干湿循环对面板混凝土抗冻耐久性的影响

Effect of Dry Wet Cycle on Frost Resistance Durability of Face Slab Concrete

针对我国北方面板混凝土服役过程中遭受的干湿与冻融循环共同作用导致的混凝土性能劣化问题,以浸烘循环和冻融循环模拟实际情况并同时考虑先后次序问题,通过对试件进行0、20、40、60次的浸烘循环预处理,开展了混凝土冻融循环试验,探究了干湿循环对混凝土抗冻耐久性的影响。试验结果表明,干湿循环在一定程度上会加剧冻融循环带来的损伤,随着浸烘循环预处理次数的增加,混凝土在冻融过程中的质量、动弹性模量、超声波波速大幅降低,渗透系数大幅增加;微观上,浸烘循环预处理造成混凝土微观层面上的初始损伤并产生初始微裂纹,使水分更易侵入混凝土,导致在冻融循环中更易产生新的微裂纹及初始微裂纹的发育,从而降低混凝土抗冻耐久性。

In view of the deterioration of concrete performance caused by the combined action of dry and wet cycles and freeze-thaw cycles in the service process of panel concrete in northern China,the actual situation was simulated by immersion drying cycle and freeze-thaw cycle as well as considering the priority problem simultaneously.The concrete freeze-thaw cycle test was carried out by the pre-treatment of soak drying cycle with number of 0,20,40 and 60.The impact of dry wet cycle on the frost resistance durability of concrete was explored.The test results show that the dry wet cycle will aggravate the damage caused by freeze-thaw cycle to a certain extent.With the increase of pretreatment times of soaking and drying cycle,the quality,dynamic elastic modulus and ultrasonic wave velocity of concrete in the process of freeze-thaw will be greatly reduced,and the permeability coefficient will be greatly increased;Microscopically,the pre-treatment of soaking and drying cycle caused the initial damage and initial microcracks on the micro level of concrete,which makes it easier for water to invade the concrete,resulting in new microcracks and the development of initial microcracks in the freeze-thaw cycle,so as to reduce the frost resistance durability of concrete.