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Chapter 1
INTRODUCTION
1.1 General study
Most of the Structures such as deck slab of bridge, highway and airfield pavements are often
exposed to repetitive (fluctuating) loads by moving traffic, which cause a structure to failure
at a load level below its static capacity. Thus, fatigue loads (repeated loads) should be taken
into consideration in the design of concrete structures.
Reactive powder concrete (RPC) is a new type of concrete material. Compared with
conventional concrete, RPC has ultra-high strength, high toughness and high durability.
Combining the technical benefits and in-place costs, RPC was found to meet the
prerequisites of value engineering particularly in airport and high pavements, in bridge deck
overlays, curtain walls, sewer pipes, cavitation and erosion resistance structures such as
spillways, sluiceways, bridge piers and navigation locks, precast concrete products,
earthquake resistance structures, missile silos and energy dessipaters.
Rational design of concrete structures requires an accurate knowledge of concrete properties
under anticipated loading conditions. A large volume of information is available on behavior
of RPC under static loading conditions. However, relatively limited information is available
on behavior of RPC subjected to dynamic loadings.
In many applications, particularly in pavements and bridge deck overlays, the flexural
fatigue strength and endurance limit are important design parameters because these
structures are designed on the basis of fatigue load cycles. Plain concrete has fatigue
endurance limit of 50 to 55 percent of its static flexural strength. In RPC using the same
cross section as plain concrete could result in longer life span or high load capacity or both.In this present work an attempt has been made to evaluate the fatigue behavior of the new
steel and polypropylene fibers reinforced RPC. Hence, the study of effects of repeated loads
on RPC are to be studied in particular.
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1.2 Fatigue
Structures that are subjected to repeated loads are susceptible to failure due to fatigue.
Fatigue is a process of progressive permanent internal changes in the materials that occur
under the actions of cyclic loadings. These changes can cause progressive growth of cracks present in the concrete system and eventual failure of structures when high levels of cyclic
loads applied for short times or low levels of loads are applied for long times.
Many concrete structures such as highway pavements, highway bridges, railroad bridges,
airport pavements and bridges, marine structure, etc. are subjected to dynamic loads. Fatigue
strength data of concrete and other materials that are used in these structures for obtaining
their safe, effective and economical design are needed. A low cycle fatigue is important for
structures subjected to earthquake loads.
Although fatigue research began almost one hundred years ago, there is still lack of
understanding concerning the nature of fracture mechanism in cementitious composite
materials due to fatigue. This is partly due to complex nature of structure of such materials
and their properties are influenced greatly by a large number of parameters. Fatigue behavior
of concrete is also influenced by several parameters such as type of loadings, stress level,
rate of loading, material properties, environmental conditions, etc. The concrete properties
are dependent upon the variables such as water-to-cement ratio, cement content, air content,
curing technique, age, admixture content, etc.
1.2.1 Terms Related to Fatigue
The following are the most common terms used in fatigue analysis of materials.
1. Maximum stress (f max ): It is the maximum value of stress cycle, tensile stress being
considered positive and compressive stress negative.
2. Minimum stress (f min): It is the lowest value of stress cycle, tensile stress being
considered positive and compressive stress negative.
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3. Stress level (S): This is defined as ratio of maximum stress in stress cycle to static
flexure stress.
4. Stress ratio (R): This is defined as ratio of minimum stress to maximum stress in
stress cycle.
5. Mean stress (f m): It is defined as an average value of the maximum and minimum
stresses in a stress cycle, that is, f m = 1/2 (f max + f min ).
6. Fatigue life (N): It is defined as the number of cycles which could be withstood for a
given experimental condition.
7. Fatigue strength (f): It is defined as the intensity of cyclic stress that can be withstood
for a given number of cycles.
8. Endurance limit or Fatigue limit (f e): It is defined as the intensity of cyclic stress that
can be withstood for a given number of cycles.
1.3 Objectives of the present study.
The main objectives of the study are:
To evaluate the fatigue performance of RPC by conducting flexural fatigue tests on
beams subjected to repeated cyclic loading.
To evaluate the fatigue performance of RPC with replacement of steel fibers by
different percentages of polypropylene fibers conducting flexural fatigue tests on
beams subjected to repeated cyclic loading.
Linear regression model is developed for prediction of fatigue life and the failure
stress.
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Chapter 2
LITERATURE REVIEW
2.1 History of Reactive Powder ConcreteThe RPC is a very-high-strength, high-performance concrete material formulated to optimize
those properties that are beneficial to, and minimize those properties that are detrimental to,
strength, durability, permeability, and toughness of concrete. The initial formulation of RPC
was developed by Bouygues S.A. in their laboratories in France. Engineers working for
Bouygues mixed numerous trial batches of various combinations of cements, sands, silica
times, and water-reducing admixtures and conducted fresh and hardened properties tests of
these mixtures to determine which combinations provided the most optimal properties. Theyevaluated their results to choose a small number of optimized mixtures that they called
reactive powder concrete.
