Mechanical and microstructural properties of heat cured alkali-activated slag mortars

The effects of steam and autoclave curing on the mechanical properties and microstructure of alkali activated slag mortars (AAS) were investigated within the scope of this study. Slag was activated by the mixtures of sodium hydroxide and sodium silicate, in different Na2O and Ms (SiO2/Na2O) ratios. Test results showed that high strength mortars can be produced with very low alkali content under autoclave curing as a result of better pore size distribution, higher rate of hydrated parts of slag grains which leads to a better microstructure formation. A compressive strength value of 70 MPa has been reached by incorporation of 2% Na2O under autoclave curing. Nevertheless, steam curing presents similar mechanical performance with autoclave curing for AAS mortar activated by the solutions with high Ms values. Both curing methods were significantly effective in terms of reducing drying shrinkage of AAS mortars.

► Optimum activator solutions for GGBFS were determined for steam and autoclave curing.
► Microstructure and mechanical properties of heat cured AAS mortars were presented.
► High strength mortars were produced with very low activator contents under autoclaving.
► Steam curing needs high Ms value activator for high strength mortar.
► Heat curing significantly reduced the drying shrinkage values of mortars.