新型混杂纤维增强水泥基材料（HyFRCC）的流变性能

发布时间：2018-06-06 08:41

本文选题：混杂纤维 + 流变性能　；参考：《大连理工大学》2016年硕士论文

【摘要】：混杂纤维增强水泥基复合材料(HyFRCC)较掺加单一纤维的水泥基复合材料具有更加优异的力学性能,且更大程度契合水泥基复合材料多层次、多尺度的结构特征而受到诸多关注。本论文中,将毫米级的钢纤维(SF)、聚乙烯醇(PVA)纤维与微米级的碳酸钙晶须(CW)进行混杂,以期获得纤维正混杂效应,并以廉价碳酸钙晶须部分替代钢纤维和PVA纤维,最大限度降低纤维成本。围绕“新型混杂纤维增强水泥基复合材料(HyFRCC)流变性能”这一主题,主要进行了这种新型HyFRCC拌合物的流变性及流动性能、硬化后的抗压强度和弯曲性能等的研究。重点关注了纤维混杂形式、基体材料选取和HyFRCC的配合比优化等几个方面内容。主要成果及结论总结如下：(1)由于碳酸钙晶须大比表面积、大长径比的特性,掺加水泥砂浆后表面吸附水作用明显,导致拌合物的流变性变化：晶须通过其在硬化水泥砂浆微观层次具有的裂缝桥连、裂缝偏转和晶须拔出机制,显示出较好的增强效果；当碳酸钙晶须掺量占材料总体积达1.5%时,砂浆的抗压和抗折强度最大,比空白试件分别增大27.6%和12.6%。(2)水泥砂浆中掺加PVA纤维后,拌合物的性能明显变差,而钢纤维在体积掺量小于0.75%时对流动性有一定的促进作用；受到纤维自身抗拉强度、弹性模量和纤维在不同流动度砂浆中分散性的影响,13mm钢纤维、6mm和12mm长度的PVA纤维掺量分别达到1.0%、1.0%和0.5%时,对试件弯曲韧性的提高效果最为明显。(3)为充分发挥不同尺度纤维在水泥基复合材料中不同层次的作用,将钢纤维、PVA纤维和碳酸钙晶须以不同形式进行混杂,探讨其对水泥砂浆拌合物性能和力学性能的影响。当按照体积掺量为1.5%钢纤维+0.4%PVA纤维+1.0%晶须混杂时,可获得工作性较好、弯曲韧性最佳的混杂纤维增强水泥砂浆。(4)在得到的最佳新型HyFRCC配比的基础上,分别以粉煤灰和硅灰作为掺合料按照不同比例替代水泥,进行基体配合比优化。粉煤灰掺量达到15%时,试件弯曲韧性达到最大值,同时具有更好的工作性能。硅灰掺量超过5%时,砂浆拌合物工作性开始变差；但掺量达11%时,试件具有最大的抗压强度和弯曲韧性。(5)以最佳的新型HyFRCC配比为基础,研究拌合物不同的流变性对硬化后材料力学性能的作用效果。采用最佳减水剂掺量为水泥质量的0.7%,拌合物具有最大的流动性时,晶须等纤维材料能够分散的更加均匀,获得最佳的等效抗弯强度值和弯曲韧性,分别为13.11 MPa和25.18N·m。
[Abstract]:Hybrid fiber reinforced cement matrix composites (HyFRCCs) have more excellent mechanical properties than cement matrix composites with single fiber, and have attracted much attention due to their multi-level and multi-scale structural characteristics. In this paper, the millimeter grade steel fiber, polyvinyl alcohol (PVA) fiber and micron calcium carbonate whisker (CW) were mixed in order to obtain the positive fiber mixing effect, and the cheap calcium carbonate whisker was used to partly replace the steel fiber and PVA fiber. Minimize fiber cost. The rheological properties, flowability, compressive strength and flexural properties of the new hybrid fiber reinforced cement matrix composites (HIFRC) were studied in this paper. Emphasis is placed on fiber hybrid form, matrix material selection and optimization of HyFRCC mixture ratio. The main results and conclusions are summarized as follows: (1) due to the characteristics of large specific surface area and large aspect ratio of calcium carbonate whisker, the surface adsorbing effect of cement mortar on the surface is obvious. The rheological change of the mixture: the whisker shows a good reinforcing effect by its crack bridge connection at the micro level of hardened cement mortar, crack deflection and whisker pull-out mechanism, and when the amount of calcium carbonate whisker is 1.5% of the total volume of the material, The compressive and flexural strength of mortar is the largest, which is increased by 27.6% and 12.6% than that of blank mortar, respectively. After adding PVA fiber into cement mortar, the properties of the mixture become worse obviously, while the steel fiber can promote the fluidity of cement mortar when the volume content is less than 0.75%. Under the influence of tensile strength, elastic modulus and dispersion of fiber in mortar of different fluidity, the content of PVA fiber of 13mm steel fiber 6mm and 12mm length reaches 1.0% and 0.5%, respectively. In order to give full play to the effect of different scale fibers in different layers of cement matrix composites, the steel fiber PVA fiber and calcium carbonate crystal should be mixed in different forms. The effect of cement mortar on the properties and mechanical properties of cement mortar was discussed. When the volume of 1.5% steel fiber 0.4%PVA fiber is mixed with 1.0% whisker, the hybrid fiber reinforced cement mortar with the best flexural toughness and good workability can be obtained. Fly ash and silica fume were used as admixtures to substitute cement in different proportions to optimize the matrix mix ratio. When the content of fly ash reaches 15, the bending toughness of the specimen reaches the maximum value, and it has better working performance. When the amount of silica fume exceeds 5, the workability of mortar begins to deteriorate, but when the content reaches 11, the specimen has the maximum compressive strength and flexural toughness. The effect of different rheological properties of the mixture on the mechanical properties of hardened materials was studied. When the content of water reducing agent is 0.7 of the cement mass, when the mixture has the greatest fluidity, the fiber materials such as whisker can be dispersed more evenly, and the best equivalent flexural strength and flexural toughness are obtained, which are 13.11 MPa and 25.18 nm, respectively.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU528

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