溶出法测定既有混凝土构件水溶性碱含量和估算孔溶液碱度
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摘要
混凝土孔溶液碱度是诱发和维持AAR的必要条件,其准确测定是诊断和预测AAR的基础。为比较不同途径和测试方法获取的混凝土水溶性碱含量以及孔溶液碱度之间相关性,分别采用热水浸出法和改进ASTMC114对比研究了配合比碱含量不同的既有混凝土构件的水溶性碱含量,并估算其孔溶液碱度。结果表明,针对4组碱含量不同的高性能混凝土构件,实际测定的水溶性碱含量及据此估算的孔溶液碱度与基于配合比计算的结果之间没有明显相关性。芯样水溶性碱含量随水中浸出时间延长而增加。混凝土配合比碱含量相同,但组分不同的2组芯样,其水溶性碱含量和孔溶液碱度也存在明显差别。建议针对现代混凝土系统研究配合比碱含量与实际碱含量之间的对应关系,以安全、科学和经济地预防其AAR危害。
The alkalinity of concrete pore solution is the necessity to initiate and maintain AAR. Its accuracy determination is fundamental for the diagnosis and prognosis of AAR in field concrete. In order to compare the correlations between the results of water soluble alkali content and the alkalinity of pore solutions obtained by different ways and testing methods,the water soluble alkali contents,as well as the alkalinity of the pore solutions in the field concrete structures obtained by hot water extracting and modified ASTM C114 were investigated. Results show that,for the 4 group of concrete cores from precast members with different alkali contents,there is no obvious correlation between results in water soluble alkali contents and the alkalinity of pore solutions obtained by water extraction test and by calculation from the mix proportions. The water soluble alkali increases with the increasing of the extraction time in water. Concrete cores with same alkali content calculated by mix proportion, but with different constituents,there are obvious differences both in the water soluble content and the alkalinity of pore solutions. In order to avoid AAR in modern concrete in a safe,scientific and economical way,systematic study on the correlations between the alkali contents calculated by mix proportion and the actual harmful alkali content in casted concrete is required.
The alkalinity of concrete pore solution is the necessity to initiate and maintain AAR. Its accuracy determination is fundamental for the diagnosis and prognosis of AAR in field concrete. In order to compare the correlations between the results of water soluble alkali content and the alkalinity of pore solutions obtained by different ways and testing methods,the water soluble alkali contents,as well as the alkalinity of the pore solutions in the field concrete structures obtained by hot water extracting and modified ASTM C114 were investigated. Results show that,for the 4 group of concrete cores from precast members with different alkali contents,there is no obvious correlation between results in water soluble alkali contents and the alkalinity of pore solutions obtained by water extraction test and by calculation from the mix proportions. The water soluble alkali increases with the increasing of the extraction time in water. Concrete cores with same alkali content calculated by mix proportion, but with different constituents,there are obvious differences both in the water soluble content and the alkalinity of pore solutions. In order to avoid AAR in modern concrete in a safe,scientific and economical way,systematic study on the correlations between the alkali contents calculated by mix proportion and the actual harmful alkali content in casted concrete is required.
引文
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[3]BérubéM A,Dorion J F,Rivest M.Laboratory assessment of alkali contribution by aggregates to concrete and application to concrete structures affected by ASR[J].Cement and Concrete Research,2002,32(8):1215-1227.
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[5]Berra M.Effect of fly ash on alkali-silica reaction[A].Proceeding of 10th International Conference on AAR in Concrete.Melbourne,Australia,1996:61-71.
[6]Duchesne J,BérubéM A.The effectiveness of supplementary cementitious materials in suppressing expansion due to ASR:another look at the reaction mechanisms-Part2:pore solution chemistry[J].Cement and Concrete Research,1994,24(2):221-230.
[7]Leming M L,Nguyen B Q.Limits on alkali content in cement-Results from a field study[J].Cement Concrete and Aggregates,2000,22(1):41-47.
[8]Barneyback R,Diamond S.Expression and analysis of pore fluids from hardened cement paste and mortars[J].Cement and Concrete Research,1981,11(2):279-285.
[9]孟志良,周卫.论萃取孔溶液法测定混凝土有效碱[J].混凝土,2001,(2):39-40.
[10]孟志良,蒋登辉.溶出法测定有效减[J].混凝土,2001,(6):9-10.
[11]Sagüés A A,Moreno E I,Andrade C.Evolution of p H during in-situ leaching in small concrete cavities[J].Cement and Concrete Research,1997,27(11):1747-1759.
