Fracture characteristics and damage evolution of manufactured sand-based ultra-high performance concrete using tensile testing and acoustic emission monitoring

To address the challenges posed by the excessive exploitation of natural river sand, manufactured sand (MS) was used as a substitute material for natural sand to produce manufactured sand-based ultra-high performance concrete (UHPMC). This study aims to investigate the effects of MS replacement ratio, stone powder content, steel fiber content, and steel fiber shape on the fracture characteristics and damage evolution of UHPMC under tensile load through tensile tests combined with acoustic emission (AE) technology. The research results indicated that the stress-strain behavior of UHPMC could be divided into low strain hardening, low strain softening, and high strain softening. The tensile strength and energy absorption of the UHPMC were less correlated with MS replacement ratio. The tensile strength showed a trend of first increasing and then decreasing with the increase of stone powder content, and UHPMC with a 4% stone powder content presented the better tensile strength. The tensile damage process of UHPMC was mainly concentrated in the range of tensile strain from 0.0002 to 0.0025. The microstructure analysis of the UHPMC matrix revealed that an optimal amount of stone powder enhances the bond property between MS and mortar, thereby improving tensile performance. AE monitoring indicated that AE amplitude and AE energy provide sensitive identification capabilities for classifying the elastic state, strain hardening, and strain softening stages of UHPMC. The findings of this study contribute to understanding the fracture characteristics and damage evolution of UHPMC, promoting the engineering application of MS in ultra-high-performance concrete.