铣削型钢纤维与超高性能混凝土的界面粘结性能研究

Interfacial Bond Performance Between Milling Steel Fiber and Ultra-highPerformance Concrete

超高性能混凝土(UHPC)优异的性能主要取决于钢纤维与基体的协同工作,为探讨铣削型钢纤维在UHPC中的适用性,本工作通过钢纤维拉拔试验,研究了铣削型钢纤维与UHPC的界面粘结性能,分析了纤维埋深、纤维有无端勾、基体有无纤维、养护条件四个因素的影响及其机理,并与镀铜微丝钢纤维进行对比。结果表明:四种类型的钢纤维(镀铜平直型S、镀铜端钩型H、铣削平直型MS和铣削型MH)在UHPC中的粘结强度大小顺序为H型>MH型>MS型>S型;随着纤维埋深增加,S型、H型和MS型钢纤维在UHPC中的粘结强度减小,而MH型钢纤维则增大;端勾有助于提升钢纤维在UHPC中的粘结强度和拉拔能,并影响拉拔荷载-位移曲线的形状;基体掺入2%(体积分数)钢纤维亦能略微提高钢纤维在UHPC中的粘结强度和拉拔能;与蒸养条件相比,标养条件下界面粘结强度降低,但也使得铣削型钢纤维的拔出行为更明显,提高了拉拔能。铣削型钢纤维与UHPC界面粘结强度较高,但其较低的纤维抗拉强度影响了粘结性能的发挥,建议开发适用于UHPC的高强铣削型钢纤维。

The excellent performance of ultra-high performance concrete(UHPC)mainly depends on the cooperative work between steel fiber and matrix.In order to study the applicability of milling steel fiber in UHPC,the bonding properties between milling steel fiber and UHPC was investigated by steel fibers pullout experiment.Meanwhile,copper coated microfilament steel fiber were used for comparison.The influence and mechanism of four factors(i.e.,fiber buried depth,hooked-end,matrix fiber and curing system)on the bonding properties between milling steel fiber and UHPC were analyzed.The result of experiment indicated that the bonding strength of steel fibers(i.e.,straight’S’,hooked-end’H’,milling straight’MS’and milling‘MH’steel fibers)in UHPC is in the order of H>MH>MS>S.With the increase of fiber buried depth,the bonding strength of S,H and MS steel fiber in UHPC decreases,and MH steel fiber increases by the contrary.The hooked-end is helpful to improve the bonding strength and pullout energy of steel fiber in UHPC,and affects the shape of pullout load-displacement curve.Adding 2vol%steel fiber into the matrix can also slightly improve the bonding strength and pullout energy of steel fiber in UHPC.The bonding strength with standard curing system is lower than that with steam curing system,but it also makes the pullout behavior of milling steel fiber more obvious and improves the pullout energy.The bonding strength between milling steel fiber and UHPC is high,but its low fiber tensile strength affects the bonding perfor-mance.It is suggested to develop high-strength milling steel fiber suitable for UHPC.