The Compatibility and Efficiency of Low Alkali South African Cements with New Generation Super Plasticisers

5/28/2018 The Compatibility and Efficiency of Low Alkali South African Cements with New Generation Super Plasticisers

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The Compatibility and Efficiency of Low Alkali South African

Cements with New Generation Super Plasticisers

By

Mikhail Bramdaw

(200823954)

A Project Investigation Report submitted to the Faculty of Engineering and the

Built Environment as partial fulfilment of the requirements of the degree

BACCALAUREUS INGENERIAE

In

CIVIL ENGINEERING SCIENCE

At

UNIVERSITY OF JOHANNESBURG

STUDY LEADER: Mr Jannes Bester

7 December 2011


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ANTI-PLAGIARISM DECLARATION

Title: Mr.

Full name: Mikhail Bramdaw

Student number: 200823954

Course: Civil Project Investigation 4B (PJS 4B)

Lecturer: Mr Jannes Bester

Plagiarism is to present someone elses ideas as my own. Where material written by other

people has been used (either from a printed source or from the internet), this has been

carefully acknowledged and referenced. I have used the Harvard Convention for citation and

referencing. Every contribution to and quotation from the work of other people in this essay

has been acknowledged through citation and reference. I know that plagiarism is wrong.

I understand what plagiarism is and am aware of the Universitys policy in this regard. I know that I would plagiarise if I do not give credit to my sources, or if I copy sentences

or paragraphs from a book, article or Internet source without proper citation.

I know that even if I only change the wording slightly, I still plagiarise when usingsomeone elses words without proper citation.

I declare that I have written my own sentences and paragraphs throughout my essay and Ihave credited all ideas I have gained from other peoples work.

I declare that this assignment is my own original work. I have not allowed, and will not allow, anyone to copy my work with the intention ofpassing it off as his or her own work.

SIGNATURE .DATE..


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Abstract

In South Africa little testing has been done on the compatibility or efficiency of polymer

based super-plasticisers with South African manufactured cements. This investigation project

aimed to show that the cements tested were compatible with these new super-plasticisers

despite being produced from different manufactures. It also aimed to show that efficiency and

compatibility of the cement-super-plasticiser combination is dependent on the alkali content

of the cement.

The investigation was done by choosing three cements from different manufactures and

testing these cements against three different polymer based super-plasticisers. For each of the

cement-super-plasticiser combinations different dosages of the admixture were tested. Theconcrete mixes were tested for workability and strength to give an indication of the

compatibility as well as the efficiency of the cements with the super-plasticisers.

The workability of the concrete was measured using the slump test, slump retention test and

the Tattersall Two-Point Tester. The results from these tests gave insight into the concrete

behaviour in the fresh state.

The strength of the concrete was measured using the compressive strength test at 3 days. The

strength is the most important characteristic of hardened concrete and therefore was a crucial

property to investigate.

The tests concluded that cement with lower alkali content was less sensitive to changes in

super-plasticiser type and changes in dosage. This cement was also more efficient than the

other two cements with higher alkali content. It also showed that a super-plasticiser based on

phosphonate polymers is better suited for slump retention ability, while a polycarboxylate

polymer super-plasticiser is better suited for its efficiency in providing a mix with a better

slump and higher strength.


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Acknowledgements

I acknowledge the following individuals for their help and guidance which aided in the

completion of this report:

Mr Jannes Bester (University of Johannesburg, APK)Study Leader Salome Potgieter (University of Johannesburg, APK) - for assisting with research at the

UJ library

Ansie Martinek, Martha de Jager and Susan Battison (C&CI)for assisting with researchat the C&CI library

Nick Sfarnas (University of Johannesburg, DFC) for assisting with the use of theTattersall Tester and testing facilities at the Doornfontein laboratory

Petrus Jooste (C&CI) for providing information on how to calibrate and operate theTattersall Tester

Amit Dawneerangen (Afrisam, Roodepoort) for assisting with the chemicalcomposition test and general guidance.


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Table of Contents

ANTI-PLAGIARISM DECLARATION .................................................................................... i

Abstract ......................................................................................................................................ii

Acknowledgements .................................................................................................................. iii

Table of Contents ...................................................................................................................... iv

List of Tables ........................................................................................................................... vii

List of Figures ........................................................................................................................ viii

List of Symbols .......................................................................................................................... x

Chapter 1 .................................................................................................................................... 1

Introduction ................................................................................................................................ 1

1.1 Problem Definition........................................................................................................... 1

1.2. Aim ................................................................................................................................. 2

1.3. Objectives ....................................................................................................................... 2

1.4. Limitations ...................................................................................................................... 2

1.5. Methodology ................................................................................................................... 3

1.6. Layout of this Project Investigation ................................................................................ 4

Chapter 2 .................................................................................................................................... 5

LITERATURE REVIEW .......................................................................................................... 5

2.1 Concrete Properties .......................................................................................................... 5

2.1.1. Rheology .................................................................................................................. 5

2.1.1.1. Slump and Slump Retention ................................................................................. 6

2.1.1.2. Plastic Viscosity .................................................................................................... 7

2.1.1.3. Air Content............................................................................................................ 7

2.1.2. Strength .................................................................................................................... 8

2.2. Super-plasticisers ............................................................................................................ 8


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2.3. Cement Composition ...................................................................................................... 9

2.4. Rheological Tests .......................................................................................................... 11

2.5. Tattersall Two-Point Tester .......................................................................................... 12

Chapter 3 .................................................................................................................................. 17

Experimental Design ................................................................................................................ 17

3.1. Requirements ................................................................................................................ 17

3.2. Materials ....................................................................................................................... 17

3.3. Mix Design.................................................................................................................... 19

3.4. Grading Analysis .......................................................................................................... 20

3.5. Tests .............................................................................................................................. 22

3.6. Efficiency Rating System ............................................................................................. 23

3.7. Expected Results ........................................................................................................... 23

Chapter 4 .................................................................................................................................. 24

Test Results .............................................................................................................................. 24

4.1. Slump Test .................................................................................................................... 24

4.2. Slump Retention............................................................................................................ 27

4.3. Plastic Viscosity ............................................................................................................ 32

4.3.1. Calibration.............................................................................................................. 32

4.3.2. Results .................................................................................................................... 33

4.4. Air Content.................................................................................................................... 38

4.5. Hardened Density.......................................................................................................... 41

4.6. Strength ......................................................................................................................... 44

4.7. Efficiency ...................................................................................................................... 47


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Chapter 5 .................................................................................................................................. 49

Conclusions .............................................................................................................................. 49

5.1. Summary of work ......................................................................................................... 49

5.2. Main conclusions .......................................................................................................... 49

5.2.1. Slump ..................................................................................................................... 49

5.2.2. Slump Retention..................................................................................................... 50

5.2.3. Plastic Viscosity ..................................................................................................... 51

5.2.4. Air Content............................................................................................................. 51

5.2.5. Hardened Properties ............................................................................................... 51

5.3. Suggestions for further work ........................................................................................ 52

5.4. Outcomes satisfied ........................................................................................................ 52

Bibliography ............................................................................................................................ 54

Appendix AChemical Test Results ...................................................................................... 56

Appendix BTattersall Two Point Test Results..................................................................... 57

Appendix CPictures Taken During Practical ..................................................................... 100


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List of Tables

Table 2.1: Rheology of Cement Paste, Mortar and Concrete................................................... 7

Table 2.2: Viscosities of Selected Materials........................................................................... 16

Table 3.1: Chemical Composition of Cements....................................................................... 18

Table 3.2: Mix design Results for a 1000 litre mix................................................................ 19

Table 3.3: Mix design Results for a 20 litre mix.................................................................... 20

Table 3.4: Grading results for andesite crusher sand.............................................................. 20

Table 3.5: Tests performed during practical........................................................................... 22

Table 4.1: Slump Test Results for CEM A............................................................................. 24

Table 4.2: Slump Test Results for CEM B............................................................................. 25

Table 4.3: Slump Test Results for CEM C............................................................................. 26

Table 4.4: Readings from Tattersall Tester for Calibration with Canola Oil......................... 32

