Factors affecting the strength of reactive powder concrete rpc

INTERNATIONAL JOURNAL and Technology (IJCIET), ISSN 0976 – 6308
International Journal of Civil Engineering OF CIVIL ENGINEERING AND
(Print), ISSN 0976 – 6316(Online) Volume 3, Issue 2, July- December (2012), © IAEME
TECHNOLOGY (IJCIET)
ISSN 0976 – 6308 (Print)
ISSN 0976 – 6316(Online)
Volume 3, Issue 2, July- December (2012), pp. 455-464
IJCIET
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FACTORS AFFECTING THE STRENGTH OF REACTIVE POWDER
CONCRETE (RPC)

Khadiranaikar R.B. and Muranal S. M.

Mr. Santosh M. Muranal M.Tech (Str.Engg)
Assistant Professor, Dept. of Civil Engineering
Basaveshwar Engineering College
Vidyagiri, BAGALKOT-587102
Karnataka, India
Email-Id: murnal.santosh@gmail.com
Dr. R. B. Khadiranaikar M.E, PhD(IIT, Delhi)
Professor, Dept. of Civil Engineering
Basaveshwar Engineering College
Vidyagiri, BAGALKOT-587102
Karnataka, India
Email-Id: dr.rbknaikar@gmail.com

ABSTRACT

Reactive Powder Concrete (RPC) is catching more attention now days because of its high
mechanical and durability characteristics. RPC mainly comprises of cement, silica fume,
silica sand, quartz powder and steel fibers. RPC has been able to produce with compressive
strength ranging from 200 MPa to 800 MPa with flexural strength up to 50 MPa. Although
suitable guidelines are not available to produce RPC in India, the present study focuses on
developing RPC of compressive strength up to 150 MPa. Along with the development of
RPC, various factors affecting the strength of RPC are studied. The 100×100×100 mm size
RPC cube specimens were cast by varying the constituent materials and cured at both normal
and high temperature before testing for their strength. The compressive strength of 146 MPa
was achieved with the mix considered. It is observed from the study that w/b ratio, silica
fume content, quartz powder, high temperature curing significantly affects the compressive
strength of RPC. It was observed that addition of quartz powder and high temperature curing
increases the compressive strength up to 10 percent when compared with specimens tested
after normal room temperature curing. The material can be effectively utilized in the
production of precast elements/PSC structures.

455

International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308

Keywords: Reactive powder concrete, silica fume, quartz powder, accelerated curing, compressive
strength.

1. INTRODUCTION

Reactive Powder Concrete (RPC) is an ultra high strength and high ductile composite material with
advanced mechanical properties. Reactive powder concrete is a concrete without coarse aggregate, but
contains cement, silica fume, sand, quartz powder and steel fiber with very low water binder ratio.
The absence of coarse aggregate was considered by inventors to be key aspect for the microstructure
and performance of RPC in order to reduce the heterogeneity between cement matrix and aggregate
(Richard et al. 1995).
The original concept of RPC was first developed, in early 1990, by researchers at Bouygues
laboratory in France. The addition of supplementary material, elimination of coarse aggregates, very
low water/binder ratio, additional fine steel fibers, heat curing and application of pressure before and
during setting were the basic concepts on which it was developed (Richard et al. 1995). Compressive
strength of RPC ranges from 200 to 800 MPa, flexural strength between 30-50 MPa and Young’s
modulus up to 50-60 GPa. There is a growing use of RPC owing to the outstanding mechanical
properties and durability. RPC structural elements can resist chemical attack, impact loading from
vehicles and vessels, and sudden kinetic loading due to earthquakes. Ultra high performance is the
most important characteristic of RPC (Gilliland et al. 2007). RPC is composed of more compact and
arranged hydrates. The microstructure is optimized by precise gradation of all particles in the mix to
yield maximum density. It uses extensively the pozzolonic properties of highly refined silica fume and
optimization of the Portland cement chemistry to produce highest strength hydrates (Cheyrezy et al.
1995; Reda et al. 1999).
RPC will be suitable for pre-stressed application and for structures acquiring light and thin
components such as roofs of stadiums, long span bridges, space structures, high pressure pipes, blast
resistance structures and the isolation and containment of nuclear wastes (Gowripalan et al. 2003;
Bonneau et al. 1996; Hassan et al. 2005). In India the work on RPC has started from last few years.
SERC, Chennai, worked towards the development of the UHSPC with and without steel fibers and the
effect of various heat curing regimes adopted on the strength properties of the mixtures (Harish et al.
2008). Dili A.S. and Manu Santhanam (2004) have studied mix design, mechanical properties and
durability aspects of RPC. The utility of RPC in actual construction is minimal or nil in India, it is
because of non-availability of sufficient experimental data regarding production and performance of
RPC. So the basic objective of the current investigation is to experience the production of RPC. The
key issues of the study are: to develop RPC of compressive strength up to 150 MPa, to determine the
effect of silica fume content on compressive strength, to determine the effect of high temperature
curing on the compressive strength and to determine the effect of addition of quartz powder on the
compressive strength of RPC.
As the standard code is not available to design RPC, here an attempt is made to design RPC mix with
locally available materials referring literature. The RPC cube specimens were cast and cured for both
normal and high temperature curing. The cured specimens were tested to evaluate the compressive
strength.

