【作者】 王哲；

【导师】 高淑玲；

【作者基本信息】 河北工业大学 ， 土木工程， 2020， 硕士

【摘要】 近年来,由水泥为基体制成的混凝土已经不能满足各种环境条件实际工程要求,纤维增强水泥基复合材料(以下简称“ECC”)的问世一定程度上解决了混凝土脆性大、变性能力差、裂纹控制能力弱等缺点,虽然其在常温下具有较强的韧性、裂缝控制以及应变硬化能力,但传统ECC中使用了大量的水泥和日本可乐丽公司生产的PVA纤维,使其材料成本居高不下,造成可持续性指标MSI(Material Sustainability Indicators)偏高,所以为了节约成本、生态化发展ECC以及实现高延性,本文将工业副产品粉煤灰大量替代水泥(等量替代率分别为65%、70%和78%),国产PVA纤维替代进口PVA纤维,以达到高水平性价比要求。尽管ECC具有较高的拉伸延性和耐久性,在各种土木工程应用中具有吸引力,但是在使用寿命期间,火灾是ECC结构最严重的风险之一,故本文引入耐高温纤维(玄武岩纤维/钢纤维),等量(0.5%)取代PVA纤维,在常温下研究粉煤灰掺量与单掺上述三种纤维、混掺上述两种纤维对15组配比ECC受压性能和直接拉伸性能的影响,实验结果得出相比于另两种粉煤灰掺量,70%粉煤灰掺量对所有不同种类纤维试件极限强度、极限应变降低程度影响较小,下文以70%粉煤灰掺量为基础,研究高温自然冷却后不同温度(200℃、400℃、600℃)对上述单掺ECC和混掺HECC(混杂纤维增强水泥基复合材料)残余受压性能和残余直接拉伸性能的影响(加热前后外观形态、质量损失、破坏形态、残余强度、残余应力-应变全曲线),研究显示钢纤维相比于玄武岩纤维经高温作用后可使残余强度和残余应变维持在较高水平。由于普通砂浆抹面层、砌筑砂浆层和砖体三种材料对温度敏感性不同,砌体结构经过高温后体内会形成不同的应力梯度,甚至导致外抹面层脱落后整体结构随时发生倒塌的危险,所以将上述HECC代替普通砂浆抹面层应用于加固内部砌体结构,与单掺PVA纤维加固层砌体结构和普通砂浆抹面层砌体结构在不同温度下作对比,进行棱柱体压缩试验和三联体剪切试验,分别分析竖向荷载下无筋砌体墙体抗压承载能力和加固层与砌体结构的抗压粘结强度以及从初始抗剪强度角度评价残余抗剪切粘结性能,对比结果可知温度小于200℃时,混掺有玄武岩纤维(PB组)或钢纤维(PS组)的加固层组承压能力较大,PB组拥有较强的能量消耗能力,但其抗剪强度降低程度最大,超过200℃时PS组承压能力、抗剪承载能力和变性能力均最大,保持了相对较好的残余承载能力以及变性能力,此加固层有望替代现有普通砂浆抹面层。更多还原

【Abstract】 Although ECC is equipped with high tensile ductility and durability,and is attractive in various civil engineering applications,fire is still one of the most serious risks of ECC structures during its service life.Therefore,this article introduces high-temperature fiber(basalt fiber/steel fiber),and the equivalent(0.5%)replaces PVA fiber.The influence of fly ash content,single blending of the above three kinds of fibers,and blending of the above two kinds of fibers on the compression performance and direct tensile performance of15-component ECC was studied at room temperature.The experimental results show that compared with the other two kinds of fly ash content,the influences of 70% fly ash content on the ultimate strength and ultimate strain reduction of all different types of fiber specimens were less.The following is based on 70% fly ash content,and the effect of different temperatures(200℃,400℃,600℃)after high temperature natural cooling on the residual compressive properties and residual direct tensile properties of the above-mentioned single-mixed ECC and mixed HECC(hybrid fiber reinforced cement-based composites)was studied(Appearance shape,Quality loss,Broken shape,Residual strength,Residual stress-strain full curve before and after heating).Studies had shown that steel fibers could maintain a higher level of residual strength and residual strain than basalt fibers after high temperature.Because the three materials of ordinary mortar plastering layer,masonry mortar layer and brick body have different temperature sensitivity,the masonry structure will form different stress gradients in the body after high temperature,and even cause the overall structure to collapse at any time after the outer plastering layer falls off danger.Therefore,the above HECC was used to replace the ordinary mortar surface layer to strengthen the internal masonry structure,and compared with the single-doped PVA fiber reinforced layer masonry structure and the ordinary mortar surface layer masonry structure at different temperatures,prism compression test and triplex shear test were performed.The compressive bearing capacity of the unreinforced masonry wall and the compressive bond strength between the reinforcement layer and the masonry structure under vertical loads are analyzed separately,and the residual shear bond performance is evaluated from the perspective of the initial shear strength.The comparison results showed that when the temperature was less than 200 ℃,the pressure-bearing capacity of the reinforced layer group mixed with basalt fiber(PB group)or steel fiber(PS group)were greater.Compared with other groups,the energy consumption capacity of PB group were stronger,but its shear strength decreased the most.When the temperature exceeded 200℃,the PS group’s pressure-bearing capacity,shear capacity and denaturation capacity were the largest,maintaining relatively good residual load-bearing capacity and denaturation capacity.This reinforcement layer is expected to replace the existing ordinary mortar surface layer.更多还原