钢纤维间距对UHPC双丝拉拔性能的影响

通过双根钢纤维拉拔试验,研究超高性能混凝土（UHPC）中钢纤维间距（2?mm、 4?mm、6?mm、8?mm、10?mm和12?mm）对钢纤维在UHPC中拉拔性能的影响,采用0.2?mm的镀铜直圆形钢纤维,制作6组双丝试件和1组单丝试件进行拉拔试验. 通过拉拔荷载-滑移曲线、平均黏结强度、钢纤维最大拉拔应力等参数,并结合扫描电子显微镜（SEM）,观察了拔出后钢纤维的微观外貌、UHPC基体的隧洞微观形态和破坏部位的微观形态,全面分析了钢纤维的间距对UHPC基体-钢纤维拉拔性能的影响. 试验结果表明：钢纤维拉拔结果具有一定的离散性;双丝拉拔试验的最大拉拔荷载小于相应单丝结果的两倍;钢纤维和UHPC基体隧洞有着不同程度的损伤,双丝试件中的钢纤维表面划痕和基体隧洞的孔洞破坏较单丝严重,单丝试件的隧洞内壁则相对完整.

Effect of Steel Fiber Spacing on Double Fibers Pullout Performance of UHPC

The influence of steel fiber spacing （2, 4, 6, 8, 10 and 12 mm） on the pullout performance of steel fiber in ultra-high performance concrete（UHPC） matrix was studied by the double steel fiber pullout test. Six sets of double fiber specimens and one set of single fiber specimens embedded with 0.2 mm copper-plated straight round steel fibers were fabricated. Based on the parameters of the pullout load-slip curve, average bond strength, and maximum pullout stress, and combined with scanning electron microscope （SEM）, the micro-appearance of steel fibers after pulled out, the micro-morphology of UHPC matrix tunnel and the failure part were observed. The influence of steel fiber spacing on the pullout performance between UHPC matrix and steel fibers was analyzed. The steel fiber pullout test results showed certain discreteness; the maximum pullout load of double fibers pullout test was less than twice that of the corresponding single fiber pullout test. The steel fiber and UHPC matrix tunnel had different degrees of damage. The scratches on the surface of steel fiber and the holes in the matrix tunnel of double fiber specimen were more serious than those of the single fiber specimen, while the inner wall of the single fiber specimen was relatively complete.