STUDIES ON REACTIVE POWDER CONCRETE-ULTRA HIGH STRENGTH CONCRETE SEMINAR REPORT Submi tted by
N. SIVA RAM KRISHNA ROLL NO: 141519 in the parti parti al f ul fi ll ment ment of the r equir ements ments for Th e award award of the degr degre ee of
MASTER OF TECHNOLOGY IN ENGINEERING STRUCTURES
Under The Guidance of Dr.D.Ravi Prasad Assistant Professor in Civil Engineering Department Department
NATIONAL INSTITUTE OF TECHNOLOGY WARANGAL-506004
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NATIONAL INSTITUTE OF TECHNOLOGY WARANGAL-506004
CERTIFICATE
This is certified that N. SIVA RAMA KRISHNA has submitted the seminar report on “
STUDIES ON REACTIVE POWDER CONCRETE- ULTRA HIGH STRENGTH st
CONCRETE in partial fulfillment of the 1 semester M.Tech course in Engineering ”
Structures as prescribed by the National Institute of Technology, Warangal during . academic year 2014-2015 under the guidance of Dr .D.Ravi Pr asad
Dr.D.Ravi Prasad
Assistant Professor Department of Civil Engineering 2
ACKNOWLEDGEMENTS I express my deep sense of gratitude to Dr.D.Ravi P rasad sir, Assistant Professor in Department of Civil Engineering, National Institute of Technolog y, Warangal for his invaluable guidance, motivation and constant encouragement throughout the course of this seminar work. I will remain thankful to all the faculty members of Depa rtment of Civil Engineering, NIT Warangal for their support during the course of this work. Finally, we express gratitude to our parents for supporting us in every walk of life.
N. Siva Rama Krishna
M.Tech (Engineering Structures) National Institute of Technology, Warangal
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ABSTRACT Concrete is a versatile and critical material for the construction of infrastructure facilities throughout the world. A new developing material known as reactive powder (RPC) is available that differs significantly from traditional concretes. It is catching more attention nowadays because of its high mechanical and durability characteristics. RPC mainly comprise of c ement, 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. There is no coarse aggregate is present in RPC. Since coarse aggregate is the weak link the concrete. The production of very high strength normal weight Reactive powder concrete (RPC) requires detailed investigation of number of factors that have and what can be done to optimized their contribution to the attainment of very high compressive strength. In the present seminar I will focus to study the effects of w/c ratio, amount of silica fume, curing conditions and the effect of mineral, chemical admixtures to achieve compressive strength.
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CONTENTS 1. INTRODUCTION 2. LITERATURE REVIEW 3. COMPOSITION OF REACTIVE POWDER CONCRETE 4. BENEFITS AND LIMITATIONS OF RPC 5. EXPERIMENTAL PROCEDURE 6. RESULTS & DISCUSSIONS 7. CONCLUSIONS 8. REFERENCES
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INTRODUCTION RPC is ultra-high-strength and high ductility cementations composite with advanced mechanical and physical properties. It is a special concrete where the microstructure is optimized by precise gradation of all particles in the mix to yield maximum density. It doesn’t contain 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. RPC with trade name ‘DUCTAL’ was developed in France by researchers Mr. Richard and Mr. Cheyrezy in the early 1990s at Bouygues, laboratory in France. The world’s first RPC structure, the Sherbrooke Bridge in Canada, was constructed in July 1997. 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 av ailable to produce RPC in India, the present study focuses on developing RPC of compressive strength up to 150 MPa. Without using steel fibers we can produce strength up to 200 MPa. This new material demonstrates greatly improved strength and durability characteristics compared with traditional or even high-performance concrete. Classified as Ultra-High Performance Concrete (UHPC), or Reactive Powder Concrete (RPC). The improved properties of RPC are obtained by improving the homogeneity of the concrete by eliminating large aggregates, increasing compactness of the mixtures by optimizing packin g density of fine particles, and using fine steel fibers to provide ductility. RPC will be suitable for pre-stressed application and for structures acquiring light and thin components such as roofs of stadiums, long sp an bridges, space structures, high pressure pipes, and blast resistance structures and the isolation and containment of nuclear wastes.
