A study on aggregate selection for fire resistance ...

A study on aggregate selection for fire resistance concrete for tunnel

lining

Sarvesh Mali, Technical Manager, Boral Construction Materials, Australia

Dr Faiz Uddin Ahmed Shaikh, Associate Professor, Dept. Of Civil Eng., Curtin University, Australia Tony A Thomas, Partner, Construction Material Research, Australia

The growth in the construction of tunnels worldwide has been increased in urban areas due to expanding

and new developing cities. The population growth has generated challenges to traffic management and

a shortage of space in the cities. It is seen that tunnels create spaces and improved traffic conditions.

The concrete tunnel requires sustainable and reliable service life of more than 120 years. The design

service life is based on the functional requirement of the concrete that is its mechanical properties, the

durability of concrete and its resistance to fire. Concrete usually contains 60% to 80 % of aggregate by

volume. Coarse aggregate contributes to spalling of concrete when exposed to fire. This paper studied

the performance of various types of locally available Western Australian (WA) coarse aggregates,

manufactured from a source rock, limestone, granite, dolerite and basalt in fire resistance and spalling

of concrete. The aggregates of different mineralogy impact the properties of concrete in a fire in differing

ways and to different degrees. Based on the review of the aggregates, a testing program was

performed on concrete specimens exposed to fire to assess the concrete structural performance. The

paper presents the selection of the concrete aggregate that will assist in developing a concrete

product to achieve the mechanical properties, durable concrete, and fire resistance properties of the

concrete. The paper presents a systematic process for the selection of aggregate to develop a

concrete suitable for the tunnel lining to achieve a service life greater than 120 years and the

performance of concrete exposed to fire. The paper contributes to engineering awareness and

contributes to quicker decision making for the selection of aggregates for fire resistance concrete.

Keywords: Concrete, Fire resistance, Coarse aggregate, Polypropylene fibres, Thermal conductivity

1. Introduction

Failure of concrete structures in fire occurs due to some of the key issues listed as follows:

• explosive spalling of the concrete surface in contact with the fire. • differential expansion of concrete with contained steel at higher temperatures. • differential expansion of the concrete component materials (aggregates, sand, and hydrated

binders). • reduced strength of the hydrated concrete binder at higher temperatures. • reduced strength of the contained reinforcing steel at higher temperatures.

Key concrete mix factors that are observed and reported to impact on fire resistance include: • concrete thermal conductance. • aggregate type and properties used in concrete. • concrete mix binder types and proportions. • concrete water/binder ratio and binder content. • use of additives such as polypropylene fibres to the mix. • the moisture content of the concrete at the time of the fire.

In the earlier concrete studies, when the material is exposed to a temperature up to 300°C [1] generally no spalling was observed but not all types of aggregates may be suitable to resist high temperatures. The concrete contains around 60-80% of its total volume as aggregate; hence the type of aggregate used will affect the performance of the concrete.

Figure 1 shows the strength/temperature relationship for carbonate aggregate, sand-lightweight

aggregate and siliceous aggregate. While the siliceous aggregate concrete strength reduces by half at

temperatures of 1200ºF, the carbonate and lightweight aggregate concrete maintain nearly 100% of

their original strength.

Figure 2 shows a comparison of the thermal conductivity of concrete based on aggregate types, with

the increase in temperature. It is observed that the lower the thermal conductivity of the concrete, the

slower the temperature rise when concrete is exposed to fire [2-8]. The mineralogical

characteristics of aggregates greatly affect the thermal conductivity of the concrete and thermal

stress in the concrete is the primary reason for spalling in concrete [9-10].

Figure 2. Thermal conductivity of

concrete based on the aggregate type

[Adopted reference 2]

Studies performed on concrete made with carbonate aggregates provides better spalling resistance

compared with natural siliceous aggregate concrete [11-15]. Some studies [16] were also conducted on

the difference in the behaviour of concrete at elevated temperatures with limestone and dolomite

aggregates. At temperatures above 500°C aggregates such as siliceous or calcareous are damaged

and the cracks across the aggregates are developed. The bonding of cement paste and aggregate also

disintegrates[17].

Several research papers have demonstrated the

strong relationship between the aggregate

Coefficient of Thermal Expansion (COTE) and the

COTE of concrete containing that aggregate

depending on the proportion of that rock type in

the concrete mix. Each aggregate type will have

different coefficients of thermal expansion (COTE)

at varying temperature ranges. This expansion

with temperature rise, in microstrain per °C, is

illustrated by typical COTE values in Table 1

below for common aggregate types [18]:

As the concrete temperature rises from exposure

to fire, differential temperatures caused by heat

Table 1. – Typical COTE Values

flow and moisture movement in the concrete will lead to differential stresses due to the varying thermal

expansion. Concrete with a higher COTE and the same thermal resistivity will undergo larger stresses

across a thermal gradient. And so, it has been considered that an aggregate component with lower

COTE produces a more “fire-resistant” concrete than an aggregate with higher COTE.

