PROPERTIES OF REACTIVE POWDER CONCRETE

Properties of RPC:

The mixture design of Reactive Powder Concrete primarily involves the creation of a dense granular skeleton. Optimization of the granular mixture can be achieved by the use of packing models.

Property of RPC	Description	Recommended value	Type of failure eliminated
Reduction in aggregate size	Coarse aggregate are replace by fine sand, with a reduction in the size of the coarse aggregate by a factor of about 50.	Maximum size of fine sand is 600 µm	Mechanical, chemical & thermo- mechanical
Enhanced mechanical properties	Improved mechanical properties of the paste by the addition of silica fume	Young’s modulus values in 50-75 Gpa range	Distribution on the mechanical stress field
Reduction in aggregate to matrix ratio	Limitation of sand content	Volume of the paste is at least 20 % voids index of non-compacted sand	By any external source (for example formwork).

Mechanical Performance and Durability of RPC:

The Reactive Powder Concrete family includes two types of concrete, designated RPC 200 and RPC 800, which offers interesting implicational possibilities in different areas. Mechanical for the two types of RPC are given in the table. The high flexural strength of RPC is due to addition steel fibres.
Comparison of RPC 200 Mpa and RPC 800 Mpa:

Property	RPC 200 Mpa	RPC 800 Mpa
Pre-setting pressurization, Mpa	None	50
Compressive strength (using quartz sand), Mpa	170 to 230	490 to 680
Compressive strength (using steel aggregate), Mpa	-	650 to 810
Flexural strength, Mpa	30 to 60	45 to 141

Comparison of HPC (80 Mpa) and RPC 200 Mpa:

Property	HPC (80 Mpa )	RPC 200 Mpa
Compressive strength, Mpa	80	200
Flexural strength, Mpa	7	40
Modulus of elasticity, Gpa	40	60
Fracture toughness, J/m2	<103	30×103

Table shows typical mechanical properties of RPC compared to a conventional HPC having compressive strength of 80 Mpa. As fracture toughness, which is a measure of energy absorbed per unit volume of material to fracture, is higher for RPC, it exhibits high ductility. Apart from their exceptional mechanical properties, RPC have an ultra-dense microstructure, giving advantageous water proofing and durability characters. These materials can be therefore be used for industrial and nuclear waste storage facilities.
RPC has ultra-high durability characteristic resulting from its extremely low porosity, low permeability, limited shrinkage and increasing corrosion resistance. In comparison to HPC, there is no RPC given in table enable its use in chemically aggressive environments and where physical wear greatly limits the life of other concretes.

Laboratory investigations of Materials used in RPC:

The materials used for the laboratory study, there is specification and properties have been presented in the table.
Materials used in the study and their properties:

Sl.no	Sample	Specific gravity	Particle size range
1.	Cement, OPC, 53-grade	3.15	31 µm – 7.5 µm
2.	Micro silica	2.2	5.3 µm – 1.8 µm
3.	Quartz powder	2.7	5.3 µm – 1.3 µm
4.	Standard sand, grade-1	2.65	0.6mm – 0.3 mm
5.	Steel fibres (30 mm)	7.1	Length: 30 mm and diameter:0.4 mm
6.	River sand	2.61	2.36 mm – 0.15 mm

Mixture design of RPC and HPC:

The process of mixture selection of Reactive Powder Concrete and High Performance Concrete is given below. Considerable numbers of trial mixtures were prepared to obtain good RPC and HPC mixture proportions.
MIXTURE PROPORTIONS OF RPC AND HPC:

Material	Mixture proportions
	RPC – F	HPC – F
Cement	1.00	1.00
Silica fume	0.25	0.12
Quartz powder	0.31	-
Standard sand grade 1	1.09	-
River sand	0.20	-
30 mm steel fibers	0.03	0.023
Admixture (polyacrylate based)
Water	0.4	0.4

Workability and density were recorded for the fresh concrete mixtures. Some RPC specimens were heat cured by heating in a water bath at 90^o C after until the time of testing. Specimens of RPC and HPC were also cured in water at room temperature. The performance of RPC and HPC was monitored over time with respect to the following parameters.

• Fresh concrete properties.
• Compressive strength
• Flexural strength
• Water absorption

RPC Fresh concrete properties:
The workability of RPC mixtures (with and without fibres), measured using the mortar flow table test as r\per ASTMC109¹⁶, was in the range of120-140%. On the other hand, the workability of HPC mixtures (with fibres), measured using the slump test as per ASTM C231¹⁷, was in the range of 120-150mm. The density of fresh RPC and HPC mixture was found to be in the range of 2500-2650 kg/m³.
Compressive strength:
The compressive strength analysis throughout the study shows that RPC has higher compressive strength than HPC, as shown in fig. compressive strength is one of the factors linked with durability of a material.

The maximum compressive strength of RPC obtained from this study is as 200Mpa, while the maximum strength obtained for HPC is 75Mpa. The incorporation of fibres and use of heat curing was seen to enhance the compressive strength of RPC by 30 to 50%. The incorporation of fibres did not affect the compressive strength of HPC significantly.
Flexural strength of RPC:
Plain RPC was found to possess marginally higher flexural strength than HPC. Table clearly explains the variation in flexural strength of RPC and HPC with the addition of steel fibers. Here the increase of flexural strength of RPC with the addition of fibers is higher than that of HPC.
As per literature, RPC 200should have an approximate flexural strength of 40 Mpa. The reason for low flexural strength obtained in the study could be that the fibers used (30mm) were long and their diameter was relatively higher. Fibre reinforced RPC (with appropriate fibres) has the potential to be used in structures without any additional steel reinforcement. This cost reduction in reinforcement can compensate the increase in cost by the elimination of coarse aggregates in RPC to some extent.
Flexural Strength at 28 days, Mpa

RPC	RPC –F	HPC	HPC – F
NC	NC	NC	NC
11	18	8	10

Water absorption of RPC:
A common trend of decrees in the water absorption with age is seen here both for RPC and HPC. The percentage of water absorption of RPC, however, is very low compared to that of the HPC. The quality of RPC is one among the desired properties of nuclear waste containment materials.