Performance of CO2-cured alkali-activated blast-furnace slag incorporating magnesium oxide

Abstract

This study investigated characteristics of alkali -activated slags incorporating magnesium oxide (MgO) subjected to CO 2 curing. The samples were prepared by adding 2%, 5%, and 10% MgO to the total binder mass. The mixture was activated with potassium hydroxide (KOH) and cured in a CO 2 incubator for 3 days. The compressive strength of the MgO-incorporated CO 2 -cured alkali -activated slag was higher than that of the conventional alkali -activated slag at all ages up to 28 days. No reduction in the strength was observed over time. The enhanced strength was independent of MgO content. Combined X-ray diffraction with thermogravimetric analysis showed MgO accelerated the alkali activation by dissolving more Ca and Al ions from the slag. CO 2 curing supplied carbonate ions and produced calcium carbonate and hydrotalcite. The former aided in achieving a higher level of early age strength and gel pore refinement. Larger amount of the carbonates was formed under high MgO contents, which further enhanced the strength.