Zero-eccentricity direct-tension testing of thermally damaged cement-based materials

This study presents some results on direct-tension strength of two cementitious mortars using a test set-up specifically designed to virtually eliminate any load eccentricity. The tests were conducted on cement mortars with and without condensed silica fume after being exposed to high temperature (200, 300, 400 and 500 °C). Direct-tension tests were also carried out at room temperature (20 °C) for reference. The specimens were exposed to high temperature and were then allowed to cool to room temperature before testing up to failure. The strength values measured in this study exhibit a trend that is similar to that exhibited by the compressive strength cited in the literature. The results show that mortar specimens exhibited a small increase in strength at temperatures up to 200 °C for regular mortar and up to 230 °C for silica fume mortar. At temperatures above 200/230 °C, the residual tensile strength of the mortar decreases significantly and rapidly. Adding silica fume to the cement mortar increases the resistance to high temperature.