seminar report on reactive powder concrete (Civil engineering).docx

Reactive powder concrete A Seminar Report Submitted in partial fulfillment of the requirements of the degree of BACHELOR OF TECHNOLOGY IN CIVIL ENGINEERING

By D. Siddhartha(UG101218)

DEPARTMENT OF CIVIL ENGINEERING NATIONAL INSTITUTE OF TECHNOLOGY, WARANGAL 2013-2014

Table of Contents Abstract................................................................................................................................. 4 1. Introduction ....................................................................................................................... 5 1.1 Defining Reactive powder concrete ............................................................................. 5 1.2 History and development of RPC ................................................................................. 5 1.3 Scope of RPC .............................................................................................................. 5 2. Composition of RPC.......................................................................................................... 6 2.1 Introduction.................................................................................................................. 6 2.2 RPC components ........................................................................................................ 6 2.2.1 Cement ................................................................................................................. 6 2.2.2 Sand ..................................................................................................................... 6 2.2.3 Quartz powder ...................................................................................................... 7 2.2.4 Silica fume ............................................................................................................ 7 2.2.5 Steel fibers ............................................................................................................ 7 2.2.6 Super plasticizer.................................................................................................... 7 2.2.7 Table showing components of RPC ...................................................................... 7 2.3 Mix proportion of RPC ................................................................................................. 8 3. Properties of RPC ............................................................................................................. 9 3.1 Introduction.................................................................................................................. 9 3.2 Typical properties of RPC 200 ................................................................................... 10 3.3 Typical properties of RPC 800 ................................................................................... 10 3.4 Comparison of RPC and HPC ................................................................................... 11 3.5 Fresh concrete properties .......................................................................................... 11 3.6 Compressive strength ................................................................................................ 12 3.7 Flexural strength ........................................................................................................ 12 3.8 Water absorption ....................................................................................................... 13 3.9 Water permeability..................................................................................................... 13

3.10 Resistance to chloride ion penetration ..................................................................... 14 4. Factors effecting strength of RPC ................................................................................... 15 4.1 Silica Fume Percentage............................................................................................. 15 4.2 Quartz Powder........................................................................................................... 15 4.3 Curing Regime........................................................................................................... 15 4.4 Compressive and tensile properties of RPC at elevated temperatures ...................... 15 4.5 Effect of pre-setting pressure ..................................................................................... 15 5. Advantages ..................................................................................................................... 16 6. Limitations ....................................................................................................................... 16 7. Structures built using RPC .............................................................................................. 17 8. Case study ...................................................................................................................... 17 8.1 THE SIDEWALK SYSTEM OF THE QINGHAI-TIBET RAILWAY BRIDGE ................ 17 8.2 Pedestrian bridge in Sherbrooke ............................................................................... 18 9. References ..................................................................................................................... 19

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 and in some cases can replace traditional steel reinforcement. RPC will allow the concrete industry to optimize material use, generates economic benefits, and build structures that are strong and durable. Present seminar mainly discusses on composition and Mix proportion of RPC, properties and factors effecting RPC and comparison between High performance concrete (HPC) and RPC and limitations of RPC and few case studies.

1. Introduction 1.1 Defining Reactive powder concrete Reactive powder concrete (RPC) is 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, super plasticizer 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.

1.2 History and development of RPC The concept of reactive powder concrete was first developed by P. Richard and M. Cheyrezy and RPC was first produced in the early 1990s by researchers at Bouygues laboratory in France. The world’s first Reactive Powder Concrete structure, the Sherbrooke Bridge in Canada, was erected in July 1997. 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. 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. 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.

1.3 Scope of RPC 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. In India the work on RPC has started from last few years. 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.

2. Composition of RPC 2.1 Introduction RPC is composed of very fine powders (cement, sand, quartz powder and silica fume), steel fibers and super plasticizer. The super plasticizer, used at its optimal dosage, decreases 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. Richard and Cheyrezy indicate the following principles for developing RPC: 1. Elimination of coarse aggregates for enhancement of homogeneity 2. Utilization of the pozzolonic properties of silica fume 3. Optimization of the granular mixture for the enhancement of compacted density 4. The optimal usage of super plasticizer to reduce w/c and improve workability 5. Application of pressure (before and during setting) to improve compaction 6. Post-set heat-treatment for the enhancement of the microstructure 7. Addition of small-sized steel fibers to improve ductility Application of these principles without steel fibers produces a matrix with very high compressive strength, but with ductility no better than that of conventional mortar. The inclusion of fibers improves tensile strength, and also makes it possible to obtain the required level of ductility.

2.2 RPC components 2.2.1 Cement Cement is binding material for production of primary hydrates. Its particle size ranges from 1µm to 100µm. Optimum cement properties are C3S: 60% C2S: 22% C3A: 3.8% C4AF: 7.4% 2.2.2 Sand Coarse aggregates are replaced by fine sand. It gives strength to the concrete. Maximum size of sand is 600µm. Size ranges from 150µm to 600µm. It eliminates mechanical chemical and thermo mechanical failures.

2.2.3 Quartz powder Its particle size ranges from 5µm to 25µm. It must be in crystalline form. 2.2.4 Silica fume Silica fume is used for filling voids and enhance rheology and for production of secondary hydrates. Its particle size ranges from 0.1µm to 1µm . 2.2.5 Steel fibers It should have good aspect ratio and should be able to improve ductility. Its length ranges from 13mm to 25mm. It should be straight. 2.2.6 Super plasticizer A copolymer of acrylic ester (CAE), a polynaphtalene Sulfonate (PNS) and a polymelamine sulfonate (PMS) are normally employed for the purpose. These admixtures are synthetic polymers. 2.2.7 Table showing components of RPC Component

Selection parameter

Function

Particle size

Sand

Good hardness Readily available and low cost.

Gives strength

150 µm to 600 µm

Cement

C3S: 60% C2S: 22% C3A: 3.8% C4AF: 7.4%

Binding material, Production of primary hydrates

1 µm to 100 µm

Quartz powder

Fineness

Max. reactivity during heat-treating

5µm to 25µm

Silica fume

Very less quantity of impurities

0.1µm to 1µm

Steel fibers

Good aspect ratio

Filling the voids, Enhance rheology, Production of secondary hydrates Improve ductility

Reduce w/c

Polyacrylate based

Super plasticizer Less retarding characteristic

Table 1 Components of RPC

Length 13mm to 25mm Dia. 0.15 – 0.2 mm

2.3 Mix proportion of RPC The RPC family includes two types of concrete, designated RPC 200 and RPC 800. Mix proportion (by weight) given by P. Richard and and M. Cheyrezy. RPC 200 Non fibered

RPC 800 Fibered

Portland cement

1

1

1

1

Silica Steel aggregates aggregates 1 1

Silica fume

0.25

0.23

0.25

0.23

0.23

0.23

Sand

1.1

1.1

1.1

1.1

0.5

-

Quartz powder

-

0.39

-

0.39

0.39

0.39

Super plasticizer

0.016

0.019

0.016

0.019

0.019

0.019

Steel fibre L=12 mm

-

-

0.175

0.175

-

-

Steel fibre L=3 mm

-

-

-

-

0.63

0.63

Steel aggregates