Influence of ground blast furnace slag replacement for fly ash on compressive strength of Geopolymer concrete

Abstract

The paper investigates the effect of ground blast furnace slag (GBFS) replacement for fly ash on the compressive strength of geopolymer concrete. Geopolymer concrete specimens were prepared with GBFS replacement ratios of 50%, 75%, 85%, 90%, and 100% and were cured under heating (at 100oC for 4 hours) and ambient condition (in the laboratory). Compression tests were performed on cylindrical specimens (20 x 10 cm) at 7 and 28 days. The highest compressive strength results were 32,4 and 25,9 MPa, respectively, for thermal curing and ambient curing conditions for GBFS replacing 90% of fly ash at 28 days. Although not achieving the same strength as the heatcured specimen, the ambient cured geopolymer concrete specimen still shows the feasibility and mechanical stability under natural environmental conditions, thereby promoting the wide application of this material in construction site without depending on heating equipment. Thus, geopolymer concrete mixture using a reasonable ratio of GBFS replacing fly ash without heat-cured can be a suitable solution for construction works, ensuring compressive strength.

Keywords:  Geopolymer; compressive strength; ground blast furnace slag; fly ash; ambient curing.