Increasing the Shelf Life of Portland Cement

Strategies to counteract the negative effects of extended storage for cement generally fall into one of two categories: either pretreat the cement to prevent or interfere with prehydration, or introduce new admixtures during the mixing of concrete that can compensate for prehydration that has already occurred. This study focusses on the former, with alkyl ketene dimer (AKD) wax and AKD + paraffin wax additions that are introduced during clinker milling, to slow the prehydration of cement under moist storage conditions. AKD and AKD + paraffin additions are shown to function as effective grinding aids, and mortar strength and calorimetry tests demonstrate improved resistance to degradation of hydration reactions attributed to prehydration, based on accelerated aging exposure conditions of 37 ± 2 ℃ and 95–100% RH.