Durability Index Performance of High Strength Concretes Made Based on Different Standard Portland Cements

Stephen O Ekolu,Sheena Murugan

doi:10.1155/2012/410909

Abstract

A consortium of three durability index test methods consisting of oxygen permeability, sorptivity and chloride conductivity were used to evaluate the potential influence of four (4) common SANS 10197 cements on strength and durability of concrete. Twenty four (24) concrete mixtures of water-cement ratios (w/c's) = 0.4, 0.5, 0.65 were cast using the cement types CEM I 42.5N, CEM II/A-M (V-L) 42.5N, CEM IV/B 32.5R and CEM II/A-V 52.5N. The concretes investigated fall in the range of normal strength, medium strength and high strength concretes. It was found that the marked differences in oxygen permeability and sorptivity results observed at normal and medium strengths tended to vanish at high concrete strengths. Also, the durability effects attributed to use of different cement types appear to diminish at high strengths. Cements of low strength and/or that contained no extenders (CEM 32.5R, CEM I 42.5N) showed greater sensitivity to sorptivity, relative to other cement types. Results also show that while concrete resistance to chlorides generally improves with increase in strength, adequately high chloride resistance may not be achieved based on high strength alone, and appropriate incorporation of extenders may be necessary.

Highlights

Increased durability requirements and specifications have been quoted for many infrastructural projects in South Africa recently, especially contracts issued by the South African National Roads Agency
Four different cement types were selected for the study, namely: (i) CEM 1 42.5N Portland cement with about 5% minor additional constituents and a strength enhancer; (ii) CEM II/A-M (V-L) 42.5N Portland composite cement, which incorporates finely ground, high-purity limestone interground with Portland cement clinker, 15% quality siliceous fly ash, and a strength enhancer; (iii) CEM IV/B-V 32.5R, which incorporates 40% fly ash, that is interground with the clinker together with a strength enhancer; (iv) CEM II/A-V 52.5N, which is formulated from Portland cement clinker and between 6 to 20% siliceous fly ash with a strength enhancer
The consortium of three South African index tests consisting of oxygen permeability, sorptivity, and chloride conductivity were used to assess the durability performance of the concrete mixtures

Summary

Introduction

Increased durability requirements and specifications have been quoted for many infrastructural projects in South Africa recently, especially contracts issued by the South African National Roads Agency. The transport mechanisms by which aggressive agents can ingress into concrete in form of fluids, gas, or liquid are primarily (a) permeability being movement of the media through the pores and cracks of concrete due to pressure differences, (b) diffusion being transportation under concentration gradients, and (c) suction resulting from capillary forces in dry or partially dry materials. The resistance to these transport mechanisms is related to the pore interconnectivity, pore sizes, and the tortuosity of pores and cracks. This leads to the importance of design of Advances in Materials Science and Engineering the concrete mixtures including the kind of material systems used

High-Strength Concretes and High-Performance Concretes

Experimental

Results and Discussion

Conclusions