Acousto-optic characterization of splitting tensile damage of ultra-high performance concrete

In order to study the splitting tensile failure characteristics of ultra-high performance concrete (UHPC), three different loading rates (0.1, 0.01, 0.001 mm/s) were used for the splitting tensile loading. During the loading process, the digital image correlation (DIC) method was used to observe the crack evolution by non-contact deformation. At the same time, the acoustic emission (AE) technology was used to dynamically monitor the entire failure process of UHPC, and the failure characteristics of the specimen were analyzed based on the DIC strain cloud map and AE parameters. The results show that due to the incorporation of steel fibers, the brittleness of concrete is improved, and the post-peak load-displacement curve of UHPC decreases more gently without a sharp decline. The higher the loading rate, the higher the splitting tensile strength measured by UHPC, which conforms to the law of concrete rate effect. When the loading rate is increased from 0.001 mm/s to 0.01 mm/s and from 0.01 mm/s to 0.1 mm/s, the splitting tensile peak load is increased by 27.9 % and 28.5 % respectively. The digital image correlation method is used to measure the deformation of UHPC splitting tensile experiment, and continuous deformation data can be obtained, which can completely capture the development process of cracks. It is proved that DIC can well reflect the evolution process of cracks on the surface of specimens. The analysis based on RA-AF value can quickly and effectively determine the type of crack development in concrete. According to the analysis results, the crack types of UHPC splitting tensile experiment are mostly tensile cracks, and the proportion of tensile cracks in the total cracks increases with the increase of loading rate.