Mechanisms of ASR surface cracking in a massive concrete cylinder

Relative humidity and strains within a massive concrete cylinder (450 mm X 900 mm) in the drying and the re-saturating process were measured for elucidating the process of ASR surface cracking in concrete. The expansion behavior of mortars in dry atmospheres with various R.H. values and the re-saturating process was revealed. Non- or less-expansive layers were formed in near-surface regions in the concrete cylinder in the drying process, but ASR expansions actively progressed in inner portions. After re-saturating, R.H. values of near-surface regions rapidly increased with time, but expansions in the regions were found to be very small. However, in the middle portions, of which R.H. values were kept 80% ~ 90% R.H. in the drying process, expansion actively progressed, resulting in further development of surface cracks in the re-saturating process.