General trends in the tensile behaviour of thermally-damaged concrete

The mechanical properties of concrete exposed to fire have been the subject of a number of investigations in the last fifty years. Nonetheless, the wide range of materials at issue, after the advent of high-performance concrete, makes the results of the previous studies difficult to be generalized. This is particularly true for the tensile response, due to the challenging experimental conditions and to the still not standardized test methods. Hot vs. residual test conditions, direct vs. indirect tensile loading, restrained vs. free strain localization, notched vs. unnotched specimens are some of the possible options that make the tests from different sources hard to compare. In this paper the results collected by the authors on several different concrete mixes are drawn together with the twofold objective to clarify the relations among the most common direct- and indirect-testing techniques and to sketch any possible general trend in the tensile properties of ordinary and special concretes exposed to high temperature.