预应力钢绞线与超高性能混凝土黏结性能试验研究

An Experimental Study on Bonding Properties of Prestressed Strands with Ultra High Performance Concrete

超高性能混凝土(UHPC)是具有超高强度、高韧性、高耐久性的新型水泥基复合材料,UHPC与钢绞线的黏结性能也与普通混凝土存在差异,且缺乏关于超高性能混凝土与钢绞线黏结性能的设计标准。因此,通过对36个常温自然养护的UHPC与钢绞线中心拉拔试验进行研究,研究参数为黏结长度和保护层厚度,根据试验获取了其荷载滑移曲线、破坏形态、黏结强度。分析试验数据表明:UHPC与钢绞线的极限黏结应力为7.01～11.65 MPa,均值为8.78 MPa,明显优于普通混凝土的。当直径为15.2 mm钢绞线的保护层厚度大于30 mm后,保护层厚度对黏结强度的影响较小。相对于普通混凝土,UHPC中1×7钢绞线的传递长度和锚固长度均可减少50%,建议对于抗压强度大于150 MPa的UHPC,钢绞线传递长度取25d,锚固长度取35d。

Ultra-high-performance concrete(UHPC)is a relatively new class of composite material characterized with its ultra-high strength,high toughness and high durability.There is no design standard about the bonding performance of UHPC with prestressed strands,which is rather different from that of ordinary concrete.Therefore,based on the study on the central drawing tests of 36 UHPC with stranded strands under normal temperature natural curing,with bonding length and thickness of protective layer the research parameters,the load slip curves,failure modes and bond strength have thus been obtained.The analysis and test data show that the ultimate bond stress between UHPC and strand is 7.01~11.65 MPa with an average value of 8.78 MPa,which is obviously superior to ordinary concrete.When the thickness of protective layer of steel strands with a diameter of 15.2 mm is greater than 30 mm,the thickness of protective layer has little effect on the bonding strength.Compared with that of ordinary concrete,the transfer length and anchorage length of 1×7 strand in UHPC can be reduced by 50%.It is recommended that for UHPC with a compressive strength greater than 150 MPa,the transfer length of steel strands should be 25d and the anchorage length 35d.