Concrete Technology and Special Concrete

Presentation

On

Reactive Powder Concrete

Reactive powder concrete

Introduction

• Reactive powder concrete (RPC) is the generic name for a class of

cementious composite materials developed by the technical division of

Bouygues, in the early 1990s. It is characterized by extremely good

physical properties, particularly strength and ductility

• A composite material & ultra high strength with mechanical properties.

• Mixture of fiber reinforced, super plasticized, silica fume, cement &

quartz sand with very low water cement ratio.

• Quartz sand used instead of ordinary aggregate, therefore increases

compressive strength.

RPC Composition

• RPC is able to obtain its improved properties by using a very dense mix, consisting of fine particles and fibers.

• Low w/cm ratio : 0.16 to 0.24 (as low as 0.13)

• Type 20M (like type II) Portland cement (no C3A less HoH)

• Silica fume (25% by weight)

• Water

• High dosages of super plasticizer

• Fine quartz sand (SG=2.75)

• Steel fibers (2.5-10% by volume) for toughening

• No rebar needed!

• Cured in steam bath for 48 hrs @ 190ºF (88ºC) after initial set, placed under pressure at the molding stage

RPC Mix and Placing

• Can be mixed and produced in a ready-mix truck and still have similar strengths to those made in a central mixer.

• Self-placing, requires no internal vibration.

• Despite its composition, the large amount of super plasticizer still makes it workable

• Function parameters

• Give strength to aggregate

• Binding material

• Maximum reactivity during heat-treating

• Filling the voids

• Improve ductility

• Reduce water binding

Principle

• Chard and Cheyrezy indicate the following principles fordeveloping RPC:

• Elimination of coarse aggregates for enhancement of homogeneity

• Utilization of the pozzolanic properties of silica fume

• Optimization of the granular mixture for the enhancement ofcompacted density

• The optimal usage of super plasticizer to reduce w/c and improveworkability

• Application of pressure (before and during setting) to improvecompaction

• Post-set heat-treatment for the enhancement of the microstructure

• Addition of small-sized steel fibres to improve ductility

Properties of RPC

• Compressive strength

• Flexural strength

• Water absorption

• Water permeability

• Resistance to chloride ion penetration

• Homogeneity

• Compactness

• Micro-structure

• Material ductility

• Almost no shrinkage or creep

• Light weight

• Long life

• Aesthetic possibilities

Properties of RPC

1. compressive strength

• Higher compressive strength than HPC

• It is a factor linked with durability of material.

• Maximum compressive strength of RPC is approximately 200MPa.

Properties

2. Flexural Strength

• Plane RPC possess high flexural strength than HPC (Up to 100mpa)

• By introducing steel fibers, RPC can achieve high flexural strength.

3. Water Absorption

The percentage of water absorption of RPC, however, is very low compared to that of HPC. This quality of RPC is one among the desired properties of nuclear waste containment materials.

Water absorption

Properties

4. Water permeability

It can be seen from the data that water permeability decreaseswith age for all mixtures. 28th day water permeability of RPC isnegligible when compared to that of HPC (almost 7 timeslower). As in the case of water absorption, the use of fibresincreases the surface permeability of both types of concrete.

Properties

5. Resistance to chloride ion penetration

• Increases when heat curing is done in concrete

• Heat cured RPC show higher value than normal cured RPC.

• This property of RPC enhances its suitability for use in nuclear wastecontainment structures.

6. Homogeneity

• Improved by eliminating all coarse aggregates

• Dry components for use in RPC is less than 600 micro meter.

7. Compactness:

• Application of pressure before and during concrete setting period.

8. Microstructure:

• Microstructure of the cement hydrate can be changed by applying heat treatmentduring curing.

9. material ductility:

• Material ductility can be improved through the addition of short steel fibres.

RPC Applications :• RPC's properties, especially its high strength characteristic suggests the material might be good for

things needing lower structural weight, greater structural spans, and even in seismic regions, it

outperforms normal concrete. Below are a few examples of real-world applications, though the

future possibilities are endless.

• First bridge that used RPC was a pedestrian bridge in Sherbrooke, Quebec, Canada. (33,000 psi

~230MPa) It was used during the early days of RPC production. Has prompted bridge building in

North America, Europe, Australia, and Asia.

• Portugal has used it for seawall anchors

• Austrailia has used it in a vehicular bridge

• France has used it in building power plants

• Qinghai-Tibet Railway Bridge

• Shawnessy Light Rail Transit Station

• Basically, structures needing light and thin components, things like roofs for stadiums, long bridge

spans, and anything that needs extra safety or security such as blast resistant structures

Application

• Sherbrooke pedestrain bridge

Benefits

• It has the potential to structurally compete with steel.

• Superior strength combined with higher shear capacity result in significant dead load reduction.

• RPC can be used to resist all but direct primary tensile stress.

• Improved seismic performance by reducing inertia load with lighter member.

• Low &non-interconnected porosity diminishes mass transfer, making penetration of liquid/gas 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.

• No code

• 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.

• Owing to its high durability, RPC can even replace steel in compression members where

durability issues are at stake (e.g. in marine condition).

• Since RPC is in its developing stage, the long-term properties are not known.

References

• ASTM Standard Designation C1202-97, “Standard Test Method for Electrical Indication of Concrete’s Ability to Resist Chloride Ion Penetration,” ASTM, Pennsylvania, 2001.

• ASTM Standard Designation C109-99, “Standard Test Method for Compressive Strength of Hydraulic Cement Mortars,” ASTM, Pennsylvania, 2001.

• ASTM Standard Designation C143-00, “Standard Test Method for Slump of Hydraulic Cement Concrete,” ASTM, Pennsylvania, 2001.

• Advances in Materials Science and EngineeringVolume 2012 (2012), Article ID 860303, 6 pages (Experimental Research on Fire Resistance of Reactive Powder Concrete),

• http://constructionduniya.blogspot.in/2013/04/reactive-powder-concrete.html