16
2.0 REVIEW OF LITERATURE
2.1 GENERAL
Many Researchers have studied the effect of replacement of
Portland cement by Metakaolin and also on fibre addition on the
mechanical and durability properties of ordinary Portland cement
concrete. The literature being reviewed is given under four sections.
(1) Review of literature of concrete containing pozzolanic materials
such as Metakaolin.
(2) Review of literature of SFRC on workability, compressive
strength, tensile strength and modulus of elasticity.
(3) Review of literature of SFRC on impact resistance.
(4) Review of literature of OPCC, MKC & SFRC on exposure to
elevated temperatures.
(5) Review of literature of OPCC on compressive strength, split
tensile strength, flexural strength and modulus of elasticity when
exposed to different thermal cycles.
2.2 REVIEW OF LITERATURE OF CONCRETE
CONTAINING POZZOLANIC MATERIALS SUCH AS SILICA
FUME AND METAKAOLIN
Yogendran et al. (1987)19 made an attempt to modify the properties
of concrete with respect to its strength and other properties by using
silica fume and chemical admixtures. They concluded that optimum
replacement of cement by silica fume for high strength is found to be
15% for a water cementatious ratio of 0.34 at all age.
17
Alhozaimy, A.M., et al (1995)37 carried out experimental
investigations on the effects of adding low volume fractions (<0.3%) of
calculated fibrillated polypropylene fibres in concrete on compressive
flexural and impact strength with different binder compositions. They
observed that polypropylene fibres have no significant effect on
compressive (or) flexural strength, while flexural toughness and
impact resistance showed increased values. They also observed that
positive interactions were also detected between fibres and pozzolans.
F.Curcio, B.A. De Angelis, and S.Pagaliolico (1998)43 in their
investigation, super-plasticized mortars containing Metakaolin (MK) as
15% replacement of cement and with a water/binder ratio of 0.33
have been characterized with four commercially available MK samples
have been studied and compared to silica fume. Three out of four
Metakaolin samples showed improvement in compressive strength at
early ages, when compared to SF, but at 90 days and later the
difference is reduced. The difference in the compressive strength
between the specimens with micro fillers and the control decreases
after 28 days, because of a smaller slow down of the hydration rate in
the control. This can be related to the fineness of the micro-filler in
the specimens with Metakaolin. At 90 and 180 days Metakaolin and
silica fume specimens gave similar strengths.
F.Curcio and B.A. De Angelis (1998)44 in their investigation, cement
pastes containing Metakaolin have been studied with a co-axial
cylinder rotational viscometer. They show a dilatent behavior that is
strongly dependent on the water /binder ratio, on the level of cement
18
replacement by Metakaolin and on the fineness of the latter.
Dilatency is caused by the angular and plate like shape of Metakaolin
particles. They concluded that, dilatancy is governed by water to
binder ratio, amount of Metakaolin and its fineness. Finally, the
dilatant properties can be explained by considering the plate like and
angular shape of MK particles in comparison with SF.
Handong yan, Wei Sun, Husiu chen (1999)45 in their investigation,
the impact and fatigue performance of high-strength concrete (HSC),
silica fume high-strength concrete (SIFUHSC), steel fibre high strength
concrete (SFR HSC), and steel fibre silica fume high-strength concrete
(SSF HSC) under the action of repeated dynamic loading were studied.
The mechanisms by which silica fume and steel fibres, reduce the
damage were investigated.
The results indicate that, steel fibre effectively restrained the
invitation and propagation of cracks during the failure. The presence
of steel fibres in high strength concrete was effective in restoring the
structure under fatigue and impact by delaying the damage process.
Silica fume effectively improved the structure of the inter-face,
eliminated the weakness of the interfacial zone, reduced the number
and size of cracks, and enhanced the ability of steel fibres to resist
cracking and restrain damage. As a result, the incorporation of steel
fibres and silica fume can together increase greatly one performance of
HSC subjected to impact and fatigues. The filler effect of silica fume
can reduce the number and size of the original cracks in the
interfacial zone and in the bulk of concrete and enhanced the
19
interfacial effect. Steel fibres mainly strengthen, toughen and resist
cracking in HSC.
J.M. Kinuthia et al. (1999)46 An experimental investigation is made
by the authors in studying the workability of concrete incorporating
combinations of pulverized fuel ash (PFA) and Metakaolin (MK) as
partial replacements for Portland cement (PC). The aim of the
research work is to explore the potential of using PFA and MK as
blends with PC in terms of the flow properties of the resulting
concrete. Mixtures containing 0, 10, 20, 30 and 40% total
replacement of cement with combinations of Metakaolin (0-15%) and
PFA (0-40% for concretes with water-to-binders ratios of 0.4, 0.5 and
0.6 were prepared. Workability of the concrete was measured by the
slump, compacting factor and vee-bee time tests. The following
conclusions are made by the authors.
i). The workability of PC-MK concrete is substantially reduced with an
increase in MK content. The workability reduction caused by MK is
attributed to its high chemical activity and high specific surface,
resulting in increased intake and hence greater water requirement.
The influence of MK on compaction and flow is reduced to the
thixotropic nature of clay suspension and to a reduction of void space
due to the improved dispersal of the MK particles.
ii). The workability of PC-PFA concrete without super plasticizer
increases significantly with increase in PFA content. For PFA contents
above 10% PFA workability falls. The reduction in workability is
attributed to flocculation/coagulation at low PFA concentration and
20
the increase in workability at high concentration is attributed to
neutralization of positive charges on cement particles and their
resultant dispersal. When super plasticizer is used as a dispersing
agent, no fall in workability is observed.
iii). Loss of workability due to the present of MK can be compensated
for by the incorporation of PFA. The degree of restoration of
workability, provided by PFA, is influenced significantly by the cement
replacement level, the MK/PFA ratio and the W/b ratio-dispersed
mixture is a critical MK/PFA ratio at which the loss in workability
imparted by the MK is exactly compensated for by the gain in
workability imparted by the PFA.
Kinuthia J.M. et al (2000)48 The contribution by the authors in this
paper forms a part of an ongoing investigation examining the potential
of using Metakaolin, pulverized fuel ash (MK-PFA) blended for cements
in concrete. The investigation involves the examination of the effect of
the blends on the strength development and factors affecting
durability including chloride penetration, carbonation and water
transport properties. The following conclusions were made by the
authors:
i) Although the early compressive strength of concrete is reduced by
the incorporation of PFA as a partial replacement for cement,
pozzolanic action develops in the medium term and up to 30% PFA
may be used without detriment to the strength at 90 days. PFA is
particularly effective in this respect at the moderately low water-to-
binder ratios of 0.4 and 0.5.
21
ii) Up to 15% partial cement replacement by Metakaolin results in
considerable enhancement in strength in both the short and the
medium term. The strength enhancement is obtained for all the water
to binder ratios used (0.4-0.6).
iii) The contrasting roles played by PFA and Metakaolin in the
strength development, particularly at the early stages, can be
compared to produce effective blends for cement. At short curing
times, only mixtures with low PC replacement levels and high MK/PFA
ratios achieve strength in excess of the control. However, after 90
days curing, mixtures with high PC replacement levels and low
MK/PFA ratios also achieve strengths in excess of the control.
iv) The incorporation of small quantities of PFA, as partial cement
replacement, results in an acceleration of PC hydration, which in turn
gives rise to increased strength.
M.Frias, M.I.Sanchez derojas, J.Cabrera (2000)49 In their
experimental work, the influence of the pozzolanic activity of the
Metakaolin(MK) on the hydration heat has been studied in comparison
to the behaviors of other traditional pozzolanic materials such as
flyash and silica fume. The results revealed that MK mortars produce
a slight heating increase when compared to a 100% Portland cement
mortar, due to the high pozzolanic activity of MK. With respect to the
hydration heat, MK-blended mortar showed closer behaviors to silica
fume than to fly ash.
Moises Frais, Joseph Cabrera. (2000)50 the authors shows the
results of an investigation focusing on the effect of Metakaolin (MK) on
22
the micro-structure of MK-blended pastes. Pastes containing 0%,
10%, 15%, 20% and 25% of MK were prepared at a constant
water/binder ratio of 0.55 and cured at 200c for hydration periods
from 1 to 360 days. They investigated total capillary and gel porosity
evolution with the curing period and also estimated the degree of
hydration in the ordinary Portland cement and Metakaolin blended
pastes. The values of the degree of hydration are calculated from the
amount of Ca(OH)2 present in the paste and from the data of
differential thermal analysis (DTA) thermogravimetry (TG). A good
association between porosity and degree of hydration has been
established.