Reactive powder concrete obtains its name from the behavior and composition of its
component materials. The component materials are the same as those that are normally found
in conventional concrete and differ only in percentages. Cementitious materials are cement
and silica fume, aggregates are sands, and water and high-range water-reducing admixtures
(HRWRA) are used to hydrate the cementitious materials and provide fluidity to the mixture.When additional stiffness of the mixtures is required, silica flour can be added and to provide
flexural strength and toughness, steel fibers are incorporated. Reactive powder concrete uses
the word powder in its name to emphasize that all dry particles are kept to small powder
sizes. This helps to promote its homogeneity. The word reactive is used in the name to
indicate that it is formulated to maximize the effect of its reactive components. Much effort is
taken to maximize the cementitious components of RPC. Table 1.1 describes the basic
principles that were employed to obtain RPCS high -performance properties. Reactive
powder concrete mixes are characterized by high silica fume content and very low
water/cement ratio. Coarse aggregate is eliminated to avoid weaknesses of the
microstructure; the addition of superplasticizer is used to achieve a low water/binder (cement
and silica fume) ratio and heat-treatment (steam curing) is applied to achieve high strength
[10].
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Table 1.1 Basic Principles for the composition of RPC
HomogeneityParticle sizes and composition chosen for optimumeffectReactive elements chosen for high silica content
Compactness Particle volumes and sizes chosen for optimum packingFormulated to produce very low porosity
MicrostructureHigh silica contents improves paste/aggregatehomogeneityHeat curing improves strength
Ductility Addition of micro-fibers provides ductility andtoughness
Reactive powder concrete mixes are characterized by high silica fume content and very low
water/cement ratio. Coarse aggregate is eliminated to avoid weaknesses of the
microstructure, the addition of superplasticizer is used to achieve a low water/binder (cement
and silica fume) ratio and heat-treatment (steam curing) is applied to achieve high strength
[10]. Owing to the fineness of silica fume and the increased quantity of hydraulically active
components, it has been called Reactive Powder Concrete. Silica fume is an essential
ingredient of RPC (a by-product of the fabrication of silicon metal, ferrosilicon alloys and
other silicon alloys) [9]. The material comprises extremely fine particles and not only fills up
the space between the cement grains, but also reacts with the cement. From a physical point
of view, the silica fume particles appear to be perfectly spherical, with diameters ranging
from less than 0.1 microns to approximately 2 microns, so that the average silica fume sphere
is approximately 100 times smaller than the typical cement particle [9].
From a chemical point of view, the silica fume behaves as if it were a crystal of
portlandite, Ca(OH) 2. In the descriptions of the Australian Standard (AS 3582.3), silica fume
is also known as condensed silica fume and microsilica, and contains no less than 85 %
silica dioxide (SiO 2). The earliest silica fume utilization was the use of 15 % silica fume to
replace cement in the construction of a tunnel in Oslo in 1952. Silica fume use became more
common in the late 1970 s when it was used as a supplementary cementitious material in
concrete in Europe, and in the early 1980 s in North America. Following work by Bache and
co-workers in Denmark and a significant research effort in the early 1980 s in other
countries, silica fume was rapidly accepted as a supplementary cementitious material for
concrete almost everywhere in the world in the following 5 years. The use of
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superplasticizers in concrete began in the 1960s and was a milestone in concrete technology.
Using such techniques the production of concrete of high compressive performance and
ductility was achieved, as high workability could be maintained at a very low water/cement
ratio [16]. High fluidity and good workability can be achieved through the addition of
superplasticizer, which enhances the microstructure of the concrete.
2.2 Development of RPC
RPC was developed by the French engineers in the 1990 s [12]. Richard and
Cheyrezy presented the initial composition in which they eliminated coarse aggregates to
enhance the homogeneity. The bond between the coarse aggregate and the cement paste are
the weakest links in the matrix, so to improve strength the coarse aggregates were removed
from the composition. However, other studies have indicated that addition of coarse
aggregate does not necessarily reduce the compressive strength. The use of the coarse
aggregates led not only to the decrease in cementitious paste volume fraction, but also
necessitated changes in the mixing process and in the consequent mechanical properties.
RPC containing coarse aggregate was more easily fluidized and homogenized. The mixing
time was found to be shorter than for RPC without coarse aggregates. Formulations with and
without coarse aggregate exhibited a similar behaviour under compressive loading, although
with somewhat different modulus of elasticity and strain at peak stress, which was dependent
on the stiffness of the aggregates. The lower paste volume fraction and the physical
resistance of the stiffer basalt aggregate resulted in a lower autogenous shrinkage of the RPC
containing coarse aggregates. The initial purpose of adding coarse aggregates was to reduce
the cement usage so that the costs of construction could be lowered. Work has been
undertaken where artificial aggregate was used to replace natural ones with clinker-
aggregates resulted in an increase of strength (by about 20 MPa) compared to natural
aggregates [18].
Observation of the microstructure shows that silica fume addition leads to significant
improvement. Owing to the size of particle of silica fume (1/100 of a cement particle). Hence
the space between cement particles can be filled by the silica fume particles. Hence the pores
and voids can be considerably reduced in the matrix. The porosity of RPC never exceeds 9%
by volume in the pore diameter range of 3.75 nm to 100 micron. The reaction between
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Portland cement and a supplementary cementitious materials results in a very dense
microstructure and an improved bond between the binder and the aggregate. Several
researchers indicated that a reduced capillary porosity and changed pore size distribution are
achieved as a result of silica fume addition [20]. With reference to hydration, the reaction of
the calcium hydroxide produced by the cement hydration with the silica fume, results in a
higher content of calcium-silicate-hydrate (CSH), the main source of strength in hardened
concrete.
