Experimental Study On Road Performance Of Recycled Aggregate For Waste Concrete Pavement

With the development of our country’s economy and the acceleration of urbanization,old bridges,roads and buildings have been demolished,and a large number of construction waste has also been generated,of which waste concrete accounts for a large proportion.At present,the ways of repairing concrete pavement in our country are divided into two categories: one is to directly overlay concrete or asphalt concrete pavement after treatment of old pavement diseases,or to transform the old pavement into asphalt pavement structure after breaking and stabilizing the old pavement slab,but the effect of repairing is not good;the other is to rebuild the pavement after removing the old pavement slab,so as to treat both the specimens and the specimens,but this not only causes waste of resources,but also It will destroy the surrounding environment.On the other hand,with the rapid development of highway construction in China,inorganic binder stabilized materials are widely used in road base and subbase,among which cement stabilized gravel-like materials are the most widely used.Because the recycled aggregate after crushing of waste concrete pavement slab has similar pavement performance with natural aggregate,and is more environmentally friendly,which conforms to the green construction concept of our country,this paper uses recycled aggregate after crushing of waste concrete pavement slab to replace natural aggregate in road base with different substitution rate,and stabilizes gravel base with recycled aggregate cement.The pavement performance of the floor is evaluated.(1)Taking the recycled aggregate crushed by jaw crusher and impact crusher as the research object,the physical and mechanical parameters of recycled aggregate,such as apparent density,crushing value,needle-like particle content,water absorption and mud content,were tested and tested.The adaptability of recycled aggregate was evaluated by comparing with the aggregate index requirements of cement stabilized crushed stone semi-rigid base.According to the evaluation results,the recycled aggregate crushing technology of waste concrete pavement wasoptimized.(2)Screening test of recycled aggregate is carried out.According to the results of screening,the screening gradation of recycled aggregate is determined when the replacement rate is 0%,40%,70% and 100%,respectively.According to this gradation,vibration compaction test with cement content of 4%,5% and 6% is carried out to determine the optimum moisture content and maximum dry density.(3)Cylindrical and beam specimens were formed by static pressure method,and the mechanical properties of cement stabilized macadam including unconfined compressive strength,splitting tensile strength,compressive elastic modulus and flexural tensile strength were tested.According to the test results of mechanical properties,the semi-rigid base material of cement-stabilized macadam base with cement content of 5% was selected for drying shrinkage test,and the drying shrinkage performance of recycled aggregate cement-stabilized macadam base was evaluated.(4)The results show that the apparent density of recycled coarse aggregate is smaller than that of natural coarse aggregate,and its crushing value,water absorption,mud content and needle flake content are higher,but it still meets the requirements of current specifications for semi-rigid base material of high-grade highway;when the cement content is constant,with the increase of replacement rate of recycled aggregate,the maximum dry density decreases and the optimum moisture content increases.When the cement content and age are fixed,the strength and compressive modulus of recycled aggregate cement stabilized macadam base increase with the increase of replacement rate of recycled aggregate,but they are still smaller than those of natural aggregate cement stabilized macadam base.With the increase of replacement rate of recycled aggregate,the drying shrinkage coefficient increases.