The total porosity decreases up to 28-56 days of curing time.
They observed that, up to 28 to 56 days of curing the porosity is same
for all the mixes. Beyond 56 days the porosity of all the Metakaolin
mixes increasing when compared with OPC mix. Similar phenomenon
is observed for capillary porosity. The best evidence of the influence of
MK on the refineness of the pore structure was detected in pores with
radius smaller than 100 0A. Between 7-90 days, the gel porosity of MK
mixes increase, while the OPC mix remains practically constant. The
results show the necessity of obtaining important improvement in the
porosity reducing the average pore diameter and gel porosity.
Measured lime contents show the total consumption of MK (10% to
15%) at 90 days of hydration time. A good statistical relationship has
been found between the degree of hydration and the porosity.
23
Brooks et.al. (2000)51 after studying the effect of silica fume,
Metakaolin, fly ash and ground granulated blast furnace slag on
setting times of high strength concrete, they concluded that there was
increase in the retarding effect up to 10% replacement of cement by
Metakaolin and as the percentage replacement is increased, the
retarding effect is reduced.
Shannag (2000)52 designed and studied very high compressive
strength of 69 to 110 MPa along with incorporation of locally available
natural pozzolana and silica fume. He concluded that 15%
replacement of cement with silica fume along with 15% natural
pozzolan gave relatively higher strength than without natural
pozzolan.
A.Shvarzman, K.Kovler, G.S.Grader G.E.Shter (2001)54 The effect of
heat treatment parameters on the dehydroxylation/amorphization
process of the kaolinite based materials such as natural and artificial
kaolin clays with different amounts of amorphous phase (Metakaolin)
was investigated by the above authors. The process of
dehydroxylation/amorphization of kaolinite were characterized by
DTA/TGA with mass-spectrometry and x-ray power diffraction. The
influence of the heat treatment, temperature and content of the
amorphization phase on pozzolanic activity was studied. The results
obtained are important for an optimization of the process of the
Metakaolin large scale production and its use as a pozzolanic
admixture.
24
At the calcination temperature below 4500C kaolin clays show
relatively low level of the dehydroxylation degree, less than 0.18. In
the range from 4500C to 5700C, the degree of dehydroxylation sharply
increased to 0.95, and finally at the temperature range between 570
and 7000C the kaolinite was fully dehydroxylated since the only
moderate change of degree of dehydroxylation was observed in this
range (from 0.95 to 1.0). It was found that the dehydroxylation is
accompanied with the kaolinite amorphization which affects the
activity of additives. A method of qualitative evaluation of amorphous
phase content (APC) in treated materials was developed and applied
for characterization of the investigated samples. Therefore, even with
the partial dehydroxylation of kaolinite accompanied with
approximately 55% ammorphization, the material may be considered
as very active pozzolanic admixture (according to ASTM 618). This
finding seems to be extremely important for reduced energy demand
during the production of Metakaolin.
K.A.Gruber, Terry Ramlochan, AndreaBoddy, R.D.Hooton,
M.D.A.Thomas (2001)55
The investigations carried out by the above authors revealed
that the temperature rise in MK-PC mortars (above 5% MK and up to
at least 15% MK) is greater than that in equivalent PC mortar (other
than at very low MK levels). The increase in heat evolution during
initial hours of hydration was resulted from the combined effect of
accelerated Portland cement hydration and pozzolanic reaction. The
temperature rise in PFA-PC mortars is less than that in equivalent PC
25
mortars, this is attributed to the dilution of the PC by the PFA coupled
with the latter‟s negligible pozzolanic activity during the reaction, both
the rate of heat evolution and the total heat evolved.
Xia Oquian and Zongjinli (2001)56 studied the stress–strain
relationships of concrete containing 0% to 15% of Metakaolin at an
incremental rate of 5%. They concluded that incorporation of
Metakaolin up to 15% has increased the tensile and compressive
strength and also peak strain is increased at increasing rate of
Metakaolin up to 15%. Incorporation of Metakaolin has slightly
increased the compressive elasticity modulus.
Poon et al (2001)57 investigated the rate of pozzolanic reaction of
Meta kaolin in high performance cement mortars. They studied the
hydration progress of Metakaolin in terms of its compressive strength,
porosity and pore size distribution. They concluded that the higher
pozzolanic reactivity results in a higher rate on strength development
and its pore structure refinement for the cement pastes at earlier
ages.
W.Aquino, D.A.Lange, J.Olek (2001)58 Attempt is made by the
authors to study the influence of SF (Silica Fume) and HRM (High
Reactivity Metakaolin) on the chemistry of ASR (Alkali Silica reaction)
products. They observed that silica fume and high reactivity
Metakaolin reduce expansion due to ASR. Also they observed that the
calcium content of ASR products is increasing with time in all the
samples without mineral admixtures and a lower level of calcium was
detected in samples containing mineral admixtures. In addition, X-
26
ray micro-analysis showed that calcium content increases with time in
ASR products. It was found that as ASR reaction proceeds, the
calcium to silica reaction of the reaction products increases following
a linear trend. From the results it is suggested that calcium in gel
products may be responsible for expansion.
D.M.Roy, P.Arjunan, M.R.Silsbee (2001)60 In their investigation,
effects of aggressive chemical environments were evaluated on the
mortars prepared with low-calcium fly ash/Metakaolin (MK)/silica
fume (SF)/ordinary Portland cement (OPC) and at various replacement
levels. The natural adverse chemical environmental conditions were
simulated using sulphuric acid, hydrochloric acid, nitric acid, acetic
acid, phosphoric acid and a mixture of sodium and magnesium
sulphates. They proposed resistance of the above mortars against the
chemical environment was in concurrence with compressive strength
measurements.
The results show some interesting trends with respect to acid
resistance. Substitution of SF, MK, or FA under certain conditions
has been shown to increase the chemical resistance of such mortars
over those with plain Portland cement. The mortar made from all three
series showed poor resistance to higher acid concentrations of 5%
sulphuric acid, 5% acetic acid, and 5% phosphoric acid environments.
Chemical resistance increased in the order of SF to MK to FA series
and decreased as the replacement level is increased from 0-10%
weight replacement level to 15-30% weight level. They observed that
27
compressive strength is increasing in the order of fly ash to Silica
fume to Metakaolin.
Megat Johari M.A. et al. (2001)61 In their investigation, the effect of
Metakaolin (MK) on the creep and shrinkage of concrete mixes
containing 0%, 5%, 10% and 15% MK has been studied. The
outcomes showed that autogenous shrinkage measured from the time
of initial set at the early age of the concrete was decreased with the
inclusion of MK, but the long – term autogenous shrinkage measured
for the age of 24 hrs was increased at 5% replacement level, the effect
of Metakaolin has increased the total autogenous shrinkage
considering from the time of initial set. While at replacement levels of
10% and 15% it reduced the total autogenous shrinkage. The total
shrinkage (autogenous plus drying shrinkage) measured from 24 hrs
was reduced by the use of MK, while drying shrinkage was
significantly less for the MK concrete than for the control concrete.
At higher Metakaolin replacement levels, the total creep, basic creep
as well as drying creep was significantly reduced. On overall,
compared with the control concrete, the greater part of the total
shrinkage of the MK concrete is constituted by autogenous shrinkage,
the smaller part being drying shrinkage. Particularly at higher
Metakaolin replacement levels, drying creep, basic creep and total
creep were greatly reduced.
Jamal M.Khatib, Roger M.Clay (2003)74 in their investigation, the
water absorption (WA) by total immersion and by capillary rise of
concrete containing Metakaolin (MK) is studied. Cement was partially
28
replaced with up to 20% MK. The results show that the presence of
Metakaolin is greatly beneficial in reducing the water absorption by
capillary action. There is a systematic reduction in water absorption
by capillary action with the increase in Metakaolin content in
concrete. Between 14 and 28 days curing, there is slight increase in
absorption by total immersion and by capillary rise for all MK
concretes.
The partial replacement of cement with MK reduces the water
penetration in to concrete by capillary action. The water absorption of
concrete by total immersion, however is slightly increased in concrete
containing Metakaolin. WA decreases with duration of curing for all
MK concretes up to 14 days. Between 14 and 28 days of curing, there
is a slight increase in water absorption. After 28 days of curing there
is little change in WA. An increase in the total pore volume leads to
an increase in water absorption.