Table 4.5: Calibration Data for Tattersall Tester.................................................................... 32

Table 4.6: Example of Tattersall Result Calculation.............................................................. 34

Table 4.7: Tattersall ResultsCEM A................................................................................... 35

Table 4.8: Tattersall ResultsCEM B................................................................................... 36

Table 4.9: Tattersall ResultsCEM C................................................................................... 37

Table 4.10: Air Content Results for CEM A.......................................................................... 38

Table 4.11: Air Content Results for CEM B.......................................................................... 39

Table 4.12: Air Content Results for CEM C........................................................................... 40

Table 4.13: Density Results for CEM A................................................................................. 41

Table 4.14: Density Results for CEM B................................................................................. 42

Table 4.15: Density Results for CEM C................................................................................. 43

Table 4.16: Strength Results for CEM A................................................................................ 44

Table 4.17: Strength Results for CEM B................................................................................ 45

Table 4.18: Strength Results for CEM C................................................................................ 46

Table 4.19: Efficiency Rating Table for CEM A.................................................................... 47

Table 4.20: Efficiency Rating Table for CEM B.................................................................... 47

Table 4.21: Efficiency Rating Table for CEM C.................................................................... 48


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List of Figures

Figure 2.1: Effect of super plasticizing admixture................................................................... 9

Figure 2.2: Classification and Composition % of South African cements.............................. 10

Figure 2.3: Tattersall Two Point Tester Apparatus Motor and Processing Unit..................... 12

Figure 2.4: Tattersall Two Point Tester Apparatus Sample Holder and Impeller................... 13

Figure 2.5: Tattersall Two Point Tester Impeller Blade.......................................................... 13

Figure 2.6: Sample Holder Showing the Filling Mark............................................................ 14

Figure 3.1: Grading curve for andesite crusher sand............................................................... 21

Figure 4.1: Slump Test Results for CEM A............................................................................ 24

Figure 4.2: Slump Test Results for CEM B............................................................................ 25

Figure 4.3: Slump Test Results for CEM C............................................................................ 26

Figure 4.4: Slump Retention CEM A with SP A.................................................................... 27

Figure 4.5: Slump Retention CEM A with SP B..................................................................... 27

Figure 4.6: Slump Retention CEM A with SP C..................................................................... 28

Figure 4.7: Slump Retention CEM B with SP A.................................................................... 28

Figure 4.8: Slump Retention CEM B with SP B..................................................................... 29

Figure 4.9: Slump Retention CEM B with SP C..................................................................... 29

Figure 4.10: Slump Retention CEM C with SP A................................................................... 30

Figure 4.11: Slump Retention CEM C with SP B................................................................... 30

Figure 4.12: Slump Retention CEM C with SP C.................................................................. 31

Figure 4.13: Graph of Calibration Results to Calculate G...................................................... 33

Figure 4.14: Tattersall Test Graph for Calculation of h......................................................... 34

Figure 4.15: Tattersall TestCEM A..................................................................................... 35

Figure 4.16: Tattersall TestCEM B..................................................................................... 36

Figure 4.17: Tattersall TestCEM C..................................................................................... 37


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Figure 4.18: Air Content Results for CEM A......................................................................... 38

Figure 4.19: Air Content Results for CEM B......................................................................... 39

Figure 4.20: Air Content Results for CEM C......................................................................... 40

Figure 4.21: Density Results for CEM A................................................................................ 41

Figure 4.22: Density Results for CEM B................................................................................ 42

Figure 4.23: Density Results for CEM C................................................................................ 43

Figure 4.24: Strength Results for CEM A............................................................................... 44

Figure 4.25: Strength Results for CEM B............................................................................... 45

Figure 4.26: Strength Results for CEM C............................................................................... 46


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List of Symbols

gValue related to shear stress (Nm)

hValue related to plastic viscosity (Nms)

FForce (N)

GCalibration Constant Based on Newtonian Fluid (m3)

K - Calibration Constant Based on non-Newtonian Fluid

NSpeed of Impeller Blades (1/s)

TTorque (Nm)

Shear Stress (N/m2= Pa)

- Plastic Viscosity (Ns/m2= Pa.s)


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Chapter 1

Introduction

1.1 Problem Definition

Recently in South Africa and particularly in the Gauteng region there was a focus on the

rehabilitation of road infrastructure using concrete. Due to this, a mix design was created with

the use of new generation polymer based super-plasticisers and microfibers to produce an

ultra-thin, high strength concrete for the use in concrete pavements. Therefore, it was made

possible for parts of the national highway system to be upgraded using this ultra-thin, high

performance concrete.

The N12 highway was one of the highways that were being upgraded with the use of ultra-

thin concrete pavements. After placement of the concrete, a section on the N12 highway

failed and the reason for failure was unknown. The mix design for this concrete mix was

done in Pretoria. When the mix was tested in the laboratory, the mix passed all tests.

However, when put in place on the N12 highway, the concrete failed. Investigations were

done into what had caused the failure and it was accepted that the failure could possibly be

related to the chemical compatibility of the cement with the super-plasticiser.

Cements produced in different parts of South Africa have slightly altered chemistries, thus

the reaction between the cement and the super-plasticiser may not always be the same. The

altered chemistries of cements with the same specified class suggests that the failure was due

to a different reaction with the cement.

A different chemical reaction would cause a change in how the admixture reacts with the

cement and affect the efficiency of the super-plasticiser. This in turn will affect the rheology

i.e. viscosity, slump and slump retention of the concrete. These properties of fresh concrete

are vital to the design of an ultra-thin pavement mix as the concrete needs to be self-

compacting and remain pumpable for a reasonable period of time.

An investigation will be done into the compatibility and efficiency of three selected

admixtures with three cements. Particular attention will be placed on the effect that the mix

combinations have on the workability and slump retentions. Each of the nine combinations of


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cement with super-plasticiser will be tested at varying admixture dosages ranging from 0.4%

- 1.2% of cementitious material in increments of 0.2%.

1.2. Aim

The aim of this project investigation was to determine, by laboratory work, whether the

compatibility of cements with polymer based super-plasticisers remained the same (with

regard to rheology and strength) regardless of where and by whom it is manufactured and

regardless of the alkali content of the cement. The project also aimed to show the effect that

alkali content and dosage has on the efficiency of the cement with super-plasticiser

combination.

1.3. Objectives

The objectives of this project investigation report are as follows:

1. Evaluate the compatibility and efficiency of each mix with regards to rheology(Slump, Slump Retention, Plastic Viscosity and Air Content)

2. Evaluate the compatibility and efficiency of each mix with regard to Density andStrength.

In order to check the compatibility of the cement with the super-plasticiser the test results

was required to show that the cement performed similarly regardless of which super-

plasticiser was being tested with the cement. Large variations in results for a given property

of the concrete mix or a test that cannot yield a result would indicate incompatibility of the

cement with super-plasticiser combination.

A rating system was used to evaluate the efficiency of the selected super-plasticisers and

cements. This is further described in the experimental design section of this project

investigation report (Chapter 3).

1.4. Limitations

For the purposes of this report, the compatibility of the cements with super-plasticisers were

evaluated with regard to slump, slump retention, viscosity, air content, hardened density and

3-day strength. Other concrete properties were not investigated.


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Only one type of aggregate was used which was andesite from the Eikenhoff quarry. The

coarse aggregate used was 19mm stone and the fine aggregate used was unwashed crusher

sand.

The three cements that were chosen were all CEM II type cements. This aided in creating a

standard mix design which provided data to fairly compare the cements, of the same

classification, to each other.

Each of the cement with super-plasticiser combinations were tested at 5 different dosages of

super-plasticiser. These dosages were 0.4%, 0.6%, 0.8%, 1.0% and 1.2% of the cementitious

material.

1.5. Methodology

A literature review was done to gather information regarding polymer based super-

plasticisers and cement composition (with focus on the alkali content) and the effect they

have on the properties of concrete mixes. Thereafter, research was done to determine how to

measure the rheology of the concrete mixes. From the literature review the Tattersall Two-

Point Tester was chosen to measure the concretes workability and therefore more research

was done on how to calibrate and operate the Tattersall Two-Point Tester.

