Influence of replacement and specific surface Blaine of finely ground limestone powder on mortar strength

The influences of replacement of Portland cement by ground limestone as well as its specific surface on the mortar strength were discussed. The binder was composed of cement and limestone, which was prepared by eight replacement levels of limestone powder (0, 5, 10, 15, 20, 25, 30 and 35) of binder by mass and four levels of specific surface Blaine (350, 600, 800 and 1000 m²/kg). The specimens demoulded were cured in water, which was controlled temperature (20+1) °C until 3d, 7d, 28d, 56d and 90d and then the strength were tested. The results demonstrate that the compressive strength and flexile strength of samples incorporating different replacement levels and various specific surfaces of limestone powder increases steadily with ages. The strength decreases generally with the increase of replacement level of limestone powder when the SSB is constant, while as the strength is higher than controlled mortar without limestone powder when the replacement level is low and the effect becomes visible for flexible strength. The composite cement strength with 15% limestone powder replacement meet the requirement of the 52.5R. Furthermore, the hydration products and microstructure are investigated by scanning electron microscope (SEM) at different ages and the hydration characteristics of mortar with limestone powder replacement is theoretically revealed.