Sabir, B.B. et al (2002)66 The authors reports the influence of the
composition of Portland cement, pulverized fuel ash and Metakaolin
(PC-PFA-MK) binders on sorptivity and strength development of
Portland Cement – Pulverised Fuel Ash - Metakaolin concrete cured
both in water and in air and on carbonation depth, and relates this to
measured changes in absorptivity of the concrete. Concrete mixtures
covering four different total cement replacement levels (10%, 20%,
30% and 40%) for PC-PFA-MK concrete with various MK/PFA
proportions, water and air cured for upto 18 months were
investigated. The change in compressive strength and absorptivity
29
with age at all cement replacement levels under both water and air
curing are compared with those of the control Portland cement
concrete. The results presented in this paper from part of an
investigation in to the optimization of a ternary blended cementitious
system based on ordinary Portland cement, Pulverised Fuel Ash and
Metakaolin for the development of HPC. Increasing replacement of PC
with PFA in PC-PFA air (CO2 enriched) cured concrete increases
carbonation depth where as systematically replacing the PFA with MK
in PC-PFA-MK concrete reduces carbonation depth.
Jain-Tong Ding and Zongjinli (2002)65 investigated the properties of
concrete by incorporating 0% to 15% cement replacement by
Metakaolin (or) silica fume. They concluded that by incorporation of
Metakaolin and silica fume, they can reduce the free drying shrinkage
and restrained shrinkage cracking width. Also they can reduce the
chloride diffusion rate significantly.
Luccourard et al. (2003)73 studied the durability of mortars
containing Metakaolin. The studies on transport and chemical
behaviors by means of chloride diffusion tests and sulfate immersion
were carried out. They concluded that 10% to 15% replacement of
cement by Metakaolin lead to low decrease of workability and best
mechanical performance and inhibition effect on chloride diffusion
and sulfate attack for 20% Metakaolin.
T.Ramlochan, et al. (2003)67 the expansive behaviors of heat cured
mortars containing pozzolans and slag was investigated by the
authors. In almost all the mortars, the addition of any amount of
30
pozzolans and slag to the mixture usually reduced the onset of
expansion, the rate of expansion, and long-term expansion. However,
the efficiency of a particular pozzolan (or) slag in controlling expansion
may depend on its Al2O3 content. Metakaolin, which contains a
higher amount of reactive Al2O3, was the most effective at controlling
expansion at relatively low cement replacement levels. Slag and fly
ash which are also sources of Al2O3 were also effective at suppressing
expansion at higher replacement levels. Silica fume was less effective
at controlling expansion at conventional replacement levels, and even
at higher replacement levels expansion may be delayed.
Zongjin Li, Zhu Ding (2003)68 in their investigation, the physical
and mechanical properties of Portland cement (PC) containing
Metakaolin (MK) or combination of MK and slag and the compatibility
between such materials and super-plasticizers were studied. The
following conclusions are made by the authors:
MK is a new active mineral admixture used in cement concrete
products. It has a positive effect on the mechanical properties of
cement. However, MK blended cement has a poorer fluidity compared
to Portland cement under the condition which used the same amount
of super plasticizer. By the addition of ultra fine slag this can be
improved. By incorporating 10% MK and 20% (or) 30% ultra-fine slag
jointly into PC, not only the fluidity of blended cements was improved,
but above the 28-day compressive strength of the cements was
enhanced. Metakaolin is a high active pozzolanic mineral admixture.
The formula can prompt the hydration of PC, shorten the setting time
31
of cement, increase the water requirement and increase the fluidity
losing of the fresh paste. However, slag can delay the reaction of
cement hydration and prolong the setting time of cement paste. Both
MK and slag can react with CH released by cement clinker hydration
to produce secondary C-S-H gel inside the cement paste matrix.
Therefore the macroscopic property of cement was improved. XRD
analysis indicates that more Calcium Hydroxide was consumed after
adding both mineral admixtures.
Jamal Khatib and Roger (2003)74 investigated the water absorption
by total immersion and by capillary rise of concrete containing
Metakaolin up to 20% replacement level. They concluded that water
absorption of curing for all Metakaolin concretes up to 14 days and
between 14 and 28 days of curing there is a small variation in
absorption.
E.Badogiannis, V.G.Papadakis, E.Chaniotakis, S.Tsivilis (2004)82
in their investigation, the effect of Metakaolin on concrete, kaolin was
thermally treated at defined conditions, and the produced Metakaolin
was superfine ground. For comparison, a commercial MK of high
purity was used and the strength development of Metakaolin concrete
was evaluated using the K - value (efficiency factor). The produced
Metakaolin as well as the commercial one imparted similar behaviour
with respect to the concrete strength. Both conventional and
commercial Metakaolins demonstrate very high K-values (close to 3.0
at 28 days) and are depicted as HR pozzolanic materials that may lead
towards concrete production with an exceptional performance.
32
Juenger et al. (2004)85 studied the alkali-silica reactivity of large
silica fume derived particles. They reported that under accelerated
testing agglomerated silica fume decrease expansion when used as a
5% replacement of reactive sand.
Fabien Lagier, Kimberly E.Kurtis (2007)93 in their investigation, the
research on two Metakaolins which vary principally in their surface
area, and Portland cements of varying composition were examined via
isothermal calorimetry for pastes at water cementitious materials ratio
of 0.50 containing 8% cement replacement by weight of Metakaolin.
The following preliminary conclusions are made by the authors:
i). The Metakaolins examined appear to have a catalyzing effect on
cement hydration, leading to acceleration in the reaction rates, an
increased in cumulative heat evolved during early hydration and for
some cements apparently an increased intensity in heat evolved
during certain periods of each hydration. The surface area of the
Metakaolin also seems to influence these early hydration behaviors,
with the higher surface area material producing a greater rate of heat
evolution, greater cumulative heat, and greater intensity during early
hydration. It is proposed that the Metakaolin may act to enhance
dissolution of cementitious phases and or by providing nucleation, in
addition to increasing the solubilized aluminium in the system at early
ages.
ii). Strongly exothermic reactions appear to occur between the
cements and Metakaolin examined, particulars in the first 24 hours,
and these reactions seem to be most closely allied with the “Third
33
Peak” experiential in calorimetry related to the reaction of calcium
aluminate phases.
iii). The reaction of MK appears to be quite sensitive to variation in
total alkali content in the cement. When the alkali content increases
the beginning of MK appears to result in amplification of the third
peak viewed during calorimetry. It is proposed that an increasing rate
of Metakaolin dissolution with increasing cement alkali-content may
accelerate (or) intensify the reaction of C3A phase.
David G. Snelson et al. (2008)94 investigated the effect of using
Metakaolin and flyash as partial replacements with cement on the rate
of heat evolution during hydration. It was observed that adding flyash
to Portland cement enhanced the Portland cement hydration in the
very early stages of hydration, but at extended periods an increase in
flyash replacement causes a systematic reduction in heat output.
When combining Metakaolin and flyash in ternary blending, the
Metakaolin has a dominant influence on the heat output versus time
profiles.
2.3 REVIEW OF LITERATURE OF SFRC ON
WORKABILITY, COMPRESSIVE STRENGTH, TENSILE
STRENGTH AND MODULUS OF ELASTICITY
Romualdi and Batson (1963)1 after conducting impact test on fibre
reinforced concrete specimens, they concluded that first crack
strength improved by addition of closely spaced continuous steel
fibres in it. The steel fibres prevent the adverting of micro cracks by
34
applying pinching forces at the crack tips and thus delaying the
propagation of the cracks. Further, they established that the increase
in strength of concrete is inversely proportional to the square root of
the wire spacing.
Sridhara, S., et al. (1971)2 carried out experimental investigations to
study the blast resistance of concrete, by adding different types of
fibres like, nylon, coir and Jute at various percentages by volume of
concrete. They concluded that fibres increased the impact and shatter
resistance of concrete. Out of nylon fibres even at low fibre contents
found to be the most effective reinforcement for increasing the impact
strength of the concrete.
Jack Synder and David hankard (1972)3 investigated mortars and
concrete by reinforcing small short steel fibres in flexure. They
concluded that there is significant increase in the first crack strength
and ultimate strength. Due to addition of coarse aggregate to a
reinforced mortar there is decrease in the first crack and ultimate
strength of the material.
Rajagopalan and others (1973)4 developed equations to predict the
first crack and ultimate moment of resistance of the SFRC beams with
steel fibres. Also they concluded that there is much improvement in
ductility and large rotation capacity which can be used effectively in
redistribution of movements in beams and frames.
Swamy, R.N (1975)5 After experimental investigations on the flexural
strength of concrete by using small short steel fibres, he concluded
that the first crack strength is significantly improved. Also he has
35
derived equations to determine the first crack flexural and ultimate
flexural strength of the composite based on experimental and previous
investigations.
