复合盐蚀环境下喷射混凝土离子分布规律及氯离子扩散系数
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摘要
通过分析(干湿循环+复合盐侵蚀)共同作用下普通混凝土、普通喷射混凝土和钢纤维喷射混凝土孔隙液中pH值、Cl~-、SO_4~(2-)和Ca~(2+)分布情况,研究了喷射混凝土离子分布规律和氯离子扩散系数。结果表明:各混凝土pH值和Ca~(2+)浓度随深度分布规律相似,均为表层最低并随深度增加而升高,且在同一深度随龄期增加而降低;普通混凝土表层Cl-浓度最高且扩散深度最大,钢纤维喷射混凝土的表层Cl-浓度最低和扩散深度最小;SO_4~(2-)在各混凝土内部的分布大致分为富集区、过渡区和稳定区三段;表面自由Cl-含量Cs为普通混凝土>普通喷射混凝土>钢纤维喷射混凝土,且随侵蚀龄期的增长而逐渐上升;混凝土的Cl-扩散系数D随侵蚀龄期的增长而降低,符合幂函数变化规律。
The pore solution of pH value,Cl~-,SO_4~(2-) and Ca~(2+)distribution situation of ordinary concrete,ordinary shotcrete and steel fiber shotcrete are analyzed under the combined action of( wetting and drying cycles + compound salt erosion),the ions distribution regularity and chloride ion diffusion coefficient of shotcrete are investigated. The results show that the pH value and Ca~(2+)concentration distribution regularity with depth of each concretes are similar,and all lowest on surface,increase with depth increasing,and decrease with the age increasing in the same depth. The Cl-concentration of ordinary concrete surface is the highest,and its diffusion depth is the lowest,but steel fiber shotcrete contrasting with ordinary concrete. The distribution of SO_4~(2-) in the concrete can be divided into three segments,rich region,transition region and stable region. The Csof ordinary concrete > ordinary shotcrete > steel fiber shotcrete,and increase gradually with the age increasing. The D reduced gradually with the age increasing,which is in accordance with the law of the variation of power function.
The pore solution of pH value,Cl~-,SO_4~(2-) and Ca~(2+)distribution situation of ordinary concrete,ordinary shotcrete and steel fiber shotcrete are analyzed under the combined action of( wetting and drying cycles + compound salt erosion),the ions distribution regularity and chloride ion diffusion coefficient of shotcrete are investigated. The results show that the pH value and Ca~(2+)concentration distribution regularity with depth of each concretes are similar,and all lowest on surface,increase with depth increasing,and decrease with the age increasing in the same depth. The Cl-concentration of ordinary concrete surface is the highest,and its diffusion depth is the lowest,but steel fiber shotcrete contrasting with ordinary concrete. The distribution of SO_4~(2-) in the concrete can be divided into three segments,rich region,transition region and stable region. The Csof ordinary concrete > ordinary shotcrete > steel fiber shotcrete,and increase gradually with the age increasing. The D reduced gradually with the age increasing,which is in accordance with the law of the variation of power function.
引文
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[2]Ye H L,Jin N G,Jin X Y,et al.Model of chloride penetration into cracked concrete subject to drying-wetting cycles[J].Construction and Building Materials,2012,36:259-269.
[3]Yuan X L,Li B X,Cui G,et al.Effect of mineral admixrutes on durability of concrete in wetting-drying cyclic sulfate environment[J].Journal of the Chinese Ceramic Society,2009,37(10):1754-1759.
[4]Chen Y J,Gao J M,Tang L P,et al.Resistance of concrete against combined attack of chloride and sulfate under drying-wetting cycles[J].Construction and Building Materials,2016,106:650-658.
[5]Debska D.The effect of exposition conditions on the durability of cement concrete with dolomite aggregate sourced near Kraków,Poland[J].Construction and Building Materials,2015,108:673-680.
[6]Dehwah H A F.Effect of sulfate concentration and associated cation type on concrete deterioration and morphological changes in cement hydrates[J].Construction and Building Materials,2007,21:29-39.
[7]姚维益,金祖权,高嵩,等.温度和氯盐对混凝土硫酸盐化学腐蚀的影响[J].沈阳工业大学学报,2015,37(4):475-480.
[8]Jin Z Q,Sun W,Zhang Y S,et al.Interaction between sulfate and chloride solution attack of concretes with and without fly ash[J].Cement and Concrete Research,2007,37:1223-1232.
[9]乔宏霞,何忠茂,余红发,等.混凝土硫酸盐腐蚀的力学性能和微观结构研究[J].建筑科学,2011,27(1):25-28.
[10]Shi J J,Sun W,Jiang J Y,et al.Influence of chloride concentration and pre-passivation on the pitting corrosion resistance of low-alloy reinforcing steel in simulated concrete pore solution[J].Construction and Building Materials,2016,111:805-813.
[11]Williamsona J,Burkan I O.The effect of simulated concrete pore solution composition and chlorides on the electronic properties of passive films on carbon steel rebar[J].Corrosion Science,2016,106:82-95.
[12]Muhammad W,Raja R H.Passive film formation and corrosion initiation in lightweight concrete structures as compared to self compacting and ordinary concrete structures at elevated temperature in chloride rich marine environment[J].Construction and Building Materials,2015,78:144-152.
[13]Cusson D,Lounis Z,Daigle L.Benefits of internal curing on service life and life-cycle cost of high-performance concrete bridge decks-a case study[J].Cement Concrete Composites,2010,32(5):339-350.
[14]Song Z J,Jiang L H,Chu H Q,et al.Modeling of chloride diffusion in concrete immersed in Ca Cl2and Na Cl solutions with account of multi-phase reactions and ionic interactions[J].Construction and Building Materials,2014,66:1-9.
[15]Nanukuttan S V,Basheer P A M,Mc Carter W J,et al.The performance of concrete exposed to marine environments:predictive modelling and use of laboratory/on site test methods[J].Construction and Building Materials,2015,93:831-840.
[16]金伟良,张奕,卢振勇.非饱和状态下氯离子在混凝土中的渗透机理及计算模型[J].硅酸盐学报,2008,36(10):1362-1369.
[17]Thomas A.Sprayed concrete lined tunnel[M].New York:Taylor&Francis,2012.
[18]牛荻涛,王家滨,马蕊.干湿交替喷射混凝土硫酸盐侵蚀试验[J].中国公路学报,2016,29(2):82-89.
[19]Wang J B,Niu D T,Zhang Y L.Mechanical properties,permeability and durability of accelerated shotcrete[J].Constructure and Building Materials,2015,95:312-328.
[20]Niu D T,Wang Y D,Ma R,et al.Experiment study on the failure mechanism of dry-mix shotcrete under the combined actions of sulfate attack and drying-wetting cycles[J].Construction and Building Materials,2015,81:74-80.
[21]Mangat P S,Molloy B T.Prediction of long term chloride concentration in concrete[J].Materials and Structures,1994,27(6):338-346.