不同减摩条件下变长度活性粉末混凝土的三轴试验研究

Triaxial test study of reactive powder concrete with different sizes under different friction reducing conditions

使用常规三轴实验,对同一直径(43.6 mm)、4种长径比(0.5、1、2和3)的素活性粉末混凝土(RPC)圆柱试样,在保持围压恒定的条件下单调地施加轴向压缩应变.试样两端采用3种减摩条件:直接与金属压头接触(条件A),分别垫有2层0.1 mm厚聚四氟乙烯薄膜(条件B),分别垫有层间涂润滑脂的3层0.1 mm厚聚四氟乙烯薄膜(条件C).每一档围压对应一种加载路径:长径比为0.5、1.0和3.0的试样,采用两档围压(5、70 MPa);长径比为2.0的试样,采用5档围压(0、5、20、35、70 MPa).试验结果表明:在同围压、同长径比的条件下,条件B试样与条件C试样的强度及破坏模式相近;当围压为5 MPa,长径比小于2.0时,不同长径比的条件A试样与条件C试样在抗压强度上均有明显差异,但这2种减摩条件所表现的强度与长径比之间关系正好相反;当围压为70 MPa时,条件A试样的抗压强度有尺寸效应,条件C试样无显著的尺寸效应.围压的增加显著地约束了裂纹的扩展.

Cylinder specimens of plain reactive powder concrete (RPC) with a constant diameter of 43.6 mm and with four length-diameter ratios (0.5, 1, 2 and 3) were tested by monotonic growth of axial compressive strain under a designed confining pressure. Then the conventional triaxial test was conducted. Three friction reducing conditions, which used none friction reducing material (called condition A), 2 layers of polytetrafluoroethylene film with 0.1 mm thickness (called condition B) and 3 layers of polytetrafluoroethylene film (0.1 mm thickness) with lubricating grease between films (called condition C), were adopted at each end of the specimen. Each confining pressure represented a loading path. When the length-diameter ratios of the specimen were 0.5, 1.0 and 3.0, the specimen were tested under two different confining pressures (5 MPa and 70 MPa). When the length-diameter ratio was 2.0, there were 5 different confining pressures (0 MPa, 5 MPa, 20 MPa, 35 MPa and 70 MPa). The test results show that the strength and failure mode of the specimen with condition B is similar to those of the specimen with condition C under same confining pressure and same length-diameter ratio. The compressive strength of specimen with condition A and condition C shows different trend with varied length-diameter ratio when the confining pressure is 5 MPa and the length-diameter ratio is less than 2.0. The specimen with condition A shows an obvious size effect on compressive strength when the confining pressure is 70 MPa, while the effect is not found among the specimens with condition C. It is obvious that confining pressure can restrain the development of crack.