In this study, the flexural behavior of reinforced concrete beams, which have a partial replacement of cement by glass powder in two cases: with exposure of the specimens to E.T up to 600O C and without. Ten beam specimens were used with dimensions (1550 mm, 150 mm, 180 mm) in a variable proportion of substitute (0%,5%, 10%, 15%, and 20%) by weight, including the control specimen with 0% substitute of cement. Five specimens were for each case. The glass powder used in the study was W.G. On each beam, a two-point loading test was performed, and they were gradually loaded until the point of failure. The central deflection of the beams was measured at each load increment, and the beginning of cracks and the failure mode was seen. In addition, the compressive strength test was a part of the experimental control test for specimens. The results show that there was an effect on the workability of the admixture, making it stiffer. At normal temperatures, the add of glass powder to the concrete mix increased the bending moment capacity of beams with 5% and 10% glass powder but decreased for beams with 15% and 20% glass powder compared to the control specimen. But in another case, with exposure to E.T up to 600O C, the bending moment capacity of beams with 10%, 15%, and 20% glass powder increased but decreased for the beam with 5% glass powder compared to the control specimen. The initial cracking load of beams with 5%, 10%, and 20% was decreased concentrations at normal temperatures, with a 15% concentration resulting in an initial cracking load that was 50% higher than the control specimen. However, E.T had a varying impact on the initial cracking load of the beams. The substitute of 10%, 15%, and 20% percent of cement increased the strength of the mortar by 9.2%, 15%, and 19%, respectively, at normal temperatures.