constructionduniya: Reactive Powder Concrete

Reactive Powder Concrete (RPC) is a high strength ductile material formulated from a special combination of constituent materials. These materials include Portland cement, silica fume, quartz flour, fine silica sand, high-range water-reducer, water, and steel or organic fibers. The technology of the material is covered by many patents in a Ultra High Performance Concrete.

The following are the characteristics of RPC:

STRENGTH

Compressive

120 to 150 MPa

(17000 to 22000 psi)

Flexural

15 to 25 MPa

(2200 to 3600 psi)

Modulus of Elasticity

45 to 50 GPa

(6500 to 7300 ksi)

DURABILITY

Freeze/thaw

(after 300 cycles)

100%

Salt-scaling

< 60 g/m² (< 0.013 lb/ft³)

Abrasion

(relative volume loss index)

1.7

Oxygen permeability

<10-20 m² (< 10-19 ft²)

Cl- permeability

(total load)

< 10 C

Carbonation depth

< 0.5 mm (< 0.02 in.)

Why RPC is better than other concrete in terms of strength and durability?

This new family of materials has compressive strengths of 25,000 to 33,000 psi (170 to 230 MPa) and flexural strengths of 4000 to 7000 psi (30 to 50 MPa), depending on the type of fibers used. The ductile behavior of this material is a first for concrete. The material has a capacity to deform and support flexural and tensile loads, even after initial cracking. These performances are the result of improved micro-structural properties of the mineral matrix—especially toughness—and the control of the bond between the matrix and the fiber.

The durability properties are those of an impermeable material. There is almost no carbonation or penetration of chlorides and sulfates, and high resistance to acid attack. Resistance to abrasion is similar to that of rock. The superior durability characteristics are due to the low and disconnected pore structure, which is generated as a result of the use of a combination of fine powder materials (maximum grain size of 600 microns), selected for their relative grain size and chemical reactivity. The net effect is a maximum compactness and a small disconnected pore structure.

There is almost no shrinkage or creep, which makes the material very suitable for applications in prestressed concrete. The use of this material for construction is simplified through the elimination of reinforcing steel and the ability of the material to be virtually self-placing or dry-cast. It can be produced with customary industrial tools by casting, injection, or extrusion.

Due to the use of powder-like components and the fluidity, the material has the ability to replicate the macro- and micro-texture of the formwork. The result is a final product that can have a full range of colors and textures with a high quality surface.

This new technology is consistent with the construction trends and demands for reducing labor, materials, construction time, and environmental impact, while increasing safety, security, durability, and the service life.

Components with functions parameters:

Components:

Sand

Cement

Quartz powder

Silica fume

Steel fibers

Superplasticiser

Function parameters:

Give strength to aggregate

Binding material

Maximum reactivity during heat-treating

Filling the voids

Improve ductility

Reduce water binding

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 superplasticizer
Fine quartz sand (150-600μm) (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 Properties:

The previously mentioned composition allows for the following properties:

1.Compressive Strength:

· Up to 120,000 psi (200 to 800 MPa!)

· 15,000 psi (~100MPa) or greater 24 hours after initial set

2.Tensile Strength:

· 3000 to 7000 psi (20 to 50 MPa, twice as strong as normal concrete in compression) .

· 6-13 MPa tensile strength after first cracking!

3. Flexural Strength:

· ~14000 psi (100 MPa) flexural strength at first cracking is higher than ultimate flexural strength of normal concrete.

4. Young's Modulus 50 to 75 GPa

5. Fracture energies ranging from 15,000 to 40,000 J/m² (plastic failure rather than brittle).

RESISTANCE TO CHLORIDE ION PENETRATION:

Increases when heat curing is done in concrete. Heat cured RPC show higher value than normal cured RPC.

HOMOGENITY:

Improved by eliminating all coarse aggregates. Dry components for use in RPC is less than 600 micro meter.

MATERIAL DUCTILITY:

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

CONTAINMENT OF NUCLEAR WASTE

Used for isolation and containment of nuclear wastes. It has been used for blocking & stabilization of containment waste.

Almost no shrinkage or creep
Light weight
Long life
Improved homogeneity and aesthetic possibilities

RPC Mix and Placing:

Shipped either in 50-lb. preblended bags or 1,500-lb. "bigbags."
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 superplasticizer still makes it workable

BENEFITS:

Ø It has the potential to structurally compete with

steel.

Ø Superior strength combined with higher shear

capacity result in significant dead load reduction.

Ø RPC can be used to resist all but direct primary

tensile stress.

Ø Improved seismic performance by reducing

inertia load with lighter member.

Ø Low &non-interconnected porosity diminishes

mass transfer, making penetration of liquid/gas non-existent.

RPC Drawbacks :

Ø Higher cost

Ø No Code!

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