Appraisal of geopolymer lightweight aggregates sintered by microwave radiations

Abstract

This work was designed for the production of geopolymer based lightweight aggregate (LWA) using industrial by-products. Combination of fly ash (FA) and silica fume (SF) were used as precursors, whereas, combination of sodium hydroxide and sodium silicate were used as activator. Small amount of sodium bicarbonate was also used for surface hardening and early strength development. Pellets of dif- ferent sizes were crafted manually and cured by microwave radiations just for 5 minutes. The physico- mechanical properties of produced pellets (LWA) were discussed in light of: morphology, density, water absorption, specific gravity, porosity, aggregate impact value, and particle crushing strength. The prop- erties of LWA were also compared with literature reported synthetic LWAs cured with different tech- niques. The water absorption and specific gravity of LWAs were within the specified range provided by ACI standard. Mechanical strength properties briefed that the produced LWAs were strong enough to resist compressive load comparable to natural LWAs and many other synthetic LWAs. Thus, proposed curing method, microwave irradiation, has been found to be a sustainable and fast curing technique than conventional energy-intensive curing regimes. The results also confirmed that produced LWAs have po- tential to replace natural LWAs both in cast-in-place and precast concrete elements with possible eco- nomic, environmental, and technical benefits.