大流动性UHPC制备与体积稳定性研究

发布时间：2018-02-27 03:32

本文关键词： 超高性能混凝土大流动性体积稳定性微观结构　出处：《哈尔滨工业大学》2015年硕士论文　论文类型：学位论文

【摘要】：超高性能混凝土(UHPC)是近年来各国学者研究的热点问题。但由于其工艺复杂,无法现场浇筑施工,收缩较大等因素严重影响其实际应用。本文在基本配合比优化设计的基础上,通过复掺高性能减水剂与消泡剂制备出大流动性、力学性能优良的超高性能混凝土材料,并研究了膨胀剂与减缩剂对超高性能混凝土体积稳定性的影响规律。研究结果表明:随着砂胶比增大,超高性能混凝土流动度降低,抗压强度先增大后降低;当硅灰掺量为所用水泥量的25%时,UHPC的抗压强度较高;掺入适量粉煤灰可以在一定程度上提高UHPC砂浆流动度,但对强度影响不大;石英粉的掺入会很大程度上降低UHPC砂浆流动度,但对强度有促进作用。最终得到常温养护下超高性能混凝土的基本配合比为:水泥:硅灰:石英砂(粗):石英砂(细):水=1:0.25:0.6125:0.4785:0.2125。消泡剂的掺入能有效降低UHPC新拌砂浆的含气量,平均降幅可达到50%;并且能够有效地提高其抗压强度,最大可提高20%;充分振动的情况下,相同消泡剂掺量的高水胶比UHPC砂浆的含气量较低水胶比降低60%左右,抗压强度最高可提高50%;对于高水胶比的超高性能混凝土来说,消除气泡比降低水胶比对强度的改善效果更加显著。减缩剂的引入对UHPC的收缩起到很好的抑制作用,但对强度影响较大,会使其自收缩降低39.9%,干燥收缩降低47.3%;膨胀剂的引入对UHPC收缩的抑制效果并不明显,但对其强度不会有太大影响,会使其自收缩降低16%,干燥收缩降低29.5%。消泡剂的引入会在很大程度上降低UHPC内部的大孔含量,增加微小孔的含量,对优化孔结构与孔径分布,从而显著提高超高性能混凝土强度。
[Abstract]:UHPC) is a hot issue studied by scholars all over the world in recent years. However, due to its complex technology, it can not be used in situ, and its practical application is seriously affected by large shrinkage. This paper is based on the optimization design of basic mix ratio. High performance concrete materials with high fluidity and excellent mechanical properties were prepared by mixing high performance water reducing agent and defoaming agent. The effect of expansion agent and shrinkage reducer on the volume stability of UHPC is studied. The results show that with the increase of the ratio of sand and binder, the flow degree of UHPC decreases, and the compressive strength increases first and then decreases. When the content of silica fume is 25% of the cement used, the compressive strength of UHPC is higher, the fluidity of UHPC mortar can be improved to some extent by adding proper amount of fly ash, and the fluidity of UHPC mortar will be greatly reduced by the addition of quartz powder. But it can promote the strength. Finally, the basic mix ratio of UHPC under normal temperature curing is obtained as follows: cement: silica fume: quartz sand (coarse: quartz sand: water: 1: 0.25: 0. 125: 0. 4785: 0. 2125). The addition of defoamer can effectively reduce the gas content of UHPC freshly mixed mortar. The average drop can reach 50%, and the compressive strength of the mortar can be increased by 20%. Under the condition of full vibration, the air content of UHPC mortar with the same amount of defoamer is about 60% lower than that of UHPC mortar. The maximum compressive strength can be increased by 50%. For the super high performance concrete with high water-binder ratio, the effect of eliminating bubbles is more remarkable than reducing the strength of water-binder ratio. The introduction of reducing agent has a good effect on the shrinkage of UHPC. However, the effect on the strength is greater, which will reduce the autogenous shrinkage by 39.9% and the dry shrinkage by 47.3%. The inhibition effect of the expansion agent on the shrinkage of UHPC is not obvious, but it will not have much effect on its strength. The defoamer can reduce the content of macropore in UHPC to a great extent, increase the content of micropore, optimize the pore structure and pore size distribution, and increase the strength of UHPC.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

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