From the recommendations by the sponsor of this project, it was decided that three CEM II

cements from different manufactures be used in the mixes. A mix design was created using

the Cement and Concrete Institute method for mix design. This mix would be used to

evaluate the concrete properties of each combination by using the same mix design for all

tests that followed. Each of the three cements were analysed to show their chemical

compound composition. This was used to show how alkali content affects the compatibility

and efficiency of the cements with the polymer based super-plasticisers.

An investigation into the workability and strength of each concrete mix was then evaluated

by the following tests: the slump test, the slump retention test, the air content test, the

Tattersall Two-Point Test and the 3 day compressive strength cube test.

From the results obtained the efficiency of each mix was analysed using an efficiency rating

system. The ratings from this system made it possible to draw conclusions between the alkali

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1.6. Layout of this Project Investigation

Chapter 2 consists of an overview of the literature found and judgements made based on this

literature. It was also stated how this literature is necessary for the completion of the report.

Particular attention was paid to the cement alkali content and the methods for working with

the Tattersall Two Point Tester.

Chapter 3 follows with a summary of the experimental design. The 5 mix designs are stated

for each of the 5 dosages that were tested. This is then followed by the tests that were

performed during the practical. This chapter includes a description of the rating system used

to evaluate efficiency of the products.

Chapter 4 provides a summary of all the test data, and then followed by a more specific

summary of the data gathered per test. Also included in this chapter are the calibration results

for the Tattersall Two Point Tester. Included in this section is an example of the calculations

that were done to obtain the results.

Chapter 5 summarises the findings and results of this investigation along with

recommendations for further work. This chapter discusses the relationship found between the

alkali content of the cements with the results obtained from the testing that was done.


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Chapter 2

LITERATURE REVIEW

2.1 Concrete Properties

Before the investigation could be carried out, it was important that an understanding be

gained for what the concrete properties that will be investigated are, and how they would

most likely be affected. By understanding what these properties are and how they change

depending on the mix design makes it easier to draw conclusions about how the super-

plasticisers are affecting the concrete. The concrete properties that will be investigated are

rheology, and strength.

2.1.1. Rheology

In order to evaluate a concrete mixs rheology, an understanding for this term needs to be

gained. Rheology is the science of the deformation and flow of matter. (Banfill, 2003) In

other words rheology refers to the fresh properties of a concrete mix, specifically the

workability of the concrete as well as the workability retention. The use of ultra-thin, high

strength concrete in pavements requires that the concrete that is being placed is pumped and

is self-compacting. This leads to the rheological requirements for the concrete to be

important. The concrete is required to have a workability that lends itself to being pumped

easily.

High workability can be achieved in different ways. The easiest and most cost effective

method of increasing the workability and flow of the mix is to increase the water to cement

ratio (W/C) so that the mix contains a higher percentage of water in the mix design. This

method, although easy, comes at the cost of a reduction in strength. The loss of strength

makes the mix unsuitable for the use in pavements as a high strength concrete is required.

A second method of increasing the workability of the concrete mix is with the use of an

admixture. Admixtures such as plasticisers and super-plasticisers, also known as water

reducers, work by redistributing the cement particles evenly. (Addis, 2008) The even

distribution of cement particles allow for the concrete to flow easier.


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By assessing the rheology of each mix, it will then be possible to see how the super-

plasticiser affects each of the three different cements. The rheology will be assessed by

investigating the slump and slump retention, viscosity and air content of the concrete.

2.1.1.1. Slump and Slump Retention

The slump test is a commonly used test that is done to assess the workability of a concrete

mix. This test is used, as the apparatus needed for the test is relatively cheap compared to

other tests and is easier to perform than the other tests. Results from the slump test are also

immediately available as the reading is just measured with a ruler. However, although this

test is simple and easy to perform, it is also prone to inaccuracies.

The slump test is sensitive to operator technique, whether it is intended or not. (Tattersall,

1991) The slump test also has a very limited range. Slumps of highly workable mixes cannot

be evaluated as they simply collapse and slumps of low workability concrete cannot be

evaluated as they all give roughly the same result. (Tattersall, 1991) Although the test is not

suitable for highly workable concrete, it was specified by the sponsor that a slump of between

125mm and 175mm be achieved, therefore, the mix design was adjusted accordingly.

Slump retention is the ability of the concrete mix to maintain its workability over a period of

time. This is important for the use in ultra thin high strength concrete, as the concrete mix is

required to retain its workability for long periods of time so that it can be pumped without the

concrete starting to harden.

Generally, super-plasticisers increase slump loss in comparison to an equivalent plain mix

with no admixture. The lower the W/C ratio of the concrete mix, the higher the slump loss.

(Felekoglu & Sarikahya, 2008) However, it was suggested by the sponsor of the super-

plasticisers used that the new polymer based super-plasticisers would allow the concrete toretain its slump for a time of two hours. This is supported by work done by Felekoglu and

Sarikahya were they state that the polycarboxylate based super-plasticisers are able to extend

the flow retention of concrete mixes. (Felekoglu & Sarikahya, 2008) The slump retention

may last for about two hours. After this time period, the concrete mix will return to its

original state of workability. (Holcim South Africa, 2006)


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2.1.1.2. Plastic Viscosity

The term viscosity refers to a how a fluid reacts to force that is applied to it. It gives an

indication of the frictional forces within the fluid. These frictional forces will slow down the

movement of the fluid. Therefore a higher viscosity correlates to higher frictional forces in

the fluid, therefore this results in the fluid moving slower when a force is applied to it as

compared to a fluid with a lower viscosity. (Serway & Jewett, 2004)

This means that a highly workable mix will have a low viscosity since it requires a low force

applied to in to cause it to continue to flow. This property defines the rheology of the

concrete much better than the slump as it more accurately defines how the mix will behave

with the application of a force.

Table 2.1: Rheology of Cement Paste, Mortar and Concrete (Banfill, 2003)

Material Cement Paste,

Grout

Mortar Flowing

Concrete

Self-compacting

Concrete

Concrete

Yield Stress

N/m2

10-100 80-400 400 50-200 500-2000

Plastic Viscosity

Ns/m2

0.01-1 1-3 20 20-100 50-100

Structural

Breakdown

Significant Slight None None None

2.1.1.3. Air Content

The air content refers to the amount of air that is present in the concrete when the concrete is

in its fresh state. The air in the concrete often takes the form of tiny air bubbles. These air

bubbles significantly increase the workability of the concrete. (Tattersall, 1991) The air

content will be measured to show if the super-plasticisers are entraining the same amount of

air into each concrete mix.


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2.1.2. Strength

The strength of the concrete in its hardened state is probably the most important property of

concrete as it is a substance used for its structural characteristics. Often, to increase strength,

the water-cement ratio is reduced but this will then decrease the workability. (Addis, 2008)

Therefore it is necessary to use a super-plasticiser to reverse this effect of a reduction in

workability.

2.2. Super-plasticisers

According to Rivera-Villarreal, super-plasticisers are divided into four main groups:

1.

Sulfonated Naphthalene-Formaldehyde Condense (SNF)2. Sulfonated Melamine-Formaldehyde Condense (SMF)3. Modified Lignosulfonates (MLS)4. Others; including polyacrylates, polystyrene sulfonates and polycarboxylate polymers

(PCP)

(Rivera-Villarreal, 1999)

The super-plasticisers that were chosen to be used in the experiment are polycarboxylate

based polymers. Polycarboxylate polymers produce maximum water reduction among the

different super-plasticisers groups. The water reduction can be as much as 20 to 35%. This

makes it well suited for concretes that require a high fluidity and flow retention. (Marais,

2009)

Another property of the PCP super plasticizer is the early strength development. (Marais,

2009) These properties of the PCP makes it well suited for the use in ultra thin concrete

pavements as the early strength development means that the road can be opened to the public

quickly, and the high reduction in water means that the W/C ratio can be reduced leading to

an increase in concrete strength.

