Microstructure and mechanical properties of FA/GGBS-based geopolymer

This study presents the microstructure and mechanical properties of geopolymer paste made from low-calcium fly ash (FA) and ground granulated blast-furnace slag (GGBS) through alkalination. The use of GGBS and FA is not only for sustainable construction but also for reducing the emission of CO2 due to the use of Portland cement. Different replacement ratios of GGBS to FA were used to determine the effect of GGBS presented to the compressive strength of geopolymer specimens. The alkaline activator solution used is a combination of sodium hydroxide (NaOH) 14 M and sodium silicate (Na2SiO3). A compressive strength test on cylindrical specimens (50 mm x 100 mm) at the ages of 7, 14, and 28 days was carried out. The results showed that the compressive strength increased with the increase of GGBS in the mixes (up to 100 MPa). Moreover, SEM-EDS, XRD, and TG-DTA characterization methods were conducted to investigate the microstructure, phase composition, and thermal stability of the geopolymer specimens respectively