Impact resistance properties of U-shaped fiber-reinforced concrete modified with PU binder

Abstract

The inherent brittle characteristic of cement-based composite is considered one of its shortcomings in concrete structural applications. This study developed U-shaped fiber-reinforced concrete modified with polyurethane binder (FRC-PU) mixtures to investigate its impact strength properties under multiple drop-weight impact tests. Response surface methodology using a central composite design (RSM/CCD) model was employed to optimize the concrete mixture and evaluate the impact strength properties. The micro steel fiber (SF) and PU binder were used as input parameters to evaluate the responses, such as first crack strength (N1) and failure strength (N2). Moreover, digital image correlation (DIC) was used to monitor the failure of the U-shaped and cube specimens under impact and compression tests. The FRC-PU mixture was produced by adding a SF at 0 %, 0.5 %, 0.75 %, and 1 % by volume fraction. PU binder was incorporated into the FRC-PU mixture at 0–30 % (interval of 10 %) by cement weight. The results indicated that the compressive strength of concrete containing PU binder only revealed a significant decrease with increased PU binder content. The combined effect of SF and PU binder significantly improved the impact strength of FRC-PU specimens at the two cracking stages with increasing ductility index. The highest ductility index was recorded in the specimen containing a higher amount of SF and PU binder. The optimized FRC-PU mixture can be achieved by adding 13.1 % PU binder and 0.95 % fiber volume fraction. DIC technique monitoring showed that the fracture process of the FRC-PU specimen under compression and impact strength test depends on the amount of SF and PU binder in the concrete.