[12]BérubéM A,Frenette J,Rivest M,et al.Measurement of the Alkali Content of Concrete Using Hot-Water Extraction[J].Cement,Concrete,and Aggregate,2002,24(1):28-36.
[13]ASTM C114-2000.Standard Test Methods for Chemical Analysis of Hydraulic Cement[S].Annual Book of ASTM Standards.Vol.04.01,2001.
[14]Rivard P,BérubéM A,Ollivier J P.Decrease of pore solution alkalinity in concrete tested for alkali-silica reaction[J].Materials and Structures,2007,40(9):909-921.
[15]Rivard P,BérubéM A.Effect of drying-rewetting on the alkali concentration of the concrete pore solution[J].Cement and Concrete Research,2003,33(6):927-929.
[16]Rásánen V,Penttala V.The p H measurement of concrete and smoothing mortar using a concrete powder suspension[J].Cement and Concrete Research,2004,34(5):813-820.
[17]王景贤.既有结构混凝土中碱含量的检测[J].建材技术与应用,2009,(3):25-27.
[18]Brouwers H J H,van Eijk R J.Alkali concentration of pore solution in hydration OPC[J].Cement and Concrete Research,2003,33(2):191-196.
[19]Fournier B,Chevrier R,de Grosbois M,et al.The accelerated concrete prism test(60℃):Variability of the test method and proposed expansion limits[C]//Proc.of the 12th Int.Conf.on AAR in Concrete,Beijing(China),2004:314-323.
[2]Constantiner D,Diamond S.Alkali release from feldspars into pore solutions[J].Cement and Concrete Research,2003,33(4):549-554.
[3]BérubéM A,Dorion J F,Rivest M.Laboratory assessment of alkali contribution by aggregates to concrete and application to concrete structures affected by ASR[J].Cement and Concrete Research,2002,32(8):1215-1227.
[4]Nixon P J,Page C L.Pore solution chemistry and alkali aggregate reaction[J].ACI Special Publication,1987,100:1833-1862.
[5]Berra M.Effect of fly ash on alkali-silica reaction[A].Proceeding of 10th International Conference on AAR in Concrete.Melbourne,Australia,1996:61-71.
[6]Duchesne J,BérubéM A.The effectiveness of supplementary cementitious materials in suppressing expansion due to ASR:another look at the reaction mechanisms-Part2:pore solution chemistry[J].Cement and Concrete Research,1994,24(2):221-230.
[7]Leming M L,Nguyen B Q.Limits on alkali content in cement-Results from a field study[J].Cement Concrete and Aggregates,2000,22(1):41-47.
[8]Barneyback R,Diamond S.Expression and analysis of pore fluids from hardened cement paste and mortars[J].Cement and Concrete Research,1981,11(2):279-285.
[9]孟志良,周卫.论萃取孔溶液法测定混凝土有效碱[J].混凝土,2001,(2):39-40.
[10]孟志良,蒋登辉.溶出法测定有效减[J].混凝土,2001,(6):9-10.
[11]Sagüés A A,Moreno E I,Andrade C.Evolution of p H during in-situ leaching in small concrete cavities[J].Cement and Concrete Research,1997,27(11):1747-1759.
[12]BérubéM A,Frenette J,Rivest M,et al.Measurement of the Alkali Content of Concrete Using Hot-Water Extraction[J].Cement,Concrete,and Aggregate,2002,24(1):28-36.
[13]ASTM C114-2000.Standard Test Methods for Chemical Analysis of Hydraulic Cement[S].Annual Book of ASTM Standards.Vol.04.01,2001.
[14]Rivard P,BérubéM A,Ollivier J P.Decrease of pore solution alkalinity in concrete tested for alkali-silica reaction[J].Materials and Structures,2007,40(9):909-921.
[15]Rivard P,BérubéM A.Effect of drying-rewetting on the alkali concentration of the concrete pore solution[J].Cement and Concrete Research,2003,33(6):927-929.
[16]Rásánen V,Penttala V.The p H measurement of concrete and smoothing mortar using a concrete powder suspension[J].Cement and Concrete Research,2004,34(5):813-820.
[17]王景贤.既有结构混凝土中碱含量的检测[J].建材技术与应用,2009,(3):25-27.
[18]Brouwers H J H,van Eijk R J.Alkali concentration of pore solution in hydration OPC[J].Cement and Concrete Research,2003,33(2):191-196.
[19]Fournier B,Chevrier R,de Grosbois M,et al.The accelerated concrete prism test(60℃):Variability of the test method and proposed expansion limits[C]//Proc.of the 12th Int.Conf.on AAR in Concrete,Beijing(China),2004:314-323.