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LITERATURE REVIEW Many researchers have carried out studies on RPC in the past years to assess the properties and its behavior. Some of the works carried out re discussed below: Richard and Cheyrezy (1995) developed an ultra-high strength ductile concrete with the basic
principles of enhancing the homogeneity by eliminating the coarse aggregate and enhancing the microstructure by post-set heat treatment. In addition, the ductility and tensile strength of conc rete is increased by incorporating small, straight, high tensile micro fibers. Two types of concretes are developed and designated as RPC 200 and RPC 800. These concretes had exceptional mechanical properties, which resulted in elimination of reinforcement, and reduction of materials resulting in reduction of self-weight resulting in cost savings. The concrete finds its ap plications in industrial and nuclear waste storage silos. Chan and Chu, [2002 ] has studied the effect of silica fume on the bond characteristics of steel fiber in
matrix of reactive powder concrete (RPC) by bond strength, pullout energy, etc. Various silica fume contents ranging from 0% to 40% are used in the mix proportions. Results of them show that the incorporation of silica fume can effectively enhance the fiber – matrix interfacial properties, especially in fiber pullout energy. Dili and Manu Santhanam (2005) developed two RPC mixes of 200MPa and 800MPa strength,
which could be suitable for nuclear waste containment structures. The workability and durability properties were studied for the designed RPC mix. Also characterization of mechanical properties was carried out. The durability test carried out for the RPC mixes showed that the flow table test was in the range of 120%-140% and the water and chloride ion Permeability is extremely low. These test results indicates the suitability of the designed RPC mix for nuclear waste containment structures. S. Lavanya Prabha [2010] conducted a study on complete stress-strain curves from uniaxial
compression tests. The effect of material composition on the stress strain behavior and the toughness index were studied. The highest cylinder compressive strength of 171.3 MPa and elastic modulus of 44.8 GPa were recorded for 2% 13 mm length fibers. The optimum fiber content was found to be 3% of 6mm length or 2% of 13mm length fibres. A new measure of compression toughness known as MTI (modified toughness index) was proposed by them and it is found to range from 2.64 to 4.65 for RPC mixes.
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COMPOSITION OF REACTIVE POWDER CONCRETE RPC is composed of very fine powders (cement, sand, quartz powder, steel aggregates and silica fume), steel fibres (optimal) and a super plasticizer. The super plasticizers, used at its optimal dosage, decrease the water to cement ratio (w/c) while improving the workability of the concrete. A very dense matrix is achieved by optimizing the granular packing of the dry fine powders. This compactness gives RPC, ultra-high strength and durability. Reactive powder concretes have compressive strengths ranging from 200 MPa to 800 MPa. Mr. Richard and Mr. Cheyrezy indicate the following principles for developing RPC. 1. Enhancement of homogeneity by elimination of coarser aggregates. 2. Enhancement of compacted density by optimization of the granular mixture. 3. Enhancement of the microstructure by Post-set heat-treatment 4. Enhancement of ductility by addition of small-sized steel fibres 5. Application of pressure before and during setting to improve compaction 6. Utilization of the pozzolonic properties of silica fume. 7. The optimal usage of super plasticizer to reduce w/c and improve workability.
Table 1 lists salient properties of RPC, along with suggestions on how to achieve them. Table 2 describes the different ingredients of RPC and their selection parameters. Th e tables are obtained from literature. The mixture design of RPC primarily involves the creation of a dense granular skeleton. Optimization of the granular mixture can be achieved either by the use of packing models or by particle size distribution software, such as LISA [developed by Elkem ASA Materials].
Table: 1 Properties of RPC enhancing its homogeneity and strength Property of
Description
Recommended Values
RPC
Types of failure eliminated
Coarse aggregates are Reduction in
replaced by fine sand,
Maximum size of fine
Mechanical,
aggregate size
with a reduction in the
sand is 600 µm
Chemical &
size of the coarsest
Thermo-mechanical
aggregate by a factor of about 50. 8
Improved mechanical
Young’s modulus
Enhanced mechanical
properties of the paste
values in 50 GPa – 75
Disturbance of the
properties
by the addition of silica
GPa range
mechanical stress field.
fume Reduction in aggregate
Limitation of sand
Volume of the paste is
to matrix ratio
content
at least 20% greater
By any external source
than the voids index of
(e.g., formwork).
non-compacted sand.
