Development of High Strength Geopolymer Concrete using Low Molarity Naoh

Abstract

The development of geopolymer concrete (cementless concrete) offers great promise as an alternative construction material for the conventional Portland cement concrete. It uses industrial wastes as the ingredients in the binder thereby avoiding storage, disposal and environmental problems. The present work deals with a successful development of fly ash based and fly ash + GGBS based geopolymer concretes having 28 days compressive strength of 50 MPa and 70 MPa using NaOH solutions of low molarity at ambient curing. Twenty different mixes using NaOH solutions of molarity 3, 4, 5 and 6 were selected based on previous experience and judgment, cast and tested for compressive, splitting tensile and flexural strengths at different ages. Other parameters being the same, the water binder ratio is observed to have a significant effect on the compressive strength realized. The results obtained for geopolymer concretes are compared with those of corresponding conventional Portland cement concretes. The average compressive strength developed by geopolymer concrete (GPC) at 7 days is about 80%-86% of the 28 days strength. The compressive strength developed by the corresponding conventional concrete at 7 days is about 60% of the 28 days strength. The average splitting tensile strength developed by GPC at 7 days is about 50%-60% of the 28 days strength. The splitting tensile strength developed by corresponding conventional concrete at 7 days is about 37 %-45% of the 28 days strength. The average flexural strength developed by GPC at 7 days is about 62%-74% of the 28 days strength. The flexural strength developed by corresponding conventional concrete is about 39 %-44% of the 28 days strength. GPC in general attains higher early strength when compared to the corresponding ordinary Portland cement concrete. This is of great significance in practice as it reduces the time of deshuttering and increases the pace of construction with consequent cost savings.