Effect of CO2 capture on the performance of CaO-activated slag pastes and their acid resistance

Abstract

Carbonation of CaO-activated slag shows great potential in terms of storing CO2, reducing emissions by reducing cement consumption and recycling steel slag. This study investigates the effect of quicklime dosage and CO2 capture time on the performance of CaO-activated slag experimentally. CO2 capture time varies from 0 to 15 min, and the addition of quicklime as CO2 carrier increases from 10 % to 30 %. The fluidity behavior of fresh pastes, and hydration evolution, strength behavior and acid resistance of hardened pastes before and after carbonation were analyzed. The experimental results show that more addition of quicklime and extended CO2 fixation time decrease the fluidity but increase the shear stress and apparent viscosity, which are associated with chemical reaction of quicklime and generation of large amounts of nano-sized CaCO3. Increased addition of quicklime improving the alkaline environment promotes the pozzolanic reaction of CaO-activated slag and enriches the content CO2 carrier. Hence, longer CO2 fixation time improves the filling effect of nanoscale CaCO3 on the hardened matrix obviously, and leads to better mechanical performance. Additionally, both more addition of quicklime and extended CO2 fixation time increase the acid resistance of hardened pastes chemically and physically. Therefore, this study will provide novel carbonated binders, which are benefit to the energy saving, emission reduction and environmental protection.