A pilot study on the effects of temperature on the material properties of prestressed concrete and the use of thermogravimetric analysis in the assessment of heat-affected concrete.

摘要

An understanding of the material property changes in building materials due to exposure to a fire is needed for accurate damage assessment of a structure. Discussion pertaining to material property changes and the bond between concrete and prestressing steel following elevated temperature exposures is presented. Evaluation of the use of thermogravimetric analysis (TGA) as a post-fire analysis tool to determine the maximum temperature exposure of concrete is also included.; Heated concrete cylinders were tested to determine the compressive strength and modulus of elasticity changes of concrete. Heated steel prestressing strands were tested in tension to determine changes in the ultimate stress and modulus of elasticity. Changes in the bond performance were investigated by conducting pull-out tests on prestressing steel embedded in concrete specimens. Using mortar and cement paste samples, TGA was evaluated as a possible option for determining the temperature exposure of cementitious materials. TGA was also performed on concrete samples extracted from heated cylinders to determine if the temperature profile could be predicted.; The results from this project are intended to serve as the basis for the development of useful tools in the forensic investigations of prestressed concrete members after fire exposure. Using TGA to determine the exposure of an element could provide information on the history of a fire, identifying the maximum temperature exposure within an element and a general evaluation of the duration of the heat exposure. Based on this information, changes in the material properties can be predicted, resulting in more reliable investigations of prestressed concrete members exposed to fire.