Exploring sulfate optimization techniques in Limestone Calcined Clay

This study assessed the feasibility of different methods for sulfate optimization of limestone calcined clay cements (LC3). LC3-based pastes were studied with kaolinite and montmorillonite calcined clays and different gypsum contents. Quartz powder was used in reference systems. The sulfate optimization was done using isothermal calorimetry, compressive strength, thermogravimetric analysis, and chemical shrinkage analysis at different ages. Overall, there is no single best technique to predict sulfate optimization in LC3, carefully combining multiple techniques can assist in more coherent decision-making, such as isothermal calorimetry with compressive strength within 72 h. We recommend the optimum LC3 sulfate content based on criteria established by the decision-maker (academia or industry). Either based on mechanisms and kinetics reactions, phase assemblage, compressive strength, or shrinkage of LC3 mixtures containing different SO3 content. Also, the results of montmorillonite-LC3 systems were satisfactory without accelerated sulfate depletion.