Relating LC³ microstructure, surface resistivity and compressive strength development

Concrete surface resistivity can be measured non-destructively, providing an indirect measurement of microstructural development which can be related to strength development. However, relating surface resistivity and strength can be challenging for limestone calcined clay cements (LC3) since they contain mineral components of varying composition and reactivity. In this study of LC3 formulations, concrete surface resistivity until 56 days of hydration and mortar compressive strength at 3, 7, and 28 days were investigated to explore the relationship between these properties while examining the influence of mixture proportioning, limestone particle size and gypsum dosage on LC3 surface resistivity and strength development. Microstructural development of these blends was also assessed by thermogravimetric analysis and formation factor. The results suggest a strong logarithmic relationship between the resistivity and strength development, which can both be predicted by the portlandite consumption. These correlations can allow prediction of later-age strength based on early-age resistivity and portlandite consumption.