Study On Processing Technology And Performance Optimization Of High Content Recycled Asphalt Brick

The regeneration of asphalt pavement refers to the recycling and reuse of old pavement asphalt materials,so as to achieve the purpose of saving mineral resources,protecting the natural environment and reducing the cost.It is generally believed that the operation of digging,collecting,pretreatment(breaking and screening)of asphalt pavement that has stopped using or needs to be rebuilt,and then mixing with appropriate amount of new aggregate and asphalt to prepare for recycled materials that meet the requirements of road construction for the purpose of being used in the field of general road engineering,belong to the traditional utilization field of RAP.Such recycling method has great limitations on the amount of RAP.When the amount of recycled materials is higher,the construction technology and road performance of recycled asphalt mixture will be greatly affected.Therefore,in order to achieve large-scale recycling of RAP,it must be generalized,not only to achieve hot recycling of pavement,but also to be processed into other forms of commercial products to replace high energy consumption building materials.Referring to Marshall design method,the mix design of 100%RAP of recycled asphalt mixture was determined.Under the condition of the default optimum oil-stone ratio,the design temperature was discussed with the compressive strength and the strength loss under freeze-thaw water as the indexes.The optimum moulding density of asphalt brick was determined by the void fraction(VV),relative density of gross volume,compressive strength and freeze-thaw strength ratio as reference indexes.Based on the compressive strength ratio and freeze-thaw strength ratio,the forming methods of specimens were selected.According to analysis,the results showed that all the asphalt bricks made of AC-13 mixture had different degrees of surface aggregate shedding.Thus,the maximum nominal diameter of aggregate should be properly reduced.The appropriate forming temperature range is 145-155 C,not the higher the temperature,the better.In the aspect of moulding method,the effect of rolling moulding on the compressive strength and freeze-thaw strength ratio of asphalt brick is the best,while the effect of static pressing is the worst.Secondly,according to the experimental results,it was found that there were many problems in the use performance of asphalt brick prepared with recycled materials.Then,through the method of mathematical statistics,the amount of external admixture was screened and compared,and the optimum amount of external admixture was determined as 0.5% of the amount of the added asphalt.The mix proportion of asphalt bricks was optimized.According to three kinds of fine gradation and three kinds of different asphalt content,the performance of improved asphalt brick was analyzed.The results showed that the change of gradation and the amount of new asphalt added had little effect on freeze-thaw strength ratio and angular damage size.The optimum asphalt-stone ratio should be controlled between 5.8% and 6.3%.When the conditions were satisfied,the finer gradation should be selected as far as possible in mix design.