Charles H.Henage (1976)6 developed an analytical method based on
ultimate strength approach, which has taken into account of bond
stress, fibres stress and volume fraction of fibres. After his
investigations, he concluded that the incorporation of steel fibres
significantly increases the ultimate flexural strength, reduces crack
widths and first crack occurred at higher loads.
Shah and Naaman (1976) had conducted tensile flexural and
compressive tests on mortar specimens reinforced with different
lengths -*and volumes of steel and glass fibres. The flexural tensile
strength of the reinforced samples was 2 to 3 times that of plain
mortar while corresponding strains or deflections were as much as ten
times that of mortar. The stresses and strains at first cracking were
not notably diverse from those of plain mortar. The values of the
modulus of elasticity and the extent of nonlinearity were observed to
depend on the method of deformation measurement. Extensive micro
cracking was observed on the surfaces of failed flexural specimens
indicating a significant contribution of the matrix even after the first
cracking. For steel fibre reinforced specimens, the peak loads and
deformations appear to be linearly related to the fibre parameter
Vf*L/D. After breakdown, steel fibres pulled out while a large amount
of the glass fibres broke.
36
Naaman and Shah (1976)7 reported that for a large number of fibres,
the fibre contribution depends significantly on the capacity of the
matrix to withstand the forces enclosed by the fibres bridging the
cracked surfaces. They observed that spalling and disruption of the
mortar matrix leads to a substantial of the steel fibres in concrete
matrices necessary to increase both the bond properties of the fibre
and the matrix.
Hughes and Fattuhi (1976)8 carried out experimental investigations
on the workability of fresh fibrous concrete. They concluded that the
workability depends upon the properties and proportions of the
ingredients and also the workability decreases with increase in sand
content, volume fraction of fibres, aspect ratio, and length of the fibres
and with lesser water/cement ratio.
Krishna Raju et al. (1977)9 after conducting experimental
investigation on the compressive strength and bearing strength of
steel fibre reinforced concrete with fibre content varying from to 0% to
3%, they concluded that, both compressing and bearing strength
increases with increase in fibre content. Also the experimental results
were predicted by theoretical method.
Kormeling, Reinhardt and Shah (1980)10 after carrying out
investigations on the influence of using steel fibres on the static and
dynamic strength of RCC beams using hooked straight and raddled
fibres, they concluded that incorporation of above type of fibres
increased the ultimate moment and reduces the crack width and
average crack spacing.
37
Ramakrishnan et al. (1980)11 carried out experimental
investigations on properties of concrete like, flexural fatigue, static
flexural strength, deflection, modulus of rupture, load deflection
curves, impact strength to first crack, ultimate tensile, compressive
strength, plastic workability including vee-bee, slump and inverted
cone time by reinforcing two types of steel fibres (straight and fibre
with deformed ends) in the concrete. From the investigations, they
concluded that no balling of fibres occurred in the cone of hooked
fibres, the compressive strength is slight higher than the normal
concrete, excellent anchorage by hooked fibres resulting in ultimate
flexural strength. Also the hooked end fibres have greater ability to
absorb impact than straight fibre reinforced concrete.
Kukreja, C.B. et al. (1980)12 carried out experimental investigations
on the direct tensile strength, indirect tensile strength and flexural
tensile strength of the fibrous concrete and compared with the various
aspect ratios of the fibres as 100, 80 and 60 respectively. They
observed that maximum increase in direct tensile strength obtained
by fibres of aspect ratio 80 with 1% as volume fraction. Finally they
concluded that indirect tensile cracking stress is an inverse function
of fibre spacing and fibre reinforcement is more effective in improving
the post cracking behaviors, than the first cracking.
Narayanan and Palanjian (1982)13 carried out experimental
investigation on the properties of fresh concrete like workability in
terms of vee-bee time by incorporative crimped steel fibres of circular
cross-section. They concluded that vee-bee time increases when the
38
aspect ratio (l/b) of fibres is increased. Balling would occur with
smaller fibre content of larger aspect ratio. Also they concluded that
optimum fibres content increases linearly with increase in fine
aggregate content.
Narayanan and Kareem-palanjian (1984)15 have studied the effect of
addition of crimped and un-crimped steel fibres on the compressive
strength, splitting tensile strength and modulus of rupture of
concrete. They concluded that fibres with higher aspect ratio
exhibited greater pull – out strength and more effective than fibres
with smaller aspect ratios. Crimped fibres possess higher bond
strength than un-crimped steel fibres, finally they concluded that the
strength of concrete after adding steel fibres, is related to the aspect
ratio of fibres, fibre volume fraction and bond characteristics the
fibres. But these factors are accounted by a single parameter called
as fibre factor „F‟, Increase in the Compressive strength, splitting
tensile strength, and modulus rupture of concrete are shown by an
equation in terms of fibre factor „F‟ and strength of normal concrete.
S.P. Shah, et al. (1986)16 have found the impact resistance of steel
fibre reinforced concrete using modified charpy impact testing
machine. The size of the specimens was 76mm x 25mm x 230mm
and compressive strength was found using 76mm x 152mm cylinders.
They used brass-coated steel fibres at different volume fractions of
0.5%,1% and 1.5% were used. They observed that the impact
resistance improved with fibre additions.
39
Nagarkar, et al. (1987)17 after conducting experimental investigation
on concrete reinforced with steel and nylon fibres, they concluded that
the increase in compressive strength, splitting tensile strength and
flexural strength of concrete is more prominent in case of addition on
steel fibres than nylon fibres. They observed that compressive
strength is increased in the range of 5 to 7%, split tensile strength in
the range of 15 to 45% and flexural strength in the range of 20% to
60% respectively.
Nakagawa et al. (1989)20 carried out experimental investigation on
the compressive strength of concrete by incorporating short discrete
carbon fibres, Aramid fibres and high strength vinyl on fibres. They
concluded that compressive strength decreased as the volume fraction
of fibres is increased.
Ramakrishna et al. (1989a)21 conducted experiments to compare the
first cracking strength and static flexural strength of plain concrete
and steel fibre reinforced concrete. They used hooked end fibres upto
1% by volume. They concluded that hooked - end fibres gave
maximum increase in the above mentioned properties when compared
to straight steel fibres.
Rachel Detwiler and Kumar Mehta (1989)22 concluded that silica
fume concrete showed the greatest improvement in strength due to
combination of cement hydration and the pozzolanic reaction between
7 and 28 days.
Ghosh et al.(1989)23 after conducting experiments on cylinder split
tensile strength and modulus of rupture of concrete by using low
40
fibre content (0.4% to 0.7%) with straight steel fibres, they concluded
that split cylinder testing method is recommended for determining the
tensile strength of fibre - reinforced concrete as in the case of normal
concrete.
Kukreja and Chawla (1989)24 After conducting experimental
investigations on concrete by using straight bent and crimped steel
fibres with aspect ratio 80, they published a paper on “flexural
characteristics of steel fibre reinforced concrete”. They concluded that,
based on steel fibre content, its type and orientation, behaviour can
range from brittle to very ductile, all for the same range of flexural
strength.
Parviz Soroushian & Ziad Bayasi (1999)25 carried out experimental
investigations on the relative effectiveness of straight, crimped
rectangular, hooked - single and hooked - collated with aspect ratio of
about 60 to 75. They observed slightly higher slumps with crimped
fibres and hooked fibres are found to be more effective in enhancing
the flexural and compressive behavior of concrete than the straight
and crimped fibres.
Ezeldin and howe (1991)26 investigated the flexural strength
properties of rapid - set cement incorporated with four types of low
carbon steel fibres (two were hooked, one was crimped at ends and
one was crimped though out at ends). They concluded that the
flexural strength is controlled by the fibre surface deformation, aspect
ratio and volume fraction. They further concluded that steel fibres are
41
very effective in improving the flexural toughness of rapid-set
materials.
S.K. Saluja et al. (1992) 27 carried out experimental investigations on
the compressive strength of concrete by incorporating straight steel
fibres of aspect ratios 75, 90 and 105. They concluded that steel
fibres are effective in increasing the compressive strength to a
maximum of 13.5% at 1.50% fibre content. Also an equation was
developed to predict the experimental results.
Sameer, E.A., and Balarguru P.N. (1992)29 experimentally
investigated the stress-strain behavior of steel fibre reinforced
concrete with and without silica fume. They proposed a simple
equation to predict the complete stress-strain curve. They observed a
marginal increase in the compressive strength, the strain
corresponding to peak stress and the secant modulus of elasticity.
Also they concluded that increase of silica - fume content renders the
fibre reinforced concrete more brittle than non-silica fume concrete.
