低热水泥混凝土早期塑性开裂风险研究  

Study on the risk of early plastic cracking of low heat cement concrete

作　　者：胡昱[2] 牛旭婧 杨宁 李庆斌[2] 牟荣峰 乔雨 鹿永久 刘伟佳 HU Yu;NIU Xujing;YANG Ning;LI Qingbin;MU Rongfeng;QIAO Yu;LU Yongjiu;LIU Weijia(China Three Gorges Projects Development Co.,Ltd.,Chengdu 610017,China;State Key Laboratory of Hydroscience and Engineering,Tsinghua University,Beijing 100084,China;China Three Gorges Corporation Test Center Wudongde Engineering Center,Yichang 443133,China)

机构地区：[1]中国三峡建设管理有限公司,四川成都610017 [2]清华大学水沙科学与水利水电工程国家重点实验室,北京100084 [3]中国长江三峡集团公司试验中心乌东德工程分中心,湖北宜昌443133

出　　处：《混凝土》2021年第3期19-22,26,共5页Concrete

基　　金：国家自然科学基金(51979145,51839007)。

摘　　要：坝区大风、干热、强降温等气候特点,使得混凝土存在发生早期塑性开裂的可能。通过测定极端天气环境下(如:大风干热、大风寒潮)混凝土的含水量、贯入阻力和早期塑性开裂行为,对表面不处理、覆盖保温被和掺加聚乙烯醇(Polyvinyl alcohol,PVA)纤维低热水泥混凝土的早期塑性开裂风险进行了研究。结果表明:在上述两种极端环境作用下,覆盖保温被是十分有效的保湿、抗裂措施,可以明显阻止低热水泥混凝土表层水分的蒸发和散失,进而显著降低甚至完全抑制早期塑性开裂的发生。掺加PVA纤维有利于提高混凝土的塑性抗开裂能力,这主要是与纤维的桥接阻裂作用以及它们三维乱向均匀分布阻止了浆料离析所产生的沉降裂缝有关。不过,PVA纤维的加入为水分的向外迁移提供了连通通道,导致水分蒸发速率明显增大,这可能会在一定程度上加大低热水泥混凝土早期失水收缩开裂的风险。鉴于覆盖保温被可以有效阻止水分蒸发散失的作用效果,今后研究可考虑将其与PVA纤维结合使用,以更好地降低极端环境作用下低热水泥混凝土的早期塑性开裂风险。Early plastic cracking of concrete may occur due to the climate characteristics of strong wind,dry heat and strong cooling in dam area.In this experiment,the risks of early plastic cracking of low heat cement concrete with untreated surface,covered with heat preservation quilt and incorporated with polyvinyl alcohol(PVA)fiber were investigated,by determining free water content,penetration resistance and early plastic cracking behavior of concrete under extreme environments(i.e.strong wind-dry heat,strong wind-cold wave).The results indicate that covering heat preservation quilt is an effective method to prevent water loss of concrete under the extreme environmental conditions mentioned above.It can reduce or even completely prevent the early plastic cracking of low heat cement concrete.In addition,incorporating PVA fiber is beneficial to improve the early plastic cracking resistance of concrete.It is mainly related to the bridging effect of fibers and their three-dimensional uniform distribution preventing settlement cracks caused by slurry segregation.However,PVA fibers provide connecting channels for the outward migration of water,which leads to a significant increase in the evaporation rate of free water,and hence an increase in the risk of early plastic cracking of concrete.In view of the effect of covering insulation on preventing the evaporation of water,a combined method composed of PVA fiber and coving heat preservation quilt can be considered in the future research to reduce the risk of early plastic cracking of low heat cement concrete under extreme environment.

关 键 词：低热水泥混凝土 大风干热 大风寒潮 塑性开裂 保温被 PVA纤维 

分 类 号：TU528.01[建筑科学—建筑技术科学]