初凝超30 min超早强UHPC制备及其机理  

Preparation and Mechanism of Super-Early-Strength UHPC with Initial Setting Time over 30 min

作　　者：李传习[1,2] 夏雨航 王圣杰 邓帅 蒋健 LI Chuanxi;XIA Yuhang;WANG Shengjie;DENG Shuai;JIANG Jian(School of Civil Engineering,Changsha University of Science&Technology,Changsha 410114,China;Hunan Dexixiangdong Technology Co.,Ltd.,Changsha 410114,China)

机构地区：[1]长沙理工大学土木工程学院,长沙410114 [2]湖南德习湘栋科技有限公司,长沙410114

出　　处：《硅酸盐通报》2023年第5期1630-1639,共10页Bulletin of the Chinese Ceramic Society

基　　金：国家自然科学基金(52078059);湖南省交通科技项目(202016);长沙理工大学研究生“实践创新与创业能力提升计划”项目(CLSJCX22042)。

摘　　要：针对既有交通线路快速抢通和抢通后寿命确保的需要,研发了具有足够施工时间的超早强(数小时达到开放强度)超高性能混凝土(UHPC)。基于最大密实度理论的UHPC配方,试验研究了普通硅酸盐水泥(OPC)替代率对硫铝酸盐-硅酸盐复合体系(SAC-OPC体系)混凝土力学性能与施工性能的影响,确定了OPC替代率;通过正交试验确定影响SAC-OPC体系混凝土力学性能和工作性能的早强组分(硫酸锂、硫酸铝)、增强组分(纳米碳酸钙)、调凝组分(粉体缓凝剂、四硼酸钠),制备了初凝时间36 min、3 h抗压/抗折强度41.4/17.0 MPa的超早强UHPC,以及初凝时间40 min、3 h抗压/抗折强度36.2/13.9 MPa的超早强UHPC。通过SEM和XRD分析,探究了具有足够施工时间超早强UHPC的性能形成机理。结果表明:随OPC替代率增大,UHPC的凝结时间先减后增,扩展度持续增大,早期力学性能大致呈下降趋势,后期力学性能大致呈上升趋势;超早强与初凝时间延长主要源于协同水化作用与早强组分、增强组分和调凝组分的累加效应。In response to ensuring the rapid opening and post-opening life of existing traffic lines rehabilitation,ultra-high performance concrete(UHPC)was developed with sufficient construction time and super-early-strength(reaching open strength within several hours).Based on the UHPC mixture proportion designed via maximum compactness theory,the effect of the substitution rate of ordinary Portland cement(OPC)on the mechanical performance and workability of sulphoaluminate-ordinary Portland cement system(SAC-OPC system)concrete was studied via experiments,and the OPC substitution rate was determined.Super-early-strength UHPC with initial setting time of 36 min and 3 h compressive/flexural strength of 41.4/17.0 MPa and super-early-strength UHPC with initial setting time of 40 min and 3 h compressive/flexural strength of 36.2/13.9 MPa are prepared via the orthogonal tests on the mechanical performance and workability of SAC-OPC system concrete with early strength agents(lithium sulphate,aluminum sulphate),enhancing agents(nano calcium carbonate)and slow-setting agents(slow-setting powder,sodium tetraborate).The mechanism for the performance formation of super-early-strength UHPC with sufficient construction time was studies by SEM and XRD.The results show that,with the increase of OPC substitution rate,the setting time of UHPC decreases first and then increases,the slump extension continues to increase,and the mechanical performance of UHPC generally shows a decreasing trend in the early stage and an increasing trend in the later stage.The super-early-strength and prolonged initial setting time are mainly due to the cumulative effect of the synergistic hydration and early strength agents,enhancing agents,and slow-setting agents.

关 键 词：超高性能混凝土 硫铝酸盐-硅酸盐复合体系 超早强 力学性能 初凝时间 扩展度 

分 类 号：TU528[建筑科学—建筑技术科学]