再生粗骨料取代率对约束再生混凝土动态力学行为的影响

Effects of recycled coarse aggregate replacement ratios on dynamic mechanical behavior of confined recycled aggregate concrete

通过箍筋约束再生混凝土棱柱体动态力学性能试验,获取不同再生粗骨料取代率下约束再生混凝土单轴受压动态应力-应变关系全曲线;研究取代率对约束再生混凝土力学和变形性能的影响规律。不同再生粗骨料取代率、体积配箍率或应变率下约束再生混凝土应力-应变曲线形状无明显区别,曲线的上升段基本一致,而下降段差异较为明显。随着再生粗骨料取代率的增加或应变率的提高,下降段曲线随之变陡;箍筋约束在很大程度上可以改善再生混凝土的脆性,随着体积配箍率的提高,下降段曲线明显随之趋于平缓。再生粗骨料取代率对受压峰值应力和极限应变的影响规律不明显;随着再生粗骨料取代率、加载速率或箍筋约束的提高,约束再生混凝土受压峰值应变均随之增大。初步提出受压峰值应变的再生粗骨料取代率影响因子模型。根据初始弹性模量变化规律,提出不同取代率下约束再生混凝土受压初始弹性模量计算公式。

Through the dynamic mechanical experimental tests of recycled aggregate concrete( RAC) prisms confined by transverse hoops,the uniaxial compressive strain-strain complete curves of confined recycled aggregate concrete( CRAC)with different recycled coarse aggregate( RCA) replacement ratio( R) under dynamic monotonic loading conditions were obtained. The influence regularities of RCA replacement ratio on the performance of the mechanics and deformation of CRAC were investigated. It is found that for the uniaxial compressive strain-stress complete curves of CRAC,the ascending portions of the curve are basically consistent with each other under various replacement ratios, hoop confinements or strain rates. However,the descending branches exhibit obvious differences. With the increase of the replacement ratio or the strain rate,the descending branch changes in a steepening trend. However,with the increase of the volume stirrup ratio,the descending branch changes obviously in a flattening trend. Through the confinement of the transverse reinforcement,the ductility of RAC,which is slightly lower than that of NAC,is significantly improved. The influence of the replacement ratio on the compressive peak stress and the ultimate strain is not obvious. With the increase of the RCA replacement ratio,the strain rate or the confinement of the hoop reinforcement,the compressive peak strain is increased. According to the changing law of the characteristic parameters related to the stress-strain curve,the model of the influence factor of RCA replacement ratio for the compressive peak strain is initially proposed in this study. In addition,the initial modulus of elasticity of CRAC under various RCA replacement ratios is developed.