Balaguru and Shah (1992)30 said that fibre geometry (aspect ratio)
plays of vital role in the performance of straight fibres. They said that
ductility increases with the increase in aspect ratio, with the
condition, that fibres should be mixed uniformly with the concrete.
The matrix composition contributes in at least two ways to strength
and energy absorption. The first is its bonding characteristics with
the fibre and the second is the brittleness of the matrix itself, which
plays an important role in the behavior of steel fibre reinforced
concrete.
42
Balaguru and Shah (1992)31 In their state of art report say that, the
other factors to be considered in the design are, modulus of elasticity,
strain at peak load and post peak behavior. They said that the
addition of fibres increases the strain at peak load and results in a
less steep and more gradual descending branches. Finally, fibre
reinforced concrete has been found to absorb much more energy
before failure when compared to normal concrete.
Faisal F Wafa and S.A. Ashour, (1992) 32 carried out experimental
investigations on properties like, cube compressive strength, splitting
tensile strength and modulus of rupture of concrete by incorporating
hooked - end steel fibres with 0% to 1.5% as volume fraction. They
concluded that addition of 1.50% by volume of hooked end fibres
resulted in 4.6% increase in compressive strength, 59.80% increase in
split tensile strength and 67% increase in modulus of rupture of plain
cement concrete. Also they developed equations for predicting the
experimental results.
Bayasi and Zeng (1993)34 proposed that flexural behavior of
polypropylene fibres be characterized by the post-peak flexural
resistance. They found that long fibres were more favorable for
enhancing the post-peak resistance. The effect of silica fume on the
compressive properties of synthetic fibre-reinforced concrete by using
fibrillated polypropylene and polyethylene erphalate polyester fibres
was studied by bayasi celik. He concluded that both types of fibres
improved the compressive behavior by enhancing the toughness and
also, both the fibres increased the strain at peak compressive stress.
43
Agrawal, A.K. Singh and Singhal D. (1996)39 studied the effect of
fibre reinforcing index on the compressive strength and bond behavior
of steel fibre reinforced concrete by using straight circular Galvanized
Iron fibres with aspect ratios of 60, 80 and 100. The maximum fibre
content was taken as 1.50% by volume of concrete. The results show
an increase in compressive and bond strength of steel fibre reinforced
concrete when compared to normal concrete. They also developed
relationships to relate compressive and bond strength with fibre
reinforcing index (FRI).
Gupta A.P., et al. (1998)41 carried out experimental study on
compressive strength of concrete by using crimped steel fibres of
circular in cross-section with three volume fractions of 0.5%, 1.0%and
1.5% and with two aspect ratios 55 and 82. They proposed an
equation to quantify the effect of fibre addition on compressive
strength of concrete in terms of reinforcing index (RI) based on
regression analysis.
Singh, A.P. & Dr. Singhal, D., (1998)42 After studying the
permeability of steel fibre reinforced concrete by using plain steel
fibres at various percentages (0% & 4%) they observed that
permeability is decreasing significantly with the addition of fibres and
it continued to decrease with the increase in fibre content. Also linear
relation ship was observed between permeability and compressive and
tensile strength for plain cement concrete.
R.M. Vasan et al (1999)47 investigated the effect of hook shaped steel
fibres of circular in cross-section on the compressive strength, flexural
44
strength, impact strength and modulus of elasticity of high strength
concrete. From the results, they observed that the above properties of
concrete were improved due to the addition of 0.5% volume of steel
fibres.
Nataraja, Dhang, Gupta (2001)62 studied the effect of addition of
crimped round steel fibres on the splitting tensile strength of concrete.
They proposed equations based on linear regression analysis to
correlate splitting tensile strength with the fibre reinforcing index.
Linear relation ship between splitting tensile strength and the flexural
strength, split tensile strength and compressive strength were also
proposed.
O.Kayali et al. (2003)69 carried out experimental investigation on the
effect of polypropylene and steel fibres on high strength light weight
aggregate concrete. Sintered fly ash aggregates were used in the light
weight concrete. By adding polypropylene fibres at 0.56% by volume
of the concrete caused a 90% increase in the indirect tensile strength
and a 20% increase in the modulus of rupture, where as addition of
steel fibres at 1.70% of volume of concrete increased the indirect
tensile strength by about 118% and 80% increase in modulus of
rupture. Finally there is a significant gain in ductility when steel
fibres are used.
Kaushik S.K., et al. (2003)70 carried out experimental investigation
on the mechanical properties of reinforced concrete by adding 1.0%
volume fraction of 25mm and 50 mm long crimped type flat steel
fibres. It was observed that short fibres acts as crack arrestors and
45
enhances the strength, where as long fibres contributed to overall
ductility. They concluded that best performance was observed with
mixed aspect ratio of fibres.
Peter H.Bischoff (2003)72 studied the post cracking behavior of
reinforced tension members made with both plain and steel fibre -
reinforced concrete. He concluded that specimens with steel fibres
exhibited increased tension stiffening and smaller crack spacing,
which both contributed to a reduction in crack widths. Also it is
observed that cyclic loading did not have a significant effect on either
tension stiffening (or) crack width control for the specimens tested.
Kolhapure B.K. (2006)91 investigated experimentally the mechanical
properties of concrete using recron 3S fibres along with super
plasticizer. He concluded that compressive strength, tensile strength
and flexural strength is increased by 30%, 23% and 24% when
compared to plain concrete.
2.4 REVIEW OF LITERATURE OF SFRC ON IMPACT
RESISTANCE
Romualdi and Batson (1963)1 after conducting impact test on fibre
reinforced concrete specimens, they concluded that first crack
strength improved by addition of closely spaced continuous steel
fibres in it. The steel fibres prevent the adverting of micro cracks by
applying pinching forces at the crack tips and thus delaying the
propagation of the cracks. Further, they established that the increase
46
in strength of concrete is inversely proportional to the square root of
the wire spacing.
Sridhara, S., et al. (1971)2 carried out experimental investigations to
study the blast resistance of concrete, by adding different types of
fibres like, nylon, coir and Jute at various percentages by volume of
concrete. They concluded that fibres increased the impact and shatter
resistance of concrete. Out of nylon fibres even at low fibre contents
found to be the most effective reinforcement for increasing the impact
strength of the concrete.
Swamy, R.N. (1974)3 studied the mechanical properties and
applications of fibre reinforced concrete using polypropylene, glass,
asbestos and steel fibres. The factors influencing the effectiveness of
fibre reinforcement and the efficiency of stress transfer were
discussed. The author concluded that Asbestos, glass and steel fibres
can be used at higher temperature than the low modulus fibres like
nylon and polypropylene which lose their load carrying capacity
around 1000C. The great improvements in impact resistance and
ductility at failure provided by glass, steel and plastic fibres are not
reflected by asbestos, whose characteristic property is its high tensile
strength.
Charles H. Henage (1976)6 developed an analytical method based on
ultimate strength approach, which has taken into account of bond
stress, fibres stress and volume fraction of fibres. After his
investigations, he concluded that the incorporation of steel fibres
47
significantly increases the ultimate flexural strength, reduces crack
widths and first crack occurred at higher loads.
E.K. Schrader (1981)13 has developed a simple, portable and
economical test device which measures the impact resistance. This
impact test device is called the schrader‟s test device and the test
method is called drop weight test method. The number of impact
blows delivered by a drop hammer is accumulated until the first
visible crack occurs and until the test specimens is forced to separate
by continued impacting. The test is best suited for fibrous concrete.
Initial data shows that it can also serve as an indication of other
material properties such as toughness, strain capacity and fatigue
performance.
Shah S.P., et al. (1986)16 have found the impact resistance of steel
fibre reinforced concrete using modified charpy impact testing
machine. The size of the specimens was 76mm x 25mm x 230mm
and compressive strength was found using 76mm x 152mm cylinders.
They used brass-coated steel fibres at different volume fractions of
0.5%, 1% and 1.5% were used. They observed that the impact
resistance improved with fibre additions.
Alhozaimy, A.M., et al. (1995)37 After experimental investigations
they concluded that increased effectiveness of fibres in the presence of
pozzolans could be caused by the improved fibre to matrix bonding
associated with the action of pozzolans in the concrete.
Balasubramanian et al. (1996)41 studied the impact resistance of
steel fibre reinforced concrete using drop weight test method. They
48
varied the fibre volume fractions as 0.5% to 2% for each of the three
types of steel fibres (Straight, Crimped and Trough shaped fibres).
These fibres were of aspect ratio 80. They concluded that impact
resistance increased with increase in fibre volume fraction. Also they
concluded that among the three types of fibres, crimped fibres showed
higher impact resistance than straight and trough shape fibres.
