Synopsis
The effect of the free water, age and curing conditions upon the strengthlloading-rate relationship of concrete, mortar and neat cement paste was studied. It was found that the moisture content at the time of testing was one of the most important factors influencing this relationship, but any variables such as age or curing regime which affect the internal structure of the solid phase also have an influence. The data obtained under the different loading methods indicated that, when a specimen made from cement paste is loaded at slower rates up to approximately one-third of its ultimate strength value, the resulting ultimate strength is increased. However, ifa slower rate of loading is continued throughout the test, the ultimate strength is decreased significantly. This result is used to find the analytical form of the relationship between the stress-strain curve and strain rate of concrete and equations are proposed which closely agree with the existing data.
