基于工业扫描分析混凝土气泡结构与抗盐冻性能
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摘要
利用工业扫描(CT)技术对混凝土盐冻过程中气泡结构变化进行可视化表征和定量计算.研究发现引气是提高混凝土抗盐冻性能最重要的手段,建议含气量为5%~7%,同时气泡间距系数与混凝土抗盐冻性能有直接关系,气泡间距系数小于238μm时混凝土具有较好的抗盐冻性能.引气混凝土由于内部有大量小而封闭的气泡,其气泡间距系数较小,盐冻过程中气泡能够缓解结冰压,降低盐冻破坏的程度;非引气混凝土由于结冰压无法释放,当结冰压大于混凝土所能承受的膨胀力时,会在表面产生微裂缝并逐渐扩展,最终造成表面浆体剥落,形成盐冻破坏.
This paper utilizes the industrial computerized tomography to visualize and to calculate the microstructure change of concrete during cyclic freeze-thaw test.The results indicate that entraining air is the sufficient way for improving the frost resistance of concrete,and the suggested air content is5%~7%.Also,the air void space directly affects the frost resistance of concrete,and concrete can well resist frost damage when the air void space is shorter than 238 μm.The airentrained concrete has significant amount of fine air voids with shortened air void space,and the fine air voids can release the ice forming pressure during freezing,thus protecting the concrete from frost damage.The ice forming pressure can barely release for non-air entrained concrete,and micro-cracks forms when the ice forming pressure exceeded the allowable stress of concrete,and finally results in material loss or frost damage.
This paper utilizes the industrial computerized tomography to visualize and to calculate the microstructure change of concrete during cyclic freeze-thaw test.The results indicate that entraining air is the sufficient way for improving the frost resistance of concrete,and the suggested air content is5%~7%.Also,the air void space directly affects the frost resistance of concrete,and concrete can well resist frost damage when the air void space is shorter than 238 μm.The airentrained concrete has significant amount of fine air voids with shortened air void space,and the fine air voids can release the ice forming pressure during freezing,thus protecting the concrete from frost damage.The ice forming pressure can barely release for non-air entrained concrete,and micro-cracks forms when the ice forming pressure exceeded the allowable stress of concrete,and finally results in material loss or frost damage.
引文
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[15]FAA.AC150/5220-24.Airport Foreign object debris(FOD)detection equipment[R].Washington D C:[s.n.],2009.
[16]PIERRE-CLAUDE A,ROBERT F.Science and technology of concrete admixtures[M].[S.l.]:Woodhead Publishing,2015.
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[18]MAYERCSIK N P,VANDAMME M,KURTIS K E.Assessing the efficiency of entrained air voids for freeze-thaw durability through modeling[J].Cement and Concrete Research,2016,88,43.
[2]JACOBSEN S,SCHERER G W,SCHULSON E M.Concrete-ice abrasion mechanics[J].Cement and Concrete Research,2015,45(73):79.
[3]杨全兵.混凝土盐冻破坏机理(Ⅱ):冻融饱水度和结冰压[J].建筑材料学报,2012,15(6):742.YANG Quanbing,One of mechanisms on the deicer-frost scaling of concrete(II):degree of saturation and ice-formation pressure during freezing-thawing cycles[J].Journal of Building Materials,2012,15(6):742.
[4]段桂珍,方从启.混凝土冻融破坏研究进展与新思考[J].混凝土,2013,35(5):16.DUAN Guizhen,FANG Congqi,Research progress and new thinking of destruction of concrete due to freeze-thaw cycles[J].Concrete,2013,35(5):16.
[5]PIGEON M,PLEAU R.Durability of concrete in cold climates[M].London:E&FN Spon,1995.
[6]蒋元駉,韩素芳.混凝土工程病害与修补加固[M].北京:海洋出版社,1996.JIANG Yuanjiong,HAN Sufang.Failure,patching and strengthening of concrete engineer[M].Beijing:Ocean Press,1996.
[7]刘军,刑锋,董必钦.混凝土孔结构和渗透性能关系研究[J].混凝土,2007,29(12):35.LIU Jun,XING Feng,DONG Biqin,Researchship between pore structure and permeability[J].Concrete,2007,29(12):35.
[8]ZHANG J,TAYLOR P.Pore size distribution in cement pastes in relation to freeze-thaw distress[J].Journal of Materials in Civil Engineering,2015,27(3):04014123.
[9]张士萍,邓敏,吴建华,等.孔结构对混凝土抗冻性的影响[J].武汉理工大学学报,2008,30(6):56.ZHANG Shiping,DENG Min,WU Jianhua,et al.Effect of pore Structure on the Frost Resistance of Concrete[J].Journal of Wuhan University of Technology,2008,30(6):56.
[10]杨全兵.混凝土盐冻破坏——机理、材料设计与防治措施[D].上海:同济大学,2006.YANG Quanbing.Deicer-frost deterioration of concretemechanisms,materials design and preventive measures[D].Shanghai:Tongji University,2006.
[11]公路水泥混凝土路面施工技术规范:JTG F30 2003[S].北京:人民交通出版社,2003.Technical specification for construction of highway cement concrete pavements:JTG F30-2003[S].Beijing:China Communications Press,2003.
[12]闫西乐.孔结构对水泥基材料抗盐冻性能影响规律的研究[D].南京:东南大学,2015.YAN Xile.Influence of pore structure on cement-based materials frost resistance property[D].Nanjing:Southeast University,2015.
[13]周继凯,潘杨,陈徐东.压汞法测定水泥基材料孔结构的研究进展[J].材料导报A:综述篇,2013,4(27):72.ZHOU Jikai,PAN Yang,CHEN Xudong,Research advances in mercury porosimetry study of pore structure in cement-based materials[J].Materials Review,2013,4(27):72.
[14]普通混凝土拌合物性能试验方法标准:GB/T50080 2002[S].北京:中国建筑工业出版社,2002.Standard for Test Method of Performance on Ordinary Fresh Concrete:GB/T50080 2002[S].Beijing:China Architecture&Building Press,2002.
[15]FAA.AC150/5220-24.Airport Foreign object debris(FOD)detection equipment[R].Washington D C:[s.n.],2009.
[16]PIERRE-CLAUDE A,ROBERT F.Science and technology of concrete admixtures[M].[S.l.]:Woodhead Publishing,2015.
[17]LI W,POUR-GHAZ M,CASTRO J,et al.Water absorption and critical degree of saturation relating to freeze-thaw damage in concrete pavement joints[J].Journal of Materials in Civil Engineering,2012,24(3),299.
[18]MAYERCSIK N P,VANDAMME M,KURTIS K E.Assessing the efficiency of entrained air voids for freeze-thaw durability through modeling[J].Cement and Concrete Research,2016,88,43.