2. EXPERIMENTAL DETAILS

2.1 Raw Materials

2.1.1. Cement
The Ultra-Tech 53 Grade Ordinary Portland Cement (OPC) which complies with IS: 12269-1987
is used in the present study. The physical and chemical properties are given in Table 1.

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Table 1 Properties of 53 Grade OPC
Sl.No. Particulars Test Results IS 12269 Requirement
Chemical Properties:
CaO - 0.7SO3
0.80 min
1 0.87 1.20 max
2.8 SiO2 + 1.2Al2O3 + 0.65 Fe2O3
1.02 Max
Lime Saturation Factor (%)
2 TriCalcium silicate (C3S) 45.38% -
3 DiCalcium silicate (C2S) 27.06% -
4 TriCalcium aluminate (C3A) 7.04% -
5 Tetra Calcium Aluminoferrate (C4AF) 13.44% -
6 Al2O3 / Fe2O3 1.20 0.66 min
7 Insoluble Residue (% by mass) 2.25 5.00 max
8 Magnesia (% by mass) 1.0 6.00 max
9 Sulphuric Anhydride (% by mass) 2.01 3.00 max
10 Total Loss on Ignition (% by mass) 1.8 4.00 max
11 Total Chlorides (% by mass) 0.016 0.10 max
Performance Improver: 2.5
12 Limestone (%) 2.4 5 max
Fly ash (%)
Physical Properties:
13 Fineness (Specific surface) (m2/kg) 294 225 min
14 Setting time (min)
a. Initial 160 30
b. Final 255 600
15 Soundness test
a. By Le Chatelier (mm) 1.0 10.0 max
b. By Autoclave (%) 0.090 0.8 % max
16 Compressive strength (MPa)
a. 3 days 37.0 27.0 min
b. 7 days 48.8 37.0 min
c. 28 days 68.8 53.0 min

2.1.2. Ultrafine Powders
The Silica fume – 945 D from Elkem India Ltd. which complies with ASTM C 1240 –
95a and IS:15388-2003 is used in the study. It is in grey powder form which contains latently
reactive silicon dioxide and no chlorides or other potentially corrosive substances. The
physical and chemical properties are mentioned in Table 2.
Quartz Powder - The crushed quartz with particle size ranging from 10 µm to 45 µm is
used. The specific gravity of quartz powder is 2.6

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Table 2 Physical and chemical properties of silica fume
Sl. No. Properties
1 Form Ultra fine amorphous powder
2 Colour Grey
3 Specific gravity 2.2
4 Bulk Density 700 kg/m3 Densified
5 Specific surface 25 m2/g
6 Particle size 15 µm
7 Sio2 90%
8 H2 O 1%

2.1.3. Aggregate
The fine silica sand is the large sized aggregate in RPC. It is yellowish-white high purity
silica sand. The particle size of sand is 150 µm – 600 µm. The particle distribution graph of
all fine materials is shown in Fig.1

