【作者】 林志鹏；

【导师】 郑建岚； 罗素蓉；

【作者基本信息】 福州大学 ， 建筑与土木工程（专业学位）， 2021， 硕士

【摘要】 超高性能混凝土(UHPC)是一种具有高流动性、高强度、高耐久性、高韧性等优点的新型水泥基复合材料,将其作为装饰材料来使用能够解决普通装饰混凝土抗拉强度低、韧性差、自重大、易开裂等缺陷,有利于拓展其应用范围,实现结构装饰一体化。本文采用高白度的原材料制备具有装饰效果的UHPC,研究材料组成对白色UHPC流动性、抗压强度、抗折强度和弯曲韧性的影响。完成的主要工作和成果如下:1、通过设计以石英砂细度模数、砂胶比、水胶比和石英粉掺量为参数的16组配合比,进行白色UHPC流动性、抗压强度和抗折强度试验,确定制备白色UHPC的配合比设计参数。结果表明:水胶比对白色UHPC性能的影响最大。在石英砂细度模数为2.6、砂胶比为0.8、水胶比为0.18和石英粉掺量为25%的条件下,白色UHPC的性能最佳。2、通过流动性、抗压强度、抗折强度和薄板四点弯曲试验,以矿物掺合料种类和掺量为参数,设计12组配合比,研究矿物掺合料对白色UHPC性能的影响,对比标准养护与蒸汽养护对其强度的影响,并结合微观试验分析强度的增强和劣化机理。结果表明:锆硅灰和偏高岭土对流动性有改善作用,而白硅灰的掺量大于20%后,白色UHPC的流动性下降。对抗压强度和抗折强度而言,不同矿物掺合料存在不同的最佳掺量,其中白硅灰对白色UHPC强度的贡献最明显,掺量在20%时,抗压强度和抗折强度达到最大值,标准养护28d龄期下,分别达到120.6MPa和21.6MPa。矿物掺合料对白色UHPC韧性指数的影响相对较小,偏高岭土对弯曲韧性有显著的不利影响。蒸汽养护降低白色UHPC的总孔隙率,但增大有害孔和多害孔的占比,同时导致纤维与基体间的缝隙更加明显,因此蒸汽养护后,白色UHPC的抗压强度并未提高,抗折强度显著降低。3、以纤维种类、长度和掺量为参数,设计20组配合比,研究纤维对白色UHPC流动性、抗压强度、抗折强度和弯曲韧性的影响。研究表明:掺入不同纤维后,白色UHPC的流动性均随着纤维的掺量和长度的增大不断下降,其中聚丙烯纤维(PP纤维)对流动性的影响最小。耐碱玻璃纤维(GF)对白色UHPC的增强效果最好,随着掺量和长度的增大,增强效果越显著;PP纤维的掺量越小、长度越大,对白色UHPC的增强作用越强;PVA纤维对强度的影响相对较小。对于弯曲韧性而言,掺入GF可以有效延缓基体开裂,提高抗弯强度,但改善脆性的能力较差;PP纤维对强度的贡献不如GF,但掺入PP纤维后,韧性指数显著增大,延性有效提高;PVA纤维的掺入会使基体提前开裂,但能显著提高韧性指数。掺入4.0%的PP纤维或2.0%的PVA纤维后,白色UHPC薄板出现多缝开裂现象。4、通过上述研究,本文在标准养护条件下,得到流动度大于200mm,抗压强度大于110.0MPa,抗折强度大于17.0MPa,弯曲韧性指数满足高韧性应变硬化材料要求的白色超高性能装饰混凝土的制备方法。更多还原

【Abstract】 Ultra-high performance concrete(UHPC)is a new cement-based composite material of high flowability,high strength,high durability,and high toughness.Used as a decorative material,it can overcome the defects of common decorative concrete,such as,low tensile strength,poor toughness,heavy self-weight,and easy cracking,which is conducive to the expansion of relevant applications and integration of structure and decoration.In this paper,high whiteness raw materials were used to prepare UHPC with decorative effect,and the effects of material composition on flowability,compressive strength,flexural strength and flexural toughness of white UHPC were studied.The main work and achievements are as follows:1.The tests of flowability,compressive strength,and flexural strength for the white UHPC were carried out based on 16 groups of mix proportion designed by fineness module of quartz sand sand-binder ratio(s/b),water-binder ratio(w/b),and quartz powder content as parameters,so as to determine an appropriate mix proportion for preparing white UHPC.The results show that the effect of w/b on the performance of white UHPC is the most significant,and the performance of white UHPC is optimal when the fineness module of quartz sand is 2.6,s/b is 0.8,w/b is 0.18,and quartz powder content is 25%.2.Through the tests of flowability,compressive strength,flexural strength,and four-point bending,with mineral admixture variety and content as parameters,12 groups of mix proportion were designed to study the influence of mineral admixture on the performance of white UHPC.The influence of standard curing and steam curing on the strength of white UHPC was compared,and the mechanism of strength enhancement and degradation was analyzed by microscopic tests.The results show that zirconium silica fume and metakaolin can improve the flowability of white UHPC,while the flowability of white UHPC is poor when the content of white silica fume is more than 20%.In terms of compressive strength and flexural strength,different mineral admixtures have different optimal content,among which white silica fume has the greatest contribution to the strength of white UHPC.When the content of white silica fume is 20%,the compressive strength and flexural strength reach the maximum,and reach 120.6MPa and 21.6MPa respectively under the standard curing age of 28 days.The influence of mineral admixture on the toughness index of white UHPC is relatively small.The contribution of zirconium silica fume to the toughness is slightly higher than that of white silica fume,while metakaolin has a significant adverse effect on the flexural toughness.Steam curing reduces the total porosity of white UHPC,but increases the proportion of harmful hole and multi-harmful hole,and makes the gap between fiber and matrix more obvious.Therefore,after steam curing,the compressive strength of white UHPC does not increase,and the flexural strength decreases significantly.3.With fiber type,length and content as parameters,20 groups of mix proportion were designed to study the influence of fiber on flowability,compressive strength,flexural strength and flexural toughness of white UHPC.The results show that the flowability of white UHPC decreases with the increase of fiber content and fiber length,and polypropylene fiber(PP fiber)has the least effect on flowability.Alkali-resistant glass fiber(GF)has the best enhancement effect on white UHPC,and furthermore,with the increase of content and length,the effect becomes more significant.The lower the content and the longer the length of PP fiber,the stronger the enhancement effect on white UHPC.The effect of PVA fiber on the strength is relatively small.For the flexural toughness,the addition of GF can effectively delay the matrix cracking and improve the flexural strength,while the ability to improve the brittleness is poor.The contribution of PP fiber to the strength is less than that of GF,but the PP fiber may promote the toughness index significantly,and increase the ductility of white UHPC effectively.The addition of PVA fiber can make the matrix crack in advance,but effectively improve the toughness index.When the content of PP fiber is 4.0% or the content of PVA fiber is 2.0%,multiple cracks appears on the thin plate of white UHPC.4.The study mentioned above obtains a method for preparing white ultra-high performance decorative concrete,of which the fluidity is greater than 200 mm,compressive strength is greater than 110.0MPa,flexural strength is greater than 17.0MPa,and flexural toughness index meets the requirements for high toughness strain hardening materials under the standard curing conditions.更多还原