Experimental Study On The Mechanical Properties Of Recycled Asphalt Pavement

Recently,regeneration with some technologies is the main research about RAP?Recycled Asphalt Pavement?.The cyclic utilization of RAP is not enough,and study on RAP used as subbase is rare.It can turn waste into wealth that RAP is used as roadway embankment fill.Therefore,this paper conducts experiments to investigate fundamental physical properties and mechanical characteristics of RAP,so that it can be reference for further study on RAP as subbase fills.The main researches and conclusions of this paper are as follows:1.Made comparison between linear creep model and non-linear creep model to choose suitable model as the theorical basis for RAP.The model combined with Hook and Newton can only express linear creep,while some researchers indicate that asphalt shows non-linear viscoelasticity.The power function type and hyperbolic type are widely used to describe non-linear creep.Therefore,this paper decided to choose non-linear creep models to derive applicative creep model for RAP.2.Based on laboratory tests,conducted the research on the physical properties,compaction and permeability characteristics of RAP.Results show that RAP belongs to well-grade gravelly soil,which is easy to compact,and the compaction properties are similar to clay soil;the smaller the initial void ratio of RAP is,the greater the modulus of compression,which can provide great bearing capacity.With high degree of compaction,the permeability coefficient of RAP is generally greater than 0.01cm/s,proving that RAP can be well fills.3.According to consolidated drained triaxial test,this paper analyzed the influences on stress-strain characteristics and strength of RAP.CD test results indicate that its stress-strain curve shows non-linear feature obviously,and the sample presents strain-hardening characteristic during shearing.With the compacted temperature increasing,the cohesiveness of old asphalt in RAP gets strengthen that enhances the cohesion of RAP,while the internal friction angle almost remains unchanged.Therefore,it's suggested that the construction of RAP as fills should be in summer.Besides,this paper adopts regression analysis method to study the relationship among the failure deviator stress,effective confining stress and compacted temperature,and the formula is??₁-?₃?_f=3.3?₃'+1.39T+19.1.The calculated value fits well with the experimental value.4.By the triaxial creep test,the creep characteristics of RAP were explored under different effective confining pressure and deviator stress level,to work out the creep model for RAP.There are two stages when the creep failure doesn't occur:?a?the creep deformation increases quickly with time at the initial creep stage,but the strain rate decreases gradually;?b?at the second stage,the strain rate decreases very slowly and the axial strain tends to stable.When RAP sample occurs creep failure,there is the other failure stage that axial strain increases rapidly.According to contrastive analysis,it is demonstrated that hyperbolic type model can describe the relationship between strain and time well when the deviator stress level is 0.4;while the Mesri model explains better when ???>0.4;when it comes to creep failure stage,the polynomial model is more suitable to express the creep properties of RAP.