Bindiganavalie. V and Banthia. N (2002)64
The authors on the topic “Some studies on the Impact Response
of Fibre Reinforced Concrete” made an attempt to examine two major
issues related to impact loading on plain and fibre reinforced concrete.
Firstly, within the context of drop weight impact tests, a number of
machine parameters were examined including capacity size (150J –
15,000J) and drop heights (1.2m – 2.5m). It was found that the
machine parameters strongly control the experiential material
response to impact. Secondly, a comprehensive test program
launched where steel and polymer fibres with widely different
constitutive properties were compared as reinforcement in concrete
under impact loading.
Based on the experimental investigation they observed that
For cement – based materials, the measured impact response is
highly dependent on the characteristics of the drop-weight impact
machine used for testing. The pulse duration was found to depend
upon the drop-height, with greater drop-height leading to shorter
pulses. Results appear to be far less sensitive to the mass of the
49
hammer than to the drop-height. This observation forms a useful
basis for standardizing impact testing of plain and fibre reinforced
concrete. Results from two different machines with varying hammer
masses can be compared if the drop height were identical.
Crimped polypropylene fibre is less effective than steel fibre at
quasi-static rates of loading. However, a higher stress rates, in
performed better than the steel fibre. This „switch‟ in the behavior of
FRC is attributed to the greater strain rate sensitivity of polypropylene
visa vis steel.
Song, Hwang and Shou (2004)82 carried out experimental
investigations to study the impact resistance of steel fibre reinforced
concrete using drop weight test method. They used hooked end fibres
with 0.55mm in diameter and 35mm long. They concluded that steel
fibrous concrete improved to various degrees to first crack and failure
strengths and residual impact with standing capacity over the non-
fibrous concrete.
2.5 REVIEW OF LITERATURE OF OPCC, PPC & SFRC
WHEN EXPOSED TO ELEVATED TEMPERATURES
Mohammed Bhai G.T.G (1983)14 The experimental work done by
Prof.G.T.G. MOHAMMED BHAI, describes tests carried out to
determine the effect of high temperatures on the residual compressive
strength of concrete used in Mauritius. The rock formation in
Mauritius, an island of the volcanic origin is mostly basaltic. The
course aggregate used for making concrete in Mauritius is invariably
50
crushed basalt. The fine aggregate can be either coral sand or
crushed basalt. The effect of method of cooling and that of age after
heating were included in the investigation. In order to determine
whether any physical or chemical changes take place in the coral sand
and basalt on heating-ray diffraction tests were carried out, one on un
heated sample and other three on samples which has been heated for
two hours to 2000C, 5000C and 8000C respectively and then cooled
down to room temperature.
The following conclusions were drawn by the author:
1) When subjected to high temperatures the residual strength of
concrete made with coral sand is significantly less than that of
concrete made with basalt sand. This appears to be due to some
chemical/physical changes, which occur, in coral sand when heated
beyond 3000C.
2) The method of cooling has no significance influence on the
residual strength of concrete heated up to 4000C, but for higher
temperatures air cooled specimens have a lower residual strength
than water cools ones.
3) Air-cooled specimens show a further loss in strength from one
day to seven days after heating. Water cooled specimens, however
exhibited a recovery in strength over the same period.
R.Sarshar and G.A. Khoury (1993)35 The authors carried out
experimental investigations on the uniaxial compressive strength
conducted on cement paste and concrete specimens heated to
temperatures up to 6000C. They investigated on the concrete cement
51
paste and aggregate and a cement blend containing 65% slag
replacement of ordinary Portland cement by weight. They concluded
that at 6000C, the hot compressive strength of this material was 85%
of the value measured before heating. Also they concluded that, both
material and environmental factors have a significant influence during
the heat cycle and after cooling. In several cases the fast cooling
resulted in higher residual strength. Specimens containing slag
retained a higher proportion of their strength, than specimens
containing 100% OPC after quenching from 5200C.
Abha Mittal et al. (1994)36 The authors on the topic “Residual
Strength in concrete after exposure to elevated temperature” reveal
that the loss of concrete strength when exposed to higher
temperatures and the recovery of lost strength due to dehydration of
concrete with time was a support of evidence for the earlier
experimental works done on the effect of high temperatures on
compressive strength of concrete.
Based on the Experimental investigations they concluded:
An increase in compressive strength for exposure to lower
temperature below 1000C this may be partly attributed to accelerated
hydration of unhydrated cement. The compressive strength is
drastically affected in higher ranges of temperature and the time of
exposure.
With time, there is a recovery of compressive strength due to
rehydration of concrete. The recovery may be about 80 percent of the
initial strength. This was also been observed by other research
52
workers, that concrete which has been heated at temperature below
5000C rehydrates while cooling down and gradually regains most of its
lost strength.
B.Zhang, N.Bicanic, C.J.Pearce and G.Balabanic (2000)53 An
investigation is done by the above authors to study the effect of
elevated temperature (tm) related to the explosive period (th) and the
curing age (ta) on the residual fracture properties of normal strength
concrete (NSC) and high strength concrete (HSC), by conducting three
point bending tests on preheated beams. Most beams were exposed to
temperature between 1000C and 6000C for 12 hrs at 14 days. The
weight loss (W) was also monitored. The following conclusions are
made by the authors.
i). Weight loss is a parameter that can help to distinguish three
different regimes. When the heating temperature is under 2000C, the
weight loss is completely caused by the quick evaporation of capillary
water, and the concrete undergoes a physical process. For a
temperature between 2000C and 4000C, the weight loss is mainly
caused by the gradual evaporation of gel water, and the concrete
undergoes a mixed physio-chemical process. For a temperature over
4000C, the weight loss is mainly caused by the evaporation of
chemically bound water (dehydration) and decomposition, so the
concrete undergoes longer weight loss, but a greater curing age slows
down the evaporation rate because of further hydration.
ii). The concrete strength parameters do not change very much
when the temperature is under 2000C, there after they decrease
53
rapidly with increasing heating temperature. A longer explosive period
increases the strengths slightly at lower temperatures but reduces
them at higher temperatures. A greater curing age always helps to
increase strength.
iii). The concrete brittleness has been assessed using the
characteristic length. Increasing temperature decreased the
brittleness, but this reduction is obtained with a significant loss of
strength for higher temperature. The brittleness decreases much
more rapidly for high-strength concrete. A longer exposure period
decrease the brittleness but a greater curing age increases the
brittleness slightly. The brittleness of the concrete always decreases
with increasing weight loss, and the rate of decrease becomes much
greater for higher weight loss.
Maria de Lurdes et al. (2001)60 Authors carried out experimental
investigations on the compressive strength of steel fibre reinforced
high strength concrete (SFHSC) subjected to high temperatures. The
concrete samples were preheated to various temperatures, and the
subsistence of a cooling stage was measured as a variable. They
concluded that during the heating phase the compressive strength of
the SFHSC was shown to be more affected by high temperatures than
normal - strength concrete without fibres. In general, a gain in
compressive strength in the specimens was observed after cooling,
except at 3000C, there was always a gain in compressive strength after
the specimens cooled for all maximum preheating temperature levels.
This recovery varied according to the maximum heating temperature
54
level, but reached as much as 20% for maximum heating
temperatures of 500 – 6000C. At 2000C, the residual strength was
higher than the concrete strength before heating.
Sun. W.Luo X, Chan. S.Y.N (2001) Studied the “Properties of high
performance concrete exposed to high temperature”. Pore structure
measured by means of mercury intrusion porosimetry (MIP) was
studied to determine the changes in the interior structure of the
concrete before and after high temperatures. They concluded that
thermal shock for matured concrete was not a principal factor causing
spalling of high performance concrete. Inclusion of steel fibres
improved the residual properties, if they did not melt at high
temperatures.
Phan, L.T. Law son, J.R. and Davis, F.L. (2001) studied the “Effects
of elevated temperatures on heating characteristics, spalling and
residual properties of HPC”. They conducted experimental study on
HPC with and without silica fume. They observed that the differences
in modulus of elasticity are less significant and the potential for
explosive spalling increased in high performance concrete specimens
with lower water to cement ratio and silica fume.
Long T. Phan and Nicholas Carino J. (2002)63 In their experimental
investigations, mechanical properties of high strength concrete
exposed to elevated temperatures were measured by heating 100 x
200 mm cylinders at 50C/min to temperature up to 6000C. After
Heating was done with and without a continued stress, properties
were considered at elevated temperatures as well as after cooling to
55
room temperature. Four mixtures with different water-cementitious
materials ratios (w/cms) were used, out of which two mixtures
enclosed silica fume. Measured compressive strengths and elastic
modulii were normalized with respect to room temperature values, an
analysis of variance was used to determine whether the test condition,
the values of w/cm, or the presence of silica fume affected the results.
