Study On The Application Of Crushed Pebble Asphalt Mixture In Expressway At High Altitude

Tibet is located in an area of high cold and high altitude,with a harsh environment and fragile ecology,so it is difficult to recover once it is destroyed.The aggregate needed for highway engineering is strictly restricted.The construction of roads in Tibet should not only face the test of high cold and high altitude environment,but also solve the problem of lack of aggregate in this area.However,Tibet is rich in river pebble resources,if it can be used as aggregate in asphalt pavement construction,it can increase the source of aggregate,protect the environment,and reduce the cost.In this paper,suitable crushing equipment is selected for market research,and pebbles are crushed through excellent crushing process.In view of the poor water stability of crushed pebble asphalt mixture,the measures to improve the water stability are put forward.This paper first analyzes a variety of stone processing equipment combination scheme,and finally selects jaw crusher-impact crusher-vertical shaft crusher as the best crushing combination scheme.In view of the problems existing in the crushing quality of pebbles,the processing process was optimized,and the technical index of crushing quality control was put forward.Secondly,this paper proposes to use the drawing loss rate as the evaluation method of adhesion between asphalt and aggregate.The water stability of the crushed pebble asphalt mixture was studied by using anti-stripping agent,cement replacement part of the ore powder,and silane coupling agent KH570 modified aggregate improvement measures.The best proportion of compound improvement measures is determined based on orthogonal experimental design.The results show that the order of improving the water stability of asphalt mixture by adding modifier is 0.75%KH570 > 2% cement > 0.3% anti-stripping agent.Under the orthogonal experimental design,the compound improvement measures have the most significant effect on improving the water stability of crushed pebble asphalt mixture.Finally,in view of the complex climatic conditions in Tibet,this paper designs a test scheme to simulate the influence of freeze-thaw cycle on broken pebble asphalt mixture,and evaluates the water stability of broken pebble asphalt mixture by immersion Marshall test and freeze-thaw splitting test.The low temperature performance of crushed pebble asphalt mixture is evaluated by trabecular bending test,and its high temperature performance is evaluated by rutting test and uniaxial penetration strength test.The results show that the asphalt mixture with compound improvement measures has excellent high temperature performance,water stability and low temperature performance.Finally,combined with the physical project of Linzhi Expressway in Tibet,the actual use of the physical project shows that the crushed pebble asphalt mixture has good road performance and good effect.to provide theoretical support and technical guidance for the popularization and application of broken pebbles in Tibet.