The Application Of The Rubber Asphalt Technique In Highway Pavement

Currently, the sustainability has already become one of the most importanttopics in the transportation engineering. Environmentally friendly, eco systemprotective and recycling techniques are widely studied in recent years. Rubberasphalt pavement, as a typical environmentally friendly pavement technique, hasaroused many interests for decades. In this study, according to the designingtheory of the thin surface with strong foundation (TSWSF) applied in SouthAfrica, the highway pavement structure prepared with rubber asphalt has beeninvestigated, and the application properties of a testing road have been studied aswell.First, the mechanical performances of several typical TSWSF pavementswere calculated based on plastic layer system theory. The results show that withthe increasing of the modulus of the soil foundation, the loading capability of therubber asphalt structure was increased obviously, while the tensile stress of therubber asphalt structure was decreased, and the comp ressive strain at the top ofthe soil foundation was decreased as well. When the modulus of the soilfoundation is larger than60MPa, the mechanical standards of the thin rubberasphalt structure is similar to the normal asphalt concrete pavement with soilfoundation modulus of35MPa, which is able to satisfy the requirements of theheavy transportation conditions. The cost of the rubber asphalt structure wasanalyzed, and it was found that the rubber asphalt pavement has a verycompetitive cost benefit comparing with the normal pavement structure.Second, the effect of the soil foundation modulus to the typical pavementstructure performances has been demonstrated by theoretical calculationaccording to the requirements of the soil foundation modulus to the rubberasphalt pavement structure. The results show that the thickness of the foundationlayer and the surface layer are able to be decreased, which can result in thedecrease of the tensile stress at the bottom layer. The variation of the foundationlayer thickness and the modulus are extremely important to the tensile stress ofthe bottom of the half rigid foundation. To maintain the relatively low tensilestress status at the bottom of the foundation layer, the thickness of the surface issuggested higher than9cm. According to the empirical designing method fromAASHTO-93, the influence of the soil foundation modulus to the service life hasbeen predicted.Third, the gradation design of the rubber asphalt mixture and theirproperties were studied. According to the indoor test results, the rubber asphaltmixture technique requirements were developed based on the current standards. Moreover, the special construction techniques in the fie ld and the key processingproblems were summarized.Finally, the testing road was built in the double layer highway in Liaoningprovince. The materials, gradation designing, and the construction processingwere recorded in details. The foundation surface deflection, pavement deflection,flatness, friction coefficient, structure depth, and the surface cracks weremonitored. The results show that the double layer rubber asphalt pavementstructure has a better general loading capability than normal triple layer asphaltpavement. Due to the high plasticity of the pavement, the anti-cracking propertiesat low temperatures are better than normal asphalt pavement as well. The resultcan be considered as a reference in the real highway rubber asphalt pavements.