The current world population growth implies a constant increase of cement production in the following decades. Therefore, the search for materials with lower environmental impacts is necessary in order to curb the CO₂ emissions inherent to cement production. Several supplementary cementitious materials (SCM) have been used to partially replace the clinker used in the composition of cement. For instance, there is growing interest in the use of calcined clays as SCM due to their high pozzolanic reactivity and large availability. Different parameters influencing the behavior of calcined clay have been studied, such as the calcination conditions, the nature of the calcined clays or the impact of their structure on their reactivity. Although, the use of calcined clays is generally associated with high water demand, the parameters influencing their water demand are poorly understood.
The main aim of this work is to identify physical and chemical characterization techniques such as inductively coupled plasma (ICP) spectroscopy, zeta potential measurements and microcalorimetry which can give useful information on the parameters governing the high water demand of a calcined clay in a cement mortar formulation. Both refined model calcined clays and industrial calcined clays, showing differences in spreading behavior, have been characterized.