【正文】 ed mean squares(AMS)determined as provided in Table source of variation carrying highest F or AMS value was treated as first rank,which indicates the major contributor to the ,the source of variation carrying the lowest F or AMS value was treated as last rank,which indicates minor contributor to the percentage of contribution by the sources of variation to the response properties was also determined by obtaining the ratio of the Fstatistic for the source of variation to the sum of the Fstatistic values for all the sources of example,if we consider the response Va,from Group A,it may be observed that gradation(G)has major influence on the variations in air voids contribution to the varia tion is 52%as seen in Table 5. susceptibility The moisture susceptibility of the PFC mixes was evaluated based on the tensile strength ratio(TSR).The TSR refer to the ratio of average indirect tensile strength(ITS)of the wetconditioned subset to the average indirect tensile strength of dryconditioned subset,tested at a temperature of 25177。 ε is the error term。 β is the variation due to binder content(BC)。 μ is the mean of response。 γw=density of water。Characterization of porous friction course mixes for different Marshall paction efforts Department of Cvili Engnieernig,Natoina lInsttiute of Technology Karnataka,Surathka,lMangaolre 575 025,India ABSTRACT Porous friction courses(PFCs)are mainly remended as surface drainage layers on highspeed roadcorridors and runway and sound attenuation characteristics are considered to bet he indicesf orp erformancea ssessmento fP ft her easonsf or thel osso fp ermeabilityi nP FCs is densification under heavy ,resistance to ravelling too,is of main concern in the case of underpacted paper summarises the details of laboratory investigation on the characterization of PFC mixes corresponding to four different gradations and two binder contents,for three levels of the Marshallc indings oft he investigations uggestt hat thes electiono ft hec ompaction level for PFC mix design should be based on the design traffic level,and the gradation selected. 2021 Elsevier rights reserved. Keywords: Porous friction course Porous asphalt Marshall paction Air voids Voids in coarse aggregate Permeability Moisture susceptibility Abrasion loss 1. Introduction Porous friction courses(PFCs)are typical opengraded asphaltic mixes,posed of relatively uniformlygraded aggregate and asphalt cement or modified binders,and are mainly used to serve as drainage layers,either at the pavement surface or within the pavement structure[1].Pavements surfaced with opengraded asphaltic mixes were found to improve wet weather skidresistance,minimize hydroplaning,reduce splash and spray,improve night visibility during wet weather conditions,and reduce traffic tyrenoise[2,3].In countries like the United States of America,Japan,the United Kingdom,Malaysia,Australia,New Zealand,and South Africa,opengraded mixes are in use as surface layers over highspeed and heavily trafficked highway pavements[2–8].These are also remended for surfacing runway pavements[910].Many agencies around the world use different terminologies for opengraded mixes,and specifications that are slightly various terminologies used include opengraded asphalt(OGA), porous asphalt(PA),opengraded friction course(OGFC),and porous friction course(PFC). . Background The higha irv oidsc ontenti nP FCsc ontributet owardsp avement surface drainage and in attaining noise ,accelerated asphaltfilm aging,may subsequently lead to loss of cohesion in the mastic,consequently poor adhesion between the mastic and aggregate results in with the use of opengraded mixes in the USA indicated that ravelling was one of the major issues to be tackled[11].Thus,structural durability of PFCs needst o bee nsured basedo n the resistance to ravelling[12].Some of the experiences with PFCs in Japan,the poor performance was related to the lack of paction,or paction at lower temperatures than the specified[6].Permeability and sound attenuation characteristics are the main measures of performance life of PFCs[2].Studies performed on test sections in Denmark,indicated that deteriorated mastic materials clogged the largesized air voids in PFCs,which led to the formation of higher percentage of smallsized voids[12].Clogging was found to be more pronounced on older pavement,especially along the wheel path,and also in the emergency lanes [13].Although,PFCs are posed of relatively uniformlygraded aggregate[1],the use of thicker PFCs may undergo secondary densification during service,resulting in loss of ,the loss of permeability can be directly related to clogging of voids due to internal and external materials,and densification under traffic[2]. An optimal design mix should ensure high air voids content and good resistance to for mix design of PFCs remended by various agencies include the evaluation of draindown losses in loose hot mixes,air voids content,stoneonstone contact condition,permeability,and the abrasion resistance using the Cantabro abrasion test method[4,7,8,15].One of the major differences observed in the specifications by various agencies is that of the consideration of traffic volume in the optimum mix selection minimum air voids content and the maximum abrasion loss specified by some of the agencies were dependent on the traffic volume[4,7,8],whereas,this dependency was not considered by many agencies in the USA[2,10,15,16].The level of Marshall paction suggested by many agencies were found to be 50 blows per face,irrespective of the traffic addition,in the recent past many researchers adopted the same level of the Marshall paction for the design of PFC mixes[17–20].However,some of the researchers adopted or suggested the lower levels