干湿循环与持续轴压荷载对水泥砂浆耐硫酸盐侵蚀性能的影响

Influence of Dry-Wet Cycle and Continuous Axial Load onSulfate Resistance of Cement Mortar

为分析持续轴压荷载和干湿循环对水泥砂浆耐硫酸盐侵蚀性能的影响,通过宏-微观试验,对比不同工况下砂浆的表观现象、质量、膨胀率、强度的劣化特性并探究其侵蚀机理。结果表明:持续轴压荷载和干湿循环均显著加剧砂浆劣化,且应力越大影响越大;应力比0.4工况的砂浆线膨胀率最高增长0.67%,其抗压强度最大损失40.72%;干湿循环工况的砂浆线膨胀率最高增长0.43%,其抗压强度最大损失29.63%;较低持续轴压荷载前期减缓硫酸盐侵蚀而后期加剧,较高持续轴压荷载直接增多砂浆内部缺陷,加剧化学侵蚀,导致宏观性能大幅下降;干湿循环作用下硫酸盐结晶与钙矾石、石膏等腐蚀产物共同导致砂浆微观结构劣化和缺陷扩展,持续轴压荷载不改变硫酸盐的侵蚀机理,但显著影响侵蚀进程;二项式函数能够较好的描述砂浆硫酸盐抗压强度的劣化规律。研究成果可以为水工结构的耐久性评价与保护层设计提供指导和支撑。

To analyze the influence of sustained axial compression loads and wet-dry cycles on the sulfate erosion resistance of cement mortar,a combination of macroscopic and microscopic experiments was conducted.We compared the appearance phenomena,appearance quality,expansion rate,and strength degradation characteristics of the cement mortar under different conditions aiming to explore the erosion mechanisms involved.The results revealed that both sustained axial compression loads and wet-dry cycles significantly exacerbated the deterioration of mortar,with a more notable effect observed at higher stress levels.The mortar subjected to a stress ratio of 0.4 exhibited the highest increase in linear expansion rate,reaching 0.67%,and experienced the greatest loss in compressive strength,with a reduction of 40.72%.Under dry-wet cycles,the mortar displayed a maximum increase in linear expansion rate of 0.43%and a significant loss in compressive strength of 29.63%.Lower sustained axial compression loads initially mitigated sulfate erosion in the early stages but aggravated it later on.Conversely,higher sustained axial compression loads directly increased internal defects within the mortar,intensifying chemical erosion and leading to a substantial decline in macroscopic performance.The combined effect of wet-dry cycles and sulfate crystallization,calcium aluminate,gypsum,and other corrosion products contributed to the deterioration of the mortar's microstructure and the expansion of defects.Although the erosion mechanism of sulfates remained unaffected by sustained axial compression loads,these loads significantly influenced the erosion process.The degradation pattern of sulfate-resistant compressive strength in mortar can be effectively described by a binomial function.The research findings provide valuable guidance and support for the durability evaluation and the design of protective layers in hydraulic structures.