Influence of limestone powder on hydration properties of complex binders

In this paper, the influence of limestone powder on hydration properties of complex binder was studied by determining compressive strength of mortars and hydration heat of complex binders. Meanwhile, microcosmic analysis such as mercury intrusion porosimetry, scanning electron microscope and X-ray diffractometer, were also performed on those mortars. Because of the smaller particle size of limestone powder, it can form better gradation as fillers in the cementitious system. With the increasing limestone powder content, the proportion of small pores with diameter smaller than 50 or even 20 nm, which has little effect on the properties of the composite, increased and could make pores finer and improve the pore structure. At earlier period (28 days) limestone powder acts filling and accelerating effects by speeding up the hydration process of complex binder, but it will react with ordinary Portland cement to produce calcium monocarboaluminate hydrates, acting its activate effect at later period (180 days). Owing to its activate effect, it will improve early compressive strength, and also increase hydration exothermic rate while shorten its induction period.