The PCP super-plasticiser products are known to be sensitive to cement chemistry and

therefore the performance of the admixture will differ with different cements. (Marais, 2009)

It is important to do trial mixes to observe the effectiveness of the admixture as under dosing

will lead to having a mix that is not as fluid as required, while an overdose will cause a lack

of cohesiveness and may lead to segregation.


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Figure 2.1: Effect of super plasticizing admixture. (Addis, 2008)

2.3. Cement Composition

The type of cement as classified according to SANS 50197: Composition, specification and

conformity criteria for common cements. However, these classifications are general and the

actual percentages of clinker, GGBS, limestone and fly ash differ within these classes. This

means two cements of the same classification made by different manufactures can have

different chemical compositions.


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Figure 2.2: Classification and Composition % of South African cements. (Holcim South

Africa, 2006)

In the study done by Schober and Mder on the compatibility of polycarboxylate super-

plasticisers with cements and cementious blends, it was shown that a low-alkali cement was

more compatible than the higher alkali cements with the super-plasticisers that were tested.

(Schober & Mder, 2003) Work done by Golaszewski and Szwabowski supports the idea that

lower alkali cements are better suited for use with the polymer based super-plasticisers.

(Golaszewski & Szwabowski, 2002)

The level of alkali found in cement is determined by evaluating the amount, by percentage, of

alkali metal compounds that are present in the cement. The alkali metal compounds that are

found in cements are Na2O (Sodium oxide) and K2O (Potassium oxide). (Holcim South

Africa, 2006)

The percentages of these compounds in the cement are then converted to a Na2Oeq(Sodium

oxide equivalent). This is done by the use of the following formula:


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This formula is derived using the molar mass of the compounds to relate them to each other.

In order for the cement to be classified as a low alkali cement the Na2Oeqis required to have a

value of less than 0.6%. (Holcim South Africa, 2006)

2.4. Rheological Tests

Work done by Tattersall, G.H. suggests that the most effective way of evaluating the

rheology or workability of a concrete mix is by using a two-point tester. He recommends this

test as it overcomes the inaccuracies of the other standard tests for measuring workability.

(Tattersall, 1991)

Rheology is not a measurable characteristic of concrete; however, there are many different

tests which give an indication as to the behaviour of the mix in terms of its rheology. The

most effective way in South Africa to test the rheological behaviour of concrete mixes is with

the use of the Tattersall Two Point Tester. (Jooste, 2006)

Fortunately, the apparatus for the Tattersall Two-Point Test was available for use during this

practical, therefore it was decided that this apparatus would be employed to evaluate the

rheology of the concrete mixes.


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2.5. Tattersall Two-Point Tester

Figure 2.3: Tattersall Two Point Tester Apparatus Motor and Processing Unit.


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Figure 2.4: Tattersall Two Point Tester Apparatus Sample Holder and Impeller.

The tester measures pressures in the transmission when turning an impeller in the mix at

different speeds. Plotting the relationship between the torque and the speed allows for the

calculation of yield stress and plastic viscosity. (Jooste, 2006)

Figure 2.5: Tattersall Two Point Tester Impeller Blade.(Jooste, 2006)


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Figure 2.6: Sample Holder Showing the Filling Mark. (Jooste, 2006)

The Tattersall Tester uses the principle that concrete acts as a Bingham Fluid. (Tattersall,

1991) From this principle the equation that the machine was based on was calculated.

Where:

T = Torque (Nm) g = A value relative to shear stress (Nm) h = A value relative to plastic viscosity (Nms) N = Speed of the Impeller Blades (1/s)

From the values of g and h the shear stress and plastic viscosity can be calculated using the

following formulae:


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Where:

= shear stress (N/m2) = plastic viscosity (Ns/m2= Pa.s) = Calibration Constant based on a Newtonian fluid (m3) = Calibration Constant based on a Non-Newtonian fluid (pseudo plastic fluid)

Tattersall G.H. suggests that the calibration of the machine is not required for the practical

use in the industry. The calibration of the machine is done using a linear relationship and

therefore the values for g and h would be sufficient for comparative testing. Tattersall goes on

to propose that the calibration of the machine would be too time consuming and thus not be

justified for use in practice. He suggests that by standardising the shape and dimensions of

the sample holder and impeller will eliminate the need for calibration. (Tattersall, 1991)

For this investigation project the actual plastic viscosity was recommended as a value of

interest by the sponsor and so the necessary calibration was done. This investigation only the

viscosity of the concrete was required so the calibration constant of G was calculated and the

calculation of K was not done. Canola oil was used to calibrate the machine as the plastic

viscosity was known for two different temperatures (shown in Table 2.3) and the substance

was easily available.

Water was not used to calibrate the machine as, even though it is a Newtonian fluid, it proved

difficult due to the fact that the Tattersall Testers force readings only give a reading to two

decimal points. Therefore a value for G was calculated as a zero value since the change in

force was not visible.


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Table 2.2: Viscosities of Selected Materials (The Physics Hypertextbook, 2011)

Viscosities of Selected Materials (note the different unit prefixes)

simple liquids T() (mPa s) gases T() (Pas)alcohol, ethyl (grain) 20 1.1 air 15 17.9

alcohol, isopropyl 20 2.4 hydrogen 0 8.42alcohol, methyl (wood) 20 0.59 helium (gas) 0 18.6

blood 37 34 nitrogen 0 16.7

ethylene glycol 25 16.1 oxygen 0 18.1

ethylene glycol 100 1.98

freon 11 (propellant) 25 0.74 complex materials T() (Pa s)freon 11 (propellant) 0 0.54 caulk 20 1000

freon 11 (propellant) +25 0.42 glass, room temperature 10 10

freon 12 (refrigerant) -15 ?? glass, strain point 10.

freon 12 (refrigerant) 0 ?? glass, annealing point 10.

freon 12 (refrigerant) +15 0.20 glass, softening 10.

glycerin 20 1420 glass, working 10glycerin 40 280 glass, melting 10

helium (liquid) 4 K 0.00333 honey 20 10

Mercury 15 1.55 ketchup 20 50

milk 25 3 lard 20 1000

oil, vegetable, canola 25 57 molasses 20 5

oil, vegetable, canola 40 33 mustard 25 70

oil, vegetable, corn 20 65 peanut butter 20 150250

oil, vegetable, corn 40 31 sour cream 25 100

oil, vegetable, olive 20 84 syrup, chocolate 20 1025

oil, vegetable, olive 40 ?? syrup, corn 25 23

oil, vegetable, soybean 20 69 syrup, maple 20 23oil, vegetable, soybean 40 26 tar 20 30,000

oil, machine, light 20 102 vegetable shortening 20 1200

oil, machine, heavy 20 233

oil, motor, SAE 10 20 65




propylene glycol 25 40.4

propylene glycol 100 2.75

water 0 1.79

water 20 1.00

water 40 0.65

water 100 0.28


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Chapter 3

Experimental Design

3.1. Requirements

For the purpose of this investigation, a large amount of practical testing was required. A mix

design was calculated and from there, testing could be done on the rheology and strength of

the concrete. The same mixing drum was used and the mixer was run for 5 minutes for each

batch. This was done to ensure that the mixing energy stays constant for each batch as super-

plasticisers are sensitive to a variation in mixing energy.

The Method for addition of the super-plasticisers was kept constant for each batch. The

super-plasticisers were added by mixing the fluid with 1 litre of the mixing water and then

adding the solution to the mix. The super-plasticisers were all added at 1 minute after mixing

had commenced in order to eliminate any additional variables.

Tests that were performed in this investigation were the slump test, slump retention test, a

viscosity test (using the Tattersall Two-Point Tester), an air content test and a 3 day

compressive strength cube test.

3.2. Materials

All aggregate used was andesite aggregate from the Eikenhoff quarry.

Coarse aggregate19mm stone Fine aggregateunwashed crushed sand

Cements from different manufactures that were used are specified as follows:

CEM ACem II A-L 42.5 N CEM BCem II A-M (V-L) 42.5 N CEM CCem II A-M (V-L) 42.5 N

A chemical analysis was carried out in order to determine the chemical compounds found in

each of the cements. The test also showed the amount of each of the compounds found in the


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cement as although the cements may be classified as the same category of cement the

composition may differ. From these results the cements can then be classified according to

the alkali levels in the cement. The table provided below shows the results of the chemical

analysis.

