Investigating the behavior of concrete containing waste glass and rubber as sand replacement before and after exposing to elevated temperatures

Tires and waste glass are long-lasting pollutants in nature. One of the ways to recycle waste glass and rubber is to use it in concrete, which will result in minimal extraction of natural minerals. Many engineering structures are exposed to fire hazards, and therefore it is necessary to know the mechanical properties of concrete materials at high temperatures. In this research, waste glass and rubber were used as a substitute for a part of natural fine grain (sand). The size of glass particles is between 0.2-0.85 mm and with percentages of 5%, 10% and 15% and the size of rubber particles is between 3-5 mm by volume and with percentages of 5% and 10%, replacying fine aggregates. In total, 12 mixing plans were made, and from each mixing plan, 3 cubic and cylindrical specimens were made with different percentages of glass and rubber. The compressive and tensile strength, workability, weight loss, ratio of residual compressive and tensile strength of the specimens were measured at ambient temperature and at 600 °C and the average values were evaluated. In terms of appearance, after applying heat, the color of the specimens became darker and hairline cracks were widely visible on the concrete surfaces. As expected, with increasing the rubber, the compressive strength of the speciemns decreased. After applying heat, the resistance drop of all specimens was higher than the ambient temperature state. With the increase in the rubber, the resistance decreased more, which can be attributed to the burning and destruction of rubber particles and the appearance of small holes and porosity in concrete. With increasing glass percentage, the trend of compressive strength was slightly improved. The results showed that the combined design of 5% glass and 5% rubber is the optimal design and has a more appropriate performance than other designs.