Synopsis
The influence of sustained and cyclic load histories upon the compressive properties of concrete, mortar and paste are reported. It is shown that the effects of a sustained load produce asmall increase in strength and a relatively large increase in stifiess, whereas cyclic loading results in a small decrease in strength and a relatively large decrease in stifiess. Both load histories decrease the strain at peak stress on reloading. It is proposed that sustained loads result in redistribution of stress concentrations in the cement paste and consolidation in the gel. Cyclic loads, on the other hand, produce limited microcracking. The hypothesis is supported by the substantially greater damage observed in the specimens subjected to a cyclic load and the higher specific creep, which other researchers have shown to be largely irrecoverable.
