This paper investigates the effect of steel fiber's zinc phosphate (ZnPh) treatment and shape on the strength and toughness of ultra high performance concrete (UHPC) containing granite powders under autoclaved curing.Steel fibers with four dfferent shapes were used:straight with copper plating (S),single-linear hooked-end with copper plating (G1),bi-linear hooked-end with copper plating (G2) and crimped with copper plating (L).The results obtained from customized single steel fiber pullout test and SEM-EDS observation indicated that the mechanical interlock is the dominating effect for the enhanced strength and toughness of UHPC containing granite powders.The average bonding strength and pullout energy are in the order of G1＞G2＞L＞S.The ZnPh treatment modified the fiber geometry,resulting in enhanced surface roughness,which increased the chemical bonding and static friction between the steel fibers and the UHPC matrix,and consequently raised the pullout energy of steel fibers in UHPC.Compared to G1,G2 and L steel fiber,the ZnPh treatment exhibited the most obvious effect toward S steel fiber in terms of enhanced toughness of UHPC.%采用自制的单根钢纤维拉拔试验装置等,通过拉拔试验和SEM-EDS等试验,开展钢纤维的磷酸锌(ZnPh)改性及其形状对在蒸压养护条件下的掺花岗岩石粉超高性能混凝土(UHPC)增强增韧影响机理的研究.所研究钢纤维形状包括:镀铜平直型S、镀铜单折线端钩型G1、镀铜双折线端钩型G2和镀铜波浪型L.研究表明,钢纤维的机械咬合力起主导作用,钢纤维平均粘结强度与拔出功大小顺序均为:G1＞G2＞L＞S.ZnPh改性后,钢纤维表面变粗糙,这增强了钢纤维与UHPC基体间的化学粘结力和静摩擦力,从而提高了铜纤维在UHPC中的平均粘结强度和拔出功.在UHPC韧性的提高方面,采用ZnPh改性,对S钢纤维最明显,而对异型钢纤维(G1、G2和L)则不明显.
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