The influences of silica fume and cement type on the performance of 200 MPa RPC
have been studied by Richard and Cheyrezy [11]. They concluded that an RPC mix with
CaOAl 2O3 - free cement used less water and achieved higher strength than RPC mixed with
CaOAl 2O3 content cement. They also developed an understanding of the effect of
superplasticizer type on the performance of RPC in terms of water -cement ratio and
compressive strength. They observed that the steel fibre shape and the aspect ratio do not
significantly affect the workability. The mechanical performances of these fibre-reinforced
materials appear to be essentially influenced by the amount of fibres dispersed inside the
cement matrix and the bond between the cement matrix and the fibres. Furthermore this bond
depends on the fibre characteristics (size, shape, and surface treatment). In the initial
research, heat treatment and pressure before and during setting had to be applied to achieve a
high strength. A minimum value of porosity is found to be obtained for pressed RPC with
heat treatments between 150 C and 200 C in the laboratory. The effect of curing techniques
has been investigated, and specimens under steam curing resulted in the highest compressive
strength as compared to both moist and air curing. In addition the effect of curing on flexural
strength is not found to be the same as that on compressive strength in silica fume concrete
[17].
2.3 Fatigue
General
The earliest work on fatigue of mortar specimen in compression was done by Considered in
1898 and concrete specimen by Van Ornum in 1903 (book of Rbk). Several researchers
including Batson, Ramakrishnan, Kesler, Tarto etc. presented information on studies
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concerning fatigue behavior of concrete and fiber reinforced concrete [1]. However,
substantial amount of research work on fatigue behavior of concrete began after 1930. This
report deals with investigations related to fatigue behavior of RPC made with steel fiber and
polypropylene fiber.
Parameters effecting the fatigue behavior of concrete
A large number of parameters are known to influence fatigue properties of plain concrete.
These include stress range, variation in loads, load history, rate of loading, rest periods, stress
gradients, material properties, etc. The material properties are influenced by cement content,
water-to-cement ratio, curing conditions, amount of entrained air, specimen size, aggregate
type and quality, moisture condition, age of concrete, etc.
2.3.1 Stress Level
The effect of varying load levels on fatigue is of special importance because this
condition is more representative of the actual conditions to which a structural component will
be subjected. Several studies indicated that the stress levels influences the fatigue strength
[all references]. In general, higher fatigue strength is obtained when the stress levels is
reduced.
Suresh Kumar et al (2) studied the effect the stress levels on flexural fatigue life of
High performance concrete. All specimens (100mm100mm500mm.) were simply
supported on a 400mm span and subjected to repeated loads of varying range and magnitudes
using third point loading systems. The number to repetitions to failure determined for three
stress levels 0.65, 0.70, and 0.75 for pavement quality concrete (PQC) and high volume fly
ash concrete (HVFA) and 0.65, 0.75, and 0.85 for silica fume concrete (SFC).
The scatter diagram of the test results for PQC, HVFAC and SFC are shown in Figure
2.1.The tests revealed that number of cycles increases as stress level decreases for PQC,
HVFAC and SFC.
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Figure 2.1 Scatter diagram Aravindkumar et al (3) performed an investigation to evaluate the effect of stress level on
conventional concrete (PCC) and HVFAC prisms (500mm150mm150mm) subjected to
repeated loads. Fatigue test specimens were tested under one-third point loading. PCC was
tested for eight stress levels (0.85, 0.81, 0.76, 0.71, 0.65, 0.61, 0.57, and 0.53) and HVFAC
was tested at seven stress levels (0.80, 0.75, 0.70, 0.65, 0.60, 0.54, 0.50). The test results of
PCC and HVFAC are tabulated in table 2.1and 2.2 respectively.
Table 2.1 Fatigue Life of PCC at Different Stress Levels
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Table 2.2 Fatigue Life of HVFAC at Different Stress Levels
Singh et al (4) aimed to find the two-million-cycle fatigue strengths of SFRC for different volume
fractions of steel fibres and compared with that of plain concrete. The specimens used for flexural
fatigue tests and static flexural tests were fiber concrete beams of size 500 mm100 mm100
mm. The specimens were cast in 9 batches, each batch consisting of 14 fibre concrete beams,
of which 4 were tested in static flexural condition to obtain the flexural strength of the batch
and the remaining 10 were tested in flexural fatigue condition at different stress levels to
obtain the fatigue lives of SFRC. The influence of increasing fiber content can be seen from
Fig.2.2 wherein the ordinate represents applied fatigue stress as percentage of the
corresponding static strength. Increasing the fiber content from 0.0% to at least up to 1.0%improves the fatigue performance significantly, but with further addition of fibres the
performance drops .
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Figure 2.2 S-N
relationships for steel fibre reinforced concrete 50% 50 mm+50% 25mm long fibres based on applied fatigue stress as percentage of static flexural stress.(a) V f =1.0%; (b) V f =1.5%; (c) V f = 2.0%
Girish et al evaluated the influence of stress levels on the flexural fatigue behavior of steel
fiber reinforced concrete [5]. The SFRC beam specimen of size 500mm x 100mm x 100mm
containing mixed steel fibers of size 50mm x 2mm x 0.6mm and 0.5mm 30mm in
different proportions were tested under two point flexural fatigue loading at various stress
levels (0.85, 0.8, 0.75, 0.7). It is observed that at the higher stress amplitude the concrete
specimens sustained fewer cycles to failure and as stress amplitude reduced the no. of cyclesto failure also increased gradually as shown in figure 2.3.
