Analysis of mineral formation in dolomitic concrete

Concrete production is the third largest energy consumer in the world and the calcination process used to produce Portland Cement is responsible for 7% of global CO2 emissions; hence, there is great interest in developing methods to decrease the amount of Portland Cement used in concrete. One such method is the use of supplementary cementitious materials (SCM). In a recent study, Bernard (2023) evaluated the use of dolomite aggregate of various sizes and replacement quantities on the compressive strength of mortar samples made without SCMs and with limestone SCM. The results showed that mortar made with dolomite SCM had a greater compressive strength after 1 day of curing than samples without SCM or with limestone SCM. Other researchers have also reported concretes with dolomite SCM have higher compressive strengths at shorter curing times and have suggested that the formation hydrotalcite may be the cause. The objective of this study is to determine if hydrotalcite formed in the dolomite SRM mortar samples in sufficient manner to cause the early strengthening. The mortar samples were analyzed using a Scanning Electron Microscope with an Energy Dispersive Spectrometer (SEM-EDS) and by powder x-ray diffraction (XRD). The results of the SEM-EDS analysis confirmed the presence of hydrotalcite grains within dolomite reaction rims. However, the amount of hydrotalcite in the mortar samples was too low for detection by XRD analysis. As such, the direct impact of hydrotalcite formation on early strengthening of the dolomite SCM mortar cubes is questionable. Prior studies that reported significant hydrotalcite formation in dolomite SCM concretes were cured at higher temperatures and for longer durations than the mortar samples analyzed in this study.