自密实再生块体混凝土直剪性能试验研究

对29个尺寸为300 mm×300 mm×600 mm的自密实再生块体混凝土棱柱体试件开展直剪性能和单轴受压性能试验研究。探讨了废旧混凝土块体取代率及特征尺寸对自密实再生块体混凝土的直剪强度、抗压强度的影响，并进一步分析了自密实再生块体混凝土棱柱体的直剪强度与抗压强度之间的关系。试验表明:自密实再生块体混凝土内新混凝土与废旧混凝土粘结良好；当自密实再生块体混凝土中的自密实混凝土强度高于废旧混凝土块体强度时，试件的直剪性能会由于废旧混凝土块体的取代率的增加而劣化；特征尺寸比介于0.22~0.44时，块体的特征尺寸对自密实再生块体混凝土直剪强度和抗压强度的影响不明显，可以近似忽略；自密实再生块体混凝土的剪压比随废旧混凝土块体取代率和特征尺寸均无显著变化，其值近似为0.1。基于试验结果，提出了棱柱体自密实再生块体混凝土试件的直剪强度计算公式，建立了直剪强度测试值与抗压强度计算值之间的关系，计算结果与试验值吻合良好。

EXPERIMENTAL STUDY ON THE DIRECT SHEAR PERFORMANCE OF COMPOUND CONCRETE MADE OF DEMOLISHED CONCRETE LUMPS AND SELF-COMPACTING CONCRETE

29 prisms of 300 mm×300 mm×600 mm made of normal strength demolished concrete lumps (DCLs) and high-strength fresh self-compacting concrete (SCC) were tested under two-sided direct shear loading and uniaxially compressive loading. The influences of the replacement ratio of the DCLs and the characteristic size of DCLs on the shear strength of the specimens were investigated. The results show that the SCC and DCLs are well bonded in self-compacting recycled lump concrete. When the strength of the SCC is higher than that of the demolished concrete, the incorporation of demolished concrete lumps will decrease the direct shear strength of the specimens. The influence of the block characteristic size on the direct shear strength and compressive strength of self-compacting recycled lump concrete can be approximately neglected when the block feature size ratio is between 0.22 and 0.44. The ratio of direct shear strength to compressive strength of concrete made of DCLs and SCC has no significant change with the replacement ratio and characteristic size of the demolished concrete lumps. Its value is approximately 0.1. Based on the test results, a formula for predicting the direct shear strength of self-compacting recycled lump concrete is presented. The relationship between the test value of direct shear strength and the calculated value of compressive strength is obtained. The calculation results are in good agreement with the test values.