Effects of maximum void size and aggregate characteristics on the strength of mortar

The effects of the maximum void size and aggregate shape and roughness on the flexural strength of high strength mortar were investigated. Substantial reductions in the maximum void size and air content of quartz aggregate mortars resulted in flexural strength increases. These increases in flexural strength were somewhat lower than predicted by Griffith's theory, thus suggesting that the maximum void size did not act as the critical flaw controlling the flexural strength. Factors relating to the cement-aggregate bond, including aggregate shape and roughness, appeared to affect the flexural strength more than the maximum void size.