There are some further aspects of aggregate mineralogy other than COTE that can also impact relative

fire resistance. For example, when in contact with fire the concrete surface temperature can rapidly rise

to over 1200oC. Silica as quartz not only has a high COTE but at around 600oC there is a transition from

α quartz to β quartz with an associated linear expansion of approximately 1.6% (16,000 microstrains).

This may give rise to significantly destructive stresses depending on the proportion of quartz in the

aggregate.

In the case of limestone (largely Calcium Carbonate) the COTE is quite low but at around 500-700oC

limestone dissociates the carbon dioxide component, losing strength and shrinking in volume. The

impact of this on the fire resistance of concrete can be both positive and negative. On one hand, the

concrete becomes significantly weaker but on the other hand, the stresses from expansion are reduced,

Figure 1. Strength temperature relationship

for various aggregate types [Adopted

reference 2]

Aggregate Types

Coefficient of Thermal Expansion (microstrain

per°C)

Basalt 5.9–10.3

Dolomite 7.2–11.5

Granite 6.8–9.5

Gravel 10.8–15.7

Limestone 5.9–9.2

Quartzite 11.0–13.0

Sandstone 8.6–12.1

significant thermal energy is absorbed and this results in slowing down the transfer of heat through the

concrete as well as form an “insulating blanket” of carbon dioxide at the surface of the concrete that can

reduce the fire temperature near the concrete surface[19-22].

In the case of Blast Furnace Slag aggregate, it is different again. It has a fairly stable COTE from low

temperatures up to over 1093°C and while it is in the mid-range of COTE, it doesn’t suffer the impacts

of quartz transition that occurs in rock types containing higher levels of quartz [23]

When studying the COTE of potential aggregate rock types, each type of aggregate can have a wide

range of mineral make-up that means that not all species of that rock type will perform the same.

In this study, the performance of each local aggregate was determined by the ASTM C295 standard

Guide for Petrographic Examination of Aggregates for Concrete. The analysis showed that Basalt

aggregates had a mineral make-up that is consistent with higher fire resistance properties. The mineral

make-up of local limestone was attractive as a potential aggregate but the strength capacity and

durability properties of this aggregate were poor and therefore not considered. The granite had a

relatively high plagioclase content which is positive but the quartz content makes this a borderline

material in terms of fire resistance.

Fire exposure testing was performed on the concrete specimens using the RABT-ZTV railway curve.

The concrete specimens were exposed to fire at 1200 °C for 60 minutes. There was minor spalling in

concrete containing Basalt aggregates when exposed to fire as predicated in the initial analysis following

ASTM C295. Before the selection of aggregate for concrete, an initial investigation of the aggregate

mineralogy does assist in developing a concrete product that can achieve the required structural

properties, durability and fire resistance properties. The paper presents a systematic process for the

selection of aggregate to develop concrete suitable for the tunnel lining to achieve a service life above

120 years and very good performance of concrete when exposed to fire. The paper contributes to

engineering awareness and contributes to quicker decision making for the selection of aggregates for

fire-resistant concrete[24].

2.0 Materials and methods

2.1 Mineralogy of local aggregates

Table 2. Mineralogy of local aggregates Comparison to baseline aggregate

Comparison of Local Aggregates with Fire Resistant Basalt (Deer Park Quarry, Victoria Australia)

Minerals Determined in accordance with ASTM C295 / C295Standard Guide for Petrographic Examination of Aggregates for Concrete

Minerals Aggregate with Fire resistance properties -Deer Park Basalt

WA* Local Granite

WA* Local Dolerite

WA* Local Limestone

WA* Basalt

% % % % %

Plagioclase 40 30 16 3 39

Olivine 15

Pyroxene 23 35

Actinolite 41

Volcanic Glass 17

Epidote 7 22

Albite 27 3

Quartz 22 2 9 1

Calcite 2 1 85

Sphene 1 7

Muscovite or Biotite 3 6

Haematite

Apatite 1

Zeolite 1

Smectite 8 7 4

Chlorite 2 2 5

Minerals with High Contribution 38 0 41 0 52

Minerals with Lower Contribution 40 30 16 3 39

Minerals with No Contribution 12 38 5 88 4

Minerals with Negative Contribution 10 32 8 9 5

* Western Australia

The comparative petrographic study of local aggregates was carried out to determine the likely fire

resistance properties of each aggregate. The “baseline aggregate” was selected from Deer Park Quarry

in Victoria, Australia (Deer Park Basalt). Basalt Aggregate was used as a guide for a “good performance”

of concrete aggregate in terms of fire protection [25] along with available local Western Australia (WA)

aggregates Granite, Diorite, limestone and Basalt.

