硫酸盐环境对活性粉末混凝土抗拉强度的影响  

Influence of Sulfate Environment on Tensile Strength of Reactive Powder Concrete

作　　者：安明喆[1] 王海鹏 韩松[1] 韩明明 余自若[1] 张戈[1] 

机构地区：[1]北京交通大学土木建筑工程学院,北京100044 [2]碧桂园股份有限公司,广东佛山528312

出　　处：《铁道学报》2017年第11期144-150,共7页Journal of the China Railway Society

基　　金：国家自然科学基金(51578049;51278039);中央高校基本科研业务费专项资金(2016JBM045)

摘　　要：通过硫酸盐冻融-干湿循环耦合作用试验,研究Na_2SO_4溶液浓度对预加载活性粉末混凝土劈裂抗拉强度的影响规律,并结合SEM、XRD微观分析方法研究其破坏机理。结果表明:0%、5%、10%浓度Na_2SO_4浓度溶液冻融-干湿循环耦合作用下,劈裂抗拉强度的变化经历初期劣化、强化和后期劣化共三个阶段。Na_2SO_4溶液浓度对劈裂抗拉强度的影响较大,其中,5%浓度的影响最大,其次为10%浓度,最后为0%浓度。冻融循环、干湿循环过程中的温度交变作用是初期劈裂抗拉强度下降的主要原因;侵蚀过程中产生的Na_2SO_4晶体和石膏晶体对裂缝和孔隙起到填充作用,未水化水泥和硅灰二次水化产生的修复作用,共同作用使得劈裂抗拉强度经历了强化段;后期劣化阶段结晶更好的石膏晶体与钙矾石晶体等侵蚀性产物的有害膨胀应力与Na_2SO_4结晶应力共同作用造成基体损伤。5%浓度Na_2SO_4溶液耦合循环6次后,活性粉末混凝土、C60高性能混凝土的劈裂抗拉强度损失率分别为6.09%、48.89%,活性粉末混凝土在耦合作用下的耐久性远优于C60高性能混凝土。The splitting tensile strength of preloaded reactive powder concrete under the coupled action of freezethaw-dry-wet cycling with different concentrations of Na2SO4 sulfate solution was investigated.The concrete damage mechanism was studied through SEM,XRD microstructure analysis method.The results show that under the coupled action of freeze-thaw-dry-wet cycling with 0%,5%,10% Na2SO4 concentration solution,the change of splitting tensile strength of reactive powder concrete can be divided into three stages,namely initial degradation stage,strengthening stage and later degradation stage.The concentration of Na2SO4 solution has a significant influence on the splitting tensile strength.The 5% Na2SO4 concentration solution has the greatest influence,followed by 10% and 0% concentration.The temperature alternating effect caused by freeze-thaw cycling and dry-wet cycling is the main reason for the initial degradation of splitting tensile strength.The crack filling effect of gypsum crystals and Na2SO4 crystals produced during erosion,and the repairing effect of the rehydration of unhydrated cement and silica fume are the main reasons for the increase of splitting tensile strength.In the later degradation stage,the harmful expansion stress produced by gypsum erosion products such as gypsum crystals and ettringite crystals,and the crystal stress produced by Na2SO4 crystallization caused matrix damage.The splitting tensile strength loss rate of reactive powder concrete is 6.09% after 6 times of coupled action of 5% Na2SO4 solution.However,the rate is 48.89% for C60 high performance concrete under the samecondition.The durability of the reactive powder concrete is much better than the C60 high performance concrete under this situation.

关 键 词：活性粉末混凝土 硫酸盐浓度 冻融-干湿循环 耦合作用 劈裂抗拉强度 微观机理 

分 类 号：TU528.31[建筑科学—建筑技术科学]