Experimental Research on Mix Proportion and Compressive Size Effect of ECC in the Hygrothermal Curing Environment in South China
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摘要: 为探究春夏季平均相对湿度80%、日间平均气温30℃以上的华南地区湿热环境下工程水泥基复合材料(ECC)的合理使用配比及抗压尺寸效应,以粉煤灰、聚乙烯醇(PVA)纤维、养护环境和试件尺寸为基本参数,对2类9组共108个ECC材性试件进行破坏试验。通过分析不同因素对ECC抗压、抗折和劈裂抗拉强度的影响规律,得到适于华南湿热环境的ECC合理使用配合比及其抗压尺寸效应系数。结果表明:华南自然湿热养护环境下,ECC的抗压、抗折和劈裂抗拉强度主要由PVA纤维控制,增加胶凝材料中粉煤灰掺量有利于改善ECC的抗折性能,但不利于提高其抗拉强度,粉煤灰掺量为35%、PVA纤维掺量为1.0%的ECC抗压、抗折和劈裂抗拉性能综合最;标准养护、湿热养护、温水养护条件下立方体抗压强度尺寸效应的平均系数为fcu70.7∶fcu100∶fcu150=0.93∶1.00∶0.78,轴心抗压强度尺寸效应的平均系数为fc70.7∶fc100∶fc150=0.96∶1.00∶0.93;温湿度对横截面边长为70.7 mm的立方体和棱柱体试块的ECC抗压强度尺寸效应影响较大。Abstract: In order to study the mix proportion and compression size effect of engineered cementitious composites (ECC) under hygrothermal curing environment with average relative humidity of 80% and daytime average temperature of 30 ℃ in spring and summer, material tests on 108 specimens in 2 categories involving variables of fly ash, polyvinyl alahol fiber (PVA) fibers, curing environment, and geometrical dimensions were conducted. Based on the experimental results, favorable mix proportions and size effect coefficients of the ECC under the hygrothermal curing environment were obtained. The results indicated that the compression, shearing, and tensile performance of ECC was determined by the amount of PVA fibers, and the fly ash contributed to the shear strength of ECC, but reduced its tensile strength. Under the hygrothermal curing environment of South China, the ECC mix proportion with 35% fly ash and 1.0% PVC fibers had the most favorable mechanical properties, and the size effect coefficients for cubic and prism strengths of the ECC were fcu70.7∶fcu100∶fcu150=0.93∶1.00∶0.78 and fc70.7∶fc100∶fc150=0.96∶1.00∶0.93, respectively. The temperature and humidity had obvious size effect on the prism and cube specimen with the cross section of 70.7 mm side length.
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Key words:
- mix proportion /
- curing environment /
- size effect /
- compressive strength
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