The aggregates were analysed for minerals following “ASTM C295 / C295S Standard Guide for

Petrographic Examination of Aggregates for Concrete”. Table 2 shows the comparison of the aggregate

and is discussed in section 3.1

2.2 Concrete mix properties for tunnel lining

Table 3 shows the typical requirement of the concrete used for segments for tunnel lining. A concrete

grade of 60MPa was used to meet the other early strength (tensile & compressive), shrinkage and

durability (Chloride Ion Diffusion and Water permeability) requirements for the Tunnel Lining.

Table 3. Properties of concrete for segments for tunnel linings

Description Test Method Properties

Concrete class, MPa ------ 60

Binder type ------ *GP+GGBFS+SF

Binder content (kg/m3) ------ 490

Maximum aggregate size, mm ------ 20

Water/Binder ------ 0.40

Slump, mm AS1012.3.1 100

Maximum

microstrain

drying shrinkage at 56 days,

AS1012.13

600

Steel fibres

BS EN 14889-1

Length=60mm

Diameter=0.75mm

Nominal tensile strength=1100+N/mm2

Indicative dosage =40 kg/m3

Polypropylene fibres BS EN 14889-2

Length=12mm

Diameter=0.034mm

Indicative dosage = 2kg/m3

Chloride diffusion at 56days, m2/s NT Build 443 3 x 10-12

Water permeability, mm DIN 1048.5.6 Maximum 9mm

The maximum concrete temperature at the time

of placement, °C

------

32

The maximum temperature for steam curing, °C ------ 70

Compressive strength, MPa AS1012.9

Minimum 12MPa at 8 hours

Minimum 20MPa at 24 hours

Minimum 60MPa at 28 days

Flexural strength at 28 days, MPa BS EN 14651 4.8

Indirect tensile strength at 28 days, MPa AS1012.10 5.0

*GP- General Purpose Cement, GGBFS- Granulated Grounded Blast Furnace Slag, SF- Silica Fume

2.3 Reduced strength of the hydrated concrete binder

The binder combination containing 60% GP Cement, 35% Ground Granulated Blast Furnace Slag and

5% silica fume was used considering the early strength development and durability requirements of the

cement.

Differing components of a hydrated binder can contribute to fire resistance positively or negatively. This

is discussed in formulating a recommended approach to improving the fire resistance of concrete.

The hydrated concrete binder is typically composed of minerals such as ettringite, gypsum, portlandite,

calcium carbonate, calcium silicate hydrates and residues of unreacted binder components. Each

mineral may become unstable and dissociate at various temperatures leading to slow destruction of the

binder matrix as the temperature rises in the hardened concrete. The proportions of these minerals can

determine the fire resistance of a binder or at least to some degree the rate of loss in concrete strength

under fire testing. The use of fly ash or Ground Slag as a binder in combination with Portland Cement

can also change the proportions of minerals produced on Hydration and will generally favour the

production of larger proportions of Calcium Silicate hydrates (CSH).

The temperature that different hydration products dissociate varies but as an indicative guide, an

estimate of some of these are mentioned in Table 4.

From this, it can be seen that concrete with a higher

proportion of CSH in the hydrated binder may be

able to sustain higher temperatures. Research on

fire resistance of concrete containing normal

replacements of Portland Cement with either

Ground Slag or Flyash report improved strength

retention in fire tests over that of concrete with

Portland Cement binder only. Reasons are given for

this range from the reduced Portlandite created with

these SCM’s in the binder to increased CSH

proportions [26-30].

Table 4. Estimate Temperature for

dissociation of binders

2.4 Impact of mix design and constituents on fire resistance

To meet the structural properties of the concrete mix for use in concrete subject to fire the key

components of this concrete considered were:

• a binder that has the highest possible replacement of GP Cement with Supplementary

cementitious material such as Ground Granulated Blast furnace Slag and Silica fume that will

meet the requirements of strength and durability.

• the mix contained 1.75 and 2kg/ m3 of polypropylene monofilament fibres (PPF) of

approximately the same average length as the maximum aggregate size in the mix and diameter

34 microns.