Figure 2.3 Fatigue Life at different Stress Ratio
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2.3.2 Rate of loading
The influence of the frequency of loading has been investigated by several researchers like
Rathby et al. The effect of this is illustrated in Fig. 2.4 where endurance curves are plotted
with the maximum stress in the fatigue cycle expressed as a proportion of the flexuralstrength. The lower endurance curve is based on strength values obtained at a rate of loading
equivalent to that applied in fatigue tests at 20 Hz. The upper curve is based on values
obtained from standard tests at a much slower rate of loading. In general strength values are
more readily obtainable for the standard rate of loading and therefore it is more convenient, if
less correct, to use the conventional strength (upper curve in Fig. 2.4) as a basis for
comparison; this has been done in subsequent analysis. Fatigue tests at two different
frequencies 4 and 20 Hz-showed no significant effect on fatigue performance within this
frequency range. Kesler has suggested that it is only when the strain levels are high enough
to produce significant microcracking that there is likely to be any appreciable effect of rate of
loading [6]. Since the static strength of concrete depends significantly on the rate of loading,
it is anticipated that fatigue performance would also be effected by this parameter. However,
in general, variations of the loading frequency have insignificant effects on fatigue strength
of concrete if the maximum stress level remains less than about 75% of the static strength.
However, for higher stress levels, fatigue strength decreases considerably with decreasing
frequency of loading. Under such conditions, creep effects become more dominant, probably
leading to a substantial reduction in fatigue strength with decreasing rate of loading..
Figure 2. 4 Typical endurance curves for flexural loading at 20 Hz.
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2.3.3 Age at time of loading
As expected, age and curing have a decisive effect on the fatigue strength. Concrete
inadequately cured is less resistant to fatigue than a well cured concrete at a given age. In
general, test data showed increase in fatigue strength of concrete with increase in age asshown in figure 2.5. At the same time there is a corresponding increase in the static strength.
If the fatigue loading is expressed as a proportion of the appropriate mean strength, all the
results lie close to an endurance curve very similar to that derived from constant amplitude
tests on beams cured for 6 months [6].
Figure 2. 5 Variation of fatigue endurance with age.
2.5 Advantages of RPC
The main advantage that RPC has over standard concrete is its high compressive
strength. Richard and Cheyrezy [6] demonstrated RPC with compressive strengths ranging
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from 200 to 800 MPa, and fracture energies up to 40kJ/m 2. Other advantages include low
porosity, improved microstructure and homogeneity, and high flexibility with the addition of
fibres. As a result of its superior performance, RPC has found application in the storage of
nuclear waste, bridges, roofs, piers, seismic-resistant structures and structures designed to
resist impact/blast loading. Owing to its high compression resistance, precast structural
elements can be fabricated in slender form to enhance aesthetics. Durability issues of
traditional concrete have been acknowledged for many years and significant funds have been
necessary to repair aging infrastructure. Reactive Powder Concrete possesses good durability
properties. Lower porosity and capillaries account for its endurance, RPC construction
requires low maintenance costs in its service life.
RPC usually incorporates larger quantities of steel or synthetic fibres and has
enhanced ductility and high temperature performance. This enables structural members to be
built entirely from RPC without the use of conventional transverse reinforcement, relying on
the RPC itself to resist all but the direct longitudinal tension [5].
Several landmark RPC structures exist:
Sherbrooke pedestrian bridge was erected in July 1997 in Quebec, Canada. It is the
worlds first major structure to be built with RPC. It has a 60m span of precast beams [5].
The Shepherds Gully Creek Bridge (in NSW, Australia) is a single span of 15m. It has a
width of 21m and is on a skew of 16 degrees. It is the first RPC construction for normal
highway traffic; it comprises four traffic lanes plus a footway [13].
Seoul Sunyudo footbridge (in South Korea) consists of two steel accesses carried by a
Ductal arch [13]. The span of the arch is 120 m constructed of Ductal, an ultra- high
performance concrete reinforced with fibres. Ductal is a commercial version of RPC.
Cavill and Chirgwin [15] reported that for a typical beam, the RPC solution has less than
35% of the volume of a conventional beam and need not contain any reinforcing bars;however this does not completely offset the higher cost of the materials. Saving in the
cost of the RPC solution can come from the significantly lower weight reducing the
supporting structure costs and reducing the erection costs. Consideration of life cycle
costs also favours an RPC solution.
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Sakata-Mirai Footbridge in Japan Sakata-Mirai Footbridge in Sakata in Japan does not
use any passive reinforcement. It is extremely light with dead weight of only 56 tonnes,
which is approximately one-fifth of the dead load of an equivalent conventional
prestressed concrete structure and results in an economic advantage of around 10% It is
shown in Figure 2.8.
