长龄期机制砂再生骨料混凝土的断裂参数和断裂过程区

Fracture Parameters and Fracture Process Zone of Long-age Manufactured-sand Recycled Aggregate Concrete

为研究龄期对机制砂再生骨料混凝土(Manufactured-sand recycled aggregate concrete,MSRAC)断裂机理的影响,采用数字图像相关技术对28 d和300 d龄期的MSRAC的断裂参数和断裂过程区(Fracture process zone,FPZ)进行研究,并对比分析了MSRAC的断裂行为和增韧机制。结果表明,随着龄期延长,MSRAC的名义刚度、断裂能、起裂断裂韧度和失稳断裂韧度得到明显改善,其局部微裂纹和宏观裂纹的相互作用也明显增加,但长龄期MSRAC的失效特征更加迅速和剧烈,软化阶段的脆性显著增加。此外,在裂纹失稳扩展时,MSRAC的FPZ宽度和面积随着龄期延长而增加,FPZ长度则相反。在FPZ完全扩展时,MSRAC的FPZ长度随龄期延长而降低,FPZ宽度则相反,FPZ面积是不敏感的。相比28 d龄期的MSRAC,长龄期的MSRAC具有更加强烈的骨料联锁效应,其次生裂纹和损伤范围也更加明显和宽广。

To study the effect of age on the fracture mechanism of manufactured-sand recycled aggregate concrete(MSRAC),the fracture parameters and fracture process zone(FPZ)of MSRAC at 28 d and 300 d were studied using digital image correlation technique,and the fracture behavior and toughening mechanism of MSRAC were compared and analyzed.The results indicate that the nominal stiffness,fracture energy,initial fracture toughness and unstable fracture toughness of MSRAC are significantly improved with increasing age,the interaction between local micro-crack and macro-crack also increase significantly.However,the failure characteristics of long-age MSRAC are more rapid and violent,its brittleness increases significantly during the softening stage.In addition,the FPZ width and area of the MSRAC increase with age during unstable crack propagation,while the FPZ length is opposite.When the FPZ is fully developed,the FPZ length of MSRAC decreases with age and the FPZ width increases with age,while the FPZ area is insensitive to age.Compared with the 28 d MSRAC,the long-aged MSRAC has a stronger aggregate interlocking effect,and its secondary crack and damage range are also more obvious.