Table 2: Selection Parameters for RPC components Components
Selection
Function
Particle Size
Types
Readily available
Give strength,
150 µm
Natural,
and low cost.
Aggregate
to
Crushed
parameters
Sand
Good hardness
Cement
600 µm
C3S: 60%;
Binding material,
C2S : 22%;
Production of
1 µm
OPC,
C3A : 3.8%;
primary hydrates
to
Medium
100 µm
fineness
C4AF: 7.4%. (optimum) Quartz Powder
Max. reactivity
5 µm
during heat-
to
treating
25 µm
Very less quantity
Filling the voids,
0.1 µm
Procured from
of impurities
Enhance
to
ferrosilicon
rheology,
1 µm
industry
fineness
Silica fume
Production of secondary hydrates 9
Crystalline
Steel fibers
Good aspect ratio
Improve ductility
L : 13 – 25 mm
Straight
Ø : 0.15 – 0.2 mm Super Plasticizer
Less retarding
Reduced W/C
-
characteristic
Polyacrylate based
BENEFITS AND LIMITATIONS OF RPC
Benefits of RPC: i.
RPC is a better alternative to High Performance Concrete and has the potential to structurally compete with steel.
ii.
Its superior strength combined with higher shear capacity results insignificant dead load reduction and limitless structural member shape.
iii.
With its ductile tension failure mechanism, RPC can be u sed to resist all but direct primary tensile stresses. This eliminates the need for supplemental shear and other aux iliary reinforcing steel.
iv.
RPC provides improve seismic performance by reducing inertia loads with lighter members, allowing larger deflections with reduced cross sections, and providing higher energy absorption.
v.
Its low and non-interconnected porosity diminishes mass transfer making penetration of liquid/gas or radioactive elements nearly non-existent.
Limitations of RPC: In a typical RPC mixture design, the least costly components of conventional concrete are basically eliminated or replaced by more expensive elements. The fine sand used in RPC becomes equivalent to the coarse aggregate of conventional concrete, the Portland cement plays the role of the fine aggregate and the silica fume that of the cement. The mineral component optimization alone results in a substantial increase in cost over and above that of conventional concrete (5 to 10 times higher than HPC). RPC should be used in areas where substantial weight savings can be realized and where some of the remarkable characteristics of the material can be fully utilized. Since RPC is in its developing stage, the long-term properties are not known.
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EXPERIMENTAL PROCEDURE 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 b y varying the constituent materials and cured at both normal and high temperature before testing for their strength. Materials Used in Mix design: Cement: The Ultra-Tech 53 Grade Ordinary Portland cement (OPC) which complies with IS: 12269-
1987 is used in the present study. Its specific gravity is 3.15 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 contains sio2 90%. Maximum size of the particle is 15μm. Its specific gravity is 2.2 Quartz Powder - The crushed quartz with particle size ranging from 10μm to 45μm is used. The
specific gravity of quartz powder is 2.6 Silica Sand: It is yellowish-white high purity silica sand. The particle size of sand is 150μm – 600μm. Super Plasticizer: The very low w/b ratio required for RPC can be achieved with use of super
plasticizer (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. 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 th e 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. Super plasticizer dosage varied from 1 to 4 percent for all the mixes. Detailed mix proportioning is mentioned in Table 3 from literature.
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Table 3: Proportioning of RPC mixes MIX
TM1
TM2
TM3
TM4
TM5
15% silica fume
MATERIAL
TM6
TM7
TM8
TM9
TM10
TM11
TM12
TM13
TM14
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 Fume
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
-
-
-
-
-
-
-
-
-
-
-
0.2
0.2
0.2
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 ratio
0.16
0.18
0.20
0.22
0.24
020
0.22
0.24
0.20
0.22
0.24
0.18
0.2
0.22
SP %
3
2.5
2
1.5
1
3
2.5
2
4
3
2
3
2.5
2
Curing Regime
Water curing at room temperature and steam curing at 9 0 0c for 48 hours.
Quartz Powder
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. The casted specimens were tested for 7days and 28 days compressive strength.