Particle size distribution graph
100.0

90.0

80.0
Percentage passing

70.0

60.0

50.0

40.0

30.0

20.0

10.0

0.0

0.001 0.010 0.100 1.000 Sand 10.000

Cement
Particle size (mm)
Quartz Powder

Fig. 1 Partical distribution graph of fine materials

2.1.4. Superplasticizer
The very low w/b ratio required for RPC can be achieved with use of superplasticizer
(SP) to obtain good workability. In this study, the 2nd generation of super plasticizer called
Glenium B-276 Surtec from BASF India Ltd. was used. It is an extremely high range water-
reducing agent which meets the requirements of IS: 9103-1999. The properties of
superplasticizer are given in Table 3.

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Table 3 Properties of Superplasticizer
Sl. Properties Glenium B-276
No.
1 Type of S.P. Polycarboxylate polymer
2 Appearance Dark brown
3 pH Value 6
4 Sp.Gravity 1.2
5 Solid content 40%
6 Recommended dosage 0.3 to 1.2%

2.2. Experimental Procedures
2.2.1 Mix Proportioning
To study the influence of the constituent materials, 14 different proportions were considered by
varying water-binder ratio, silica fume and quartz powder content. Cement of quantity 900 kg/m3 was
kept constant for all the mixes. The water-binder ratio of the mixes varied from 0.16 to 0.24. Silica
fume was added by 15 to 25 percent by weight of cement. 20 percent of quartz powder by weight of
cement was also added for few mixes. Superplasticizer dosage varied from 1 to 4 percent for all the
mixes. Detailed mix proportioning is mentioned in Table 4.

Table 4 Proportioning of RPC mixes
M i x TM1 TM2 TM3 TM4 TM5 TM6 TM7 TM8 TM9 TM10 TM11 TM12 TM13 TM14

Material 15% silica fume 20 % silica fume 25% Silica fume 15% Silica fume + 20%
Quartz Powder

Cement 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Silica
0.15 0.15 0.15 0.15 0.15 0.20 0.20 0.20 0.25 0.25 0.25 0.15 0.15 0.15
fume

Quartz
- - - - - - - - - - - 0.2 0.2 0.2
powder

Sand 1.33 1.28 1.24 1.19 1.15 1.16 1.11 0.91 0.98 0.98 0.92 0.82 0.82 0.82

W/B 0.16 0.18 0.20 0.22 0.24 0.20 0.22 0.24 0.20 0.22 0.24 0.18 0.2 0.22
ratio
SP in % 3 2.5 2 1.5 1 3 2.5 2 4 3 2 3 2.5 2

Curing Water curing at room temperature and steam curing at 900c for 48 hours.
regime

2.2.2 Mixing Procedure
The high speed mortar mixer is used to mix the ingredients of RPC. The mixing sequence
is as follows: 1. Dry mixing the powders (including cement, silica fume, quartz powder and
silica sand) for about 3 minutes with a low speed of about 140 rpm. 2. Addition of sixty
percentage volume of water and mix for about 3 minutes with a higher speed of about 285
rpm. 3. Addition of the remaining water and superplasticizer, and mixed for about 10 minutes
with a higher speed of about 285 rpm.

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2.2.3 Sample Preparation and Curing
For each batch of concrete, 100 x 100 x 100 mm cubes were cast to evaluate compressive strength
(IS:10086-1999). The specimens were cured at both normal temperature for 28 days and at 90° C for
48 hours, remaining 26 days at normal temperature.

2.2.4 Testing
Three cube specimens were cast and tested with each RPC mix proportion to evaluate
compressive strength at 7 and 28 days. All tests were carried out using compression testing machine.