The influence of these variables on the tendency for explosive spalling
was also examined by the authors on the topic “Effect of Test
Conditions and Mixture Proportions on Behavior of High-Strength
Concrete Exposed to High Temperatures”. Results indicated that
losses in relative strength due to high temperature exposure were
affected by the test condition and w/cm, but there were significant
interactions among the main factors that resulted in complex
behaviours. The occurrence of silica fume does not come out to have
a major effect. Measurements of temperature histories in the
cylinders revealed complex behaviours that are believed to be linked to
heat-induced transformations and transport of free and chemically
combined water.
Bowu, Xiao – Ping Su, Huili (2002) Studied the effect of high
temperature on residual mechanical properties of confined and
unconfined high strength concrete. They varied the temperature from
1000C to 9000C. Also elastic modulus decreases sharply at the higher
temperatures.
R.V.Balendran, T.M. Rana, T.Magsood, W.C.Tang (2002)
Investigated on “Strength and durability performance of high
56
performance concrete containing pulverized fuel ash, silica fume and
Metakaolin as pozzolans at elevated temperatures”. The addition of
silica fume showed poor performance with respect to strength and
spalling at higher temperatures. Finally, they concluded that addition
of pulverized fuel ash and Metakaolin improved the fire performance of
high performance concrete in terms of residual strength and
durability.
Chi-Sun Poon, Salman Azhar, Mike Anson and Yuk-hung Wong
(2002) Investigated on “Comparison of the strength and durability
presentation of normal and high strength pozzolanic concretes at
elevated temperatures”. Silica fume, fly ash and blast furnace slag
were used as pozzolans. They concluded that pozzolanic concrete
showed best performance when compared to plain concretes. After
4000C, both HSC and normal strength concrete lost their strength
rapidly and also severe deterioration and spalling was observed in
both concrete for temperatures above 4000C.
Chi-sun poon, Salman Azhar, Mike Anson, Yuk-Luny Wong
(2003)71 The authors carried out experimental investigations to
evaluate the performance of Metakaolin (MK) concrete at elevated
temperatures upto 8000c. Eight normal and high strength concrete
(HSC) mixes incorporating 0%, 5%, 10% and 20% MK were prepared.
It was found that after an increase in compressive strength at 2000C,
the MK concrete suffered a more severe loss of compressive strength
and permeability – related durability than the equivalent silica fume,
fly ash and ordinary Portland cement concretes at higher
57
temperatures. Likely to explode spalling was observed in both normal
and high - strength Metakaolin concretes and the frequency increased
with higher Metakaolin contents.
The Metakaolin concrete show a different outline of strength
gain and loss at elevated temperatures. After gaining an increase in
compressive strength at 2000C, it maintained higher strength as
compared to the corresponding SF, FA and pure OPC concretes up to
4000C. A sharp reduction in compressive strength was observed for
all HSC after 4000C followed by severe cracking and explosive spalling
within the range 400 – 8000C. MK concretes suffered more loss and
possessed lower residual strength than the other concretes. Dense
micro – structure and lower porosity are the main reasons for the poor
performance of MK concrete at elevated temperatures. Explosive
spalling was observed in both normal and high strength MK concrete
specimens particularly between 450 and 5000C. The spalling
occurrence increased with the higher Metakaolin content. The vapour
pressure build-up by dense pore – structure seems to be the obvious
reason for such spalling. The MK concrete with 5% cement
replacement showed better performance than the corresponding pure
OPC and SF concretes at all tested temperatures. No spalling was
experiential in this concrete.
V.K.R. Kodur and Tien – Chih Wang et al. (2004)83 The authors
carried out experimental investigations on the strength and stress -
strain relationship of high strength concrete (HSC) at elevated
temperatures. They investigated at 1000C, 2000C, 4000C, 6000C and
58
8000C for plain high strength concrete and fibre reinforced high
strength concrete. The variables considered in the investigations
included concrete strength, type of aggregate and the addition of steel
fibres. They concluded that the compressive strength of HSC
decreases by about a quarter of its room temperature strength with in
the range of 100-4000C. The strength further decreases with the
increase in temperature and reaches about a quarter of its initial
strength at 8000C. The increase in strains for carbonate aggregate
high strength concrete is bigger than that for siliceous aggregate high
strength concrete. They observed that plain high strength concrete
exhibits brittle properties below 6000C and ductility above 6000C.
Also they concluded that incorporation of fibres exhibits ductility over
higher temperatures and the strain at peak loading increases from
0.003 at room temperature to 0.02 at 8000C.
Srinivasa Rao K., Potha Raju. M. and Raju P.S.N. (2004)84 The
extensive use of concrete as a structural material for the high rise
buildings, storage tanks, nuclear reactors , and pressure vessels
increase the risk of concrete being exposed to high temperatures.
This has led to a demand to improve the understanding of the effect of
the temperature on concrete. The behaviour of concrete exposed to
high temperatures is a result of many factors including the exposed
environments and constituent materials. High strength concrete (HSC)
is characterized by the use of extremely low w/b ratio and a highly
compact mix using suitable methodologies. The authors in their
experimental investigation on the effect of temperature and to evaluate
59
the structural safety an attempt was made to study the residual
strength of high strength concrete exposed to high temperatures at
different ages. From this study it was found that older concrete
suffered less loss than younger concrete within the temperatures
range of 100o C to 250o C. In older concrete of 28 and 56 days of age
the behavior is similar. This may be due to completion of hydration of
cement and micro cracking around hydroxide crystals. Based on the
Experimental investigations they concluded
Rapid decrease in strength was observed at 50o C for all
exposure durations of 1, 2 and 3 hrs at 7 days age of concrete. This
may be due to incomplete hydration of cement.
An increase in strength was observed in the temperature range
of 50oC to 100oC for all exposure durations of 1, 2 and 3 hrs at 7 days
age of concrete. This may be attributed to the accelerated hydration of
cement.
A gradual reduction in strength was found with increase in
temperature from 100oC to 250oC for all exposure durations of 1, 2
and 3 hrs at 7 days age of concrete.
Behavior of 28 and 56 days concrete was similar showing
reduction in strength with increase in temperature for all exposure
durations.
Older concrete exhibited less loss of strength compared to
younger concrete at all temperatures.
Y.F. Fu, W.L. Wong et al. (2005)89 The authors carried out
experimental investigations on the effects of mineral additions and
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test conditions on the stress-strain relation of high strength concrete
when exposed to elevated temperatures. They observed that, addition
of fly ash (FA) was effective in improving the residual properties
(compressive strength and elastic modulus) of concrete. All the
concrete mixes had higher residual mechanical properties in the
stressed test than in the unstressed test. In the stressed test
condition, all the concrete mixes retain elastic modulus values close to
the inventive unheated values.
Jainzhuang Xiao and H. Falkner (2005) Carried out experimental
investigation on the residual strength of high performance concrete
using polypropylene fibres at elevated temperatures. They compared
the residual strength of HPC with and without polypropylene fibres.
Finally they observed no spalling in HPC containing fibres when
compared to any HPC specimens. Also a relationship between the
mass loss and the exposure temperature was developed.
K.D.Hertz and L.S.Soren Sen (2005) developed a new material test
method for determining whether (or) not an actual concrete may suffer
from explosive spalling at specified moisture level. They concluded
that sufficient quantities of polypropylene fibres may prevent spalling
of a concrete even when thermal expansion is restrained.
Srinivasa Rao .K., Potha Raju .M. and Raju P.S.N. ( 2006 )90: High
strength (HSC) is being used in high rise buildings ad a variety of
industrial structures which may be subjected to elevated
temperatures during operation or in case of an accidental fire. Bed
ford reported that staggering loss of £ 850 million per annum occurs
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on account of fire damage to buildings. This necessitates proper
understanding of the effects of elevated temperatures on the
properties of HSC. The authors made an attempt to study the effects
of elevated temperatures ranging from 500c and 2500c on the
compressive strength of HSC made with both ordinary Portland
cement (OPC) and Portland pozzolana cement (PPC). The residual
compressive strengths were evaluated at different ages. The results
showed that at later ages HSC made with Portland pozzolana cement
performed better by retaining more residual compressive strength
compared to concrete made with ordinary Portland cement. Based on
the experimental investigation they concluded
Both OPC and PPC concrete gained compressive strength on
heating till a temperature of 1500c at early ages of 1 and 3 days. This
could be due to acceleration in hydration process on heating. The
increase in percentage residual compressive strength in the range of
10 to 30 percent for OPC and PPC concretes when exposed to elevated
temperatures for 3 hours. Both concretes experienced reduction in
residual compressive strength at the age of 1 and 3 days beyond 1500c
temperature.
