Mechanical properties and microstructure analysis of FA-GGBS-HMNS based geopolymer concrete

Abstract

This paper presents an experimental investigation on the mechanical properties and microstructure of geopolymer concrete mixed using class F fly ash (FA), ground granulated blast-furnace slag (GGBS) and high-magnesium nickel slag (HMNS). An optimal combination of FA, GGBS and HMNS was determined using the compressive strength tests of geopolymer (GP) pastes mixed with various different replacements of FA with GGBS and/or HMNS. It was found that the replacement of FA with 20% of GGBS and 10% of HMNS in GP concrete increases the 28-day compressive strength by 100% and the 28-day splitting tensile strength by 58%. The microstructure analysis of the GP concrete using SEM, XRD, and FTIR showed the formation of aluminosilicate amorphous phase in a three-dimensional network. The SEM images revealed a fully compact and cohesive geopolymer matrix, which explains the reason why the mechanical properties of the FA based GP concrete with both GGBS and HMNS are improved.