A chemical approach to the problem of alkali-reactive carbonate aggregates

Abstract

This paper presents the results of a laboratory investigation of postulated mechanisms and potential remedial measures involving alkali carbonate reaction in concrete. This reaction involving certain carbonate (limestone) aggregates when used with high alkali cement has resulted in distress (cracking) of concrete pavements and slabs. The observed distress has been attributed to dedolomitization of the aggregates and osmotic pressures. This study was conducted to determine whether a chemical approach to the problem could reduce the expansion to acceptable levels. The results were encouraging. Expansion was reduced by as much as 50% using two common chemical substances, lithium carbonate and ferric chloride, introduced into a high alkali portland cement concrete made with a very reactive coarse aggregate, Gull River limestone from Kingston, Ontario, Canada. Another substance, dimethylsulfoxide, was tested also, with insignificant changes in measured expansion.