Figure 2.6 Sherbrooke Footbridge, Canada
Figure 2.7 Shepherds Creek Road bridge, Australia Bridge open to traffic
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Figure 2.8 Sakata-Mirai Footbridge in Japan
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Chapter 3
EXPERIMENTAL DETAILS
3.1 Introduction
In order to investigate the behavior of RPC under repeated cyclic loading, several
experimental works have been undertaken. Details of materials employed, mix proportions,
mixing sequences, design of experiments, specimen preparation, experimental tests and
apparatus used will be presented in this chapter. In general, the experimental programme is
mainly to produce, to find out the optimal composition for producing RPC using local
available materials.
3.2 Details of RPC Materials
In this experiment, the constituents used in the RPC mixtures are different from the
conventional concrete mixtures, which include ordinary Portland cement, silica fume, silica
sand, quartz powder, superplasticizer, steel fibers, polypropylene fibers and water. Details of
each constituent are recapitulated as follows.
3.2.1 Ordinary Portland Cement
The cement used throughout the experiments is Ordinary Portland Cement (OPC)
(Table 3.1) that complies with IS: 12269-1987 and has a 28-day mortar compressive strength
of 53 MPa. The density is 3120 kg/m 3 and the fineness is 3390 cm 2/g. The initial and final
setting times are 30 minutes and 565 minutes respectively. The chemical composition is
given in Table 3.1 and confirms to IS: 4032-1985.
3.2.2 Silica fume
Silica fume 920 D from Elkem India Ltd. (Table 3.2) that complies with ASTM C
1240 95a and IS:15388-2003 is used for the present study. The silica fume is extremely
fine with particle size of 0.1 m. It exists in grey powder form that contains latently r eactive
silicon dioxide and no chlorides or other potentially corrosive substances. The dry bulk
density is 0.65 + 0.1 kg. The maximum dosage recommended in literature is about 30 % of
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cement content by weight. For optimum results in concrete, it was suggested to use in
conjunction with Polycarbocilyic ether superplasticizer from its range.
Table 3.1 Properties of 53 Grade OPC
Sl. No. Particulars Test Results IS 12269 Req.Chemical Properties:
1
CaO 0.7SO 3
2.8 SiO 2 + 1.2Al 2O3 + 0.65 Fe 2O3
Lime Saturation Factor (%)
0.86
0.80 Min
1.02 Max
2 TriCalcium silicate (C 3S) 45.38% -
3 DiCalcium silicate (C 2S) 27.06% -4 TriCalcium aluminate (C 3A) 7.04% -
5 Tetra Calcium Aluminoferrate (C 4AF) 13.44% -
6 Al 2O3 / Fe 2O3 Alumina Iron Ratio (%) 1.29 0.66 Min
7 Insoluble Residue (% by mass) 1.36 3.00 Max
8 Magnesia (% by mass) 0.86 6.00 Max
9 Sulphuric Anhydride (% by mass) 2.12 3.00 Max
10 Total Loss on Ignition (% by mass) 2.97 4.00 Max11 Total Chlorides (% by mass) 0.003 0.10 Max
12 Performance Improver: Limestone (%) 2.00 Not Specified
Physical Properties:
13 Fineness (Specific surface) 303 m 2/kg 225 m 2/kg Min
14
Soundness test
a. By Le Chatelier 0.8 mm 10.0 mm Max
b. By Autoclave 0.048 % 0.8 % Max
15
Compressive strength
a. 3 days 42.0 MPa 27.0 MPa Min
b. 7 days 54.7 MPa 37.0 MPa Min
c. 28 days 71.0 MPa 53.0 MPa Min
16 Specific gravity 3.15 Not Specified
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17 Particle Size Range 31 m 7.5 Not Specified
Manufacturer: UltraTech Cement Ltd
Table 3.2 Physical and chemical properties of silica fume
Sl. No. Properties Silica fume
1 Form Ultra fine amorphous powder
2 Colour Grey
3 Specific gravity 2.2
4 Bulk Density 700 kg/m Densified
5 Specific surface 25 m /g
6 Particle size ~15m
7 Sio 2 90%
8 H 2O 1%
9 Make Elkem
3.2.3 Silica Sand
The all of mixes were produced using silica sand which replaced the coarse aggregate
from conventional concrete. The silica sand was brought from Mangalore Karnataka. It is
yellowish-white high purity silica sand. The particle sizes used in the experiments is 90 m
600 m
3.2.4 Quartz Powder
The crushed quartz used in the experiments is white powdered quartz flour which acts
as additive for cement and sand particles and in turn increasing the density. The quartz flour
is brought from Bangalore, India. The particle size ranged from 10 m to 45 m is employed.
The specific gravity of quartz powder is 2.6.
3.2.5 Superplasticizer
The very low w/b (cement + silica fume) ratio used in RPC is only possible with the use of
superplasticizer (SP) to obtain its workability. In this research, the second generation of super
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plasticizer called glenium B-233 and ASTP G - 199 surtec from BASF India Ltd. were used.
The superplasticizer are an extremely high water-reducing agent that meets the requirements
for IS:9103-1999. Descriptions are provided in Table 3.3.
