强化方式对再生混凝土断裂性能的影响

Effect of strengthening mode on fracture properties of recycled concrete

为研究不同强化方式下再生混凝土的断裂性能,设计了4组含预制裂缝的小梁试件进行三点弯曲断裂试验,分别为素再生混凝土(RC)、水玻璃溶液强化粗骨料再生混凝土(QRC)、钢纤维再生混凝土(SFRC)和水玻璃溶液强化粗骨料同时加入钢纤维再生混凝土(SFQRC)。通过强化再生粗骨料和加入钢纤维来提升再生混凝土的性能,并结合数字图像相关(digital image correlation,DIC)技术测得试件表面的全场应变和位移数据,经过整理计算得出各组试件的起裂韧度、失稳韧度和断裂能,再分析试件在不同强化方式下的变化规律。结果表明:随着强化方式从单一强化再生粗骨料或者掺纤维到复合强化,再生混凝土的断裂参数和断裂能呈正相关关系;强化骨料同时加入钢纤维的SFQRC的组合最优,其起裂韧度、失稳韧度、断裂能较RC分别提高了77.9%、251.7%、938.8%。

In order to study the fracture properties of recycled concrete with different strengthening modes,four groups of trabecular specimens with precast cracks were designed for three-point bending fracture tests.They were recycled plain concrete(RC),recycled concrete with coarse aggregate reinforced by sodium silicate solution(QRC),steel fiber recycled concrete(SFRC)and recycled concrete reinforced with coarse aggregate and steel fiber reinforced with sodium silicate solution(SFQRC),respectively.The performance of recycled concrete was improved by strengthening recycled coarse aggregate and adding steel fiber,and the full-field strain and displacement data on the specimen surface were measured by digital image correlation(DIC)technology.After finishing and calculating,the crack initiation toughness,instability toughness and fracture energy of each group of specimens were obtained,and then the variation rule of each group under different strengthening methods was analyzed.The results show that the fracture parameters of recycled concrete are positively correlated with fracture energy as the strengthening mode changes from single reinforced recycled coarse aggregate or fiber to composite reinforcement.SFQRC with reinforced aggregate and steel fiber is the best combination,and its crack initiation toughness,instability toughness and fracture energy increase 77.9%,251.7%and 938.8%,respectively,compared with RC.