Study On Processing Technic Of RAP And Pavement Performance Of Warm-mixed Recycled Asphalt Mixture

Warm-mixed recycled asphalt mixture is a new technology of environmentalprotection and energy saving. Its advantages are mainly embodied in two aspects: on theone hand, mixing temperature and molding temperature of warm mix recycled asphaltmixture are20℃to30℃lower than hot mix reclaimed asphalt mixture, effectivelyreducing the energy consumption; on the other hand, warm mix recycled asphaltmixture can improve the old asphalt mixture (RAP) blending ratio, efficientlyimplementing RAP recycling, reducing the environmental pollution and waste of landresources.At present, many kinds of warm mix technology exist at home and abroad. Studyobject of this paper focus on the warm-mixed recycled asphalt mixture based onsurfactant which is the research hotspot on all walks of life. Through the combinedmethod of experimental research and theory analysis, researches mainly focus on oldmaterial handling process, mix proportion design method, property influencing factor ofwarm-mixed recycled asphalt mixture. Some rule characteristics of warm-mixedrecycled asphalt mixture based on surfactant are revealed. Related conclusion andcontent can be summarized as follows:(1) Evaluate the RAP cluster condition and grading variability, RAP treatingtechnology are put forward. Fineness modulus ratio and coefficient of variation wereused respectively to evaluate the old material cluster status and variability. Put forwardsecondary crushing process of RAP according to the cluster condition of RAP,determine the scope of reasonable fineness modulus ratio through the test, which cancontrol the RAP cluster status. Put forward classification process according to RAPgradation variability, which can control RAP gradation variability.(2) Warm mixing mechanism are analyzed, evaluate asphalt property affected bywarm mixing agent. Warm mixing agent plays a role of lubrication in the process ofmixing, enhancing the workability of mixing asphalt mixture, improving the degree ofcompaction. Simulate the construction process, test the changing rule of asphaltperformance indicators by adding warm mixing agent in asphalt, and judge the effect ofwarm mixing agent on asphalt. The results show that warm mixing agent has little effecton asphalt performance indictors, determining method of mixing and moldingtemperature by the viscosity-temperature curve is not applicable for warm-mixed recycled asphalt mixture based on surfactant.(3) Mix proportion design method of warm-mixed recycled asphalt mixture isdiscussed. Optimum asphalt content and reasonable gradation are determined by hotmix method. Change the mixing temperature on basis of hot mix and determine the bestmixing temperature when the porosity of hot mix asphalt specimen and warm mixrecycled asphalt mixture are reaching similar level. Verify the reasonableness of the mixproportion by molding specimen on base of the determined gradation, asphalt contentand mixing temperature.(4) Evaluate the treatment process of old material and the effect of RAP content onthe performance of warm-mixed recycled asphalt mixture. Classify the RAP materialinto three kinds, including raw RAP material, RAP which processed by removal of fineaggregate and second-broken, RAP which processed by removal of fine aggregate andgrading after second-broken. Mix the warm-mixed recycled asphalt mixture using threetypes of RAP separately, and compare the differences between the performances of thethree kind mixtures. The results show: mixture formed by RAP which processed byremoval of fine aggregate and grading after second-broken has the best performance,mixture formed by RAP which processed by removal of fine aggregate andsecond-broken has the second performance, mixture formed by raw RAP material hasthe worst performance. Compare the performance changing rule of warm-mixedrecycled asphalt mixture when RAP content are0%,30%,40%,50%separately, theresults show: high temperature performance, water stability performance are improvedwith the RAP content increasing, on the contrary, low temperature performance andfatigue performance are decreased with the increase of dosage of RAP.(5) Explore low temperature performance and fatigue performance improvementmeasures of the old material. Latex additives can effectively improve the lowtemperature performance and fatigue performance of warm-mixed recycled asphaltmixture, but can not greatly improve the high temperature performance and waterstability performance.