冻融循环与硫酸盐溶液耦合作用下混凝土劣化机理试验研究
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摘要
基于多尺度研究了浓度为10%和15%硫酸盐溶液与冻融循环耦合作用下混凝土的劣化机理。从混凝土质量,抗压强度,相对动弹性模量时变规律等宏观力学指标探究了混凝土损伤劣化机制;运用CT技术和扫描电镜(SEM)技术从细微观角度研究了冻融循环与硫酸盐溶液耦合作用下混凝土的侵蚀劣化规律。研究结果表明:宏观上混凝土试样的质量损失总体呈现初期增加随后小幅下降后期快速增加的趋势、单轴抗压强度先增大后减小的变化规律;在高浓度溶液中的试样相对动弹性模量下降速率呈现出先快后慢的变化规律,在低浓度溶液中的试样相对动弹性模量下降速率开始比较缓慢随着冻融次数增加慢慢趋近于高浓度溶液中试样。细观上通过CT技术发现试样的孔隙率随着冻融次数的增加呈现先减小后增大的趋势,内部微裂纹逐步扩展直至贯通。微观上运用扫描电镜(SEM)观察到试样裂缝和孔洞内壁处生成了钙矾石和石膏,并由于其膨胀力使得混凝土结构酥松。硫酸盐侵蚀和冻融循环耦合作用下混凝土劣化过程有两个阶段:在前期硫酸盐能降低冻融循环对混凝土的劣化,在后期硫酸盐侵蚀产物膨胀力、结晶盐产生的结晶压力和冻融产生的冻胀力共同作用使混凝土加速劣化。
The deterioration mechanism of concrete with 10% and 15% sulfate solution coupled with freeze-thaw cycles was studied based on multi-scale analysis. The damage and deterioration mechanism of concrete was explored from the macroscopic mechanical indexes such as the concrete mass, the compressive strength and the time variation law of relative dynamic elastic modulus. The erosion and deterioration law of concrete under the coupling of freezing and thawing cycle and sulfate solution was studied by using CT and SEM technique. The results show that the mass loss of the concrete samples at the macro level increases in the early stage and then decreases rapidly in the later period,and the uniaxial compression strength increases first and then decreases,and the decrease rate of the relative dynamic elastic modulus in the high concentration solution shows a fast and slow change law and is low concentration in the high concentration solution. The relative elastic modulus decreases slowly in the solution,and gradually approaches the sample in the high concentration solution with the increase of freeze-thaw cycles. Through the CT technique,it is found that the porosity of the specimen decreases and then increases with the increase of the freezing and thawing times,and the internal microcracks gradually expand until through. Scanning electron microscopy (SEM) is used to observe the formation of ettringite and gypsum in the crack and the inner wall of the hole,and the concrete structure is crisp because of itsexpansion force. There are two stages in the process of concrete deterioration under the interaction of sulfate and freeze-thaw cycles. In the early stage,the sulphate can reduce the deterioration of concrete by the freezing and thawing cycle. The expansion force of the sulfate erosion products,the crystallization pressure produced by the crystallization salt and the frost heave force produced by the freezing thawing are used together to accelerate the deterioration of concrete.
The deterioration mechanism of concrete with 10% and 15% sulfate solution coupled with freeze-thaw cycles was studied based on multi-scale analysis. The damage and deterioration mechanism of concrete was explored from the macroscopic mechanical indexes such as the concrete mass, the compressive strength and the time variation law of relative dynamic elastic modulus. The erosion and deterioration law of concrete under the coupling of freezing and thawing cycle and sulfate solution was studied by using CT and SEM technique. The results show that the mass loss of the concrete samples at the macro level increases in the early stage and then decreases rapidly in the later period,and the uniaxial compression strength increases first and then decreases,and the decrease rate of the relative dynamic elastic modulus in the high concentration solution shows a fast and slow change law and is low concentration in the high concentration solution. The relative elastic modulus decreases slowly in the solution,and gradually approaches the sample in the high concentration solution with the increase of freeze-thaw cycles. Through the CT technique,it is found that the porosity of the specimen decreases and then increases with the increase of the freezing and thawing times,and the internal microcracks gradually expand until through. Scanning electron microscopy (SEM) is used to observe the formation of ettringite and gypsum in the crack and the inner wall of the hole,and the concrete structure is crisp because of itsexpansion force. There are two stages in the process of concrete deterioration under the interaction of sulfate and freeze-thaw cycles. In the early stage,the sulphate can reduce the deterioration of concrete by the freezing and thawing cycle. The expansion force of the sulfate erosion products,the crystallization pressure produced by the crystallization salt and the frost heave force produced by the freezing thawing are used together to accelerate the deterioration of concrete.
引文
[1]姜磊,牛荻涛.硫酸盐与冻融环境下混凝土本构关系研究[J].四川大学学报:工程科学版,2016,48(3):71-78.
[2]姜磊,牛荻涛.硫酸盐与冻融环境下混凝土损伤破坏准则研究[J].防灾减灾工程学报,2016,37(1):148-153.
