掺石灰石粉混凝土抗硫酸盐侵蚀性能及改善机理

Sulfate Corrosion Resistance and Improvement Mechanism of Concrete Mixed with Limestone Powder

为提高掺石灰石粉混凝土在硫酸盐环境下的耐久性能,研究掺石灰石粉混凝土抗硫酸盐侵蚀性能以及粉煤灰/矿粉改善机理,通过混凝土硫酸盐干湿循环实验,得到试件外观及抗压强度变化,采用傅里叶红外光谱、XRD、SEM/EDS分析探究侵蚀产物物相组成。研究结果表明,硫酸钠结晶作用和生成的侵蚀产物石膏导致试件膨胀开裂,强度性能下降。石灰石粉的掺入增加了侵蚀产物中石膏的含量,从而引起混凝土试件抗侵蚀性能的下降,单掺25%和50%(质量分数)石灰石粉试件抗压强度耐蚀系数分别下降了23.1%和33.9%。粉煤灰/矿粉与石灰石粉互掺时表现出互补的协同效应,改善了掺石灰石粉混凝土抗硫酸盐干湿循环侵蚀的性能。矿粉的效果优于粉煤灰,胶凝材料采用66%水泥-17%石灰石粉-17%(质量分数)矿粉组成的混凝土表现出最优的抗侵蚀性能。

In order to improve the durability of limestone powder concrete in sulfate environment,the sulfate corrosion resistance of limestone powder concrete and the improvement mechanism of fly ash/slag were studied.The appearance and compressive strength of the specimens were obtained through the sulfate dry-wet cycle test of concrete.The phase composition of the erosion products were analyzed by FTIR,XRD and SEM/EDS.The results show that the crystallization of sodium sulfate and gypsum formed in the erosion products lead to the expansion and cracking of the specimens and the decrease of the strength.The addition of limestone powder increases the content of gypsum in the erosion products,which leads to a decrease of the corrosion resistance of the concrete specimens,and the corrosion resistance coefficient of 25%and 50%(mass fraction)limestone powder decreases by 23.1%and 33.9%,respectively.When fly ash/slag and limestone powder are mixed,they show a complementary synergistic effect,which improves the performance of dry-wet cycle sulfate corrosion resistance of concrete mixed with limestone powder.The effect of slag is better than that of fly ash.The concrete composed of 66%cement-17%limestone powder-17%(mass fraction)slag shows the best corrosion resistance.