Table 3.1: Chemical Composition of Cements

TestCEM A CEM B CEM C

% % %

L.O.I. 1.71 4.40 4.41

SiO2 29.02 23.47 24.75

Al2O3 10.82 6.42 8.97

CaO 50.83 61.78 57.17

Fe2O3 3.38 2.66 3.25

MgO 1.85 1.80 1.64

TiO2 0.78 0.47 0.71

Mn2O3 0.22 0.10 0.14

Na2O 0.23 0.15 0.17

K2O 0.40 0.51 0.24

P2O5 0.25 0.10 0.16

*Na2Oeq 0.50 0.49 0.32

* Note: Sodium Oxide Equivalent = % Na2O + (0.658 * % K2O)

Super-plasticisers that were used are from the same manufacturer and are specified as

follows:

SP A, which is a new generation polymer super-plasticiser based on modifiedphosphonates.

SP B, which is a new generation polymer super-plasticiser based on polycarboxylateand modified phosphonates.

SP C, which is a new generation polymer super-plasticiser, based on modifiedpolycarboxylates.


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3.3. Mix Design

A mix design was created using the method set out by the Cement and Concrete Institute.

From the resulting mix design a trail mix was done with CEM A and SP A at a dosage of

0.8%. The mix was adjusted until a slump of 150mm was obtained. The following values for

the material properties were used in the calculation of the mix design:

RDsand= 2.92 (Holcim South Africa, 2006) RDstone= 2.92 (Holcim South Africa, 2006) RDcement= 3.1 FM = 3.1 (Grading Analysis Section 3.4) CBD = 1640 kg/m3 K = 0.94 (Addis, 2008)

Table 3.2: Mix design Results for a 1000 litre mix

Mix Design

1

Mix Design

2

Mix Design

3

Mix Design

4

Mix Design

5

W:C 0.45 0.45 0.45 0.45 0.45

Water (L) 180 180 180 180 180

Cement (Kg)* 400 400 400 400 400Sand (Kg) 1050 1050 1050 1050 1050

Stone (Kg) 780 780 780 780 780

Admixture (L)* 1.6 2.4 3.2 4.0 4.8

* Note: Although the admixtures and cements are different in each of the nine mix

combinations, the quantity remains constant to show the difference in rheology and to

eliminate additional variables.

Note: The Admixture dosages for mixes 1, 2, 3, 4 and 5 were 0.4%, 0.6%, 0.8%, 1.0%, and

1.2% respectively.

After the mix design was calculated, the mix was resized to a batch volume of 20litres or

0.02m3. This was to accommodate as much of the testing as possible with a single batch.

However, due to the quantities required for each test, two batches of concrete were made for

each of the mixes.


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Table 3.3: Mix design Results for a 20 litre mix

Mix Design

1

Mix Design

2

Mix Design

3

Mix Design

4

Mix Design

5

W:C 0.45 0.45 0.45 0.45 0.45

Water (L) 3.6 3.6 3.6 3.6 3.6Cement (Kg)* 8 8 8 8 8

Sand (Kg) 21 21 21 21 21

Stone (Kg) 15.6 15.6 15.6 15.6 15.6

Admixture (L)* 0.032 0.048 0.064 0.080 0.096

3.4. Grading Analysis

Table 3.4: Grading results for andesite crusher sandParticle size

(mm)

Mass Retained

sieve (g)

Cumulative %

Retained by Sieve

Cumulative% Passing

Sieve

9.5 0.00 0 100

6.7 4.20 0.2 99.8

4.75 27.27 1.5 98.5

2.36 566.46 28.5 71.5

1.18 499.32 52.3 47.7

0.6 312.60 67.2 32.8

0.425 113.29 72.6 27.4

0.3 96.51 77.2 22.8

0.15 144.76 84.1 15.9

0.075 69.23 87.4 12.6

pan 264.35 100 0

Total 2097.99 *310.8

FM = 310.8 100 FM = 3.1

* Note: Sum of the standard sieves up to and including the 0.15mm sieve.


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Figure 3.1: Grading curve for andesite crusher sand

0

10

20

30

40

50

60

70

80

90

100

0.01 0.1 1 10

Cumu

lative%ofmasspassingSieve

Particle Size (mm)

Grading Curve for Andesite Crusher Sand


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3.5. Tests

The following tests were performed during the investigation:

Table 3.5: Tests performed during practical

Test performed SABS/SANS Number Comments

Slump Test SABS Method862-1:1994 The Slump Test is known to

be sensitive to operator

technique therefore the same

operator was used for all the

slump tests that were

performedSlump Retention Test SABS Method862-1:1994 The slump test was re-

performed at 30min intervals

after the original slump test

up to a time of 120min.

Plastic Viscosity

Tattersall Two-Point Test

n/a The test to measure plastic

viscosity was done according

to the method described in

the literature review.

Calibration Data found in

Section 4.3.1

Air Content Test SANS 6252 Method A. A correction was made for

the air trapped in the

aggregate according to the

standard.

Strength Test SABS 860:1994,

SABS 861-2:1994,

SABS 861-3:1994,

SABS 863:1994,

SANS 0100-2:1992

During the strength test the

mass of each cube was

measured and used to

calculate density


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3.6. Efficiency Rating System

The efficiency for each of the tests was evaluated in terms of the most efficient combination

of cement and super-plasticiser. The best performer of each result was given a value of 1 with

the remaining results receiving a value proportional to 1 depending on how close the result

was to the best result. An Example is shown below:

Best Result of Slump Test, CEM CSP C @ 1.2% = 175mm

Another Result, CEM ASP C @ 1.2% = 170mm

Therefore, CEM CSP C @ 1.2% = 1

And, CEM ASP C @ 1.2% = 170mm/175mm = 0.971

The slump retention data was evaluated slightly differently. The value given to each of the

slump retention test results were calculated as follows:

3.7. Expected Results

During the testing, it was expected that the chosen low alkali cements will behave similarly,

in all tests, regardless of which manufacturer made the cement. During the testing it was

expected that the low alkali cement would be less sensitive to changes, in dosage and super-

plasticiser type, when considering its compatibility with the super-plasticisers. The cements

with higher alkali content are expected to show signs of lower efficiency with the given

super-plasticisers. Although the cements with higher alkali content may work effectively with

a given super-plasticiser at a given dosage, it may not be compatible at a different dosage.

It was expected that SP A would be the weakest in terms of slump and viscosity and the best

in terms of the slump retention ability. SP C would be the opposite of SP A, with SP B beingan intermediate super-plasticiser between the two extremes.


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Chapter 4

Test Results

4.1. Slump Test

Table 4.1: Slump Test Results for CEM A

Cem A

SP A SP B SP C

Dosage % Slump (mm) Dosage % Slump (mm) Dosage % Slump (mm)

0.4 100 0.4 100 0.4 110

0.6 140 0.6 145 0.6 155

0.8 150 0.8 155 0.8 1601.0 155 1.0 160 1.0 165

1.2 Segregation 1.2 165 1.2 170

Figure 4.1: Slump Test Results for CEM A

90

100

110

120

130

140

150

160

170

180

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Slump(mm)

Dosage %

Slump - CEM A

SP A

SP B

SP C


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Table 4.2: Slump Test Results for CEM B

Cem B

SP A SP B SP C


0.4 105 0.4 110 0.4 1200.6 145 0.6 145 0.6 155

0.8 145 0.8 150 0.8 160

1.0 145 1.0 150 1.0 165

1.2 160 1.2 155 1.2 Segregation

Figure 4.2: Slump Test Results for CEM B

90

100

110

120

130

140

150

160

170

180

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Slump(mm)

Dosage %

Slump - CEM B

SP A

SP B

SP C


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Table 4.3: Slump Test Results for CEM C

Cem C

SP A SP B SP C


0.4 145 0.4 150 0.4 1600.6 145 0.6 150 0.6 160

0.8 155 0.8 160 0.8 165

1.0 160 1.0 165 1.0 170

1.2 165 1.2 170 1.2 175

Figure 4.3: Slump Test Results for CEM C

90

100

110

120

130

140

150

160

170

180

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Slump(mm)

