摘要
兼顾优异施工及力学性能超高性能混凝土(UHPC)研制的重点之一是确定合适的水胶比。为此,以150 MPa级UHPC的原材料和配合比均不变(除用水量外)为前提,研究水胶比(0.15~0.2)对UHPC施工与力学性能的影响规律。通过相关试验得到了UHPC不同湿拌时间的扩展度、充分湿拌时间、静停一段时间的扩展度、抗压、抗折强度、四点弯曲应力挠度曲线、四点弯曲出现可视裂纹时下缘等效拉应力;对抗压、抗折强度进行了变异性分析;利用应力挠度曲线,基于规范法得到了弯曲韧性指标,并提出了其改进方法。结果表明:UHPC达最佳扩展度所需湿拌时间(充分湿拌时间)为6 min;水胶比由0.16增至0.19时UHPC扩展度基本呈线性增长,水胶比每增加0.01,UHPC扩展度平均增幅为109 mm;当水胶比、静停时间分别为0.19、4 h时,扩展度损失40 mm,损失率仅5.9%;UHPC抗压强度、抗折强度及弯曲韧性指标随水胶比的增大皆呈先增后减趋势,当水胶比分别为0.18、0.16和0.16时达到最优;应力峰值前的应力挠度曲线并不是典型全凸形曲线;可视初裂抗折强度约为抗折强度的0.85倍;UHPC试件的弯曲韧性较好,宜采用可视初裂挠度作为初始变形参考进行韧性指标计算;为保证UHPC兼顾良好施工与力学性能,建议湿拌时间、水胶比分别为6 min、0.18或0.185。
One of the key points for developing ultra-high performance concrete(UHPC)with good construction is to determine the suitable water-binder ratio.Based on the premise that the typical raw materials and mix ratio of 150MPa grade UHPC remained unchanged(except water consumption),the influence of water-to-binder ratio(0.15~0.2)on the construction and mechanical properties of UHPC were studied.Through relevant tests,the extension degree,compression resistance,bending strength,four-point bending stress-deflection curve,and equivalent tensile stress of UHPC under different wet mixing time(full wet mixing time,static stop for a period of time)were obtained.Subsequently,the variability of compressive strength and flexural strength results were analyzed;Using the stress-deflection curve,the index of bending toughness was obtained based on the standard method.At the same time,an improved method for calculating flexural toughness index of UHPC was proposed.The test results show that the full wet mixing time of UHPC is 6 min.The extensibility of UHPC increases linearly when the water-to-binder ratio increases from 0.16 to 0.19.And at this time,the average extensibility rate of UHPC increases to 109 mm with the water-to-binder ratio increases by 0.01.The extensibility loss of UHPC is 40mm,and the loss rate is only 5.9%,when the water-to-binder ratio and standing time are 0.19 and 4h.The compressive strength,flexural strength and flexural toughness index of UHPC all increase first and then decrease with increasing of water-to-binder ratio,and when the water-to-binder ratio is 0.18,0.16 and 0.16 respectively,the three mechanical properties reach the best.The stress-deflection curve before the stress peak is an atypical full convex curve.The strength of visible first crack is about 0.85 times that of flexural strength.The flexural toughness of UHPC is good,so it is better to use visible first crack deflection as the initial deformation reference to calculate the flexural toughness index.In order to ensure the good construction and mechanical properties of UHPC,the wet mixing time and water-to-binder ratio should be 6min,0.18 or 0.185 respectively.
作者
李传习
聂洁
潘仁胜
石家宽
曾宇环
贺君
Li Chuanxi;Nie Jie;Pan Rensheng;Shi Jiakuan;Zeng Yuhuan;He Jun(Key Laboratory of Bridge Engineering Safety Control of Ministry of Education,Changsha University of Science&Technology,Changsha 410114,P.R.China)
出处
《土木与环境工程学报（中英文）》
CSCD
北大核心
2020年第4期164-174,共11页
Journal of Civil and Environmental Engineering
基金
国家自然科学基金(51778069)
国家重点基础研究发展计划(973计划)(2015CB057700)
湖南省研究生科研创新项目(CX2016B386)
长沙理工大学南方地区桥梁长期性能提升技术国家地方联合工程实验室开放基金(16BCX01)。
关键词
超高性能混凝土
施工性能
力学性能
水胶比
初裂挠度
弯曲韧性
ultra-high performance concrete
construction performance
mechanical properties
water-binder ratio
first crack deflection
bend ductility