• the locally available coarse aggregate and fine aggregates were selected to verify the impact

of the fire on the concrete exposed.

2.5 Method for fire testing of concrete and mechanism of explosive spalling

National authorities have introduced temperature versus time curves in various tunnel fire testing

regulations. Three of the most commonly used curves in Europe (the RWS, HCinc and RABT fires, see

Figure 3 was designed to represent the maximum envelope for all possible fire events in road or rail

tunnels. These curves reach 1200 to 1300°C in less than 10 minutes [31- 32].

The fire resistance property of concrete was verified using the RABTZ -ZTV-railways curve Figure 3.

The concrete panels of size 1000mm X1000mm x300mm was exposed to fire at 1200°C within less

than 10 minutes for 60 minutes.

In the case of fire, the dense microstructure obstructs the transport of water vapour and promotes the

development of high pore pressure. Pore pressures and thermally induced stresses cause the concrete

to fail abruptly with a sudden release of energy.

Mineral Typical Estimate Temperature for dissociation (oC)

Ettringite 80-130

Free water loss 105 Gypsum 150 Portlandite 450 Calcium Carbonates 700

Figure 3. Characteristic time-temperature fire curves for tunnels [Adopted reference 4]

Figure 4. Mechanism of explosive spalling [Adopted Reference 37]

This type of concrete failure is termed explosive spalling, is characterised by bursting and forcible

suppression of thin layers of concrete, accompanied by a typical loud explosive noise. The failure is

progressive, which may lead to exposure of main bars, significant exposure of prestressing tendons,

significant cracking and spalling, buckling of steel reinforcement and even significant fracture and

deflection of concrete components [33]. Furthermore, it reduces concrete cross-section and can thus

lead to a partial or complete collapse of the structure.

Spalling of the concrete will occur when the intensity of the fire is such that moisture trapped within the

concrete microstructure develops thermal-induced stresses. Figure 4 shows the mechanism of

explosive spalling which is now accepted by most researchers. When concrete is exposed to elevated

temperature, capillary water vapour migrate towards the surface as well as into the core of the concrete

element (figure 4a). Since the concrete core retains significantly low temperature compared to the

surface, the water vapours migration towards the core tend to condensate (figure 4b), leading to the

formation of an impenetrable layer of condensate, so-called “moisture clog”[34], as shown in figure 4c.

Further transport of water vapour towards the core is prohibited by the impermeable layer, giving rise to

high vapour pressure (figure 4d). Additionally, the temperature gradient increases across the section and

restrains result in the development of thermal stresses in the concrete layer close to the exposed

surface (figure 4d). In this way, a high amount of potential energy is accumulated in the near-surface

zone. Once the pore pressure reaches a threshold value, this energy is violently released and the

concrete cover fails in an explosive manner (figure 4e).

Figure 5-6 show the drawing and arrangement of the concrete panel, dimension of 1000mm X1000mm

x300mm with a total of 8 thermocouples to measure the concrete specimen temperature at different

depths 1 pair at 25mm, 1 pair at 50mm, one at 75mm, 1 pair at 150mm and one at the unexposed face

placed away for fire exposed surface of the concrete.

Figure 6 shows three concrete panels of 60MPa concrete WA Local Dolerite, Basalt and Granite,

which were tested with a dosage of 1.75kg/m3 suitable polypropylene fibres (PPF) and 1 panel of

concrete with Granite aggregate with a dosage of 2kg/m3 PPF fibres.

Figure 5. Plan for the Panel and location of

thermocouples

Figure 6. Arrangement of Panels for Fire Testing

3.0 Results and discussion

3.1 Aggregates and mix design

Table 2 shows the comparison of various WA local aggregates available with the “baseline aggregate”

used as a guide for the good performance of concrete aggregate in terms of fire protection. Adding the

mineral contribution to determine the fire resistance capability of the aggregates is plotted in four

sections (mineral that contribute with high, low, no contribution and negative contribution to fire

resistance). In Figure 7 it can be seen that:

Figure 7. Mineral contribution for WA local Dolerite, limestone, Basalt and Granite

aggregates for fire resistance

WA Local Basalt and Dolerite each have a mineral make-up that is consistent with higher fire resistance

as Olivine and glass has high resistance to heat and Pyroxene crystallises at higher temperatures.

The chemical make-up of local limestone in WA is reasonable and may make it attractive as a potential

aggregate, but the strength capacity and durability properties of the material are poor and so was not

considered for further testing. The Granite has a relatively high plagioclase content which is positive but

the quartz content makes this a borderline material in terms of fire resistance.