Dosage %

Slump - CEM C

SP A

SP B

SP C


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4.2. Slump Retention

Figure 4.4: Slump Retention CEM A with SP A

Figure 4.5: Slump Retention CEM A with SP B


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Figure 4.6: Slump Retention CEM A with SP C

Figure 4.7: Slump Retention CEM B with SP A


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Figure 4.8: Slump Retention CEM B with SP B

Figure 4.9: Slump Retention CEM B with SP C


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Figure 4.10: Slump Retention CEM C with SP A

Figure 4.11: Slump Retention CEM C with SP B


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Figure 4.12: Slump Retention CEM C with SP C


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4.3. Plastic Viscosity

4.3.1. Calibration

Table 4.4: Readings from Tattersall Tester for Calibration with Canola Oil

Temperature (C) Speed (RPM) Speed (1/s) Force (N) Torque (Nm) Slope (Nms)

25

40 0.67 0.54 0.0540

0.0091636

45 0.75 0.55 0.0550

50 0.83 0.56 0.0560

55 0.92 0.56 0.0560

60 1.00 0.57 0.0570

65 1.08 0.58 0.0580

70 1.17 0.59 0.0590

75 1.25 0.59 0.0590

80 1.33 0.60 0.0600

85 1.42 0.61 0.0610

90 1.50 0.62 0.0620

Temperature (C) Speed (RPM) Speed (1/s) Force (N) Torque (Nm) Slope (Nms)

40

40 0.67 0.50 0.05

0.0076364

45 0.75 0.50 0.050

50 0.83 0.51 0.051

55 0.92 0.51 0.051

60 1.00 0.52 0.052

65 1.08 0.53 0.053

70 1.17 0.54 0.054

75 1.25 0.54 0.054

80 1.33 0.55 0.055

85 1.42 0.55 0.055

90 1.50 0.56 0.056

Table 4.5: Calibration Data for Tattersall Tester

Temperature (C) Temperature (K) Viscosity (Pa.s) T/N (Nms)

25 298.15 0.057 0.009164

40 313.15 0.033 0.007636


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Figure 4.13: Graph of Calibration Results to Calculate G

From the results G = 0.0636 m3

4.3.2. Results

The reading from the Tattersall Two Point Tester gives two sets of data, firstly the speed

which the user inputs as revolutions per minute and secondly the force exerted on the motor

as Newtons. The values are then converted to a speed as revolutions per second and a torqueby multiplying the distance of the load cell to the centre of the motor.

These calculated values are then plotted on a graph showing Torque (Nm) on the y-axis and

Speed (1/s) on the x-axis. The gradient of a best-fit linear line is the value of h (Nms). The h

value is then converted to a viscosity value () by dividing h by the calibration constant G

which was calculated above.

Due to the large number of mixes which were tested, each result was not included in this

section of the report. An example of one of the calculations is shown below in table 4.6 and

figure 4.14. The remaining calculations can be found in appendix B.

y = 0.0636x

0.007000

0.007500

0.008000

0.008500

0.009000

0.009500

0 0.02 0.04 0.06

Calculation of G

Calibration

Linear (Calibration)


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Table 4.6: Example of Tattersall Result Calculation

N (RPM) N (1/s) F (N) T (Nm) G (m) h (Nms) (Pa.s)

40 0.67 6.23 0.623 0.06364 2.6604 41.8063

45 0.75 8.13 0.813

50 0.83 10.88 1.088

55 0.92 12.12 1.212

60 1.00 15.32 1.532

Figure 4.14: Tattersall Test Graph for Calculation of h

Below is a summary of the results of the Tattersall Two Point Test in terms of the viscosities

that were calculated.

y = 2.6604x - 1.1634

0.000

0.200

0.400

0.600

0.800

1.000

1.200

1.400

1.600

1.800

0.00 0.20 0.40 0.60 0.80 1.00 1.20

Torque(Nm)

Speed (1/s)

Tattersall Test - CEM A - SP A @ 0.4%

Series1

Linear (Series1)


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Table 4.7: Tattersall Results CEM A

Cem A

SP A SP B SP C

Dosage % Viscosity (Pa.s) Dosage % Viscosity (Pa.s) Dosage % Viscosity (Pa.s)

0.4 41.8063 0.4 35.3194 0.4 31.96290.6 35.1120 0.6 27.2109 0.6 23.1189

0.8 29.0400 0.8 25.5703 0.8 20.1206

1.0 26.9657 1.0 25.2497 1.0 19.9886

1.2 Segregation 1.2 24.9291 1.2 19.7434

Figure 4.15: Tattersall Test CEM A

0.0000

5.0000

10.0000

15.0000

20.0000

25.0000

30.0000

35.0000

40.0000

45.0000

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Viscosity(Pa.s

)

Dosage %

Tattersall Test - CEM A

SP A

SP B

SP C


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Table 4.8: Tattersall Results CEM B

Cem B

SP A SP B SP C


0.4 40.4297 0.4 33.1886 0.4 30.20910.6 33.2829 0.6 27.6069 0.6 22.2514

0.8 29.0740 0.8 24.8349 0.8 20.2526

1.0 26.2869 1.0 22.3080 1.0 19.0646

1.2 25.0046 1.2 Segregation 1.2 18.7251

Figure 4.16: Tattersall Test CEM B

0.0000

5.0000

10.0000

15.0000

20.0000

25.0000

30.0000

35.0000

40.0000

45.0000

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

V

iscosity(Pa.s

)

Dosage %

Tattersall Test - CEM B

SP A

SP B

SP C


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Table 4.9: Tattersall Results CEM C

Cem C

SP A SP B SP C


0.4 31.6046 0.4 29.7189 0.4 22.45890.6 28.0594 0.6 26.3434 0.6 21.3840

0.8 27.6257 0.8 24.0240 0.8 19.1589

1.0 25.1743 1.0 22.9114 1.0 18.5366

1.2 23.8543 1.2 20.8371 1.2 17.5560

Figure 4.17: Tattersall Test CEM C

0

5

10

15

20

25

30

35

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

V

iscosity(Pa.s

)

Dosage %

Tattersall Test - CEM C

SP A

SP B

SP C


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4.4. Air Content

Table 4.10: Air Content Results for CEM A

Cem A

SP A SP B SP C

Dosage % Air Content % Dosage % Air Content % Dosage % Air Content %

0.4 2 0.4 2.2 0.4 1.8

0.6 2.1 0.6 2.2 0.6 1.8

0.8 2.2 0.8 2.5 0.8 1.9

1.0 2.4 1.0 2.5 1.0 2.1

1.2 Segregation 1.2 2.6 1.2 2.1

Figure 4.18: Air Content Results for CEM A

1

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

2.8

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

AirContent%

Dosage %

Air Content - CEM A

SP A

SP B

SP C


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Table 4.11: Air Content Results for CEM B

Cem B

SP A SP B SP C


0.4 2.1 0.4 2.2 0.4 2

0.6 2.1 0.6 2.2 0.6 2.1

0.8 2.2 0.8 2.4 0.8 2.1

1.0 2.3 1.0 2.5 1.0 2.2

1.2 2.3 1.2 Segregation 1.2 2.3

Figure 4.19: Air Content Results for CEM B

1

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

AirConte

nt%

Dosage %

Air Content - CEM B

SP A

SP B

SP C


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Table 4.12: Air Content Results for CEM C

Cem C

SP A SP B SP C


0.4 1.6 0.4 1.7 0.4 1.5

0.6 1.6 0.6 1.7 0.6 1.7

0.8 1.7 0.8 1.7 0.8 1.7

1.0 1.7 1.0 1.9 1.0 1.8

1.2 1.8 1.2 1.9 1.2 1.9

Figure 4.20: Air Content Results for CEM C

1

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

AirConte

nt%

Dosage %

Air Content - CEM C

SP A

SP B

SP C


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4.5. Hardened Density

Table 4.13: Density Results for CEM A

Cem A

SP A SP B SP C

Dosage % Density (kg/m) Dosage % Density (kg/m) Dosage % Density (kg/m)

