Sustainable use of silica fume and metakaolin in slag/fly ash-based self-compacting geopolymer composites: Fresh, physico-mechanical and durability properties

Self-compacting geopolymer concrete is a new technology in the construction industry that prevents workers from compaction operations on materials with highly concentrated alkaline liquid. The assessment of the fresh, mechanical, durability and microstructural properties of slag/fly ash-based self-compacting geopolymer composites (SCGC) with silica fume (SF) and metakaolin (MK) is the main objective of this study. Granulated blast furnace slag (GBFS), fly ash (FA), SF and MK were used as precursors in the synthesis of SCGC. Sodium silicate (SS) and sodium hydroxide (SH) solution was used as activators. Ten mixtures were created; five of them had 85% GBFS, 10% SF and 5%MK while the other five contained 85% FA, 10% SF and 5%MK. The effect of five different SS/SH values varying from 2.0 to 3.0 and curing temperature on the fresh, mechanical and durability properties of SCGC mixtures were investigated. The performance of the generated blends at high temperatures, and sulfate attack was also evaluated. Microstructure analyses were also performed by using scanning electron microscopy (SEM) images. The findings showed that the GBFS based SCGC mixture activated with SS/SH value of 2.25 produced a compressive strength of 83 MPa at 1-day heat curing at 80 °C then 28-day water curing. The results demonstrated that the FA-based SCGC mixture activated with a 2.75 SS/SH value yielded a compressive strength of 40 MPa after a 1-day heat cure at 80 °C. The results showed that GBFS/FA-based SCGC mixtures exhibited best durability resistance at SS/SH value of 3.0 when exposed to high temperature and sulfate attack.