Effect of curing temperatures on the alkali activation of crystalline continuous casting stainless steel slag

•Continuous casting slag shows hardening with alkali silicates under steam curing.•Strength improvement is initially gradual but steeper at higher temperatures.•Short term strength is dependent on alkali cations.•Porosity of the mortars is more affected by alkali cations than curing temperature.•Bonding between aggregate and matrix is majorly affected by curing temperature.

The binding properties of continuous casting stainless steel slag were studied when activated by a combination of Na silicate and 5 M NaOH as well as K silicate and 5 M KOH at steam curing temperatures of 60, 70, 80, 90, 100 and 110 °C. The slag mortars developed moderate compressive strength (∼5 MPa) at 60 °C which initially increased moderately and then steeply (>30 MPa) at higher curing temperatures. The porosity of K activated mortars was lower than for Na activated mortars. Thermal and ATR-FTIR analysis showed the formation of C–S–H type of reaction products for both activators at all temperatures, while the formation of brucite was promoted at higher curing temperatures. A much denser hydrated matrix with a better bonding with aggregates was formed at higher curing temperatures. Heavy metal leaching from the slag was dependent on its type and curing temperature of samples.