Effect of thermal cycling on the properties of high-performance concrete: Microstructure and mechanism

Abstract

The effect of thermal cycling on high-performance concrete (HPC) was evaluated by analyzing the mechanical properties and capillary water absorption considering the microstructural changes of the cement matrix and interfacial transition zone (ITZ). Backscattered electron (BSE) imaging and nanoindentation methods were used to study the mechanism behind the changes in HPC properties during thermal cycling. Under thermal cycling, the micromechanical properties of the cement matrix, and especially the ITZ, degraded. With increasing thermal cycles, the mechanical properties of all HPC grades decreased, especially for higher-strength HPC, because of major deterioration of the ITZ microstructure. Under thermal cycling, enhanced microcracking resulted in a significant increase in initial sorptivity and decrease in secondary sorptivity, especially for higher-strength HPC. The expansion of existing microcracks and formation of new ones during thermal cycling resulted in an increase in water penetration depths, and degraded micro- and macro-properties.