3. RESULTS AND DISCUSSION
Arriving at optimal composition with locally available materials is important to achieve the best
overall performance of RPC. Hence, the effects of several parameters on compressive strength were
investigated which include water-to-binder ratio, superplasticizer dosage, different percentage of
silica fume, with and without quartz powder and curing regime. During the study it was observed that
the mixes appeared to be very sensitive to any variation of the chemical composition of the binders or
particle size distribution of the fillers. As there are no standard guidelines for the mix design of RPC,
literature was referred to design the mixes. The silica fume content was varied from 15 to 25 percent
by weight of cement to find the optimum percentage of silica fume in the production of RPC. To
study the influence of addition of quartz powder to RPC, the RPC mixes were also designed with
addition of quartz powder by 20 percent by weight of cement.

3.1. Density of RPC Specimens
The density of all the specimens recorded varied between 23.3 – 24.7 kN/m3.

3.2. Effect of Water-to-Binder Ratio on Compressive Strength of RPC
The strength of concrete is very much dependent upon the hydration reaction in which water plays
a critical role, particularly the amount of water used. The effect of w/b ratio on compressive strength
under various curing ages is shown in Fig. 2. The result demonstrates that an optimal w/b ratio that
gives the highest compressive strength of RPC in the present study is 0.2. The reduction in strength at
lower w/b ratio may be due to the lack of adequate amount of mixing water in RPC to ensure adequate
compaction and proper hydration to occur.

Effect of water-to-binder ratio on compressive strength of RPC
Fig. 2 Effect
140
of 128
water-
120 120
Compressive Strength N/mm2

116
to- 110 112 binder
100 Avg.
94
ratio 80
Compressive
strength at 7 days
on
72 70 69 66
60

40
Avg.
20 Compressive
strength at 28
days
0
WB.-0.22

WB.-0.24
WB-0.16

WB-0.18

WB-0.20

compressive strength of RPC

460


Beyond this optimal w/b ratio of 0.2, it was found that compressive strength decreases
with increasing w/b ratios. This may be because of more water which is susceptible to
entraining air bubbles due to the folding action of the mixing process. As a result, more voids
are left in the matrix which increase the porosity and thus considerably reduce the
compressive strength. The compressive strengths of all mix proportions at 7 and 28 days are
tabulated in Table 5.

Table 5 Compressive strength of RPC with Glenium B- 276

Normal Curing at 27oc Accelerated Curing at 90 oc for 48 hours

Sample Compressive Compressive Compressive Compressive
no strength at 7 days strength at 28 strength at 7 days strength at 28
N/mm2 days N/mm2 days
N/mm2 N/mm2

TM-1 72 116 81 124
TM-2 70 120 83 132
TM-3 94 128 99 138
TM-4 69 110 78 121
TM-5 66 112 76 119
TM-6 62 93 - -
TM-7 58 95 - -
TM-8 56 87 - -
TM-9 61 96 - -
TM-10 55 90 - -
TM-11 57 85
TM-12 88 112 94 138
TM-13 91 117 105 146
TM-14 85 109 89 122

3.3 Effect of Silica Fume Percentage on Compressive Strength of RPC
The effect of varying percentage of silica fume on the compressive strength of RPC mix is
demonstrated in Fig. 3. It is observed that the compressive strength tends to decrease as the
silica fume dosage increases. The highest compressive strength was observed for addition of
15% silica fume. The compressive strength is seen to fluctuate in the range of 15 % to 25% of
silica fume regardless of water/binder ratio. As silica fume content increases, mix requires
more superplasticizer to disperse in fresh concrete.

461


Effect of Silica fume on Compressive strength
140

130
Compressive strength N/mm2

120

110

100 W/B 0.2
W/B 0.22
90
W/B 0.24
80

70

60
15% 20% 25%
% Silica fume

Fig. 3 Effect of silica fume on compressive strength of RPC
3.4 Effect of Addition of Quartz Powder
From the literature it is learnt that, hydrated cement alone cannot help to elevate the strength of
RPC, but other finer materials also contribute marginally. Quartz powder improves the filler effect in
RPC mix. As shown in Fig. 4 the addition of quartz powder produce the better result under
accelerated curing condition than that of normal curing condition. The results show that the addition
of quartz powder increases the compressive strength by 20% under the accelerated curing condition.
This is possible due to increased proportion of hard, fine fillers that enhance the packing density and
pore filling action.

