Flexural Strength and Fracture Properties of a Fly Ash Blended Cement

The flexural strength, fracture toughness and Young’s Modulus of an ordinary Portland cement plus 25 wt% fly ash paste (FACP) were compared with those of a control paste (HCP) at times ranging from one day to one year. At comparatively early times these properties develop more slowly in FACP. However, at comparatively late ages, e.g. ten months, FACP showed improvements over HCP for all of these properties. A complicating factor is that for both FACP and HCP, the flexural strength and toughness show maxima and the “crossover” times for the various properties differ. This paper analyses these results in terms of the observed fracture mechanism for HCP by taking into account the changes brought about in the microstructure of FACP, due to the incorporation of fly ash.