约束对单面盐冻混凝土内部损伤的影响:水分迁移  

Influence of Restraint on Salt Frost Damage of Concrete:Water Migration

作　　者：高志浩 王振地 王玲 GAO Zhihao;WANG Zhendi;WANG Ling(Beijing Jiaotong University,School of Civil Engineering,Beijing 100044,China;CCCC Highway Bridges National Engineering Research Centre Co.,Ltd.,Beijing 100011,China;China Building Materials Academy,The State Key Laboratory of Green Building Materials,Beijing 100024,China)

机构地区：[1]北京交通大学土木建筑工程学院,北京100044 [2]中交公路长大桥建设国家工程研究中心有限公司,北京100011 [3]中国建筑材料科学研究总院有限公司,绿色建筑材料国家重点实验室,北京100024

出　　处：《硅酸盐学报》2024年第11期3361-3371,共11页Journal of The Chinese Ceramic Society

基　　金：“十四五”国家重点研发计划青年科学家项目(2022YFB3708700);国家重点研发计划(2021YFB370403);国家自然科学基金(52378315)。

摘　　要：现行单面盐冻试验中,混凝土试件处于自由形变状态。然而试验中的混凝土试件仅相当于实际混凝土构件的一个单元,其在单面盐冻作用下的变形受到周围混凝土的约束作用,导致盐冻损伤行为发生改变。因此,本工作研究约束作用对单面盐冻混凝土内部损伤的影响及机理,测试了水灰比为0.60的约束态和自由态混凝土每4次盐冻循环后的相对动弹性模量(r_(n))和体积吸水率(V_(n)),实时监测了28次盐冻循环混凝土的内部相对湿度(U_(IRH))演化,计算了约束态和自由态混凝土首次循环降温过程中的孔径比。结果表明约束态混凝土的UIRH增量、r_(n)损失和V_(n)分别比自由态混凝土少30%、32%和28%。与自由态混凝土相比,约束态混凝土在降温过程中的孔径收缩较小,根据微冰透镜理论和结晶压理论,分析并证明了约束作用弱化混凝土降温过程中的水分迁移和冻融循环后的孔径扩张,进而减轻了盐冻内部损伤。Introduction De-icing salt has been a common way to melt snow accumulated on concrete structures.But this often leads to the deterioration of concrete structures.Therefore,frost resistance durability of concrete subjected to de-icing salt is crucial.Conventionally,concrete is allowed to freely deform during single-side freezing and thawing(SSFT)tests.However,a concrete specimen is only equivalent to a unit of the concrete component in actual,and its deformation subjected to SSFT is restrained by the surrounding concrete,leading to alterations in salt frost damage.The differences in the evolution of concrete’s frost damage between the laboratory and actual engineering are highlighted.The different internal damage of concrete subjected to freezing and thawing with pure water and de-icing salt is usually related to the water migration and phase transformation inside the concrete.However,the only difference between restrained concrete and unrestrained concrete is the restraint effect.The significant difference in internal damage of the two concretes subjected to SSFT cannot be explained by classical theory.Additionally,the influence of restraint effect on water migration in concrete also needs to be clarified.Thus,it is crucial to study the effect of restraint on the internal damage of concrete subjected to SSFT,which will provide guidance for the mix design of high frost resistant concrete in cold regions.In this paper,restraint ring and anchors were designed to confine the deformation of concrete to simulate the serving condition during SSFT tests.The relative dynamic elastic modulus and water absorption in volume of restrained and unrestrained concrete with a water cement ratio of 0.60 were tested after every 4 SSFT cycles.The temperature and humidity sensors were used to monitor the evolution of the relative humidity(U_(IRH))inside the concrete during the SSFT test.The influence and mechanism of restraint effect on the internal damage of concrete subjected to SSFT were clarified from the perspective of moisture

关 键 词：约束态混凝土 单面盐冻 内部损伤 内部相对湿度 水分迁移 

分 类 号：TU528[建筑科学—建筑技术科学]