Study on hydration products by electrical resistivity for self-compacting concrete with silica fume and metakaolin

Abstract

This paper investigates the hydration products of self-compacting concrete (SCC) made with binary and ternary blends of silica fume(SF) and metakaolin(MK). X-ray diffraction (XRD) and thermogravimetric analysis (TGA) test were used to measure the hydration products of pastes corresponding to self-compacting concretes. For this purpose, the reference SCC mixture at constant water to cementitious material (W/CM) ratio of 0.45 and total cementitious material content of 450kg/m3 was prepared. Other mixtures contained binary (92%PC+8%SF, 80%PC+20%MK) and ternary (72%PC+8%SF+20%MK) cementitious blends of metakaolin and silica fume. Four pastes corresponding to SCC mixtures with the same W/CM and cementitious materials were considered. Also, the electrical resistivity of SCC mixtures was measured to assess the relationship between electrical resistivity over time and calcium hydroxide (CH) content. The correlation coefficient of the relationship between Ca(OH)2 content and electrical resistivity was found to be 0.95 with positive slope for reference SCC and 0.97 with negative slope for samples containing pozzolans. It can be suggested to apply the electrical resistivity as a simple method to calculate CH content in cement paste.