The mechanical properties of Alkali-silica reactive mortars containing same amounts of silica fume and fly ash

Abstract

In this study, the Alkali silica reaction (ASR) effects on the mortars containing the same proportions of silica fume (SF) and fly ash (FA) instead of cement were investigated. SF and FA, used to control the expansion caused by ASR, were seen to have effects on the expansion and mechanical properties. In the study, SF and FA were substituted for cement in the proportions of 0.5.0%, 10.0%, 15.0% and 20.0%. ASTM C 1260 standard was used to determine the reactivity of aggregates and cement mixtures. In this experimental study, the morphology and chemical composition of the samples exposed to the effects of ASR were analyzed by using a scanning electron microscope (SEM) and Energy Dispersive X-ray (EDX). The results of 14-day experimental measurement showed that the average maximum length of extended control mortar bars was observed to be 0.34% while the lowest average 20% increase of the length SF replace was seen to be 0.04% in the mortar bar. The least strength loss in the mortars exposed to ASR was in those which had 20% SF substitution. Exposed to the effects of ASR, the mortars with 0%-20% SF substitution had a 18% better flexural strength and compressive strength compared to the mortars with FA. As observed on the SEM images, EDX done on the dense and wide ASR cracked areas showed high calcium and low silica percentage.