Experimental Investigation of the Static Expansion Tensile Behavior of Concrete after Exposure to Elevated Temperatures

Little data are available on the tensile behavior of concrete after elevated temperature exposure due to the difficulty of testing concrete in tension. Thus, we proposed a static expansion tensile method, in which a soundless (or silent) chemical demolition agent (SCDA) was used, to perform a static tension experiment on elevated concretes. Before the tests, concretes were exposed to four elevated temperatures (200, 400, 600, and 800 °C) and three heating periods (2, 3, and 4 h). Immediately after the heat treatments, static expansion tension tests were performed to analyze concretes’ physical and acoustic emission (AE) signal characteristics changes under different temperature conditions. The test results showed that the changes of surface features of concrete after being treated at high temperatures are related to the physical properties. With the exposure temperature and duration increase, the acoustic velocity of concrete decreases while the porosity increases. The AE signals were changed sharply throughout the loading process until the specimens were completely damaged. With the increase in temperature, the maximum energy of the AE signal had a downward trend; the maximum amplitude had a trend that kept stable first and then started to decrease; the trend of the b-value primarily remained stable and then reached a peak, finally decreasing abruptly. The constitutive behavior analysis of concrete found that the Continuous Caps Model (CSCM) agreed well with the concrete’s failure process. This study will provide basic information for the theoretical and engineering analysis of concrete structures after exposure to high temperatures, especially for the structural stability analysis after a fire.