环境温度对混凝土管桩氯离子扩散性能的影响
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摘要
基于Fick第二扩散定律,建立混凝土管桩中考虑环境温度和氯离子结合能力的氯离子扩散模型。针对环境温度对混凝土管桩中氯离子扩散性能的影响开展试验研究,将不同水灰比(0.30、0.45和0.55)混凝土管桩置于不同温度(21、30、50℃)的5%氯化钠盐雾中,开展为期32d的浸泡试验。依据试验结果和氯离子扩散模型,得到不同温度条件下、不同水灰比混凝土管桩中的自由氯离子浓度分布、表面氯离子浓度、氯离子表观和有效扩散系数、活化能和氯离子结合能力值。试验结果表明:随着环境温度的升高,自由氯离子浓度、表面氯离子浓度、氯离子表观和有效扩散系数增大。随着环境温度从21℃升高到30℃,氯离子结合能力显著增加,但随着环境温度从30℃升高到50℃,氯离子结合能力却略有减小。由于表观氯离子扩散系数的对数与环境绝对温度的倒数呈线性变化规律,因此,可推断氯离子在混凝土管桩中的扩散符合Arrhenius理论。
Based on Fick's second law of diffusion,the chloride diffusion equation in reinforced concrete(RC)pipe pile was developed considering the effects of environment temperature and chloride binding.The experimental study on the effect of environment temperature on chloride diffusion in RC pipe pile was conducted in this paper.RC pipe piles with different water-to-cement(w/c)ratios(0.30,0.45 and 0.55)were exposed to 5% chloride salt spray for 32 days at different exposure temperatures(21,30,50 ℃).Based on the experimental results and proposed model,the chloride concentration profiles,surface chloride concentration,apparent and effective diffusion coefficients,activation energy and binding capacity values of RC pipe piles with different w/cratios at different exposure temperatures were explored.The experimental results show that the free chloride concentration,surface chloride concentration,apparent and effective diffusion coefficients increase with the environment temperature. The binding capacity increases significantly with the increase of environment temperature from 21 to 30℃.However,the binding capacity decreases slightly when the environment temperature increases from 30 to 50℃.It could be concluded that the chloride diffusion into RC pipe pile follows the Arrhenius theory due to the linear distribution of thelog-variation of apparent diffusion coefficient with the inverse of absolute temperature.
Based on Fick's second law of diffusion,the chloride diffusion equation in reinforced concrete(RC)pipe pile was developed considering the effects of environment temperature and chloride binding.The experimental study on the effect of environment temperature on chloride diffusion in RC pipe pile was conducted in this paper.RC pipe piles with different water-to-cement(w/c)ratios(0.30,0.45 and 0.55)were exposed to 5% chloride salt spray for 32 days at different exposure temperatures(21,30,50 ℃).Based on the experimental results and proposed model,the chloride concentration profiles,surface chloride concentration,apparent and effective diffusion coefficients,activation energy and binding capacity values of RC pipe piles with different w/cratios at different exposure temperatures were explored.The experimental results show that the free chloride concentration,surface chloride concentration,apparent and effective diffusion coefficients increase with the environment temperature. The binding capacity increases significantly with the increase of environment temperature from 21 to 30℃.However,the binding capacity decreases slightly when the environment temperature increases from 30 to 50℃.It could be concluded that the chloride diffusion into RC pipe pile follows the Arrhenius theory due to the linear distribution of thelog-variation of apparent diffusion coefficient with the inverse of absolute temperature.
引文
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[19]SONG H W,LEE C H,ANN K Y.Factors influencing chloride transport in concrete structures exposed to marine environments[J].Cement and Concrete Composites,2008,30(2):113-121.
[20]ANN K Y,AHN J H,RYOU J S.The importance of chloride content at the concrete surface in assessing the time to corrosion of steel in concrete structures[J].Construction and Building Materials,2009,23(1):239-245.
[21]OTSUKI N,MADLANGBAYAN M S,NISHIDA T,et al.Temperature dependency of chloride induced corrosion in concrete[J].Journal of Advanced Concrete Technology,2009,7(1):41-50.
[2]PANESAR D K,CHIDIAC S E.Effect of cold temperature on the chloride-binding capacity of cement[J].Journal of Cold Regions Engineering,2011,25(4):133-144.
