Accelerated carbonation curing of cement mortars containing cement kiln dust: An effective way of CO2 sequestration and carbon footprint reduction

Abstract

Accelerated Carbonation curing (ACC) is an innovative curing procedure for precast concrete units, which results in sequestration of the carbon dioxide gas and its conversion into stable products. The effect of carbonation curing on mortar mixes incorporating cement kiln dust (CKD) as partial replacement of cement has been investigated in the present study. Carbonation curing was carried out for 12 h, followed by either sealed bag curing or water spray curing for 3 days. The effect of carbonation curing was studied in terms of compressive strength, porosity and pH of the mix, along with SEM to study the resultant morphology. It was observed that ACC led to better early age strength and lower porosity as compared to water cured mortars with at least 20% increase in the strength for each mix. The later age strength decreased slightly by ACC due to water loss, but could be compensated by adopting subsequent water spray. The microstructure analysis showed presence of C-S-H gel and CaCO3 for the carbonated mortars, contributing to the additional strength and reduced porosity. Stoichiometric analysis of the control mix at 3 days of casting also confirmed that carbonation curing enhances the compressive strength and decreases porosity of the mix. It was observed that the finer particle size of CKD particles and presence of alkali in CKD further promotes the carbonation reaction, and hence led to large improvement in the properties of the resultant mix.