Strength development of solely ground granulated blast furnace slag geopolymers

[Display omitted] •Mechanical and microstructure of solely GGBFS based geopolymers are investigated.•Solely binder of GGBFS based geopolymers obtained high strength after 28-day curing.•Synchrotron micro x-ray fluorescence reveals detailed distribution of tobermorite, calcite and dolomite in GGBFS samples. This paper investigates the strength development of solely ground granulated blast furnace slag geopolymers (GGBFS). An optimal combination of GGBFS with various solid/liquid and alkaline activator ratios had been determined by performing a number of compressive strength tests. It was found that GGBFS with 3.0 solid/liquid ratio and 2.5 alkaline activator ratio resulted in high compressive strength at 168.7 MPa after 28 days of curing. The microstructure analysis of the GGBFS geopolymers using SEM, FTIR and XRD revealed the formation of tobermorite and calcite (CaCO3) phases within a three-dimensional system. In addition, an advanced characterisation non-destructive technique using the synchrotron micro-XRF was performed to reveal detail phase distribution in the system. It displayed that the calcium concentration was higher at silica and alumina regions, which described the formation of tobermorite and CaCO3 as the contributing factor towards high compressive strength.