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研究了用于桥面铺装层掺不连续合成纤维(非金属纤维)混凝土的干燥收缩和时间响应。所研究的混凝土包括:乳胶改性混凝土(latex-modified concrete,LMC)、硅灰混凝土(micro-silica concrete,MSC)和粉煤灰混凝土(fly ash concrete,FAC)。这些桥面铺装层即使经过仔细的配合比设计和精细施工仍会出现早期和后期的收缩开裂,这是因为铺装层暴露于干燥环境中的巨大表面积、低水灰比和仅约55mm的厚度。因此,一般认为在铺装层中添加合成短纤维不仅可增强其抗拉强度和韧性,而且能降低混凝土的干缩应变。分别浇注了LMC,MSC和FAC素混凝土和掺有纤维的混凝土铺装层,并在同种混凝土中采用了不同类型的纤维。考虑到可施工性,其纤维的最大掺量为1.78kg/m3。对各种不同类型的铺装层混凝土均按照ASTM C157进行干缩应变测量。干缩测试结果表明掺有纤维的混凝土较之素混凝土具有较低的干缩应变。同时测定了各种混凝土的干缩经时变化、抗压强度与抗折强度及渗透性,并进行了对照分析。
The drying shrinkage and time response of concrete with discontinuous synthetic fiber (non-metallic fiber) used in bridge deck pavement were studied. The studied concrete includes latex-modified concrete (LMC), micro-silica concrete (MSC) and fly ash concrete (FAC). These bridge decks still exhibit early and late shrinkage cracking, even after careful mix design and fine construction because of the large surface area exposed to the dry environment, low water-cement ratio, and only about 55 mm thickness. Therefore, it is generally believed that the addition of synthetic staple fibers in pavement not only enhances its tensile strength and toughness, but also reduces the shrinkage strain of concrete. LMC, MSC and FAC plain concrete and fiber concrete paving were cast separately and different types of fibers were used in the same type of concrete. Taking into account the workability, the maximum amount of fiber is 1.78kg / m3. Dry shrinkage strain measurements were performed on various types of pavement concrete according to ASTM C157. Shrinkage test results show that fiber-doped concrete has lower dry shrinkage than concrete. Simultaneously, the variation of dry shrinkage, compressive strength, flexural strength and permeability of various concrete were measured and compared.