Alkali reactivity of dolomitic limestone aggregate

Abstract

Summary Additional evidence was obtained in support of the hypothesis that excessive expansion in the alkali-carbonate rock reaction is caused by moisture uptake by the previously ‘unwetted clay’ constituent. The dedolomitization reaction is shown to be necessary only to provide access of moisture to the ‘locked-in’ clay. A microscopic method was used to determine the specific surface of the dolomitc, the quantitative nature of which made it possible to define a practical upper limit below which expansion does not occur. It was also shown that relatively small percentages of illitic clay can account for the excessive expansion shown by reactive carbonate rocks. The new techniques used included measurements of dimensional change of thin rock wafers and of compacts of clay and powdered rock.