Experimental Investigation on On-site Flexural Toughness of Wet-sprayed Concrete with Silica Fume and Steel Fibers

For the prevention of rochburst, water gushing, high geostress, applied research on the on-site flexural toughness properties of wet-sprayed concrete containing silica fume(SF) and reinforced by steel fibers was carried out firstly to investigate the effect of steel fiber content and SF on flexural toughness index and the differentment from plain concrete.SF is added according to 10% of the cement mass, two mass content of steel fiber(35kg/m3,40kg/m3) was considered in this study, and large wet spraying machine was used.Concrete specimens used in flexural toughness experiment were formed in site,which containing accelerating agent has to 8%.It is the first time in China that this large-scale productive experimental study not only adopts a large number of new technologies, but also can truly reflect the on-site adhesion and hardening properties of wet sprayed concrete.Through the collaborative participation of 10 institutions, the experiment was successfully completed and effective results were achieved.The results indicated that the crack load and ultimate load of concrete were increased, flexural toughness was improved when SF and steel fiber contained, and the flexural toughness index is increasing with the increment of steel fiber, especially, the curves of load-deflection showed the peak of secondary hardening of shotcrete with 40kg steel fiber content, which means the better resistance deformation capacity and increased residual strength.So the steel fiber reinforced wet-sprayed concrete containing SF can enhance its toughness and the ability of resisting crack,improve its brittleness destroy character.