Cl^-环境下冻融循环对混凝土材料性能的影响

Effect of Freezing and Thawing Cycle on Concrete Material Under the Environment of Cl^-

对浸泡在质量分数为9.06%的饱和Na Cl溶液中的81个混凝土棱柱体试块和21个钢筋混凝土拔出试件先采用冻融循环后,进行棱柱体试件的抗压、抗折试验和钢筋黏结的拔出试验,探究了不同混凝土等级、不同浸泡龄期、不同冻融次数对材料物理性能的影响。结果表明:水胶比对冻融后混凝土的强度影响较大,添加高效减水剂有助于提高混凝土抵抗冻融破坏的能力;饱和Na Cl溶液浸泡素混凝土对其物理性质影响很小,可以忽略不计,但经过浸泡后产生裂缝,冻融循环对其影响很大;对钢筋拉拔试件来说,冻融到150次时,冻融循环对钢筋与混凝土黏结强度影响突然变大,在150次冻融循环后,由于机械摩擦力作用,冻融循环对其破坏速度趋于稳定。对棱柱体试件来说,冻融到300次循环时,棱柱体抗压、抗折损伤突然变大;另外通过SEM电镜扫描、超声波技术试验有效地解释了混凝土在冻融循环下强度降低的微观机理。

With the method of freezing and thawing cycle to the soak in the mass fraction of 9. 06% Na Cl saturated solution of 81 concrete prism and 21 reinforced concrete block which will be pulled out,then all of which will be carried out the compressive strength,flexural test and the pull-out tests reinforcement,exploring the different concrete grade,soaking ages,different number of freezing and thawing cycle on the material physical properties. The results show that the effect of water-binder ratio on the strength of the concrete after freezing and thawing is bigger. It is useful to add high efficiency water reducing agent for improving concrete resistance after freezing and thawing damage. There is little impact for plain concrete soak in saturated sodium chloride solution,which can be neglected,but with the cracks on after soaking,greater influence appears. For pulled out specimens,when it comes to the 150 times,the effect of bonding strength of concrete suddenly change bigger,after 150 times of freezing and thawing cycle,the damage speed of concrete tends to be stable because of mechanical friction. For prism specimens,when it comes to 300 times,the prism compressive strength,flexural damage suddenly become bigger. In addition, adopting SEM electron microscope scanning and ultrasonic technology can explain the microscopic mechanism of the decrease of strength of concrete under freezing and thawing cycle.