碳化、干湿与冻融耦合作用下再生混凝土耐久性能

    Durability of Recycled Concrete Under the Coupling of Carbonation, Dry-wet and Freeze-thaw

    • 摘要: 为了解决再生混凝土在复杂环境条件下的耐久性能研究匮乏问题,对5种再生混凝土进行碳化、干湿与冻融耦合作用下的耐久性试验,测试其动弹性模量、氯离子迁移系数、碳化深度及微观孔隙特征参数,并引入孔隙迂曲度指标进行分析.结果表明:交替碳化与干湿对再生混凝土的冻融劣化效果有显著促进作用,累计碳化42 d与干湿循环42次可使再生混凝土冻融损伤量增加21.9%~26.9%,抗氯离子渗透性能降低45.05%~96.18%;与单一碳化42 d相比,交替干湿循环42次与冻融循环300次可使再生混凝土的碳化深度增加1.6~3.5倍.此外,碳化、干湿作用均增大孔隙迂曲度,而冻融及三因素耦合作用均减小孔隙迂曲度;孔隙迂曲度与氯离子迁移系数及相对动弹性模量均具有显著的相关性,在一定程度上可作为再生混凝土耐久性能评价指标.

       

      Abstract: To solve the problem of insufficient research on durability of recycled concrete under complex environmental conditions, the durability tests on five types of recycled concrete under the coupling of carbonation, dry-wet and freeze-thaw cycles were carried out. The dynamic elastic modulus, chloride ion migration coefficient, carbonation depth and micro-pore characteristics were measured, and the pore tortuosity was employed for analysis. Results show that carbonation and dry-wet alternating can significantly promote the freeze-thaw degradation of recycled concrete. The cumulative carbonation for 42 days and dry-wet for 42 times can increase the freeze-thaw damage of recycled concrete by 21.9%-26.9%, and decrease the chloride ion permeation resistance by 45.05%-96.18%. Compared with single carbonation for 42 days, the carbonation depth of recycled concrete can be increased 1.6-3.5 times by alternating 42 dry-wet cycles and 300 freeze-thaw cycles. In addition, carbonation and dry-wet increase the pore tortuosity, while freeze-thaw and the coupling of three environmental factors decrease. Moreover, the pore tortuosity significantly correlates with chloride ion migration coefficient and relative dynamic elastic modulus, which indicates that it can be used as an indicator of the durability of recycled concrete.

       

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