Porous asphalt (PA) has been widely used in many countries because of its positive benefits, such as efficient water drainage, improved safety in wet weather conditions, and noise reduction. However, the attractive features of PA do not last long because of clogging, stripping, and accelerated aging. Application of fiber reinforcement materials can be a possible solution to the structural weakness in PA pavements. Fatigue of fiber-reinforced PA composite systems was investigated with a model mobile load simulator (MMLS). Carbon fiber reinforcement polymer (FRP) grids were used to strengthen the fatigue resistance of PA. FRP grids were placed between two asphalt layers as a reinforcement interlayer. The dynamic fatigue traffic loadings were applied on the top surface of reinforced specimens to investigate the performance improvement by reinforcement materials. These fatigue tests were conducted under four different conditions: absence and presence of reinforcement at dry conditions and wet conditions. The stiffness difference between unaged and aged specimens was 25% at minimum and 55% at maximum. The surface deflection of PA was successfully reduced by 23% at dry and by 48% at wet conditions by using interlaid carbon FRP grids. In addition, the reinforcement layer could increase the fatigue life by 23% at dry and by 27% at wet conditions based on MMLS test results.
Coaxial Shear Test (CAST) is used at EMPA road engineering center for determining the mechanical properties of asphalt concrete under repeated sinusoidal loading in both load and strain controlled mode at different temperatures and frequencies. CAST provides stiffness information under lateral deformation confinement, thus simulating the situation in a pavement layer under an idealized traffic loading. In order to understand the complex behavior of the system, Finite Element Analysis (FEA) of the complete test setup was carried out. The details of the FEA model as well as the data analysis procedure are described. New types of experiments, carried out with the CAST equipment, such as the determination of the water sensitivity under combined cyclic mechanical and temperature loading, are described. The distinctive features of the implementation and evaluation of the mechanical properties from experiments are discussed. 1359-5997 9 2005 RILEM. All rights reserved. RI~SUMI~ L 'essai de cisaillement coaxial (CAST) est utilis~ g7 I'EMPA pour d~terminer les propri~t~s m~caniques des m~langes bitumineux compact,s sous charge sinusoMale altern~e avec eontr61e de la charge ou du d~plaeement h des tempOratures et des fr~quenees diffOrentes. L 'essai CASTfourn# des informations sur la rigidit~ sous contrainte de d~formation lat~rale simulant la situation de l 'enrobO sous une charge de trafic id~alis~e Pour mieux eomprendre le eomportement complexe du systbme, une analyse par OlOments finis (FEA) de la g~omktrie de l'essai eomplet a OtO effectu~e. Les d~tails du modble FEA et les procedures nOeessaires pour traiter les donn~es sont diseut~s. De nouveaux types d'essais utilisant l'~quipement CAST, comme la d~termination de la suseeptibilitO h l'eau sous ehargement eyclique et avec variation eyelique de la temperature sont dOcrits. Le principe de l'impl~mentation et la mOthode d'~valuation des propri~t~s m~caniques dt partir d'essais sont diseutds. Editorial note EMPA is a RILEM Titular Member. Dr. Manfred N. Partl is a RILEM Senior Member and a member of the RILEM Technical Activities Committee (TA C). He is the Chairman of RILEM TC A TB 'Advanced testing and characterization of bituminous materials' and also participates in RILEM TCs 197-NCM 'Nanotechnology in construction materials' and CAP "CracMng in Asphalt Pavements '. Mr. Remy Gubler participates in the above-mentioned RILEM TC A TB.
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