Experiment Research On Mechanical Properties Of Recycled Aggregate Concrete After High Temperature

As a kind of green building materials, recycled aggregate concrete (RAC) has been proved to effectively recycle construction waste and solve the problem of shortage of natural resources, which is in great potential application. For the research of RAC, most scholars just focus on the mechanical properties of normal state, less concerning with mechanical properties after fire damage. In light of current research situation, the experimentation has been used to make an intensive study of mechanical properties of RAC after fire damage.Firstly, considering replacement ratio of recycled coarse aggregate, strength grade, coarse aggregate type as variable parameter,168 standard prism specimens was designed to perform in high temperature test under the temperatures of 20～800℃. The apparent phenomenon, such as surface color change, cracks appearing and extending, were observed, and the ignition loss variation law of temperature were to examine. Furthermore, ignition loss formula of RAC after high temperature is given.Secondly, the prism specimens which were placed to room temperature were performed in uniaxial compressive stress and stress-strain test to observe specimens failure process and forms, and to acquire stress-strain curves of RAC after high temperature. On the basis of data from experiment, the change relationships of stress strength, peak strain, elastic modulus, damage, ductility and power dissipation with temperature varying were analyzed, and corresponding fitting formulas were proposed.The experimental results showed that, as the temperature continued to increase, ignition loss of RAC grows, and the higher replacement ratio of recycled coarse aggregate, the greater ignition loss is. Stress-strain curves become gentle gradually, and all feature points are moved to the right. The strength and elastic modulus of concrete greatly reduced, and peak strain is more gradual increases. Concrete Initial damage and the platform of damage in development process increase, the main damage zone extended continuously with failure strain increasing gradually. The temperature rise are not weaken the ductility of concrete, which may be due to the effect of concrete stress decrease and strain increase appearing at the same time when temperature is rising, and this is the result of coordination and balance between them. When RAC failure occurs, power dissipation decreases.Finally, based on the results of experimental study, the evaluation method of RAC structure after fire was discussed.