The residual compressive strength of OPC and PPC concretes at
the age of 7, 28, 56 and 91 days decreased steadily with increase in
temperature.
OPC concrete retained more percentage of residual compressive
strength compared to PPC concrete at early ages up to 7 days.
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However, PPC concrete performed better by retaining more residual
compressive strength compared to OPC concrete at later ages.
PPC concrete appeared to have lower decrease in percentage
residual compressive strength than OPC concrete for similar
conditions. OPC concrete exhibited maximum decrease of 40 percent
residual compressive strength at 2500C whereas, PPC concrete
exhibited maximum decrease of 18 percent in residual compressive
strength.
2.6 REVIEW OF LITERATURE OF OPCC & PPC ON
THERMAL CYCLES
Bairagi N.K. and Mr. Dubal N.S. (1996)41 The experimental work
done by authors on “Effect of thermal cycles on compressive
strength, modulus of rupture and dynamic elastic modulus of
concrete” reveal the behaviour of concrete when bare to thermal
cycles. The investigation was planned to be carried out through an
experimental program on concrete specimens for which M20 grade
concrete mix was designed as per the guidelines laid down by IS
10262 – 1982. Ordinary Portland cement confirming to IS269 – 1967
was used. Locally available coarse and fine aggregates were used to
prepare the mix. . Aggregate cement ratio of 6.0 and water cement
ratio of 0.53 was used in the test program. The specimen used was
plain concrete beams of the size 100 x 100 x 500 mm. In their study
two cases of thermal cycles were chosen. In one case concrete was
heated to a maximum temperature of 600C and in another it was
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heated to a maximum temperature of 900C. The specimens were
heated in an oven from room temperature in about two hours,
maintaining the maximum temperature for about 6 hours and then
letting it cool down to room temperature in another 16 hours, all these
constitute the completion of one thermal cycle. The specimens were
subjected to 0, 30, 60, 120, 240 and 365 thermal cycles.
After subjecting to the requisite number of thermal cycles the
specimens were treated fro dynamic modulus of elasticity as measured
by the resonant frequency method. To find the dynamic modulus of
elasticity the beam was first held as a cantilever beam, with one end
fixed (held under a screw jack) and other end free. Miniature piezo
electric transducer was fixed at the free end of the specimen. An
impact was applied using an impact hammer. The beam vibrated
under this impact load. The vibrations were picked using the
miniature piezo electric transducer. The signal obtained from the
transducer was amplified using amplifiers and then the signals were
analyzed using a FFT (Fast Fourier Transform) analyzer to obtain the
natural frequency of vibration of the specimen. This value of natural
frequency was further utilized to determine the dynamic modulus of
elasticity. After completion of the dynamic modulus of elasticity test,
the specimens were tested to determine the modulus of rupture using
the two point loading as per I.S.516-1959. The compressive strength
was measured from tests carried out on broken pieces of the beam
obtained after the flexural test. Each value of the compressive
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strength and dynamic modulus of elasticity was taken as an average
of three values obtained from three identical specimens.
From the experimental investigation carried out the following
conclusions were given by them.
The dynamic modulus of elasticity decreased with increased in
the number of thermal cycles. At both 600C and 900C thermal cycles,
the rate of reduction is found to be maximum after 30 thermal cycles
and it is reduced with increase in the number of thermal cycles. At
600C the rate of reduction is found to be 17.1% for thermal cycles and
26% for 365 thermal cycles. In case of concrete subjected to 900C the
rate of reduction after 30 thermal cycles is 27% and 41% for 365
thermal cycles. The maximum reduction occurred after 365 thermal
cycles for both 600C and 900C. However the rate of reduction is
higher for specimens subject to 900C thermal cycles, as compared to
that of specimens heated at 600C thermal cycles.
Similarly, thermal cycles have an adverse effect on the
compressive strength as well. Once again the rate of reaction is found
to be maximum after 30 thermal cycles for specimens subjected to
both 600C and 900C, which is 16% and 21% respectively, and there
after decreased gradually with increase in the number of thermal
cycles. However the maximum reduction in compressive strength
occurred after 365 thermal cycles for specimens subjected to thermal
cycles at 600C and 900C which is 26% and 35% respectively, showing
that the specimens heated at 900C are more adversely affected when
compared to those heated at 600C.
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Thermal cycles affect the flexural strength as well. For flexural
strength also the rate of reduction in strength is highest at 30 thermal
cycles and it decreases gradually for further increase in thermal
cycles. The percentage reduction is 3.9% for 600C and 17% for 900C.
The rate of reduction once again being higher for specimens subjected
to 900C.
The adverse effect of thermal cycles on the studied properties of
concrete is probably due to thermal incompatibility of concrete
constituents. Investigations have shown that micro cracks exist at the
interface between coarse aggregate and cement paste even prior to the
application of load on concrete. In the case of concrete subjected to
thermal expansion of cement matrix and aggregates. Internal stress
created due to unequal expansion or contraction of the concrete
constituents might lead to an increase in the micro cracks.
Srinivasa Rao P., Sravana P. and M.V. Seshagiri Rao, (2006)89 :
Concrete structures were exposed to temperature variations mainly
due to solar radiation. As mentioned literature, concrete containing
pure OPC exhibit a steady turn down in residual compressive concrete
strength when subjected to thermal cycles. The authors made
investigation on M20 and M30 grades of concrete containing OPC and
fly ash by exposing them for various thermal cycles at different
temperatures. Mechanical properties like compressive strength,
splitting tensile strength and dynamic modulus of elasticity were
evaluated and compared. The results discovered that concrete
containing fly ash was more successful in resisting the effect of
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thermal cycles than concrete containing ordinary Portland cement.
Based on the Experimental investigations they concluded
The thermal cycles have adverse effect on the compressive
strength of ordinary concrete.
The compressive strength of ordinary concrete for M20 and M30
decreased by about 13 percent at 500 C after 28 thermal cycles.
However for fly ash concrete the compressive strength was found to
increase by 11 percent, after 28 thermal cycles at 500 C.
The compressive strength of ordinary concrete for M20 and M30
decreased by about 25 percent at 1000 C after 28 thermal cycles.
However for fly ash concrete the compressive strength was found to
increase by 11 percent, after 28 thermal cycles at 1000 C.
The split tensile strength or ordinary concrete for M20
decreased by about 14 percent and for M30 decreased by 11 percent
at 500 C after 28 thermal cycles. However for fly ash concrete the split
tensile strength was found to increase by 12 percent and 7 percent for
M20 to M30 after 28 thermal cycles at 500 C respectively.
From the literature that the specimens were heated in oven from
room temperature to maximum temperature in about 2 hours and
maintaining the maximum temperature for another six hours and
letting it cool down to room temperature in another 16 hours, all these
constitute one thermal cycle. The thermal effects have an adverse
effect on the compressive strength and dynamic modulus of elasticity
of ordinary concrete. However for fly ash concrete the compressive
strength was found to increase by 11 percent, after 28 thermal cycles
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at 1000 C. The split tensile strength was found to increase by 12
percent and 7 percent for M20 to M30 after 28 thermal cycles at 500 C
respectively.
CONCLUSIONS BASED ON THE REVIEW OF LITERATURE
The conclusions arrived from the study of the above review of
literature are as follows:
(a) The use of Metakaolin in concrete as replacement of cement
resulted in:
Pozzolanic materials like Metakaolin when used as cement
replacement materials in concrete improves the properties of concrete
due to the more consumption of Ca(OH)2, better pore refinement,
micro filling action, more resistant to permeability, Early gain of
strength, higher pozzolanic reaction and also helps in reducing the
consumption of cement. This leads to saving of natural resources and
reduction in the emission of green house gases like CO2.
The above existing literature indicates that many researchers have
studied the few strength properties of ordinary Portland cement
concrete using Metakaolin as cement replacement material. Not much
literature is available on durability properties and also no literature is
available on behaviour of Metakaolin concrete exposed to different
thermal cycles at various temperatures. Also no comprehensive study
was done on strength and durability properties of Metakaolin concrete
using crimped steel fibres. Hence, considering the gap in the existing
literature, an attempt has been made to study the strength, durability
properties, flexural behaviour of beams and slabs by addition of
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crimped steel fibres of various aspect ratios at different volume
fractions.