混合侵蚀和冻融循环条件下混凝土力学机制试验研究

Experimental study on mechanical mechanism of concrete under mixed erosion and freeze-thaw cycling

混凝土在硫酸盐侵蚀和冻融循环条件下易破坏,引发基础承载力下降。为了研究寒区盐渍土环境下混凝土的劣化机制,进行混凝土在硫酸钠和氯化钠混合溶液中的冻融循环试验,循环次数分别为0、10、20、30、40、50次;其次测量了冻融循环后混凝土的抗压强度,并结合X射线衍射试验,分析了侵蚀后混凝土内部物质的变化对力学性能的影响;最后通过冻融前后的弹性模量及质量变化,计算了损伤变量和质量损失率变化,研究了冻融循环下的混凝土损伤规律。研究结果表明:随着冻融次数的增加,混凝土力学性能大幅度弱化,内部损伤越严重,表面剥落越严重;弹性模量、抗压强度均大幅度降低,质量损失率与损伤变量均增大。混凝土内部发生了物理反应(芒硝的生成)和化学反应(石膏和钙矾石的生成),共同造成了混凝土内部结构破坏。

Under the condition of sulfate attack or freeze-thaw cycle,concrete is easily destroyed,leading to its decrease in foundation bearing capacity.In order to study the deterioration mechanism of concrete in saline soil in cold area,firstly,the freeze-thaw cycling test of concrete in mixed solution of sodium sulfate and sodium chloride is carried out,the number of cycles is 0,10,20,30,40,50 times,respectively.Secondly,the compressive strength of concrete after freeze-thaw cycling is measured,and the influence of material change on mechanical properties after erosion is analyzed by XRD diffraction test.Finally,the change of damage variable and mass loss rate is calculated by the change of elastic modulus and mass before and after freeze-thaw,and the damage law of concrete under freeze-thaw cycling is studied.The result shows that when the number of freeze-thaw increases,the concrete deteriorates,the mechanical properties weaken,the surface spalling worsens,both elastic modulus and compressive strength decreased greatly and both mass loss rate and damage variables increased.Because the physical reaction of formation of mirabilite and chemical reaction of formation of gypsum and ettringite that occur inside the concrete together cause damages to the internal structure of the clay.