橡胶/混凝土盐冻循环后性能劣化及微观结构

Performance degradation and microscopic structure of rubber/concrete after salt freeze-thaw cycles

  • 摘要: 制备普通混凝土(Normal concrete,NC)和橡胶/混凝土基体(Rubber/NC),研究盐冻循环60次内,表观现象、剥落量、抗压强度损失等性能指标劣化过程,采用超声波无损检测法评价混凝土盐冻循环破坏前后超声参数变化,建立相对波速、损伤度与抗压强度的关系,利用SEM观察盐冻循环损伤前后试件微结构变化。结果表明:随盐冻循环次数增加,混凝土试件表面剥蚀愈显著,剥落量增加,内部损伤、强度损失逐渐加剧,超声参数与抗压强度具有密切相关性;混凝土经历盐冻破坏后,内部结构呈疏松絮状,孔隙、裂纹愈加显现,密实度下降,造成宏观力学性能劣化。但弹性橡胶细集料掺入后有效缓解结冰压引起的内部开裂和孔隙扩大,各阶段橡胶/混凝土基体劣化程度均优于普通混凝土,以橡胶掺量 (与胶凝材料质量比) 10% (10%Rubber/NC)各性能指标最优,经历60次盐冻循环后,普通混凝土抗压强度损失率为58.5%,10%Rubber/NC抗压强度损失率为48.0%。

     

    Abstract: The normal concrete (NC) and rubber/NC were prepared. The performance degradation process of concrete specimens within 60 salt freeze-thaw cycles was studied, which includes changes of apparent phenomenon, flaking amount and compressive strength loss. The adaptation of ultrasonic test in evaluating the performance of concrete after salt freeze-thaw cycles was investigated. The relationships between relative velocity, damage degree and compressive strength were comparative analyzed. The micro-structure changes of concrete specimens after salt freeze-thaw cycles were observed by SEM. The results show that the surface erosion of concrete becomes more obvious, the flaking amount, internal damage and strength loss gradually increase, with the increasing number of salt freeze-thaw cycles. It has good correlation between the ultrasonic parameters and compressive strength. After the concrete undergoing salt freeze-thaw damage, the internal structure becomes loose and flocculent, increasing pores and cracks appear, and the density decreases, which results in deterioration of macro-mechanical properties. However, the deterioration degree of rubber/concrete is better than that of normal concrete at all cycle stages, because the elastic rubber fine aggregate can effectively alleviate internal cracking and pore expansion caused by icing pressure. The rubber/concrete with 10% rubber content (mass ratio to cementitious material) (10%Rubber/NC) has the best performance indicators. After 60 salt freeze-thaw cycles, the compressive strength loss rates of normal concrete and 10%Rubber/NC are 58.5% and 48.0%, respectively.

     

/

返回文章
返回