RETRACTED: Experimental study and theoretical modeling for the flexural property of multi-scale hybrid fiber reinforced SHCC

The design of multi-scale hybrid fiber reinforced strain hardening cement-based composite (MsHySHCC) can enhance the mechanical characteristics of traditional PVA-SHCC and lower the cost. In this paper, a modified kind of MsHySHCC containing additional hooked steel fibers and CaCO3 whiskers was designed. The flexural properties of the designed MsHySHCC thin-plate were studied by experimental and theoretical methods. The results indicated that partial substitution of PVA fibers by steel fibers and CaCO3 whiskers improved the flexural behaviors of MsHySHCC. Although further decrease in the content of PVA fibers along with increase in the amount of steel fibers and CaCO3 whiskers further improved the flexural bearing capacity of designed MsHySHCC, high flexural ductility could not be achieved. A semi-theoretical prediction model was derived to calculate the flexural behaviors of PVA-SHCC and MsHySHCC thin-plate. By comparing the theoretical results with the experimental results, it was found that this semi-theoretical model can adequately calculate and predict the characteristics of MsHySHCC's flexural load-deflection relationships. In order to verify the effectiveness of the designed MsHySHCC in structural strengthening application, hysteretic loop experiments of reinforced concrete (RC) columns strengthened by cast-in-place MsHySHCC thin-plate layer were also performed. The results showed that the RC column strengthened by designed MsHySHCC had a fuller hysteresis curve and skeleton curve, higher load bearing capacity, slower stiffness deterioration, higher ductility and better energy dissipation ability compared to un-strengthened column or high-strength mortar strengthened column.