EFFECT OF NANOSILICA ON THE STRENGTH OF CONCRETE WITH VOLCANIC PUMICE AS COARSE AGGREGATES

The use of concrete with volcanic pumice as aggregate is limited to masonry. The main reason for its limited utilization is that when volcanic pumice is used as a coarse aggregate in concrete, the result leads to poor performance. Such poor performance is attributed to the weak mechanical properties of volcanic pumice. Past research works show that the use of a stronger mortar counteracts the poor mechanical properties of lightweight aggregate. In this study, the mortar phase of Volcanic Pumice Concrete (VPC) was improvedthrough the incorporation of amorphous nanosilica synthesized from rice hull ash. Nanosilica was admixed in VPC at a concentration of 0.5% by weight of cement. Cylindrical test specimens were prepared, cured for 7, 14, and 28 days, and subjected to compressive and splitting tensile strength tests. Test results show that VPC specimens with 0.5% nanosilica have higher compressive and splitting tensile strength for all cases of 7, 14, and 28 days curing time compared to specimens without nanosilica. The highest percentage increase in compressive and splitting tensile strength was observed in specimens cured for seven days.