不同养护条件下超高性能混凝土（UHPC）的收缩性能研究
发布时间：2018-12-23 11:36
【摘要】：超高性能混凝土(Ultra High Performance Concrete,英文缩写为UHPC)是一种具有高强度、高韧性、高体积稳定性和优良耐久性的新型水泥基复合材料。在新型混凝土材料研究领域,收缩问题始终是所有研究学者关注的焦点,也是限制UHPC在结构工程中广泛应用的因素之一。收缩是导致混凝土开裂的主要原因,混凝土一旦开裂,则会大大降低结构的耐久性,甚至威胁到结构的安全。不同养护条件下UHPC的收缩性能是不同的,已有研究表明:UHPC经过热养护后干燥收缩值会大幅减少,其原因是热养护后UHPC中孔结构得到细化,基体变得更密实。本文研究了不同养护条件下UHPC试件的早期收缩和干燥收缩,并着重研究了热养护过程中UHPC的收缩变形特点以及热养护过后UHPC的收缩发展趋势。另外,本试验通过压汞试验、电镜观测、差热分析微观试验来进行机理分析。研究结果如下:(1)标准养护条件下,UHPC的早期收缩值较大,约为干燥收缩值的1.5倍。当龄期为65d时,UHPC的收缩趋于稳定,为1490με。(2)UHPC的温度膨胀系数为11.76με/°C。在热养护过程中,UHPC在50°C以内基本不发生收缩,当温度接近70°C时,收缩值迅速增加,最终的收缩值为450με。(3)随着配筋率的提高,UHPC在热养护过程中的收缩减小,这说明配筋能够抑制UHPC在热养护过程中的收缩。配筋UHPC在热养护过程中的弹性应变很小,约为2.4με~10.37με,所以产生的残余应力很小。(4)试件尺寸对收缩有很大的影响,小尺寸试件的收缩通常要小于大尺寸试件的收缩,这是小尺寸试件中钢纤维定向分布造成的。(5)通过对不同龄期UHPC试件的微观结构的分析,经热养护后,孔结构得到细化,生成的水化产物更多,并且减少了Ca(OH)_2和钙矾石的体积。
[Abstract]:Ultra high performance concrete (Ultra High Performance Concrete,) is a new cement matrix composite with high strength, high toughness, high volume stability and excellent durability. In the research field of new concrete materials, the shrinkage problem has always been the focus of attention of all researchers, and also one of the factors limiting the wide application of UHPC in structural engineering. Shrinkage is the main cause of concrete cracking. Once the concrete cracks, the durability of the structure will be greatly reduced, and even the safety of the structure will be threatened. The shrinkage properties of UHPC are different under different curing conditions. It has been shown that the drying shrinkage value of UHPC will be greatly reduced after thermal curing. The reason is that the mesoporous structure of UHPC is refined and the matrix becomes more dense after thermal curing. In this paper, the early shrinkage and drying shrinkage of UHPC specimens under different curing conditions are studied, and the shrinkage deformation characteristics of UHPC during thermal curing and the shrinkage trend of UHPC after thermal curing are emphatically studied. In addition, the mechanism was analyzed by mercury injection test, electron microscope observation and differential thermal analysis. The results are as follows: (1) under the standard curing conditions, the early shrinkage of UHPC is larger, about 1.5 times of the dry shrinkage. When the age is 65 days, the contraction of UHPC tends to be stable, which is 1490 渭 蔚. (2) the thermal expansion coefficient of UHPC is 11.76 渭 蔚 / 掳C. During thermal curing, UHPC basically does not shrink within 50 掳C. when the temperature is close to 70 掳C, the shrinkage value increases rapidly, and the final shrinkage value is 450 渭 蔚. (3) with the increase of reinforcement ratio, the shrinkage of UHPC decreases during thermal curing. This indicates that reinforcement can inhibit the shrinkage of UHPC during thermal curing. The elastic strain of reinforced UHPC during thermal curing is very small, about 2.4 渭 蔚 ~ 10.37 渭 蔚, so the residual stress is very small. (4) the size of specimen has a great influence on shrinkage, and the shrinkage of small size specimen is usually smaller than that of large size specimen. This is caused by the directional distribution of steel fibers in small size specimens. (5) by analyzing the microstructure of UHPC specimens of different ages, the pore structure is refined after thermal curing, and more hydration products are generated. The volume of Ca (OH) _ 2 and ettringite was reduced.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528
[Abstract]:Ultra high performance concrete (Ultra High Performance Concrete,) is a new cement matrix composite with high strength, high toughness, high volume stability and excellent durability. In the research field of new concrete materials, the shrinkage problem has always been the focus of attention of all researchers, and also one of the factors limiting the wide application of UHPC in structural engineering. Shrinkage is the main cause of concrete cracking. Once the concrete cracks, the durability of the structure will be greatly reduced, and even the safety of the structure will be threatened. The shrinkage properties of UHPC are different under different curing conditions. It has been shown that the drying shrinkage value of UHPC will be greatly reduced after thermal curing. The reason is that the mesoporous structure of UHPC is refined and the matrix becomes more dense after thermal curing. In this paper, the early shrinkage and drying shrinkage of UHPC specimens under different curing conditions are studied, and the shrinkage deformation characteristics of UHPC during thermal curing and the shrinkage trend of UHPC after thermal curing are emphatically studied. In addition, the mechanism was analyzed by mercury injection test, electron microscope observation and differential thermal analysis. The results are as follows: (1) under the standard curing conditions, the early shrinkage of UHPC is larger, about 1.5 times of the dry shrinkage. When the age is 65 days, the contraction of UHPC tends to be stable, which is 1490 渭 蔚. (2) the thermal expansion coefficient of UHPC is 11.76 渭 蔚 / 掳C. During thermal curing, UHPC basically does not shrink within 50 掳C. when the temperature is close to 70 掳C, the shrinkage value increases rapidly, and the final shrinkage value is 450 渭 蔚. (3) with the increase of reinforcement ratio, the shrinkage of UHPC decreases during thermal curing. This indicates that reinforcement can inhibit the shrinkage of UHPC during thermal curing. The elastic strain of reinforced UHPC during thermal curing is very small, about 2.4 渭 蔚 ~ 10.37 渭 蔚, so the residual stress is very small. (4) the size of specimen has a great influence on shrinkage, and the shrinkage of small size specimen is usually smaller than that of large size specimen. This is caused by the directional distribution of steel fibers in small size specimens. (5) by analyzing the microstructure of UHPC specimens of different ages, the pore structure is refined after thermal curing, and more hydration products are generated. The volume of Ca (OH) _ 2 and ettringite was reduced.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528
【参考文献】
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1 韩松;涂亚秋;安明U，
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