低湿变温环境对硫酸盐作用下水泥砂浆性能的影响

摘要/Abstract

摘要： 基于西部钢筋混凝土基础设施所处环境特点,将水泥砂浆试件在低湿变温环境中进行半浸泡硫酸盐腐蚀,结合XRD、SEM、LF-NMR和电导滴定SO^2-₄等测试手段研究了低湿变温环境对硫酸盐半浸泡腐蚀水泥基材料的影响。结果表明:对于低湿变温环境中的水泥砂浆试件,其液面以上30 mm内的水膜区硫酸盐腐蚀程度较低,而液面以上30~60 mm的蒸发区腐蚀程度较高,并出现明显剥落现象;饱和度较小的Na₂SO₄溶液对砂浆试件蒸发区的腐蚀更为严重;蒸发区1 000 nm以上的孔隙发生膨胀性盐结晶导致砂浆内部出现微裂纹且有害孔比例增加,该区域以物理膨胀破坏为主;浸泡区膨胀性腐蚀产物石膏和钙矾石的大量生成使得该区域以化学腐蚀为主。随着腐蚀产物在孔径为50~1 000 nm的毛细孔中不断累积,砂浆表层开裂且1 000 nm以上的宏观孔比例有所增加。掺入的矿粉通过其二次水化作用提高了砂浆浸泡区抗硫酸盐腐蚀能力,而石灰石粉的掺入则因稀释效应降低了砂浆抗硫酸盐腐蚀能力。

关键词: 矿物掺合料, 温度, 硫酸盐腐蚀, SO^2-₄, 孔径分布

Abstract: Based on environmental characteristics of reinforced concrete infrastructure in western China, cement mortar specimens were subjected to semi-immersed sulfate corrosion in low humidity and varying temperature. The influences of low humidity and varying temperature on semi-immersion sulfate attack cement-based materials were studied by combination of XRD, SEM, LF-NMR, and conductivity titration of sulfate ions. The results show that under low humidity and varying temperature, the mortar subjected to semi-immersion sulfate attack has a water film zone within 30 mm above the surface of sulfate solution, and the corrosion degree is relatively low. The evaporation zone above the solution surface of 30~60 mm has a higher degree of corrosion and obvious peeling phenomenon. Corrosion of evaporation zone of mortar semi-immersed in Na₂SO₄ solution is more seriously than that semi-immersed in MgSO₄ solution due to their difference in saturation under different temperatures. The expansive salt crystallization within pores above 1 000 nm is prone to the occurrence in evaporation zone, which leads to the micro cracks inside mortar and an increase in the proportion of harmful pores, resulting in physical expansion damage being the main cause of this zone. Chemical corrosion in the immersion zone of mortar is dominant due to the formation of swelling corrosion products such as gypsum and ettringite. As corrosion products accumulated in the pores with pore sizes of 50~1 000 nm, the surface of mortar cracks and the proportion of macroscopic pores with pore sizes above 1 000 nm increases. The addition of ground granulated blast furnace slag in cement increases the sulfate corrosion resistance of the immersion zone of mortar via its secondary hydration effect, and the addition of limestone powder decreases the sulfate corrosion resistance of mortar due to its dilution effect.

Key words: mineral admixture, temperature, sulfate corrosion, sulfate ion, pore size distribution

中图分类号:

TU528

贾艳涛, 李之恒, 王大富, 吴萌. 低湿变温环境对硫酸盐作用下水泥砂浆性能的影响[J]. 硅酸盐通报, 2024, 43(6): 1965-1974.

JIA Yantao, LI Zhiheng, WANG Dafu, WU Meng. Effect of Low Humidity and Varying Temperature Environment on Performance of Cement under Sulfate Attack[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2024, 43(6): 1965-1974.

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