冻融循环-碱硅酸反应对再生混凝土损伤的影响  

Effect of FTC-ASR on damage of recycled concrete

作　　者：秦拥军[1] 呙哲懿 张驰 张亚斌 QIN Yongjun;GUO Zheyi;ZHANG Chi;ZHANG Yabin(School of Architecture and Engineering,Xinjiang University,Urumqi 830047,China)

机构地区：[1]新疆大学建筑工程学院,新疆乌鲁木齐830047

出　　处：《混凝土》2024年第10期10-15,31,共7页Concrete

基　　金：国家自然科学基金(51668061)。

摘　　要：我国西北地区长期处于严寒以及盐渍土环境会导致混凝土耐久性的下降。为了研究再生混凝土在冻融循环(FTC)后,受碱硅酸反应(ASR)而发生二次损伤的规律,以再生粗骨料为变量,将再生混凝土分别进行20次、40次冻融循环后浸泡在80℃的1 mol/L NaOH溶液中进行ASR 28 d,研究再生混凝土表面形貌、膨胀率、质量损失率、相对动弹性模量等损伤指标,分析FTC作用下ASR对再生混凝土二次损伤的机理。试验结果表明:前期冻融次数的增加使得内部裂缝增多导致后期ASR反应速率提升,随着FTC次数越多,再生粗骨料取代率越高,再生混凝土受ASR作用下膨胀率越大,在再生粗骨料取代率为70%时混凝土膨胀率达到最大值;当再生粗骨料取代率小于50%时,由于试件骨料初始损伤相对较小以及碱活性较弱,呈现超叠加损伤效应,当再生粗骨料取代率为50%以上时,ASR对混凝土的二次损伤变大,产生的硅酸盐凝胶总量增多,质量损失率也随之增大;随着冻融循环次数以及再生粗骨料取代率的增加,使得试件受到更多的基体损伤,且远大于附着砂浆二次水化过程中的结构密实作用导致混凝土的相对动弹性模量的下降并且随着再生粗骨料取代率的增大,骨料中更多碱活性物质被暴露在碱溶液下,给后期ASR提供了良好的反应环境,相对动弹性模量的下降程度越大,但前期的FTC并没有影响ASR反应二次损伤相对弹性模量规律。In order to study the law of secondary damage of recycled concrete after freeze-thaw cycles(FTC)and subjected to alkali-silicicic acid reaction(ASR),the surface morphology,expansion rate,mass loss rate and relative dynamic elastic modulus of the specimens were used as damage indicators,and the recycled concrete was immersed in 1 mol/L NaOH solution at 80℃for 28 days after 20 and 40 times FTC respectively to analyse the mechanism of FTC and ASR on the damage of recycled concrete.The test results show that the increase in the number of freeze-thaw cycles in the early stage increases the ASR rate in the later stage,and the concrete swelling rate reaches the maximum at 70%of recycled coarse aggregate replacement rate.When the recycled coarse aggregate replacement rate is above 50%,the secondary damage rate of ASR on concrete becomes larger and the mass loss rate also increases.With the increase in the number of freeze-thaw cycles and the recycled coarse aggregate replacement rate,it leads to the as the number of freeze-thaw cycles and the replacement rate of recycled coarse aggregate increase,the relative dynamic modulus of concrete decreases and as the replacement rate of recycled coarse aggregate increases,more alkali-active materials in the aggregate are exposed to the alkali solution,providing a good reaction environment for ASR later on,the reaction rate of ASR is greatly increased and the relative dynamic modulus of concrete decreases to a greater extent.

关 键 词：再生混凝土 碱-硅酸反应 冻融循环 二次损伤 耐久性 

分 类 号：TU528.01[建筑科学—建筑技术科学]