Evaluation of the durability of concretes associated with flash metakaolin or silica fume

Abstract

This article reviews the effects of silica fume (SF) and metakaolin (Mk) properties on water accessible porosity, chloride ion diffusion, gas permeability and electrical resistivity. The concretes are tested with proportions of 15% and 20% of Mk and 5% and 10% of SF compared to the concretes without addition. Incorporation is based on a partial replacement of fine sand. A total of fifteen mixtures are made according to three different Water/Binder ratios: 0.50, 0.46 and 0.40. Durability indicators are evaluated for ages of 7, 28, 56 and 90 days. The incorporation of SF or Mk into cement matrices is intended to study the effect of the effective pozzolanic reaction which can improve the development of the concrete microstructure compared to control concretes. Therefore, the comparison of the tested concretes with addition shows a decrease in durability indicators as follows: (1) for porosity from 1% to 11% for SF and from 4% to 12% for Mk, (2) for the diffusion of chloride ions from 54% to 75% for SF and from 55% to 86% for Mk, (3) for gas permeability from 6% to 22% for SF and from 5% to 28% for Mk. Electrical resistivity, as well, shows an increase compared to the control mixture from 64% to 163% for SF and from 50% to 104% for Mk. A good correlation was observed between the compressive strength and the tested durability indicators of the different concretes.