081818 4.921 0.000113

9.5 0.086364 4.591 0.000106

Page 88: Mud Brick Construction

88