Table 3.3 Properties of Super Plasticizer Sl. No. Properties Glenium B-233 ASTP G-199
1 Type of S.P. Polycarboxylic ether Polycarboxylate polymer
2 Appearance Light brown Dark yellow
3 Density 1.09 1.12
4 pH Value 8 6
5 Sp.Gravity 1.1 1.2
6 Solid content 30% 40%
7Recommended
dosage0.5 to 1.5% 0.3 to 1.2%
3.3 Particle Size Distribution of RPC Materials
Table 3.4 Particle size distribution for Sand
Sieve (mm) Mass (g) % retainedCumulative %
retained% passing
4.75 0 0.0 0.0 100.02.18 8 0.4 0.4 99.61.75 14 0.7 1.1 98.91.00 18 0.9 2.0 98.00.60 51 2.6 4.6 95.50.50 60 3.0 7.6 92.50.30 710 35.5 43.1 57.00.25 695 34.8 77.8 22.20.15 395 19.8 97.6 2.50.09 42 2.1 99.7 0.4
0.063 7 0.4 100.0 0.0Pan 0 0.0 100.0 0.0
Total mass 2000 gm
Table 3.6 Particle size distribution for Quartz powder
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Sieve (mm) Mass (g) % retainedCumulative %
retained% passing
0.09 0 0 0 1000.075 25.20 25.24 25.24 74.760.063 54.65 54.73 79.97 20.03 pan 20.00 20.03 100.00 0.00
Table 3.5 Particle size distribution for Cement
Sieve
(mm)
Mass
(g)
%
retained
Cumulative
% retained
%
passing
0.15 - - - 100
0.09 3.53 3.53 3.53 96.47
0.075 45.61 45.66 49.19 50.81
0.063 43.99 44.04 93.23 6.77
pan 6.76 6.77 100.00 0.00
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Figure 3.1 Particle size distribution graph
The particle size distribution of cement, sand and quartz powder is shown in the figure 3.1.
The size of cement particle ranges from 60 - 200 m , the size of quartz powder is ranges
from 80 - 150 m and that of sand is ranging from 90 m to 4.0 mm. From the figure 3.1 it isclear that quartz powder will fill the void space between cement particles and sand particles.
3.5 Production Process of RPC
This research aims to study the production process utilizing local available materials
in India. RPC was produced under laboratory conditions, with the least complicated process.
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
0.010 0.100 1.000 10.000
P e r c e n
t a g e p a s s
i n g
Particle size (mm)
Particle size distribution graph
Sand
Cement
QuartzPowder
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Since the properties of RPC are dependent on the type and quality of the materials used,
concreting practice, curing conditions, workmanship, etc., RPC mixes developed in one place
may not be applicable to another place where the local conditions are not quite the same.
Therefore, contextual information needs to be considered in the production of RPC. So far,
there is no guideline on how RPC could be produced in India and in world. The production
process of RPC in this research is based on some previous works by other researchers, as
well as our trial-and-error approaches.
3.5.1 Brief Production Guidelines
A set of brief production guidelines proposed for producing RPC using local available
materials in this study is summarized in the following:
A. Constituent materials and Content used
A 1 Cement
Ordinary Portland Cement (OPC) that complies with IS:12269-1987 is to be used for the
production of RPC. Cement with low or zero C 3A content is preferred as it would affect
the performance of RPC. The cement content normally used for the production of RPC is
700 1000 kg/m 3.
A 2 Mineral Additive
A 2.1 Silica fume
Silica fume that complies with IS:15388-2003 can be used. It is the smallest particle with
the average particle size of 0.1 m. For production of RPC, silica fume content is
normally 15-35% of the weight of cement.
A 2.2 Quartz Powder
Local white crushed quartz flour with particle size ranges from 10 m to 45 m is
employed which helps to reduce bleeding and segregation, and modify the CaO/SiO 2
ratio of the binder. The content is generally 20-30% of the weight of cement.
A 3 Aggregate (Silica sand)
Local silica sand with high purity of silica with average particles size ranges from 150
m and 600 m is used. It is dimensionally the largest granular material in RPC mix.
Silica sand constitutes the largest percentage in RPC mix, which is about 1.4 times the
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weight of cement.
A 4 Water
Water for mixing and curing concrete shall be clean, fresh water taken from the public
supply.
A 5 Chemical admixture
A chemical admixture is defined as a constituent material of concrete other than
cementitious materials, mineral additives, aggregates and water. The admixtures shall
comply and be used in accordance with the suppliers recommendation. For production
of RPC, superplasticizer which possesses extremely high water-reducing abilities that
meets the requirements for superplasticising admixtures according to IS:9103-1999
should be used. Any chemical admixtures containing chlorides are prohibited. Large
quantities between 3 and 3.5% by weight of binder are generally added to the RPC mix.B. Maximum Water-to Binder Ratio
The water-to-binder ratio of the RPC minimum shall obtained 0.14.
C. Mixing Procedures
C 1 Dry mixing powders (including cement, silica fume, quartz powder and silica sand)
for about 3 minutes with a low speed of about 140 rpm.
C 2 Addition of sixty percentage volume of water containing half amount of
superplasticizer, and mix for about 3 minutes with a higher speed of about 285 rpm.
C 3 Addition of the remaining water and superplasticizer, and mixed for about 10
minutes with a higher speed of about 285 rpm.
D. Curing
Water curing is the most convenient, practical and economical method in curing concrete.
Temperature of water at 27 + 1C is normally applied.
To achieve higher compressive strength of RPC at early edge accelerated curing at 65 0C
and 90 0C is useful.