3.2 The impact of mix design and constituents on fire resistance

Though meeting the structural properties for the use of concrete subject to fire the key components of

concrete should contain a binder combination of 60% GP Cement, 35% Ground Slag and 5% silica

fume SF, which is suitable to optimise the competing issues of early strength development.

The coarse aggregate selected was to

reduce the “minerals with negative

contribution” component (as per the above

figure 7) to less than 10%. However, WA

Local Granite with 32% of minerals with

negative contribution was used to compare

the performance of concrete for fire

resistance as it meets all the structural

requirements for early and later age strength

(tensile & compressive), shrinkage and

durability.

Initially, in all the concrete 1.75kg/m3 of PPF

fibres were used and later 2kg/m3 of fibre

was used in WA Granite aggregate concrete

to see if that could mitigate the risk of spalling

of concrete.

Figure 8. Percentage Total Siliceous Content

from the aggregate for volume (per m3) of

concrete

The fine aggregate was to meet the structural and workability requirements of the concrete mix, the silica

content of fine sand was 94% by weight.

A combination of coarse aggregate and fine aggregate was used, the proportion was selected to be

consistent with the fire resistance requirement of the concrete. The silica material content of aggregate

shall not exceed a maximum of 65% by weight. The proportion of coarse aggregate of 1158kg/m3 and

the fine aggregate of 720kg/m3 was used for the concrete with minor concretion depending on the

density of the aggregates. The proportion was based on the analysis of the mineral makeup of the

aggregate and the fire performance predicated for concrete with WA Local Dolorite, Granite and Basalt

in comparison to the Deer Park Basalt aggregate Figure 8.

Comparing the WA local aggregates with the Deer Park Basalt aggregate the performance of WA Basalt

and Dolerite should be similar to that of Deer Park Basalt for fire resistance. The WA Granite

performance should be average compared to the other aggregates.

3.4 Performance of structural properties of concrete

Referring to Table 3 the concrete with WA Dolerite, Basalt and Granite meet the requirements of

early-age strength on steam curing at 70 °C greater than 12MPa at 8 hours and 20MPa at 24 hours.

At 28 days of WA Basalt achieved a compressive strength of 65MPa, which is lower by 37% in

comparison to WA Granite and 11% to WA Dolerite.

The concrete with WA Basalt had a lower concrete strength at 28 days in comparison to WA Basalt and

Dolerite. Concrete with all types of aggregate performed and fulfilled the structural properties and

durability requirement such as Flexural strength, Indirect Tensile strength Drying shrinkage, Chloride

diffusion and Water Permeability, as listed in Table 3.

3.5 Concrete performance for fire resistance.

Figure 9. RABT/ZTV- railways curve concrete exposed to fire during the test

Figure 9 show the RABT/ZTV - railways temperature curve for the concrete which was exposed to fire/

high temperature during the test following the test. The concrete was exposed to 1200°C within less

than a minute after the test started and kept at the same temperature for up to 60 minutes to

reproduce a similar situation in case of fire in the tunnel.

Fire testing was initially performed on the 3 concrete panels for WA Local Dolerite, Basalt and Granite

(dosage of 1.75kg/m3 PPF fibres). After reviewing the outcome of the fire test, concrete panels with WA

Local granite panel was retested using the dosage of 2kg/m3 of PPF Fibre,

Figure 10 shows the panel labelled as below:

Panel (6F)- WA Local Granite, 1.75kg/m3 PPF Panel (1D)- WA Local Dolerite, 1.75kg/m3 PPF Panel (3B)- WA Local Basalt, 1.75kg/m3 PPF Panel (6F)- WA Local Granite, 2kg/m3 PPF

SPALLING DEPTH, mm

Polypropylene Fibres 1.75kg/m3

Polypropylen

e Fibres

2kg/m3

WA Local

Granite (6F)

WA Local

Dolerite (1D)

WA Local

Basalt (3B)

WA Local

Granite (7G)

35 29 3 Nil

Table 5. Spalling Depth

Table 5 shows panel 6F- with WA Granite had a

spalling depth of 35mm, Panel 1D- with Dolerite

had a spalling depth of 29mm and panel 3B- with

Basalt had a spalling depth of 3 mm.

From the three aggregates, the best performance

against spalling after exposure to fire is for the

concrete with Basalt aggregate. As analysed and

predicated, the mineral make-up of aggregates

following ASTM C295 “Standard Guide for

Petrographic Examination of Aggregates for

Concrete”, concrete with basalt aggregate had a

high contribution of mineral make-up to fire

resistance. WA Granite aggregate had a borderline

mineral make-up fire resistance. The fire test

shows that analysis of the aggregate mineral

make-up does assist in determining the fire-

resisting property of concrete.

