Abstract This study investigates the influence of different percentages: 10, 30, and 50% of limestone powder (LS) and different curing temperatures: 50, 20, and 5°C on mechanical properties and microstructure of mass concrete. The microstructure is studied by X‐ray diffraction, thermogravimetric, and scanning electron microscopy. The results show that the mechanical strength of concrete gradually decreases with the increase of LS. Curing temperature 50°C enhances mechanical strength of LS concrete at ages of 3 and 7 days, but slightly reduces that at age of 28 days. While curing temperature 5°C significantly reduces the mechanical strength at ages of 3, 7, and 28 days. The microstructure results indicate that LS has weak chemical effect and can participate in cement hydration. Different curing temperatures can significantly influence the hydration products and microstructure of LS composite cement pastes.