An evaluation of some common Indian rocks with special reference to alkali-aggregate reactions

A review of construction materials in India indicates that in spite of major construction activities in concrete during recent years, very little is known of the vulnerability of the Indian aggregates. With this in view, detailed laboratory investigations were carried out on a large number of samples obtained from different parts of the country. Based on these, the present paper attempts to evaluate common Indian aggregates with emphasis on their susceptibility to alkali-aggregate reactions. These studies indicate high expansion of mortars composed of some seemingly innocuous aggregates such as granites, charnockites and even quartzites. Detailed petrographic examination shows that alkali reactivity of these types is related to the strain effects present in quartz grains. It is suggested that alkali-aggregate reactivity should be viewed from new angles, i.e., the textural features observed in silica minerals should be carefully studied.