Effects of hydrostatic pressure on the integrity of concrete

The effects of model inclusions on the properties of concrete subjected to simulated sea disposal conditions are described. From measurements of ultrasound transit time and diametral compression strength it has been shown that metal, ceramic and polymeric inclusions, or voids, at up to 11sup(v)/o loading, have no deleterious effect on cementitious matrix properties during pressurisation to 50 MPa and subsequent depressurisation. The formation of a narrow compaction zone around hard inclusions has been confirmed and its formation can be attributed to the difference in local elastic modulus between the cement matrix and the inclusion. No other matrix cracking was observed. A number of cementitious matrix systems have been studied and from mechanical strength, and strength degradation during pressurisation it is suggested that a 9:1 blast furnace slag/ordinary Portland cement composition is more suitable for the sea-disposal route for wastes than the currently used concrete. (author)