Essay on Concrete

10601 Words Oct 8th, 2012 43 Pages
No. 146 (2005)

Reactive Powder Concrete
N.P. Lee & D.H. Chisholm

The work reported here was funded by Building Research Levy.

© BRANZ 2006
ISSN: 0113-3675

The low flexural tensile strength of concrete has a number of undesirable consequences for its performance as an effective building material. These include the necessity for auxiliary steel reinforcement and the requirement for thick-sectioned members that are both aesthetically unappealing and consume significant quantities of aggregates. The aggregates are an increasingly scarce resource in many urban areas. An emerging technology with the potential to overcome these limitations is reactive powder concrete
(RPC). RPC is a cold-cast
…show more content…

BRANZ Study Report SR 146

N.P. Lee & D.H. Chisholm

Lee N.P. & Chisholm D.H. (2005). Reactive Powder Concrete. Study Report SR 146, BRANZ Ltd,
Judgeford, New Zealand.

RPCs were produced in the laboratory to examine the effect of a number of process variables including water-to-binder (w/b) ratio, super-plasticiser dosage, curing regime and the choice of silica pozzolan, on the compressive and tensile strength of the hardened material. Compressive strengths in excess of 200 MPa and flexural strength of 15 – 20 MPa were routinely achieved using conventional concrete mixing and curing practices. Mechanical strength was observed to directly correlate with the spatial efficiency that the dry powders’ constituents could be packed together. Consequently it is necessary for these powders to exist in distinct size classes with a wide separation between mean particle size diameters. This places a reliance on imported silica fume as an essential component of these mixes. The benefits conferred by the fume’s extremely fine sub-micron particles and spherical shape are such that substitution by indigenous geothermal silica pozzolan is impractical.

Keywords: reactive powder concrete, RPC, New Zealand materials, mix design, silica fume, curing, compressive strength.




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