Study on Fire Resistant Performance of Recycled Concrete Tubular Structures

In order to achieve the fire resistance performance of recycled concrete, four concrete tubular structure specimens were designed and tested under the high temperature. One of the specimens was made from normal concrete C20, one was made from recycled coarse aggregate concrete C20, and two were made from recycled coarse and fine aggregate concrete C20 and C40 respectively. The temperature field, the vertical displacement, the wall deflection and the fire endurance were comparatively analyzed. Results show that the rate of temperature increasing inside the concrete becomes smaller with the increase of recycled aggregate replacement rate. The temperature of specimens with recycled concrete is lower than that with normal concrete at the same position, the same force condition and the same fire condition. The load carrying capacity of specimens with recycled concrete is lower than that of the normal concrete specimen due to the bigger porosity of recycled concrete. The fire endurance decreases with the increase of recycled aggregate replacement rate in the specimens. With the increase of the strength of recycled concrete, fire resistance and fire endurance of the tubular structure decrease and the structure tends to fail in expansion under high temperature.