3.5.2 Observation
Applying the above production guidelines for producing RPC, some observations are
made during concrete mixing. A long mixing time is required for the RPC mixes for ensuring
that dry-balled particles have become plastic-flowable. The mixing process for the RPC takes
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about 15 to 20 minutes to complete. The extended mixing time was necessary to fully
disperse silica fume, break up any agglomerated particles, and allow superplasticizer for
developing its full potential.. This also implies that RPC requires long mixing time because it
contains only very fine materials. It is suggested that mixers with a high speed are
recommended to break up any agglomerated particles so as to get a homogeneous and
cohesive mix, as well as shorten the mixing time.
3.5.3 Observations during the production of RPC
3.5.3.1 Observations during compaction
Since RPC requires the use of very low w/b ratio and very high cementitious materials
content, the RPC mixes are generally thick, sticky and viscous. Compaction on such a lowworkability concrete or mortar would be a problem. For w/b ratio as low as 0.14, compaction
by vibration table would not be applicable as there is not enough water content for proper
compaction to take place. Hand tamping using a tamping rod would be the only choice.
However, hand tamping done by different people would not be the same as the force that
each of them uses would be different. The void content in the bulk of particles in the paste
may vary greatly from good compaction to bad compaction. This may seriously affect the
performance of RPC. Adding more superplasticizer can increase the workability. However,
there is a limit to the dosage of superplasticizer that can be added. Overdosage of
superplasticizer can lead to chemical incompatibility problems and excessive retardation of
the setting time (Kwan, 2003). It is therefore necessary to find out an optimal mix that can
make compaction easy.
3.5.3.2 Industrialization problems
(a) High costs
Production of RPC places more stringent requirements on material selection and
optimization of composite materials than conventional concrete. In a typical RPC mix design,
the least costly components of conventional concrete (coarse and fine aggregates) have been
replaced by more expensive materials (Silica sand and quartz powder). Silica fume is also
incorporated in RPC. Requirements of RPC for high quality raw materials result in a
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substantial increase in cost over that of conventional concrete (about 3 to 4 times higher).
Moreover, the entire mixing time for RPC takes about 15 minutes which is much longer than
that of conventional concrete which takes only about 5 minutes; and the setting time for RPC
is longer because of the use of high dosage of superplasticizer. This lengthens the entire
construction period and thus increases the cost.
On the other hand, a very high speed mixer is needed to effectively break down those
fine particles, which also leads to high consumption of energy and cost. RPC, due to its high
cost, will not replace ordinary concrete where the conventional concrete can economically
meet the performance criteria (Dauriac, 1997). Though RPC has the potential to structurally
compete with steel, the high production costs of RPC may hinder the construction industry
from accepting such products.
(b) Lack of standards and code of practice
The state of knowledge of RPC is very low in the Indian construction industry. This
new concrete technology has not been acknowledged and vigorously researched locally,
resulting in a problem as the knowledge must be transferred to those doing the work so that
the advancement becomes a state of the practice involvement through research, development
and technology transfer stages is a key to the successful application of new concrete
technology in routine design and practice.
Since the mechanical properties of RPC are different from those of normal strength
concrete (NSC), the existing design codes which are only applicable to structures made of
NSC, need to be modified. For the full implementation of RPC, it would be a long term
process and may require many years of effort. Other barriers which may hinder the
construction industry from implementation of
RPC may include:
Inadequate research
No awareness of need for RPC
The production process to complicated
May got opposition from construction industries and market due to high cost
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Chapter 4MIX DESIGN OF RPC
The reactive powder concrete mixtures with different dosage of silica fume, and with
quartz powder are designed for different w/b ratio. Table 4.1 provides the details of the RPCmix design which are based on some published recommended compositions (Richard and
Cheyrezy, 1995; Cheyrezy et al., 1995; Washer et al., 2004; Shaheen and Shrive,2006). The
RPC mixes are produced using mortar mixer with a speed of about 140-285 revolutions per
minute (rpm). The mix design obtained using mix design procedure of high performance
concrete given by P.C.Aitcin [24].
The volume of cement content like 900 kg/m 3 are considered in the present study.
The Silica fume content of 15 - 20 % by weight of cement was considered. Quartz powder of10 - 20 % by volume of cement was added to the mixes. The superplasticizer of 4 % by
volume of cement was added to the mixes. The water binder ratio of 0.22 was selected for the
mixes.
