An experimental study on geopolymer mortars based on copper slag, metakaolin and ground granulated blast furnace slag: mechanical and durability perspective

The mechanical, durability and microstructural properties of ground granulated blast furnace slag (GGBFS), metakaolin (MK) and copper slag (CS) geopolymer mortars were investigated. CS was used as a partial replacement of GGBFS and MK at different levels of 0%, 10%, 20%, and 30% by weight of the total binder. The outcomes revealed that to maximize the mechanical strength in MK and GGBFS-based geopolymer samples, a 10% CS as a replacement is required. The geopolymer based on MK containing 30% replacement of CS exhibited the lowest water absorption, showing a 32% reduction compared to the 100% MK geopolymer mortar. The GGBFS containing 20% CS performed the best in Rapid Chloride Migration Test. X-Ray Diffraction, Scanning Electron Microscopy and energy dispersive X-ray spectroscopy indicated that geopolymer mortars containing MK formed amorphous gel, sodium aluminum silicate hydrate (N-A-S-H), while geopolymer mortars based on GGBFS produced sodium (or calcium) silicate aluminum hydrate gel [N-(C)-A-S-H].