New Mitigation Strategies for Cement Prehydration

Portland cement has a limited shelf life because of the prehydration that can occur during storage. One approach to mitigating strength losses observed for concrete is to pretreat cement with a protective coating to slow the advance of prehydration. This study compared cement pretreatments with alkyl ketene dimer (AKD) wax and a combination of AKD + paraffin wax to a more traditional pretreatment approach using oleic acid. After exposing the treated cements to elevated temperature and humidity conditions, paste and mortar calorimetry tests showed improved resistance to prehydration reactions. The cements aged up to 12 weeks under the accelerated regime showed strength improvement for the mortars made with AKD and AKD + paraffin-treated cements relative to the mortars made with oleic acid-treated cement and mortars made with untreated cement. The wax can be added during clinker milling and additionally functions as a grinding aid.