Mesoscopic Mechanical Properties of HPC with ASR Inhibition after 10 Years of Exposure to Alkali Solution at 38°C

The study investigated the effect of alkali-silicate reaction (ASR) inhibition measures on the surface and central parts of high-performance concrete (HPC) specimens under long-term exposure to standard alkali solution at 38°C. The specimens were sliced to determine the microhardness of the interfacial transition zone (ITZ) between the coarse and fine aggregates and cement matrix. The ITZ microhardness distribution pattern and ITZ thickness of HPC under different ASR damage conditions were also determined. The study systematically investigated the relationship between the macroscopic and mesoscopic mechanical properties of HPC with ASR inhibition measures and its ASR damage. The results showed that the ITZ microhardness of coarse and fine aggregates has a linear relationship with ASR damage of HPC under the long-term action of standard lye. The compressive strength, flexural strength, and splitting tensile strength of HPC are closely related to the ITZ microhardness of coarse aggregates. In contrast, the axial compressive strength and compressive elastic modulus are more closely related to the cement matrix microhardness. A linear relationship between ITZ microhardness and cement matrix microhardness was established. Furthermore, the microscopic analysis combined with the microhardness law revealed that the air-entraining agent had an inhibitory effect on ASR. Finally, the correlation and rule between the ITZ thickness of coarse and fine aggregates was investigated. It was found that the fine aggregate’s ITZ thickness was smaller than that of the coarse aggregate. The ITZ thickness of the surface part of the HPC specimen increased compared to the center part of the HPC specimen under long-term ASR.