0.4 2415 0.4 2410 0.4 2435

0.6 2410 0.6 2405 0.6 2430

0.8 2410 0.8 2395 0.8 2430

1.0 2400 1.0 2395 1.0 2420

1.2 Segregation 1.2 2390 1.2 2410

Figure 4.21: Density Results for CEM A

2385

2390

2395

2400

2405

2410

2415

2420

2425

2430

2435

2440

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Density

(kg/m)

Dosage %

Density -CEM A

SP A

SP B

SP C


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Table 4.14: Density Results for CEM B

Cem B

SP A SP B SP C

Dosage % Density (kg/m) Dosage % Density (kg/m) Dosage %Density

(kg/m)0.4 2420 0.4 2415 0.4 2420

0.6 2420 0.6 2410 0.6 2415

0.8 2410 0.8 2410 0.8 2415

1.0 2405 1.0 2395 1.0 2405

1.2 2405 1.2 Segregation 1.2 2400

Figure 4.22: Density Results for CEM B

2390

2395

2400

2405

2410

2415

2420

2425

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Density(kg/m)

Dosage %

Density - CEM B

SP A

SP B

SP C


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Table 4.15: Density Results for CEM C

Cem C

SP A SP B SP C

Dosage % Density (kg/m) Dosage % Density (kg/m) Dosage %Density

(kg/m)0.4 2435 0.4 2430 0.4 2440

0.6 2430 0.6 2430 0.6 2435

0.8 2430 0.8 2420 0.8 2435

1.0 2420 1.0 2415 1.0 2430

1.2 2415 1.2 2415 1.2 2425

Figure 4.23: Density Results for CEM C

2410

2415

2420

2425

2430

2435

2440

2445

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Density(kg/m)

Dosage %

Density - CEM C

SP A

SP B

SP C


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4.6. Strength

Table 4.16: Strength Results for CEM A

Cem A

SP A SP B SP C

Dosage % Strength (MPa) Dosage % Strength (MPa) Dosage %Strength

(MPa)

0.4 16.0 0.4 15.0 0.4 18.5

0.6 16.0 0.6 15.0 0.6 18.0

0.8 15.5 0.8 14.5 0.8 17.0

1.0 15.0 1.0 13.0 1.0 17.0

1.2 Segregation 1.2 12.0 1.2 17.0

Figure 4.24: Strength Results for CEM A

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Strength(MP

a)

Dosage %

Strength - CEM A

SP A

SP B

SP C


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Table 4.17: Strength Results for CEM B

Cem B

SP A SP B SP C


(MPa)0.4 16.5 0.4 16.0 0.4 17.0

0.6 16.0 0.6 15.5 0.6 16.5

0.8 15.0 0.8 14.0 0.8 16.5

1.0 14.0 1.0 13.5 1.0 16.0

1.2 13.0 1.2 Segregation 1.2 16.0

Figure 4.25: Strength Results for CEM B

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Stre

ngth(MPa)

Dosage %

Strength - CEM B

SP A

SP B

SP C


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Table 4.18: Strength Results for CEM C

Cem C

SP A SP B SP C


(MPa)0.4 18.0 0.4 18.5 0.4 19.0

0.6 18.0 0.6 18.5 0.6 18.5

0.8 18.0 0.8 18.0 0.8 18.5

1.0 17.5 1.0 18.0 1.0 18.0

1.2 17.0 1.2 17.5 1.2 18.0

Figure 4.26: Strength Results for CEM C

16.5

17.0

17.5

18.0

18.5

19.0

19.5

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Stre

ngth(MPa)

Dosage %

Strength - CEM C

SP A

SP B

SP C


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4.7. Efficiency

Table 4.19: Efficiency Rating Table for CEM A

CEM SPDosage

% SlumpSlump

Retention ViscosityAir

content Workability Density StrengthHardened

Properties

A A 0.4 0.57 0.85 -0.38 0.77 1.81 0.99 0.84 1.83

A A 0.6 0.80 0.96 0.00 0.81 2.57 0.99 0.84 1.83

A A 0.8 0.86 0.97 0.35 0.85 3.02 0.99 0.82 1.80

A A 1.0 0.89 0.97 0.46 0.92 3.24 0.98 0.79 1.77

A A 1.2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

A B 0.4 0.57 0.85 -0.01 0.85 2.26 0.99 0.79 1.78

A B 0.6 0.83 0.93 0.45 0.85 3.06 0.99 0.79 1.78

A B 0.8 0.89 0.90 0.54 0.96 3.29 0.98 0.76 1.74A B 1.0 0.91 0.91 0.56 0.96 3.34 0.98 0.68 1.67

A B 1.2 0.94 0.94 0.58 1.00 3.46 0.98 0.63 1.61

A C 0.4 0.63 0.59 0.18 0.69 2.09 1.00 0.97 1.97

A C 0.6 0.89 0.65 0.68 0.69 2.91 0.95 0.95 1.90

A C 0.8 0.91 0.69 0.85 0.73 3.19 1.00 0.89 1.89

A C 1.0 0.94 0.76 0.86 0.81 3.37 0.99 0.89 1.89

A C 1.2 0.97 0.76 0.88 0.81 3.42 0.99 0.89 1.88

Table 4.20: Efficiency Rating Table for CEM B

CEM SPDosage

%Slump

Slump

RetentionViscosity

Air

contentWorkability Density Strength

Hardened

Properties

B A 0.4 0.60 0.86 -0.30 0.81 1.96 0.99 0.87 1.86

B A 0.6 0.83 0.93 0.10 0.81 2.67 0.99 0.84 1.83

B A 0.8 0.83 0.93 0.30 0.85 2.90 0.99 0.79 1.78

B A 1.0 0.83 0.97 0.50 0.88 3.18 0.99 0.74 1.72

B A 1.2 0.91 0.97 0.58 0.88 3.34 0.99 0.68 1.67

B B 0.4 0.63 0.82 0.11 0.85 2.40 0.99 0.84 1.83

B B 0.6 0.83 0.90 0.43 0.85 3.00 0.99 0.82 1.80B B 0.8 0.86 0.93 0.59 0.92 3.30 0.99 0.74 1.72

B B 1.0 0.86 0.97 0.73 0.96 3.51 0.98 0.71 1.69

B B 1.2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

B C 0.4 0.69 0.54 0.28 0.77 2.28 0.99 0.89 1.89

B C 0.6 0.89 0.71 0.73 0.81 3.14 0.99 0.87 1.86

B C 0.8 0.91 0.75 0.85 0.81 3.32 0.99 0.87 1.86

B C 1.0 0.94 0.82 0.91 0.85 3.52 0.99 0.84 1.83

B C 1.2 0.94 0.91 0.93 0.88 3.67 0.98 0.84 1.83


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Table 4.21: Efficiency Rating Table for CEM C

CEM SPDosage

%Slump

Slump

RetentionViscosity

Air

contentWorkability Density Strength

Hardened

Properties

C A 0.4 0.83 0.93 0.20 0.62 2.57 1.00 0.95 1.95

C A 0.6 0.83 0.97 0.40 0.62 2.81 1.00 0.95 1.94

C A 0.8 0.89 0.94 0.43 0.65 2.90 1.00 0.95 1.94

C A 1.0 0.91 0.97 0.57 0.65 3.10 0.99 0.92 1.91

C A 1.2 0.94 0.97 0.64 0.69 3.25 0.99 0.89 1.88

C B 0.4 0.86 0.90 0.31 0.65 2.72 1.00 0.97 1.97

C B 0.6 0.86 0.93 0.50 0.65 2.94 1.00 0.97 1.97

C B 0.8 0.91 0.91 0.63 0.65 3.11 0.99 0.95 1.94

C B 1.0 0.94 0.94 0.69 0.73 3.31 0.99 0.95 1.94

C B 1.2 0.97 0.94 0.81 0.73 3.46 0.99 0.92 1.91

C C 0.4 0.91 0.75 0.72 0.58 2.96 1.00 1.00 2.00C C 0.6 0.91 0.78 0.78 0.65 3.13 1.00 0.97 1.97

C C 0.8 0.94 0.79 0.91 0.65 3.29 1.00 0.97 1.97

C C 1.0 0.97 0.85 0.94 0.69 3.46 1.00 0.95 1.94

C C 1.2 1.00 0.86 1.00 0.73 3.59 0.99 0.95 1.94


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Chapter 5

Conclusions

5.1. Summary of work

A research investigation or literature review was carried out which allowed for all the

necessary information for this project to be collected. This was followed by the calculation of

the mix designs.

