Short-term environment-dependent creep and shrinkage of mature concrete

摘要

The objective of this research was to experimentally assess the relative significance of short-term environment-dependent creep and shrinkage strains on the relief of temperature-induced restraint stresses in bridges. Although substantial theoretical and experimental works have been performed on long-term creep and shrinkage effects under varying environmental conditions, controlled experimental works on short-term creep and shrinkage effects under realistic outdoor ambient conditions are lacking. In this study, multiple short-duration tests were performed on concrete cylinders (in Chicago, IL, USA) to evaluate the short-term environment-dependent creep and shrinkage of mature concrete caused by outdoor environmental variations. The results indicate that short-term environment-dependent creep and shrinkage of concrete are each limited to a maximum of approximately 15% of the corresponding changes in temperature strains. However, the values of short-term environment-dependent creep and shrinkage can be high compared with indoor (laboratory) creep and shrinkage strains occurring within the same brief time frame. Environment-dependent creep tends to compensate for an increase in temperature strains. Environment-dependent shrinkage also tends to compensate for an increase in temperature strains, except when concrete temperatures are below the freezing point. Overall, the beneficial influence of short-term environment-dependent creep and shrinkage on daily thermal strains and stresses is relatively small.