Effect of High Temperatures on Ultrahigh-Performance Concrete with Glass Powder

This article reports the high-temperature performance of ultrahigh performance cementitious composites (UHPC) with glass powder (GP) as a partial replacement for portland cement. In the several mixtures prepared, the GP replaced the cement at proportions of 10%, 20%, and 50% by volume; the mixtures were initially evaluated by the compressive strength as well as the static and dynamic modulus of elasticity tests at room temperature. Subsequently, the UHPC mixtures without and with 50% GP were submitted to different temperatures (20°C, 200°C, 400°C, 600°C, and 800°C), followed by new compressive strength and dynamic modulus of elasticity tests to evaluate their residual mechanical behavior, in addition to X-ray diffraction (XRD) and scanning electron microscopy (SEM) tests on heated samples. The results show that, after 28 days, no significant differences were observed between the compressive strength and elastic modulus of the different UHPC mixtures at room temperature. After 91 days, the XRD test in samples at room temperature showed that the mixtures with 50% GP exhibited smaller portlandite peaks, indicating its consumption by the pozzolanic effect. Further, the compressive strength of the UHPC mixtures studied had significant differences from the temperature of 600°C and higher. Compared to the reference mixture, the compressive strength of the 50% GP mixture was 14% and 28% lower at 600°C and 800°C, respectively, this decrease in strength compared to the reference can be explained by the sintering of components such as wollastonite, melilite, and aluminosilicate, as observed in XRD. In conclusion, UHPC mixtures with large amounts of glass powder have lower residual compressive strength, whereas the modulus of elasticity is not significantly influenced by the amount of glass powder.