Effect of curing regime on addtion of quartz powder
160
146
138
140
122
117
120 112 Avg. Compressive strength a t
109
105 7 da ys for norma l curing
Compressive strengthN/mm2

100 94 Avg. Compressive strength a t
91 89
88 28 days for norma l curing
85

80 Avg. Compressive strength a t
7 da ys for a ccelera ted curing

60 Avg. Compressive strength a t
28 days for a ccelera ted
curing
40

20

0
TM-12 TM-13 TM-14

Fig. 4 The effect of Quartz powder on compressive strength of RPC

462


3.5 Influence of Curing Regime
An adequate supply of moisture is necessary to ensure that hydration is sufficient to
reduce the porosity to a level such that the desired strength can be attained. The effect of
curing regime on compressive strength under various curing ages is shown in Fig. 5. Two
curing methods were exercised, one with normal water curing at 27ºC, and other at 90ºC hot
water curing for 48 hours. The compressive strength increased by 10% when cured in hot
water as compared to normal curing. This indicates that curing temperature has a significant
effect on the early strength development of RPC. The increased strength is due to the rapid
hydration of cement at higher curing temperatures of 90°C compared to that of 27°C.
Moreover, the pozzolonic reactions are also accelerated by the higher curing temperatures.

Effect of curing regime

160
146
138 138
140 132 128
124 120 121 122
116 119 117
Compressive strength Mpa.

120 110 112 112 109

100 28 days compressive
strength of nornal curing
80

60

40 28 days compressive
strength of accelerataed
20 curing

0
T-1

T-2

T-3

T-4

T-5

T-12

T-13

T-14

Specimen

Fig. 5 Effect of curing regime

4. CONCLUSIONS

From the present study the following conclusions may be drawn;
1. During the production process, it was found that an extended mixing time up to 20-30
min. is required to obtain a consistent and homogeneous mix.
2. The maximum compressive strength of RPC obtained in the present study is 146 MPa at
w/b ratio of 0.2 with accelerated curing.
3. In the production of RPC the optimum percentage addition of silica fume is found to be
15% (by weight of cement) with available superplasticizer.
4. The addition of quartz powder increases the compressive strength of RPC up to 20%
5. The high temperature curing is essential for RPC to achieve higher strength. It increases
the compressive strength up to 10% when compared with normal curing.

463


ACKNOWLEDGEMENTS

The authors would like to sincerely thank Mr. Nagesh Chitari for preparing the
specimens and helping to conduct the relevant tests. This research was funded by the
Visveswaraya Technological University, Belauam, Karnataka, India through VTU Research
Grant Scheme.

REFERENCES

1. Richard P., Cheyrezy M., Composition of Reactive Powder Concretes, Cement and
Concrete Research, Vol. 25, No. 7, pp. 1501-1511, 1995.
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Concrete Bridge Girders, Building an International Community of structural Engineers,
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3. Cheyrezy M. et al., Microstructural Analysis of RPC, Cement and Concrete Research,
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4. Reda M.M. et al., Microstructural Investigation of innovative UHPC, Cement and
Concrete Research, Vol. 29, pp. 323-329, 1999.
5. Gowripalan N. et al., Reactive powder concrete for precast structural concrete, 21st
Biennial conference concrete institute of Australia, Brisbane, pp. 99- 108, 2003.
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materials and fiber reinforced concrete, ACI structural Journal, Vol. 102, No. 5, pp. 709-
718, 2005.
8. Harish K V et al., Role of ingredients and of curing regime in ultra high strength powder
concretes, Journal of Structural Engineering, Vol. 34, No. 6, pp. 421-428, 2008.
9. Dili A S., Manu Santhanam, Investigation on reactive Powder Concrete: A developing
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10. M.N.Bajad, C.D.Modhera and A.K.Desai, “Influence Of A Fine Glass Powder On Strength Of
Concrete Subjected To Chloride Attack” International Journal of Civil Engineering &
Technology (IJCIET), Volume2, Issue2, 2011, pp. 1 - 12, Published by IAEME
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IAEME

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Factors affecting the strength of reactive powder concrete rpc

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