Effect of Aggregate Components on the Bond Strength and the Strength of Mortar

The report deals with the effect of chemical components of aggregate on the bond strength and the strength of mortar under three practical curing conditions (28 days in 20℃ water， 4 hours in 70℃ steam and 4 hours autoclave in 180℃ and 10 kg/㎠ ). Four typica1 rocks (quartzite， 1imestone， Taishufeldspar and India fe1dspar) and a blast-furnace slag were tested. The bond strengths in 20℃ or 70℃ curings werenearly the same but in autoc1ave， 1imestone， India fe1dspar and slag showed very low strength. It is shown also that the bending，compressive and sp1it-tensi1e strengths of 1imestone and India feldspar mortar specimens were remarkably lowered in autoclave curing. Scanning electron microscope observation showed that the surface of 1imestone and India fe1dspar were fissured and fine1y wrink1ed， suggesting the physica1 and chemica1 deterioration in autoclave. And it is assumed to be the cause of the low strength. Five kinds of crushed sand in market were also tested. The difference of mortar strengths between these aggregates were very small in 20℃ or 70℃ curing. In autoclave curing， however， two kinds of sand with higher SiO2 content showed higher strength. It is indicated by the present study that se1ection of curing appropriate to each aggregate was important to the effective production of concrete