ASTM_D_7460_-_10.pdf

Designation:D746010Standard Test Method forDetermining Fatigue Failure of Compacted Asphalt ConcreteSubjected to Repeated Flexural Bending1This standard is issued under the fixed designation D7460;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method provides procedures for determining aunique failure point for estimating the fatigue life of 380 mm(14.96 in.)long by 50 mm(1.97 in.)thick by 63 mm(2.48 in.)wide asphalt concrete beam specimens sawed from laboratoryor field compacted asphalt concrete,which are subjected torepeated flexural bending.1.2 The between-laboratory reproducibility of this testmethod is being determined and will be available on or beforeJune 2013.Therefore,this test method should not be used foracceptance or rejection of a material for purchasing purposes.1.3 The text of this standard references notes and footnoteswhich provide explanatory material.These notes and footnotes(excluding those in tables and figures)shall not be consideredas requirements of the standard.1.4 UnitsThe values stated in SI units are to be regardedas standard.Other units of measurement included in thisstandard are for information only.1.5 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D75 Practice for Sampling AggregatesD140 Practice for Sampling Bituminous MaterialsD979 Practice for Sampling Bituminous Paving MixturesD2041 Test Method for Theoretical Maximum SpecificGravity and Density of Bituminous Paving MixturesD3203 Test Method for Percent Air Voids in CompactedDense and Open Bituminous Paving MixturesD3549 Test Method for Thickness or Height of CompactedBituminous Paving Mixture SpecimensD3666 Specification for Minimum Requirements for Agen-cies Testing and Inspecting Road and Paving MaterialsD5361 Practice for Sampling Compacted Bituminous Mix-tures for Laboratory TestingE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with Specifications2.2 AASHTO Standards:3T 321 Standard Method of Test for Determining the FatigueLife of Compacted Hot-Mix Asphalt(HMA)Subjected toRepeated Flexural BendingPP 3 Preparing Hot-Mix Asphalt(HMA)Specimens byMeans of the Rolling Wheel CompactorR 30 Standard Practice for Mixture Conditioning of Hot-MixAsphalt(HMA)3.Terminology3.1 Definitions:3.1.1 beam modulusFlexural Beam Stiffness,as deter-mined in 10.1.3.3.1.2 failure pointthe number of cycles to failure,Nf,which corresponds to the maximum or peak NormalizedModulus Cycles(Fig.13)when plotted versus Number ofCycles.3.1.3 initial beam modulusFlexural Beam Stiffness deter-mined at approximately 50 load cycles.3.1.4 normalized modulus cyclessee Rowe and Bouldin(1):4Beam Stiffness3Cycle Number!Initial Beam Modulus3Cycle of Initial Beam Modulus!4.Summary of Test Method4.1 The four-point flexural bending test method is con-ducted on compacted beam specimens to evaluate the fatigue1This test method is under the jurisdiction of ASTM Committee D04 on Roadand Paving Materials and is the direct responsibility of Subcommittee D04.26 onFundamental/Mechanistic Tests.Current edition approved June 1,2010.Published July 2010.Originally approvedin 2008.Last previous edition approved in 2008 as D764008.DOI:10.1520/D7460-10.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3Available from American Association of State Highway and TransportationOfficials(AASHTO),444 N.Capitol St.,NW,Suite 249,Washington,DC 20001,http:/www.transportation.org.4The boldface numbers in parentheses refer to the list of references at the end ofthis standard.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 properties of an asphalt concrete mixture.A cyclic haversine(displaced sine wave with full amplitude on tension side ofzero)displacement is applied at the central H-frame thirdpoints of a beam specimen,while the outer third points are heldin an articulating fixed position.The frequency rate rangesfrom 5 to 10 Hz.This produces a constant bending momentover the center third(L/3)span(118.5 to 119 mm(4.66 to 4.69in.)between the H-frame contact points on the beam speci-men.The level of desired strain is pre-calculated and an inputfor the displacement control.The deflection at the mid-lengthposition(L/2)of a beam specimen is regulated by the closedloop control system.5.Signific