Behavior evaluation of concrete made with waste rubber and waste glass after elevated temperatures

The re-use of solid wastes (waste rubber and waste glass) to make green concrete is very important towards sustainable buildings. In this work, a novel efficient solution of replacing natural fine and coarse aggregate with waste rubber (WR) and waste glass (WG) respectively was adopted to analyze the performance of WR and WG as well as their combinations in mixtures when subjected to elevated temperatures. In present research, the river sand was replaced by WR particles at varied volume ratios from 10% to 30% and WG was used as gravels at 10%, on volume basis. These specimens were heated to 200 °C, 400 °C, 600 °C, 700 °C and 800 °C, and then they were kept for 2 h and subjected to air-cooling regime naturally. To this end, the appearance change, mass loss rate, volume change, compressive strength, split-tensile strength, and ultrasonic pulse velocity (UPV) were evaluated through a series of tests at ambient and after exposure to elevated temperatures. Also, water absorption and sorptivity tests were conducted to assess porosity as well. In addition, the scanning electron microscopy (SEM) was used to understand the influence of this two wastes on the microstructure evolution under various temperatures. According to experimental results, the compressive strength of mixtures presented a 4.32%–8.53% increasement in temperature between 20 °C and 200 °C, followed by a gradual decrease in the strength values. While split-tensile strength showed a decline at each temperature level, with a strength reduction of 60%-70% at 700 °C. On the other hand, the combined mixture mitigated damage of rubber concrete and improved its mechanical behaviors. Particularly, when the volume fractions of both WR and WG aggregates were 10% respectively, the mixture outperformed the other combination mixes concerning mechanical and durability performance of heated and unheated samples. Furthermore, the water absorption and weight loss of specimens were found to increase with temperatures, with water absorption exceeding 10% and mass loss varying from 7.88% to 9.44% at 700 °C. Whereas the ultrasonic velocity values gradually decreased. To sum up, the combination of WR and WG was proved as a promising option to enhance the performance of rubberized concrete under high temperatures.