The deterioration of engineered cementitious composites (ECCs) incorporating ultra high volume fly ash (FA) under coupled action of freeze-thaw cycles (F-T) and sulfate attack is explored in this paper. Three mixes, fly ash to cement ratio of 1.2 (FA1.2), 1.8 (FA1.8) and 2.4 (FA2.4) were investigated. ECC specimens were subjected to freeze-thaw cycles under 10% sodium sulfate solution and 10% magnesium sulfate solution, respectively. In addition, loss of weight, variation of relative dynamic elastic modulus (RDEM) and compressive strength were carried out at different numbers of F-T cycling. What’ more, microstructure of ECC was investigated after the final 150 F-T cycles. It was observed that RDEM decreased with the increase of FA content in sodium sulfate solution, on the contrary, specimens of FA1.8 showed the highest RDEM in magnesium sulfate solution. It can be found that the residual compressive strength of specimens in magnesium sulfate solution declined firstly and then increased within all F-T cycles, while it continued to decrease in sodium sulfate solution. The residual compressive strength was higher in magnesium sulfate solution than it in sodium sulfate solution, achieving the maximum of 34.7 MPa.

中文翻译：

---

复杂环境下高掺量粉煤灰纤维混凝土的耐久性

本文探讨了冻融循环（FT）和硫酸盐侵蚀耦合作用下掺入超高量粉煤灰（FA）的工程水泥复合材料（ECCs）的劣化。研究了三种混合物，粉煤灰与水泥的比例分别为1.2（FA1.2），1.8（FA1.8）和2.4（FA2.4）。ECC标本分别在10％的硫酸钠溶液和10％的硫酸镁溶液下进行冻融循环。另外，在不同的FT循环次数下进行重量损失，相对动态弹性模量（RDEM）的变化和抗压强度。此外，在最后的150个FT循环后对ECC的微观结构进行了研究。观察到，RDEM随硫酸钠溶液中FA含量的增加而降低，而FA1标本则相反。图8显示了硫酸镁溶液中最高的RDEM。可以发现，试样在硫酸镁溶液中的残余抗压强度在所有的FT循环中先下降然后增加，而在硫酸钠溶液中则继续下降。硫酸镁溶液中的残余抗压强度高于硫酸钠溶液中的残余抗压强度，达到34.7 MPa的最大值。