溴化钙对水泥基材料强度及微观结构影响

Effect of calcium bromide on strength and microstructure of cement-based materials

以溴化钙(CaBr2)作为早强组分,研究低温5℃下CaBr2的早强性能,及其对净浆水化热、产物组成、微观形貌和孔结构的影响.结果表明:CaBr2早强性能优异,且使28 d强度不降低;对温度-5~20℃具有良好适应性,温度越低,早强作用越显著.当温度低于5℃以下,掺1.0%CaBr2时,净浆1、3、7和28 d抗压强度比分别达到299%、179%、157%和134%,各龄期强度均超过对比样20℃养护下的强度.当温度为20℃时,CaBr2的掺入使水泥水化诱导期缩短、加速期提前,水化放热速率、放热量增大.CaBr2促进了低温下水泥熟料的水化,且生成水化溴氧铝酸钙[Ca4Al2O6Br2·10H2O]的新物质,大量水化产物相互堆积,细化了水化初期(7 d前)试件的孔径,最可几孔径减小,总孔隙率降低,试件微观结构更加致密.

Calcium bromide(CaBr2) was designed as an early strength component to study its early-strength properties at low temperature of 5 ℃, and its effects on the hydration heat, product composition, microstructure, and pore structure of cement pastes were discussed. The results show that, CaBr2 has a significant effect on the early strength and does not cause the 28 d strength decrease. CaBr2 had good adaptability to the temperature(-5 to 20 ℃), and the lower the temperature was, the more significant the effect of early strength was. The 1, 3, 7 and 28 d compressive strengths of the cement pastes mixed with 1.0% CaBr2 can reach 299%, 179%, 157%, and 134%, respectively at 5 ℃, and the strengths at each age have already exceeded that of the contrast sample cured at 20 ℃. At 20 ℃, the incorporation of CaBr2 shortens the induction period and advances the accelerated period of cement hydration, and increases the heat release rate and heat release. CaBr2 can promote the initial hydration of the cement clinker at the low temperature, and generate new products of hydrated calcium bromoaluminate(Ca4Al2O6Br2·10 H2O). Large amounts of hydration products are accumulated with each other, refining the pores size of cement pastes at the initial stage of hydration(before 7 d) and decreasing the most probable pore size and total porosity, thus the microstructure of specimens became denser.