自密实再生混合混凝土的单轴受压试验研究

Test study on uniaxial compressive behaviors of compound concrete made of normal-strength demolished concrete lumps and high-strength self-compacting concrete

将高强度等级的自密实新混凝土和低强度等级的废旧混凝土块体混合浇筑,制作了8个300 mm×300 mm×300 mm立方体试件和8个300 mm×300 mm×600 mm棱柱体试件,对其进行了单轴受压试验,研究了废旧混凝土块体取代率(0、20%、30%和40%)和试件形状(立方体和棱柱体)对自密实再生混合混凝土受压性能的影响。研究表明:自密实再生混合混凝土中废旧混凝土块体与新混凝土的界面并非是明显的薄弱部位;随着废旧混凝土块体取代率的增大,自密实再生混合混凝土的组合抗压强度和弹性模量都逐渐降低,废旧混凝土块体取代率对组合抗压强度的影响相比弹性模量更为显著;当荷载比小于0.8时,自密实再生混合混凝土泊松比随荷载比的增长速度与新混凝土相差不大;当荷载比位于0.8~0.9区间时,前者泊松比随荷载比的增长速度明显快于后者。并在试验结果的基础上,提出了自密实再生混合混凝土组合抗压强度、弹性模量和峰值应变的计算方法。

Eight 300 mm×300 mm×300 mm cubes and eight 300 mm×300 mm×600 mm prisms made of normal-strength demolished concrete lumps (DCLs) and high-strength fresh self-compacting concrete (SCC) were tested under uniaxially compressive loadings, and influences of the specimen's shape (cubes and prisms) and replacement ratio of DCLs (0, 20%, 30% and 40%) on the specimen's compressive behaviors have been investigated. It is found that the interfaces between DCLs and SCC are not obviously weak zones in the compound concrete. Both the combined compressive strength and the elastic modulus are reduced with the increase of the replacement ratio, and the adverse effect of the replacement ratio on the combined compressive strength is more significant than that on the elastic modulus. With the increase of the load ratio lower than 0.8, the growing rate of the Poisson's ratio of the compound concrete is similar to that of SCC, but with the increase of the load ratio between 0.8 and 0.9, the growing rate of the Poisson's ratio of the compound concrete is much faster than that of SCC. Based on the test results, empirical formulas have been proposed to predict the combined compressive strength, modulus of elasticity and peak strain of the compound concrete made of DCLs and SCC. © 2016, Editorial Office of Journal of Building Structures. All right reserved.