Further, the concrete with WA Granite aggregate,

panel 7G was tested for fire resistance with an

increase in PPF fibre dosage to 2kg/m3 and the

spalling on the concrete panel was Nil, thus

mitigating the risk of spalling.

The concrete panels as shown in Figures 5-6 had

thermocouples inserted to measure the

temperature at different depths of the concrete

panel.

Figure 11 shows following Eurocode [35], for reinforcement steel exposed to temperature under 400°C

there is no decrease in yield strength, but above this 400°C temperature limit, a significant yield-strength

loss occurs [36]. The information determined by the thermocouples show in panel 6F -WA Granite and

1D- Dolerite with 1.75kg/m3 PPF fibres that the temperature at the depth of 75 mm from the exposed

face to fire is 310°C and 300°C.

Panel 3B- WA Basalt with 1.75kg/m3 PPF fibres and panel 7G- with 2kg/m3 PPF fibres, the

temperature at the depth of 50mm from the exposed face is 380°C and 360°C, which is below the

maximum of 400°C. At 400°C there is no decrease in yield strength of the reinforcing steel hence the

reinforcing steel can be placed safely for panels 6Fand 1D with a cover of concrete at 75mm and for

panels 3B and 7G with a cover of 50mm. This information will assist the designers while calculating the

structure safety in case of fire.

Figure 10. Panels Exposed to 1200 °C High Temperature

Panel 6F Panel 1D

Panel 3B Panel 7G

Figure 11. The temperature at different depths in concrete

3.6 Compressive strength after fire testing

Figure 12. Compressive strength of core cylinders from the concrete panel after exposed to fire

Figure 12 shows the compressive strengths of concrete specimens cored from the centre and the

edge of the panels after fire testing from panel 3B (WA Local Basalt) and 7G- (WA Local Granite).

The compressive strength with standard cured concrete before fire test for panel 3B was 65MPa at 28

days and for panel 7G was 90MPa

After being exposed to fire, the average compressive strength drop of the panel between the centre

and the edge was 12.5% for panel 3B and 22.3% for panel 7G.

4.0 Conclusion

This study analysing the mineralogy of aggregate will assist in the decision making of using a suitable

and economically available type of locally aggregate for the concrete for tunnel lining. Summarising

the knowledge gain from the study is as below :

• between the four local types of aggregate available, Basalt and Dolerite would be a suitable

aggregate for fire resistance concrete and granite could be borderline aggregate.

• WA local limestone aggregate had a high potential of use in concrete for fire resistance concrete

but the strength capacity and durability properties of the material were poor and so was not

considered for further testing.

• the study made it relatively easy to reason in the selection of binder types and deciding the

type of fine aggregates and the proportion of materials in a concrete mix to achieve the

required performance of the concrete for the sustainable and reliable service life of the

structure.

• the structural properties of concrete formulated with all three aggregates, WA Dolerite, Basalt

and Granite met the requirements for early age strength, flexural strength, indirect tensile

strength and Drying shrinkage.

• durability requirement of Chloride Ion Diffusion Coefficient of concrete, and for water

penetration DIN 1048 was met by all three concrete with WA aggregates.

• the compressive strength for WA Basalt in standard cured concrete was good at 64 MPa but

may require a change in mix design (increase in binder content or lower w/c ratio) to achieve

higher compressive strengths, if necessary. This gives an understanding from all the three

mixes what could be a cost-effective mix base on the availability of aggregates locally and the

binder content.

• the 60MPa concrete met requirements for structural properties and durability provides a

range of aggregates suitable to be used in concrete.

• fire testing with a fixed PPF dosage of 1.75kg/m3 shows a close relation in the performance of aggregate mineralogy to the spalling of concrete when exposed to fire.

• the WA granite was been deemed as borderline aggregate for fire resistance concrete after the

mineralogical analysis of the aggregates. An increase in fibre dosage of PPF to 2 kg/m3

assists in mitigating the risk of spalling in the case of Granite aggregate in the concrete.

• fire testing with thermocouples in the concrete blocks assists the structural designers to

design the cover requirements for reinforcing steel and so it helps with meeting the safety

requirements of the structure in case of fire.

• reviewing the performance of the concrete the 60MPa concrete, all three aggregates is can be

used to formulate highly durable concrete.

Overall, the initial study of aggregate largely assists the concrete designer and structural designer

to develop sustainable and reliable concrete for a longer service life of the tunnel lining using locally

available materials, thus optimising the cost of the project.

5.0 Reference design codes

• American Concrete Institute (ACI) standards.