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RESULTS AND DISCUSSIONS 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, super plasticizer 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 conten t 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. Effect of water to binder ratio on compressive strength: The strength of concrete depends upon the
hydration process in which water plays critical role. The effect of W/ b ratio on compressive strength is shown in fig. 1 at different curing da ys. From the results we came to know that optimum w/b 0.2 which gives more compressive strength. The reduction strength at lower w/b ratio is due to insufficient amount of water for complete hydration process to occur.
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Beyond 0.2 strength is decreasing due to excess amount of water which will create entrainment of air bubbles. The compressive strengths of all mix proportions at 7 and 28 days are tabulated in Table 4 Table 4: Compressive strength of RPC Accelerated Curing at 900C for 48
Normal Curing at 27 C
hours
Sample No
Compressive strength at 7 days N/mm2
Compressive strength at 28 days N/mm2
Compressive strength at 7 days N/mm2
Compressive strength at 28 days N/mm2
TM-1
72
116
81
124
TM-2
70
120
85
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
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Effect of Silica fume content on compressive strength of RPC:
The effect of varying percentage of silica fume on the compressive strength of RPC mix is demonstrated in Fig. 2. 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 super plasticizer to disperse in fresh concrete.
Fig 2. Effect of Silica fume on compressive strength
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Effect of Addition of quartz powder:
Quartz powder improves the filler effect in RPC mix. Quartz powder produce the better result under accelerated curing condition than that of normal curing condition which is shown in Fig 3. The results show that the addition of quartz powder increases the compressive strength by 20% under the accelerated curing condition.
Fig 3: The effect of Quartz powder on compressive strength of RPC
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Influence of Curing Regime:
An adequate supply of moisture is necessary to ensure that hydration is sufficient to reduce th e 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. 4. 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.
Fig 4: Effect of curing regime on Compressive strength of RPC
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CONCLUSIONS Following are the conclusions that can be drawn from laboratory results: a. The maximum compressive strength of RPC obtained in the present study is 146 MPa at W/b ratio of 0.2 with accelerated curing. b. In the production of RPC the optimum percentage addition of silica fume is found to be 15% (by weight of cement) with available super plasticizer. c. The addition of quartz powder increases the compressive strength of RPC up to 20% d. 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.
Reactive Powder Concrete (RPC) is an emerging technology that lends a new dimension to the term ‘high performance concrete’. It has immense potential in construction due to its superior mechanical and durability properties compared to conv entional high performance concrete, and could even replace steel in some applications. The development of RPC is based on the application of some basic principles to achieve enhanced homogeneity, very good workability, high compaction, improved microstructure, and high ductility. RPC has an ultra-dense microstructure, giving advantageous waterproofing and durability characteristics. It could, therefore, be a suitable choice for industrial and nuclear waste storage facilities. Its application in India is very little or nil due to there is no experimental guidelines. Currently research is going on this RPC at CSIR-SERC, Chennai.
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REFERENCES
1. Richard P., Cheyrezy M., Composition of Reactive Powder Concretes, Cement and Concrete Research, Vol. 25, No. 7, pp. 1501-1511, 1995. 2. Cheyrezy M. et al., Microstructural Analysis of RPC, Ce ment and Concrete Research, Vol. 25, No. 7, pp. 1491-1500, 1995. 3. S. Lavanya Prabha., J.K.Dattatreya., Stud y on stress-strain properties of reactive powder concrete under uniaxial compression, International Journal of Engineering Science and Technology Vol. 2(11), 2010, 6408-6416. 4. MK.Maroliya., An Investigation on Reactive Powder Concrete containing Steel Fibers and FlyAsh, International Journal of Emerging Technology and Advanced Engineering, Volume 2, Issue 9, September 2012. 5. Khadiranaikar R.B. and Muranal S. M., Factors affecting the strength of Reactive Powder Concrete, International Journal of Civil Engineering and Technolo gy,Volume 3, Issue 2, JulyDecember (2012), pp. 455-464. 6. Mr.Anjan kumar M U, Dr. Asha Udaya Rao, Dr. Narayana Sabhahit,Reactive Powder Concrete Properties with Cement Replacement Using Waste Material, International Journal of Scientific & Engineering Research Volume 4, Issue 5, May-2013. 7. http://www.theconcreteportal.com/ 8. http://rebar.ecn.purdue.edu/ect/links/technologies/civil/reactive.aspx
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