A Quantitative Investigation of the Effects of Load Induced Thermal Strain on Concrete Microstructure

A quantitative microstructural investigation was carried out to determine the presence of changes in the porous volume of specimens which had been subjected to Load Induced Thermal Strain (LITS) – an irreversible strain component which occurs in mature ordinary Portland cement based materials that are heated under the presence of mechanical load. The results of mercury intrusion porosimetry and backscattered electron image analysis indicate that the porous volume of LITS affected specimens after heating and loading is similar to that of specimens which had experienced heat only treatments. Therefore the presence of a specific microstructural damage mechanism which accounts for the development ofLITS is partly discounted in the pore structure range >0.02 μm in equivalent diameter considered here. However, an increase in the variability of mercury intrusion results for affected specimens over that of heat only and control specimens and changes in pore size distribution indicates a variation in heterogeneity of material microstructure that requires further investigation.