A study on aggregate selection for fire resistance ...
Transcript of 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
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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.
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