Abstract
This research clarified the effects of microscopic thermal stress caused by the difference of coefficients of paste and aggregate on mechanical properties of early age concrete subjected to high temperature history.
When concrete was subjected to high temperature history like steam curing, compressive strength of concrete whose water to binder ratio was 30% was much lower than that of cement paste without aggregate. When water to binder ratio was 50%, the difference of coarse aggregate affected mechanical properties of concrete so much, which was caused by microscopic thermal stress. The effects of microscopic thermal stress was remarkable in concrete using ground granulated blast-furnace slag. Under high temperature history, effects of fine aggregate were also observed. A possibility was suggested that crushed sand of limestone had an effect of increasing strength due to chemical reaction with cement paste.
When concrete was subjected to high temperature history at 7days, the effects of microscopic thermal stress were small.
