再生块体混凝土的单轴受压试验

Experiment on Uniaxial Compression of Compound ConcreteMade of Demolished Concrete Lumps and Fresh Concrete

首先,将抗压强度分别为26.7,45.0,87.6 MPa的3种旧混凝土块体与普通商品混凝土进行混合浇筑,制作18个再生块体混凝土立方体试件和18个棱柱体试件.然后,进行立方体试件和棱柱体试件的单轴受压试验,研究旧混凝土的取代率及新旧混凝土的抗压强度差对再生块体混凝土受压力学性能的影响.结果表明:在添加低抗压强度(26.7,45.0 MPa)旧混凝土的试件中,新旧混凝土结合良好,界面难以辨别;在添加较高抗压强度(87.6 MPa)旧混凝土的棱柱体试件中,新旧混凝土的结合界面出现分离现象;试件的破坏形态似2个对顶的角锥形状;在新旧混凝土抗压强度差不变的情况下,再生块体混凝土的抗压强度、弹性模量、峰值应变随旧混凝土取代率的增加而降低,取代率对抗压强度影响较大,但对弹性模量、峰值应变的影响较小;在新旧混凝土抗压强度差不同、取代率相同的情况下,随着旧混凝土块体抗压强度的增大,再生块体混凝土的抗压强度、弹性模量、峰值应变均呈一定的上升趋势;再生块体混凝土的泊松比变化不明显,平均值约为0.212.

Three kinds of demolished concrete lumps(DCLs compressive strengths=26.7,45.0,87.6 MPa)were mixed with ordinary commercial concrete to cast 18 cube specimens and 18 prism specimens that both consist of compound concrete made of DCLs and fresh concrete.The uniaxial compression tests of cube and prism specimens were carried out,and the influence of the replacement ratio of DCLs and the strength difference between the new and demolished concrete on the specimen′s compressive behaviors was investigated.The results show that referring to the specimens with old concrete of low compressive strength(26.7,45.0 MPa),the old and new concrete are well combined and the interfaces are difficult to distinguish;but prism specimens with old concrete of high compressive strength(87.6 MPa),show a phenomena of separation of bonding interface between new and old concrete;the specimen′s failure shape is similar to two pyramid shapes on the top;under the condition of constant difference of compressive strength between new and old concrete,the compressive strength,elastic modulus and peak strain of the compound concrete decrease with the increase of the replacement ratio of the old concrete,and the influence of the replacement ratio on the compressive strength is more significant than that on the elastic modules and peak strain;under constant replacement ratio but different compressive strength of the new and old concrete,the increase of the strength of demolished concrete lumps increases the compressive strength,elastic modules and the peak strain;the Poisson′s ratio of the specimens varies little,≈0.212.