Five mix designs were created using the Cement and Concrete Institute method for mix

design which was then used to evaluate the mixes. These mix designs were then used for all

tests that followed.

Each mix batch was mixed as two 20litre mixes and that concrete was then used to perform

the practical tests required. The slump test, slump retention test, viscosity test, air content test

were then performed.

The remained of the mix was then placed in cubes and left to cure for 3 days in order to

perform the cube strength test. After 3 days the cubes were weighed and crushed and their

strengths were recorded.

5.2. Main conclusions

Incompatibility due to overdosing only occurred with CEM A and SP A as well as with CEM

B and SP B both at a 1.2% dosage. Incompatibility due to under-dosing occurred for CEM A

and CEM B when the super-plasticiser was used at a 0.4% dosage.

The results showed that the slump test alone is not sufficient to specify the workability. A

low slump that is not pumpable can still be classified as a pumpable mix by viscosity. It is

therefore suggested that in future mixes are specified according to both slump and viscosity.

5.2.1. Slump

The general trend amongst the slump test results is that as the dosage of the super-plasticiser

increases the slump also increases. SP C consistently gave higher values for the slump, for all


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three cements, showing that it is more efficient at increasing slump than the other two super-

plasticisers

From the results obtained in this investigation it can be said that the three chosen cements are

compatible with the chosen super-plasticisers for dosages of between 0.6% and 1.0%. At a

dosage of 0.4% the two cements, CEM A and CEM B, with higher alkali contents had low

slumps and were no longer classified as pump-able slumps.

At the highest dosage tested of 1.2% CEM A and CEM B also proved to be incompatible

with SP A and SP B respectively. CEM B had a large increase in slump with SP A at a

dosage of 1.2%. This may indicate that at higher dosages the mix possibly will segregate and

be incompatible.

CEM C which had the lowest alkali content, showed compatibility for all the dosages tested

(0.4% to 1.2%). The slumps that were produced from the tests with the different super-

plasticisers all remained in the pump-able zone for slump tests, between 125mm and 175mm.

In figure 4.3 it can be seen that the change in dosage had similar affects on the slump for each

of the super-plasticisers tested. This result reinforces the robustness of the cement as

regardless of which of the polymer super-plasticisers it is being used with, the slump will

behave in a similar manner when increasing the dosage.

In terms of efficiency CEM C with SP C proved to be the most efficient. This was an

expected result as SP C was specified by the supplier as being the strongest in terms of

increasing the slump of a mix. From the information gathered in the literature review it was

also expected that the lower alkali cement would be more efficient.

5.2.2. Slump Retention

The slump retention was the best with SP A. This was true for all the cements, reinforcing the

fact that the low alkali cements have a similar compatibility with the super-plasticisers. SP C

had a loss in slump after 120 minutes. This is not as a result of the compatibility or efficiency

of the super-plasticiser with the chosen cements but rather the design of the super-plasticiser

by the manufacturer.


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The super-plasticiser that was based on the modified phosphonates polymer was more

efficient at retaining the slump. The polycarboxylate polymer super-plasticiser was not as

efficient in retaining the slump as it was designed to retain its slump up to 90 minutes.

5.2.3. Plastic Viscosity

Although when the super-plasticiser was used at a dosage of 0.4% with CEM A and CEM B

were not pumpable according to the slump test, it did fall into the category of pumpable

concrete when it was evaluated according to viscosity.

From the graphs of the Tattersall Two Point Tester Viscosity results it can be seen that the

shape of the graphs for CEM A and CEM B show a curve that flattens as dosage increases.

This suggests that the cement-super-plasticiser combination is reaching its limit in terms of

efficiency.

CEM C did not level off as the dosage was increased therefore it suggests that the cement

would still have an increase in efficiency for some dosages higher than 1.2%. The differences

in viscosity between super-plasticisers for CEM C were not as large as for the other two

cements, this shows that the cement is less sensitive than the other two higher alkali cements.

5.2.4. Air Content

The results for air content shows that CEM C had consistently lower amounts of air than the

other two cements. This may be signs of the difference in chemical reaction when the super-

plasticiser reacts with CEM C as opposed to the other two cements.

The higher air content in CEM A and CEM B did not relate to better values in viscosity or

slump as CEM C was still more efficient in this respect.

5.2.5. Hardened Properties

The density and strength were very similar in the results that they produced. This was to be

expected as a cube with a higher density should have more material in the cube giving it a

higher strength.

CEM C did not show a large variance in strength between the super-plasticisers. The cement

also proved to be more efficient and yielded results which showed CEM C had a higher

strength as compared to the CEM A or CEM B equivalents.


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5.3. Suggestions for further work

An investigation should be done into the use of these super-plasticisers with cements that are

more sensitive to changes than the low alkali cements that were used in this investigation.

Cements with higher alkali content may show a greater variance in results for a given super-

plasticiser. Also the test should be done with a varying W/C ratio to observe what effect it has

on compatibility.

Due to the Tattersall Two-Point Tester not having a definitive user manual, it is

recommended that an investigation in order to develop a standard test procedure. Also an

investigation should be done to produce a software program, which is compatible with the

Tattersall Two-Point Tester, to make data capture and calculations quicker and easier.

From the results of this report it is evident that the slump test alone is not accurate enough to

define concrete with a high workability. The Tattersall Two-Point Tester is too big to be used

on site and it requires a power source which may not be available on site. It is therefore

recommended that an investigation be done into a more suitable method for analysing

workability both in the lab and on site.

5.4. Outcomes satisfied

ECSA outcome 1: Competence to formulate and solve the Project Investigation problem

creatively and innovatively.

This was done by the selection of the necessary tests to be done. I.e. Tattersall Two Point

Test and the Air Content Test as well as creating a suitable mix design to use as a standard.

The use of the Efficiency Rating System aided in achieving the outcome.

ECSA outcome 2: Competence to apply relevant knowledge of mathematics, basic sciences

and/or engineering sciences to solve the Project Investigation problem.

The use and calibration of the viscosity test (Tattersall Two-Point Tester). This was also

shown during the mix design calculations, grading curve, Strength test results and the

graphing and reporting of captured data.


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ECSA Outcome 4: Competence to design and conduct investigations and/or data analyses.

This was shown in the tests that were performed during this investigation and the literature

researched. The use of spreadsheets to capture and evaluate the results obtained in the tests.

Conclusions and recommendations based on the results.

ECSA outcome 5: Competence to use relevant and appropriate engineering methods, skills

and tools as required by the Project Investigation problem.

All the tests that were performed were done according to engineering standards. This was

also shown during the mix design calculations, grading curve, Strength test results.

ECSA outcome 6: Competence to communicate effectively, both in writing and orally.

This report serves to represent written communication. A lot of the background information

obtained in order for testing to be done successfully was gathered by communications with

professionals in industry either by e-mail, telephonically or in person. An oral presentation

was done as well as a poster.

ECSA outcome 8: Competence to work effectively as an individual.

The structure of this project investigation set out by the university required that the project bean individual project.

ECSA outcome 9: Competence to engage in independent learning through well developed

learning skills?

The Tattersall Two-Point Tester and the Air Entrainment Meter were two pieces of apparatus

that was not used before. Therefore it was necessary for research to be done in order to

successfully use them.

ECSA Outcome 10: Critical awareness of the need to exercise judgment and take

responsibility within own limits of comp

The Compatibility and Efficiency of Low Alkali South African Cements with New Generation Super Plasticisers

Documents

new superplasticisersdespite

efficiency andcompatibility

alkali contentof

proper citation

original work

different polymer

citation andreferencing

civil project investigation