基于盐冻性能的高寒地区桥梁混凝土优化设计及机理分析
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摘要
为探索改善高寒地区桥梁混凝土盐冻性能的可行性措施,设计正交试验,重点研究水胶比、用水量和引气量等因素对桥梁主塔C50混凝土、桥面板C40混凝土及大体积承台C30混凝土盐冻损伤规律,并提出高寒地区桥梁混凝土配合比设计参考值;借助SEM和压汞微观测试手段对桥梁混凝土进行微观分析.结果表明:桥梁混凝土盐冻性能显著性影响因素为用水量和引气量;用水量由156 kg·m~(-3)减至144 kg·m~(-3),桥面板C40混凝土剥蚀量降幅为13. 0%,300次冻融后抗弯拉强度损失率仅为20%;引气量控制在4. 5%～5. 0%时,300次冻融循环后,主塔C50混凝土的动弹模量相对值在87%以上,混凝土内部微裂缝较少,过渡区结构致密度较高,孔径分布最佳,宏观上表现为盐冻性能的提高.
To explore the feasible measures for improving the durability of concrete bridges in cold area,the orthogonal test was designed to investigate the damage law of water binder ratio,water content and air entraining agent on the bridge main tower concrete C50,bridge deck concrete C40 and platform concrete C30,and the range of parameters with salt frost resistance of concrete bridge was proposed based on the alpine region. The microscopic mechanism was analyzed by scanning electron microscope and mercury injection test. The results show that the most significant factors affecting the frost resistance of concrete are the dosage of air entraining agent and water consumption. When the water consumption is reduced from 156 kg · m~(-3) to 144 kg · m~(-3),the C40 bridge deck concrete erosion amount is decreased by13. 0%. After freeze-thaw cycles for 300 times,the loss rate of flexural tensile strength is only 20%.Controlling the gas content of 4. 5% to 5. 0% in most specimens,after 300 freeze-thaw cycles of dynamic,the relative elastic modulus of main tower concrete C50 is always above 87%,and the internal microcrack of concrete is low with high transition zone density,optimum pore distribution and increased macro frost resistance.
To explore the feasible measures for improving the durability of concrete bridges in cold area,the orthogonal test was designed to investigate the damage law of water binder ratio,water content and air entraining agent on the bridge main tower concrete C50,bridge deck concrete C40 and platform concrete C30,and the range of parameters with salt frost resistance of concrete bridge was proposed based on the alpine region. The microscopic mechanism was analyzed by scanning electron microscope and mercury injection test. The results show that the most significant factors affecting the frost resistance of concrete are the dosage of air entraining agent and water consumption. When the water consumption is reduced from 156 kg · m~(-3) to 144 kg · m~(-3),the C40 bridge deck concrete erosion amount is decreased by13. 0%. After freeze-thaw cycles for 300 times,the loss rate of flexural tensile strength is only 20%.Controlling the gas content of 4. 5% to 5. 0% in most specimens,after 300 freeze-thaw cycles of dynamic,the relative elastic modulus of main tower concrete C50 is always above 87%,and the internal microcrack of concrete is low with high transition zone density,optimum pore distribution and increased macro frost resistance.
引文
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[2]郭寅川,申爱琴,王剑,等.高寒地区桥梁混凝土抗氯离子渗透性能研究[J].建筑材料学报,2014,17(3):425-429.GUO Y C,SHEN A Q,WANG J,et al.Resistance to chloride ion permeation to concrete bridges in alpine regions[J].Journal of Building Materials,2014,17(3):425-429.(in Chinese)
[3]陈剑毅,胡明玉,肖烨,等.复杂环境下矿物掺合料混凝土的耐久性研究[J].硅酸盐通报,2011,30(3):639-644.CHEN J Y,HU M Y,XIAO Y,et al.Study on mineral admixture concrete durability under the complex environment[J].Bulletin of the Chinese Ceramic Society,2011,30(3):639-644.(in Chinese)
[4]曹大富,富立志,杨忠伟,等.冻融循环下砼力学性能与相对动弹性模量关系[J].江苏大学学报(自然科学版),2012,33(6):721-725.CAO D F,FU L Z,YANG Z W,et al.Relationship between mechanical properties and relative dynamic elasticity modulus of concrete after freeze-thaw cycles[J].Journal of Jiangsu University(Natural Science Edition),2012,33(6):721-725.(in Chinese)
[5]李强.矿物掺合料对混凝土抗盐冻性的影响[J].硅酸盐通报,2015,34(3):882-886.LI Q.Effect of mineral admixtures on salt-freezing resistance of concrete[J].Bulletin of the Chinese Ceramic Society,2015,34(3):882-886.(in Chinese)
[6]GONEN T,YAZICIOGLU S.The influence of compaction pores on sorptivity and carbonation of concrete[J].Construction and Building Materials,2007,21(5):1040-1045.
[7]李金玉,曹建国,徐文雨,等.混凝土冻融破坏机理的研究[J].水利学报,1999,30(1):41-49.LI J Y,CAO J G,XU W Y,et al.Study on the mechanism of concrete destruction under frost action[J].Shuili Xuebao,1999,30(1):41-49.(in Chinese)
[8]王稷良,申力涛,牛开民.路面水泥混凝土抗盐冻性能的影响因素[J].公路交通科技,2013,30(10):1-5.WANG J L,SHEN L T,NIU K M.Influencing factors of deicer-salt resistance of pavement cement concrete[J].Journal of Highway and Transportation Research and Development,2013,30(10):1-5.(in Chinese)
[9]薛翠真,申爱琴,郭寅川,等.盐冻耦合作用对掺CWCPM混凝土性能的影响及其机理分析[J].江苏大学学报(自然科学版),2017,38(6):713-718.XUE C Z,SHEN A Q,GUO Y C,et al.Effect and mechanism of coupling with frost and salt on concrete performance with CWCPM[J].Journal of Jiangsu University(Natural Science Edition),2017,38(6):713-718.(in Chinese)
[10]PENG G F,MA Q,HU H M,et al.The effects of air entrainment and pozzolans on frost resistance of 50-60MPa grade concrete[J].Construction and Building Materials,2007,21(5):1034-1039.