Application Of Modified Recycled Aggregate In Asphalt Mixture

With the accelerating process of urbanization and the rapid increase of social and material level, a large number of buildings which are still in service have to be discarded to be waste concrete, and the number is still increasing. It takes lots of manpower, material and financial resources to deal with these discarded concrete and the cost is huge, which have been a great burden for the local government and people. The crushing of discarded concrete to be used as recycled aggregates, on the one hand, can save a lot of high-quality sand and gravel and other non-renewable resources, protecting the environment. On the other hand, it can reduce the amount of discarded concrete, turn waste into wealth and also achieve the goal of natural resources recycling.Firstly, the fundamental properties of recycled aggregate were taken into consideration. Physical and chemical methods were used for activation. The physical activation is conducted by mechanical mixing and grinding methods, and the results show that the latter is more effective on the decrease of water absorption of recycled aggregate than the former. Chemical activation is investigated by cement grout, asphalt emulsion and organosilicone waterproofing materials. The results show that organosilicone waterproofing materials play a best role of reducing water absorption of recycled aggregate. If high temperature drying process is added, the value will reduce to nearly 0.8%.Secondly, asphalt mixture design with recycled aggregate is different from one without recycled aggregate. The effect of porous property and gradation divergence of recycled aggregate should be considered. The results show that the theoretical calculation value of the maximum theoretical relative density is less than the measured value. The greater content of recycled aggregate, the greater difference will be. The optimum asphalt content increases with the rise of the recycled aggregate content. The asphalt film thickness does not rise with the increase of asphalt content and the value is between 9.44～9.92um.Finally, the pavement performances of asphalt mixture with recycled aggregates were investigated. The higher-temperature deformation resistance of asphalt mixture is evaluated by rutting test; the lower-temperature cracking resistance of asphalt mixture is evaluated by bending test; water damage resistance property is evaluated adopting retained Marshall stability test and freeze-thaw split test. The results show that recycled aggregates can decrease the high temperature stability, increase the low temperature cracking resistance and depress the resistance of water sensitivity of asphalt mixture. The pavement performance of asphalt mixture containing proper content of recycled aggregate can completely meet the specifications demand.