Mechanical and Microstructural Characterization of Alkali-Activated Materials Based on Fly Ash and Slag

This study investigates the mechanical and microstructural characterization of alkali-activated fly ash/slag (AAFS) mortars with various ratios of fly ash to slag.The liquid/binder ratios of 0.35, 0.5 and 0.65 are considered for the AAFS mortars.4% Sodium oxide (Na 2 O) concentration of cementitious material weight in mixture and liquid sodium silicate with modulus ratio (mass ratio of SiO 2 to Na 2 O) of 1 were used as alkaline activators to alkali-activate various fly ash/slag ratios.Compressive strength test, water absorption test, drying shrinkage test, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis were conducted.Test results reveal that both fly ash/slag ratio and the liquid/binder ratio are two significant factors influencing the mechanical and microstructural characterization of AAFS mortars.The hydration products of AAFS mortars are mainly amorphous alkaline aluminosilicate and low-crystalline calcium silicate hydrate gel.