Limestone and siliceous aggregate concretes subjected to sulphuric acid attack

Abstract

Synopsis The paper reports tests to determine the relative rates of erosion of siliceous-gravel and limestone-aggregate OPC concretes subjected to sulphuric acid concentrations of 0·0016% and 0.02% by weight. Care was taken to simulate conditions not too divorced from practice. The limestone-aggregate concrete eroded to present a relatively smooth surface with no detritus. In contrast, the siliceous-aggregate concrete eroded to form a very irregular surface with considerable aggregate detritus. The rates of erosion of the siliceous-aggregate concrete were very sensitive to the quality of the cement paste matrix, whereas the rates for the limestone-aggregate concrete were relatively insensitive. The behaviour of the limestone-aggregate concrete can be exploited in certain applications. There is no increasing surface roughness or accumulation of debris to reduce flow in channels, and damage with scrapers in sedimentation tanks can be minimized with a smoother surface. Design for erosion with limestone concretes entails estimating the thickness of a sacrificial layer of concrete appropriate for the rate of acid attack and the design life of the structure.