掺纤维的桥面铺装层混凝土的收缩和时间响应(英文)

SHRINKAGE-TIME RESPONSES OF BRIDGE DECK OVERLAY MIXTURES WITH FIBROUS ADDITIVES

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。

This paper presents the experimental results and findings on the effect of discontinuous synthetic fibers（non-metallic） on the drying shrinkage-time responses of various bridge deck concrete overlay mixtures.The studied mixtures include latex-modified concrete（LMC）,micro-silica concrete（MSC）,and fly ash concrete（FAC）.These overlays typically experience shrinkage cracking at early and long-term ages even though careful mix designs and careful construction practices are employed.Reasons could be attributed to the large surface area of the overlay that is exposed to drying,their low water cement ratio,and their small typical thickness of about 55 mm.Therefore,it is believed that incorporating discontinuous synthetic fibers within the overlay mix design will not only increase their tensile strength and toughness properties but also will lower their drying shrinkage strains.In this paper,plain and fibrous mixtures were cast from the LMC,MSC,and FAC overlay types.Different types of fibers were used within the same mixture with an upper limit of the total fiber content of 1.78 kg/m^3 due to constructability limitations.The drying shrinkage strains were monitored according to ASTM C157 for the various overlay mixtures.The shrinkage results showed that the fibrous mixtures experience lower drying shrinkage strains than corresponding plain mixtures.The shrinkage-time responses for the various overlay types were also compared.Compression and flexure tests results as well as permeability test results are also presented and compared herein for the various overlay mixtures.