• American Society for Testing and Materials (ASTM) International.

• Australian Standards for the use of supplementary cementitious materials; Ground granulated blast

furnace slag.

• AS 1012.1 Methods of testing concrete - Sampling of concrete

• AS 1012.2 Methods of testing concrete - Preparing concrete mixes in the laboratory

• AS 1012.3.1 Methods of testing concrete - Determination of properties related to the consistency of

concrete - Slump test

• AS 1012.8.1 Methods of testing concrete - Method for making and curing concrete - Compression and

indirect tensile test specimens

• AS 1012.8.4 Methods of testing concrete - Method for making and curing concrete - Drying shrinkage

specimens prepared in the field or in the laboratory

• AS 1012.9 Methods of testing concrete - Compressive strength tests - Concrete, mortar and grout

specimens

• AS 1012.13 Methods of testing concrete - Determination of the drying shrinkage of concrete for samples

prepared in the field or in the laboratory

• AS 1012.14 Methods of testing concrete - Method for securing and testing cores from hardened concrete

for compressive strength

• AS 1379 Specification and supply of concrete

• AS 1478.2 Chemical admixtures for concrete, mortar and grout - Methods of sampling and testing

admixtures for concrete, mortar and grout

• AS 2758.1 Aggregates and rock for engineering purposes – Concrete aggregates

• AS 3582.2 Supplementary cementitious materials – Slag – Ground granulated blast-furnace

• AS/NZS 3582.3 Supplementary cementitious materials – Amorphous silica

• AS 3972 General purpose and blended cements

• BS EN 14651 Test method for metallic fibre concrete. Measuring the flexural tensile strength

• Concrete Society TR 31 Permeability Testing of Site Concrete - water permeability test using Figure 4.9

test rig

• NT BUILD 443 Concrete, hardened: Accelerated chloride penetration

• BS EN 14889-1 Fibres for concrete – Part 1: Steel fibres – Definitions, specifications and conformity

• BS EN 14889-2 Fibres for concrete – Part 2: Polymer fibres – Definitions, specifications and conformity

• DIN 1048 part 5 – Testing concrete, clause 7.6 water permeability

6.0 References

1. Sanket R , Aniruddha T, Bahurudeen A, Appari S, Assistant Professor, Performance of Concrete

During Fire Exposure-A Review, Structural Engineering International 3/2014

2. Erin Ashley, Fire Resistance of Concrete Structures, Concrete InFocus, Winter '07

3. Z.P. Bazant, M.F. Kaplan, Concrete at High Temperatures, first ed., Longman, London, 1996.

4. Chrysanthos Maraveas, Apostolos A. Vrakas, Design of Concrete Tunnel Linings for Fire Safety,

Structural Engineering International 3/2014

5. Khoury GA. Effect of fire on concrete and concrete structures. Prog. Struct. Eng. Mater.2000; 2:

429–447.

6. Bailey CG, Khoury GA. Performance of concrete structures in fire. Camberley, Surrey, UK: MPA –

The Concrete Centre: 2011.

7. Khoury GA, Ander berg Y. Concrete spalling review. Report submitted to the Swedish National

Road Administration, 2000.

8. Khoury GA. Passive fire protection of concrete structures. Struct. Buil. 2008; 161: 135–145.

9. M.A. Riley, Possible new method for the assessment of fire damaged concrete, Mag. Concr. Res.

43 (1991) 87–92.

10. Zhi Xing, Aggregate’s influence on thermophysical concrete properties at elevated temperature,

Construction and Building Materials 95 (2015) 18–28.

11. A. M. K. Abdelalim, G. E. Abdel-Aziz, M.A.K. El-Mohar, G.A. Salama, Effect of aggregate type on

the fire resistance of normal and self-compacting

12. XU Y., Wong. Y.L., Poon C.S. and Anson. M. “Impact of high temperature on PFA concrete”

Cement and Concrete Research, Vol. 31, No 7 , pp.1065-1073, 2001.

13. Violeta. B. B. “SCC mixes with poorly graded aggregate and high volume of limestone filler”

Cement and Concrete Research V.33, PP. 1279-1286,2003.

14. I. Hager, Behaviour of cement concrete at high temperature, Bulletin of the Polish Academy Of

Science, Vol. 61, No. 1, 2013

15. Sanket R , Aniruddha T, Bahurudeen A, Appari S, Assistant Professor, Performance of Concrete

During Fire Exposure-A Review, Structural Engineering International 3/2014

16. Professor Colin Bailey, Case study on historic fires, University of Manchester. 17. C. Alonso, C. Andrade, E. Menendez, E. Gayo, Microstructural changes in high and ultrahigh

performance concrete exposed to high temperature environments. ACI sp229, Quality of concrete

structures and recent advances in concrete materials and testing, 2005, 289‐302.

