Research on the splitting tensile dynamic mechanics performance of post-high-temperature high-performance concrete

Abstract

High-performance concrete (HPC) structures were affected by secondary hazards after a fire, research on its dynamic mechanics performance is vital for assessing post-disaster structural safety. Therefore, the mechanism which governs impact of coupling among high temperature, cooling mode and strain rate on the splitting tensile mechanics performance of HPC was delved; impact factors including five temperatures, two cooling modes and four strain rates were designed; digital image technology (DIC) and hydraulic servo instrument were adopted to investigate the splitting tensile mechanics performance of HPC with Brazilian disc. Failure mechanical parameters of HPC under varying operational conditions and full-field deformation parameters of the whole loading process were obtained. As indicated by research result, the splitting tensile strength of test specimens cooled naturally from 200 °C to 600 °C was higher than that of specimens cooled rapidly, while the splitting tensile strength under natural cooling from 800 ℃ decreased by 6 % compared with rapid cooling. At the same temperature, splitting tensile strength of HPC was gradually increased with the increase of strain rate, and Dynamic Increase Factor (DIF) was significantly increased, showing relatively high rate sensitivity. With increasing temperature, the increase in DIF for HPC declined somewhat. As revealed by the result of DIC analysis, at high temperature, damage was relatively mild at the development stage and entered the stage of abrupt change of strain field in a short time. With increasing strain rate, the overall damage duration of test specimen was significantly shortened, and cooling mode exerted no significant impact on the development of splitting tensile damage in HPC. The criterion for splitting tensile dynamic strength of post-high-temperature HPC was put forward on the basis of J criterion. Meanwhile, an analysis by backscattered electron (BSE) on microstructure of HPC revealed mechanism which governs the impact of high temperature and cooling mode on the splitting tensile dynamic mechanics performance of HPC. The research result serves as a theoretical basis for calculating and assessing the post-fire structural dynamic response of HPC.