混合料贮存期对预拌补偿收缩混凝土微观结构影响试验分析 2018-08-08

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为研究干拌混合料贮存期对预拌补偿收缩混凝土微观结构的影响,当膨胀剂掺量为 6%、砂子含水率为 1.0%时,对 6 种贮存期(3,7,10,15,20,30 d)的预拌补偿收缩混凝土进行微观结构试验。结果表明,当 干拌混合料贮存期为 3,7,10 d 时,混凝土中存在大量 C-S-H 凝胶和针棒状 AFt 晶体,密实性较好,随着贮 存期的增加,水泥石结构中孔洞直径分别为 3.075,3.979,5.885 μm,微裂缝宽度分别为 0.364,0.450,0.703 μm, 界面过渡区(intertacial transition zone,ITZ)中的粘结裂缝宽度分别为 0.554,0.949,1.280 μm. 当贮存期为 15,20,30 d 时,水泥石结构中孔洞直径分别为 6.137,6.335,7.033 μm,微裂缝宽度分别为 1.230,1.352, 1.370 μm,变化幅度较大,取向排列的 Ca(OH)2 晶体增多,C-S-H 凝胶数量相对减少,混凝土密实度下降,其 附近结构中有新微裂缝存在,且微裂缝尺寸随贮存期的增加而不断增大。

关键词:地下工程;补偿收缩混凝土;干拌混合料;贮存期;微观结构;界面过渡区

中图分类号:TU528.55 文献标识码:A 文章编号:1674-2850(2016)20-2125-08

Effects of storage periods for dry-mixed materials on microstructure of ready-mixed shrinkage-compensating concrete MA Qinyong1, 2, ZHANG Yangyang1 (1. School of Civil Engineering and Architecture, Anhui University of Science and Technology, Huainan, Anhui 232001, China; 2. Engineering Research Center of Underground Mine Construction, Ministry of Education, Anhui University of Science and Technology, Huainan, Anhui 232001, China) Abstract: In order to study the effect of the storage period for dry-mixed materials on the microstructure of the ready-mixed shrinkage-compensating concrete, microstructure test is carried out with respect to six different kinds of storage periods (3, 7, 10, 15, 20, 30 d), and with the constant expansive agent dosage of 6% and sand moisture content of 1.0%. The results show that when the storage periods of the dry-mixed materials are 3, 7, 10 d, respectively, there exist mass of C-S-H gel and AFt crystal. With the increasing storage period, the diameters of holes are 3.075, 3.979, 5.885 μm, the breadths of micro cracks are 0.364, 0.450, 0.703 μm, and the breadths of micro cracks in the intertacial transition zone (ITZ) are 0.554, 0.949, 1.280 μm. When the storage periods of the dry-mixed materials are 15, 20, 30 d, the diameters of holes are 6.137, 6.335, 7.033 μm, respectively, the breadths of micro cracks are 1.230, 1.352, 1.370 μm, and the increase amplitude is big. The Ca(OH)2 crystals in the oriented arrangement increase, while the C-S-H gel quantity decreases gradually. The intensity of concrete shows a decreasing trend, while there exist new micro cracks nearby the transition zone of the interface, and the size of the micro cracks increases gradually with the increasing storage period.

Key words: underground engineering; shrinkage-compensating concrete; dry-mixed material; storage periods; microstructure; interfacial transition zone
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