Compatibility of Superplasticizers with Limestone-Metakaolin Blended Cementitious System

Abstract

This study investigates the performance of polycarboxylate ether (PCE), polymelamine sulfonate (PMS), sodium lignosulfonate and naphthalene formaldehyde condensate (PNS) superplasticizers (SPs) with ASTM C595 Type IL cement (with up to 15% calcium carbonate) combined with 10 and 30 % metakaolin (MK) substitutions by mass. The required dosage of each SP for 10 % and 30 % MK substitutions were determined based on mini slump test to establish equivalent paste flow. At these dosage rates, the effects of SPs on setting time, hydration kinetics, and strength development were measured. Life cycle assessment (LCA) was carried out on different cement compositions used in this study to evaluate the greenhouse gas emissions and embodied energy of limestone-metakaolin blended cement with SP addition. While MK substitution decreases the workability of samples and shortens the setting time, this study shows that adequate dosages of a compatible type of SP can be used to compensate for these effects. Of the SPs examined, PCE and PMS are found to be more compatible, compared to PNS and sodium lignosulfonate, with limestone-metakaolin blended cements.