盐侵-冻融-干湿耦合作用下天然浮石混凝土的耐久性分析

内蒙古河套灌区渠道“重灌轻排”导致土壤盐碱化严重,严重影响了水工建筑的使用寿命。本文研究了河套灌区渠道中盐侵-冻融-干湿耦合作用下天然浮石混凝土耐久性,以天然浮石混凝土作为衬砌材料,模拟河套灌区渠道水工建筑实际排水工程环境进行室内加速试验。以相对动弹模量以及质量损失率为损伤评价参数,分析天然浮石混凝土的宏观损失规律;借助环境扫描电镜和能谱成分分析揭示其退化机理;最后采用Weibull分布对天然浮石混凝土的相对动弹模量的退化轨迹构建模型,获得寿命可靠度函数,并预测出其极限失效次数。结果表明:在盐侵-冻融-干湿耦合作用下天然浮石混凝土的质量损失率总体呈现上升趋势,相对动弹模量呈现出下降趋势;在多因素耦合作用下,盐溶液与混凝土水化产物进行化学反应形成侵蚀产物,侵蚀产物膨胀引起混凝土内部孔隙变大、裂缝扩展,天然浮石混凝土劣化速率提高;在多因素耦合作用下天然浮石混凝土的可靠度为三阶段退化模型,其失效机制为耗损型失效。该研究可以为天然浮石混凝土在河套灌区渠道水工建筑工程应用提供理论依据。

Analysis Durability of Natural Pumice Concrete under Salt Solution Erosion-Freeze-Thaw-Dry-Wet Coupling

The "heavy irrigation and light drainage" channels in Inner Mongolia''s Hetao irrigation area caused major soil salinization, reducing the service life of natural pumice concrete (NPC) used in hydraulic construction. In the channels of the hetao irrigation area, to investigate the durability of NPC under the coupling effect of salt solution erosion-freeze-thaw-dry-wet, the research object in this paper was NPC, which was used as a lining material to simulate the actual drainage engineering environment of hydraulic construction in the channels of Hetao irrigation area for accelerated indoor tests. Analysis of the macroscopic loss pattern of NPC utilized relative dynamic modulus and mass loss rate as damage evaluation parameters, and using Environmental Scanning Electron Microscopy and Energy Dispersive Spectrometer, the degrading mechanism of NPC was shown. Finally, the Weibull distribution is utilized to create a model for the deterioration trajectory of the relative dynamic elastic modulus of NPC in order to calculate the life reliability function and estimate the final failure number. The results show that under the coupling effect of salt solution erosion-freeze-thaw-dry-wet, the mass loss rate of NPC shows an overall increasing trend with the increase of cycle number, and the relative dynamic elastic modulus shows a decreasing trend with the increase of cycle number. Under the coupling effect of multiple factors, the salt solution reacts with the concrete hydration products to generate erosion products. The expansion of the erosion products leads to larger pores and crack expansion inside the concrete, and the deterioration of natural pumice concrete is accelerated. NPC''s dependability is a three-stage deterioration model with a depletion-type failure mechanism under the combined action of various variables. In the Hetao irrigation area, the study provides a theoretical foundation for the use of natural pumice concrete in channel hydraulic construction projects.