The details of mix design are are given below:
Table 4.1 Properties of raw material
Sl.No. Material Specific gravity
1 Cement 3.15
2 Silica fume 2.2
3 Quartz Powder 2.6
4 Quartz sand 2.6
5 Super Plasticizer 1.1 to 1.2
6 Water 1
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The two different types of fibers used with different percentage in Control RPC as shown
below
Table 4.2 percentage of fibers used in RPC
Types of
fibers
Percentage of fibers used
Control RPC RPC RPCPP1 RPCPP2 RPCPP3
Steel fibers0 2% volume
of concrete
0 0 0
Polypropylenefibers
0 0 0.2% by
weight of
cement
0.275% by
weight of
cement
0.35% by
weight of
cement
Trial 1: Cement - 900 kg/m 3 and Silica fume - 20 % [without quartz powder]
Cement = 900 kg/m 3
Silica fume = 180 kg/m 3
Water binder = 0.18 % = 194.4 ltr
Super plasticizer = 2 % = 18 ltr
Volume of cement = 900/3.15 1/1000 = 0.285 Cum
Volume of Silica fume = 180/2.2 1/1000 = 0.081 Cum
Volume of water = 0.194 Cum
Volume of super plasticizer = 0.018 Cum
Volume of sand = [1 - (0.285 + 0.081 + 0.194 + 0.018)]= 0.422
= 0.422 2.6 1000
= 1097.2 kg
Extra water for SSD condition = 2 % = (216+23)
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= 240 ml
Table 4.3 Material proportion for 1 kg of Cement
Cement Silica fume Sand Water Superplastisizer
1 0.20 1.219 0.240 0.018
With quartz powder
Volume of quartz powder = 360/2.6 = 0.138 Cum
Volume of sand = 1 - (0.285 + 0.081 + 0.194 + 0.018 + 0.138)
= 1 - 0.716 = 0.284 2.6 1000
= 738.4/900
= 0.820 1200
= 984 gm
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Chapter 5RESULTS AND DISCUSSIONS
5.1 Static Compressive Strength
Standard 150x150x150 mm cubes were tested for 28 days compressive strength in
accordance with I.S. 516-1959 using Servo controlled compression testing machine of 3000
kN capacity. The maximum compressive load on the specimen was recorded as that load at
which the specimen failed to take any further increase in load. The compressive strength was
calculated by dividing the maximum compressive load obtained by area on which the load
was applied. Average of three samples was taken as the representative value of compressive
strength of each batch of concrete. The values of compressive strengths obtained are shown
in Table 5.1. Fig 5.1 shows the testing facility.
Table 5.1 Average Static Compressive Strength Test Results
Batch
No.
28 day compressive strength of concrete (Mpa)
Control
RPC
RPC RPCPP1 RPCPP2 RPCPP3
1 144.6
2 118.4
3 124.8
Average 129.26
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Fig. 5.1 Testing of Concrete Cube
5.1 Static Flexural Strength
To obtain the maximum and the minimum load limits for the fatigue tests, it was obligatory
to estimate the static flexural strength of concrete mixes. Standard 100x100x500 mm beam
specimens were tested for static flexural strength after of 28 days of curing under three-point
loading arrangement using a 500 kN closed-loop servo-controlled actuator. Static flexural
strength tests were carried out to determine the static flexural strength of all mixes prior to its
fatigue testing because once a specimen fails under fatigue loading, it is rather impossible to
determine the static flexural strength. The load was applied at the rate of 0.5 mm/minute.
Three specimens from a particular batch of concrete were tested and maximum load was
noted from the load-deflection curve. The rest of the specimens from a particular batch of
concrete were tested in flexural fatigue with the maximum and minimum loads in fatigue
tests being determined from the static flexural strength so obtained. Static flexural strength
test results for the mixes under study are presented in Table 5.2. The static flexural strength
of RPC 29.5 Mpa .
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Table 5.2 Average Static Flexural Strength Test Results
Batch
No.
28 day compressive strength of concrete (Mpa)
Control RPC RPC RPCPP1 RPCPP2 RPCPP3
1 29.5
2 33.4
3
Average 31.45
5.3 Flexural Fatigue Analysis
After the static flexural strength of a particular batch was set up, remaining specimens were
from the same batch were tested in flexural fatigue. The fatigue parameters include static
flexural strength, stress level, stress ratio and loading frequency. The load cycle characteristic
value or stress ratio R is expressed as R= fmin/fmax, where fmin and fmax refer to the
minimum and maximum fatigue stress . The stress level S is expressed as fmax/fr, where fr
is the static flexural strength. The fatigue tests were performed with stress level ranging from0.5 to 0.3 and at constant stress ratio value of 0.1. The test was carried out in load control
mode using a continuous sinusoidal waveform with a loading frequency of 2 Hz. The test
was continued until the failure of limit was encountered. In this study, fatigue limit is defined
as when either the testing specimen fails or two million cycles limit reached without failure.
Table 5.3 Fatigue Life data obtained experimentally for Mixes under study
Stress Levels(S)
Mix
Control RPC RPC RPCPP1 RPCPP2 RPCPP3
0.3 2000000
0.4 2000000
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0.5 1202000
From the fatigue test data obtained for the different types concretes under investigation S-N
curves are developed using linear regression models, considering log normal distribution.
The linear regression model is of the form (y = ax + c) in which stress ratio (S) is taken on Y-
axis and Log (N) values are taken on the X-axis.
Figure 5.2 Relationship between stress ratio (R) and Log (N)
y = -0.6783x + 4.6243R = 0.75
0
0.1
0.2
0.3
0.4
0.5
0.6
6.05 6.1 6.15 6.2 6.25 6.3 6.35
S t r e s s L e v e
l ( S )
Number of cycles (N)
RPC
RPC
Linear (RPC)
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Chapter 6
CONCLUSIONS1. The maximum compressive strength of 129.26 MPa is achieved with cement
content of 900 kg/m 3 with water binder ratio of 0.22.
2. The numbers of cycles increases as stress level decreases from 0.5 to 0.3.
FUTURE SCOPE
Stress strain characteristics of RPC under cyclic loading
Development of stability point curve under cyclic loading
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REFERENCES