18. James T. Smith and Susan L. Tighe, Recycled Concrete Aggregate Coefficient of Thermal

Expansion, Transportation Research Record Journal of the Transportation Research Board,

December 2009

19. L. Alarcon‐Ruiz, G. Platret, E. Massieu, A. Ehracher, The use of thermal analysis in assessing the

effect of temperature on a cement paste. Cem Concr Res (2005) 35: 609‐613.

https://doi.org/10.1016/j.cemconres.2004.06.015

20. C. Alonso, L. Fernandez‐Municio, Dehydration and rehydration processes in cementitious materials

after fire. Correlation between micro and macro structural transformations. In: International

workshop of Fire design of concrete structures, from materials modelling to structural performance,

University of Coimbra, 2007, 69‐78.

21. M. Castellote, C. Alonso, C. Andrade, X. Turrillas, J. Campo, Composition and microstructural

changes of cement pastes upon heating, as studied by neutron diffraction. Cem Concr Res (2004)

34: 1633‐1644. https://doi.org/10.1016/S0008‐8846(03)00229‐1

22. U. Schneider, U. Diederichs, R. Weiß, Hochtemperaturverhalten von Festbeton (High temperature

behaviour of concrete). Sonderforschungsbereich 148, Brandverhalten von Bauteilen,

Arbeitsbericht 1975/77, Teil II, B3‐1/95, Technical University of Braunschweig, 1977.

23. National slag association, Fire resistance and heat transmission properties of concrete and

masonry made with blast furnace slag aggregate, www.nationalslagassoc.org

24. C.K. Edvardsen, COWI A.S., Kongens Lyngby, Denmark.Tailor-made concrete structures – Case

studies from projects worldwide, Tailor Made Concrete Structures – Walraven & Stoelhorst (eds) ©

2008 Taylor & Francis Group, London, ISBN 978-0-415-47535-8

25. Cement Concrete & Aggregates Australia, Fire safety of concrete Buildings, CCAA T61, July 2010

26. Haha, M.B.; Saout, G.L.; Winnefeld, F.; Lothenbach, B. Influence of activator type on hydration

kinetics, hydrate assemblage and microstructural development of alkali activated blast-furnace

slags. Cem. Concr. Res. 2011, 41, 301–310.

27. Taylor, H.F. Cement Chemistry, 2nd ed.; Thomas Telford: London, UK, 1997.

28. Sha,W.; Pereira, G. Dierential scanning calorimetry study of hydrated ground granulated blast-

furnace slag. Cem. Concr. Res. 2001, 31, 327–329.

29. Park, H.; Jeong, Y.; Jun, Y.; Jeong, J.H.; Oh, J.E. Strength enhancement and pore-size refinement

in clinker-free CaO activated GGBFS systems through substitution with gypsum. Cem. Concr.

Compos. 2016, 68, 57–65.

30. Wei, Y.; Yao, W.; Xing, X.; Wu, M. Quantitative evaluation of hydrated cement modified by silica

fume using QXRD, 27 Al MAS NMR, TG-DSC and selective dissolution techniques. Constr. Build.

Mater. 2012, 36, 925–932.

31. R. Jansson, Fire spalling of concrete – A historical overview, SP Technical Research Institute of

Sweden, MATEC Web of Conferences 6, 2013.

32. Taillefer N, Carlotti P, Lemerle C, Avenel R, Larive C, Pimienta P (2012) Ten years of increased

hydrocarbon temperature curves in French tunnels. Fire Technology 49(2): 531-549.

33. Fire Damaged Reinforced concrete Investigation, Assessment and Repair, Technical Note No.102:

April 2011

34. Shorter, G. & Harmathy, T., 1965. Moisture clog spalling. Proceedings of the Institution of Civil

Engineers, 20, pp.75–90.

35. EN 1992-1-2: 2004. Eurocode 2: Design of concrete structures – Part 1–2: General rules –

Structural fire design.

36. A.Y. Elghazouli, K.A. Cashell, B.A. Izzuddin, Experimental evaluation of the mechanical properties of steel reinforcement at elevated temperature. Fire Safety Journal. 44( 2009) 909-919.

37. Josipa Bošnjak, Joško Ožbolt Christian Große and. Jan Hofman Explosive spalling and permeability of high-performance concrete under fire – numerical and experimental investigations, Institute for Materials in Construction at the University of Stuttgart, 2014