Assessment of Hydration Stages in the Property Development of Portland Blended Cement Systems Containing Limestone Powders

In this study, hydration stages were closely tracked in mixtures containing limestone (LS) powders to establish a correlation between microstructural parameters and performance properties. Despite the poor reactivity of LS powders, the setting duration of mixtures remained unchanged up to an LS dosage of 16%, after which a slowdown in setting time was observed. Hydrated compounds like hemicarboaluminate (Hc) were detected in pastes containing LS powders at both early and later curing periods, whereas compounds like monocarboaluminate (Mc) were only found in pastes containing LS powders at later curing periods. The Ca(OH)₂ increased with an increase in the LS dosage, showing an accelerating effect at both 3 and 28 days; however, the amount of water in hydrated compounds [found in Region 4 (a) of the thermogravimetric analysis plot] was higher only at an LS dosage of 8%. Because of the development of Hc and Mc, which increased the calcium carbo aluminate hydrates, the 8% LS addition had a beneficial influence on compressive strength during all phases of hydration. The “dilution” effect and increased porosity in the matrices, however, prevented the later-age strength from improving at higher LS dosages. It is critical to note that there was a good correlation between strength and hydrate water (HW) content since the changes in the latter were reflected in corresponding changes in the former when the LS dosage was increased from 0 to 24%. The HW content appeared to display better trends than the non-evaporable water content in correlating with the strength behaviour.