Quantitative microanalyses of alkali-silica gel in concrete

Abstract

By the combination of scanning electron microscope, energy dispersive X-ray spectrometer and computer, quantitative analyses of microvolumes of alkali-silica gel at the reaction site and in cracks in concrete were carried out. In contrast to most earlier analyses of gel from alkali-silica reactions in concrete, the present investigation positively identifies regions of gel, high in calcium content. It is found that alkali-silica gel situated in a crack far from the reaction site, shows a high, approximately 20 per cent content of CaO, while gel close to the reaction site shows a low content of this element, comparable in magnitude to most earlier analyses of gel taken from the surface of the concrete. The composition of the gels analysed in this investigation compares favourably with gels synthesised by Kalousek in 1944.