[3]鲁彩凤,袁迎曙,季海霞,等.海洋大气中氯离子在粉煤灰混凝土中的传输规律[J].浙江大学学报(工学版),2012,46(4):681-690.LU C F,YUAN Y S,JI H X,et al.Chloride ion transport in fly ash concrete under marine atmospheric environment[J].Journal of Zhejiang University(Engineering Science),2012,46(4):681-690.(in Chinese)
[4]刘毅.混凝土中温度对氯离子扩散系数的影响分析[J].佳木斯大学学报(自然科学版),2013,31(3):325-327,332.LIU Y.Analysis on the influence of temperature on chloride ion diffusion in the concrete[J].Journal of Jiamusi University(Natural Science Edition),2013,31(3):325-327,332.(in Chinese)
[5]张伟平,张庆章,顾祥林,等.环境条件和应力水平对混凝土中氯离子传输的影响[J].江苏大学学报(自然科学版),2013,34(1):101-106.ZHANG W P,ZHANG Q Z,GU X L,et al.Effects of environmental conditions and stress level on chloride ion transport in concrete[J].Journal of Jiangsu University(Natural Science Edition),2013,34(1):101-106.(in Chinese)
[6]徐文冰,孙策,李进辉,等.温度对海工混凝土抗氯离子侵蚀性能的影响及寿命预测[J].公路,2014,59(10):50-54.XU W B,SUN C,LI J H,et al.Influence of temperature on marine concrete anti-chloride corrosion ability and analysis on life forecast[J].Highway,2014,59(10):50-54.(in Chinese)
[7]杨海成,杜安民,范志宏,等.温度对混凝土中氯离子扩散性能的影响[J].水运工程,2015(10):20-26.YANG H C,DU A M,FAN Z H,et al.Influence of exposure temperature on chloride diffusion in concrete[J].Port&Waterway Engineering,2015(10):20-26.(in Chinese)
[8]OH B H,JANG S Y.Effects of material and environmental parameters on chloride penetration profiles in concrete structures[J].Cement and Concrete Research,2007,37(1):47-53.
[9]SAMSON E,MARCHAND J.Modeling the effect of temperature on ionic transport in cementitious materials[J].Cement and Concrete Research,2007,37(3):455-468.
[10]CARS.Effect of temperature on porosity and on chloride diffusion in cement pastes[J].Construction and Building Materials,2008,22(7):1560-1573.
[11]NGUYEN T S,LORENTE S,CARCASSES M.Effect of the environment temperature on the chloride diffusion through CEM-1 and CEM-V mortars:An experimental study[J].Construction and Building Materials,2009,23(2):795-803.
[12]ISTEITA M,XI Y P.The effect of temperature variation on chloride penetration in concrete[J].Construction and Building Materials,2017,156:73-82.
[13]VAL D V,TRAPPER P A.Probabilistic evaluation of initiation time of chloride-induced corrosion[J].Reliability Engineering&System Safety,2008,93:364-372.
[14]HWANG C C.Analysis of diffusion and extraction in hollow cylinders for some boundary conditions[J].IOSR Journal of Engineering,2012,2(8):141-151.
[15]SHAZALI M A,RAHMAN M K,AL-GADHIB AH,et al.Transport modeling of chlorides with binding in concrete[J].Arabian Journal for Science and Engineering,2012,37(2):469-479.
[16]XI Y P,BAANT Z P,JENNINGS H M.Moisture diffusion in cementitious materials Adsorption isotherms[J].Advanced Cement Based Materials,1994,1(6):248-257.
[17]DOUSTI A,RASHETNIA R,AHMADI B,et al.Influence of exposure temperature on chloride diffusion in concretes incorporating silica fume or natural zeolite[J].Construction and Building Materials,2013,49:393-399.
[18]THOMAS M D A,BENTZ E C.Life-365service life prediction model and computer program for predicting the service life and life-cycle costs of reinforced concrete exposed to chlorides[R].Life-365 Consortium I,2000.
[19]SONG H W,LEE C H,ANN K Y.Factors influencing chloride transport in concrete structures exposed to marine environments[J].Cement and Concrete Composites,2008,30(2):113-121.
[20]ANN K Y,AHN J H,RYOU J S.The importance of chloride content at the concrete surface in assessing the time to corrosion of steel in concrete structures[J].Construction and Building Materials,2009,23(1):239-245.
[21]OTSUKI N,MADLANGBAYAN M S,NISHIDA T,et al.Temperature dependency of chloride induced corrosion in concrete[J].Journal of Advanced Concrete Technology,2009,7(1):41-50.