Microstructural investigation on the relationship between microstructure and compressive strength of cement mortars

In this study, it has been tried to define a relationship between pore structure of a cement mortar and its compressive strength. Cement mortars were prepared by adding admixtures with different ratio. Additions of admixture lead to retard the hydration process of ordinary Portland cement mortar. Microstructures of mixes were examined under scanning electron microscope (SEM). Micrographs were taken to define the area ratio values of each phase in cement mortars. The developments of area ratio values of phases for 1, 2 and 7-day old cement mortars are shown. The relationship between phases and compressive strength values was determined. The study shows that admixture retards formation of undifferentiated hydrates and, results as an increase on pore area ratio values. Therefore, the compressive strength values increase as the pore area ratio values decrease and undifferentiated hydrates values increase.