[3]慕儒,缪昌文,刘加平,等.氯化钠,硫酸钠溶液对混凝土抗冻性的影响及其机理[J].硅酸盐学报,2001,29(6):523-529.
[4]幕儒,缪昌文,刘加平,等.硫酸钠溶液对混凝土抗冻性的影响[J].建筑材料学报,2001,4(4):311-316.
[5]姜磊,牛荻涛.硫酸盐与冻融复合作用下混凝土劣化规律[J].中南大学学报:自然科学版,2016,47(9):3208-3216.
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[7]Hua Q Y,Xiao M S,Mei J R,et al.Influence of alternation of sulfate attack and freeze-thaw on microstructure of concrete[J].Advances in Materials Science and Engineering,2015(1):1-7.
[8]金祖权,陈惠苏,侯保荣,等.引起混凝土在冻融循环过程中的氯离子渗透与孔结构[J].中南大学学报:自然科学版,2012,43(5):1963-1968.
[9]Cwirzen A,Penttala V.Aggregate-cement paste transition zone properties affecting the salt frost amage of high-performance concretes[J].Cement and Concrete Research,2005,35(2):671-679.
[10]苑立冬,牛荻涛,姜磊,等.硫酸盐侵蚀与冻融循环共同作用下混凝土损伤研究[J].硅酸盐通报,2013,32(6):1171-1176.
[11]张云清,余红发,孙伟,等.冻融循环作用下混凝土的硫酸盐应力腐蚀特性[J].土木建筑与环境工程,2010,32(6):147-152.
[12]葛勇,杨文萃,袁杰,等.硫酸盐溶液中混凝土抗冻融干湿循环性能[J].东南大学学报:自然科学报,2006,36(增刊Ⅱ):234-237.
[13]尹小涛,葛修润,党发宁,等.基于CT实验的混凝土破损机理生态学研究[J].混凝土,2006(8):21-24.
[14]尹小涛,党发宁,丁卫华,等.岩土CT图像,中裂纹的形态学测量[J].岩石力学与工程学报,2006,25(3):539-544.
[15]陈厚群,丁卫华,蒲毅彬,等.单轴压缩条件下混凝土细观破裂过程的X射线CT实时观测[J].水利学报,2006,37(9):1044-1050.
[16]田威,张鹏坤,谢永利,等.冻融环境下基于CT技术混凝土孔隙结构的三维分布特征[J].长安大学学报:自然科学版,2016,36(3):49-55.
[2]姜磊,牛荻涛.硫酸盐与冻融环境下混凝土损伤破坏准则研究[J].防灾减灾工程学报,2016,37(1):148-153.
[3]慕儒,缪昌文,刘加平,等.氯化钠,硫酸钠溶液对混凝土抗冻性的影响及其机理[J].硅酸盐学报,2001,29(6):523-529.
[4]幕儒,缪昌文,刘加平,等.硫酸钠溶液对混凝土抗冻性的影响[J].建筑材料学报,2001,4(4):311-316.
[5]姜磊,牛荻涛.硫酸盐与冻融复合作用下混凝土劣化规律[J].中南大学学报:自然科学版,2016,47(9):3208-3216.
[6]陈四利,宁宝宽,胡大伟.硫酸盐和冻融双重作用对混凝土力学性质的影响[J].工业建筑,2006,36(12):12-15.
[7]Hua Q Y,Xiao M S,Mei J R,et al.Influence of alternation of sulfate attack and freeze-thaw on microstructure of concrete[J].Advances in Materials Science and Engineering,2015(1):1-7.
[8]金祖权,陈惠苏,侯保荣,等.引起混凝土在冻融循环过程中的氯离子渗透与孔结构[J].中南大学学报:自然科学版,2012,43(5):1963-1968.
[9]Cwirzen A,Penttala V.Aggregate-cement paste transition zone properties affecting the salt frost amage of high-performance concretes[J].Cement and Concrete Research,2005,35(2):671-679.
[10]苑立冬,牛荻涛,姜磊,等.硫酸盐侵蚀与冻融循环共同作用下混凝土损伤研究[J].硅酸盐通报,2013,32(6):1171-1176.
[11]张云清,余红发,孙伟,等.冻融循环作用下混凝土的硫酸盐应力腐蚀特性[J].土木建筑与环境工程,2010,32(6):147-152.
[12]葛勇,杨文萃,袁杰,等.硫酸盐溶液中混凝土抗冻融干湿循环性能[J].东南大学学报:自然科学报,2006,36(增刊Ⅱ):234-237.
[13]尹小涛,葛修润,党发宁,等.基于CT实验的混凝土破损机理生态学研究[J].混凝土,2006(8):21-24.
[14]尹小涛,党发宁,丁卫华,等.岩土CT图像,中裂纹的形态学测量[J].岩石力学与工程学报,2006,25(3):539-544.
[15]陈厚群,丁卫华,蒲毅彬,等.单轴压缩条件下混凝土细观破裂过程的X射线CT实时观测[J].水利学报,2006,37(9):1044-1050.
[16]田威,张鹏坤,谢永利,等.冻融环境下基于CT技术混凝土孔隙结构的三维分布特征[J].长安大学学报:自然科学版,2016,36(3):49-55.
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