ASTM D7958D7958M-17 Standard Test Method for Evaluation of Performance for FRP Composite Bonded to Concrete Substrate using Beam Test.pdf

1、Designation: D7958/D7958M 17Standard Test Method forEvaluation of Performance for FRP Composite Bonded toConcrete Substrate using Beam Test1This standard is issued under the fixed designation D7958/D7958M; the number immediately following the designation indicates theyear of original adoption or, in

2、 the case of revision, the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method describes the apparatus and procedurefor evaluating the performanc

3、e of wet lay-up or pultrudedFiber-Reinforced Polymer (FRP) composite systems adhe-sively bonded to a flat concrete substrate. The test determinesthe maximum force that an FRP system can bear beforedetaching from a concrete beam tested in flexure. Failure willoccur along the weakest plane within the

4、system composed ofthe FRP composite, adhesive, and concrete substrate.1.2 This test method is used for assessment and comparisonof FRP systems subject to environmental conditioning. Thistest method is not intended for job approval or productqualification purposes.1.3 This test method is intended for

5、 use with adhesive-applied FRP systems and is appropriate for use with FRPsystems having any fiber orientation or combination of plyorientations comprising the FRP composite, although the testcondition only considers forces in the direction parallel to thebeam longitudinal axis.1.4 The values stated

6、 in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system are not exact equivalents; therefore, each systemmust be used independently of the other. Combining valuesfrom the two systems may result in nonconformance with thestandard.1.4.1 Within

7、the text, the inch-pound units are shown inbrackets.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, health and environmental practices and deter-mine the a

8、pplicability of regulatory limitations prior to use.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued

9、by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:C31/C31M Practice for Making and Curing Concrete TestSpecimens in the FieldC33/C33M Specification for Concrete AggregatesC39/C39M Test Method for Compressive Strength of Cylin-drical

10、Concrete SpecimensC42/C42M Test Method for Obtaining and Testing DrilledCores and Sawed Beams of ConcreteC78 Test Method for Flexural Strength of Concrete (UsingSimple Beam with Third-Point Loading)C125 Terminology Relating to Concrete and Concrete Ag-gregatesC150/C150M Specification for Portland Ce

11、mentC192/C192M Practice for Making and Curing Concrete TestSpecimens in the LaboratoryC511 Specification for Mixing Rooms, Moist Cabinets,Moist Rooms, and Water Storage Tanks Used in theTesting of Hydraulic Cements and ConcretesC617 Practice for Capping Cylindrical Concrete SpecimensD883 Terminology

12、 Relating to PlasticsD3039 Test Method for Tensile Properties of Polymer Ma-trix Composite MaterialsD3878 Terminology for Composite MaterialsD7565 Test Method for Determining Tensile Properties ofFiber Reinforced Polymer Matrix Composites Used forStrengthening of Civil StructuresE4 Practices for For

13、ce Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE122 Practice for Calculating Sample Size to Estimate, WithSpecified Precision, the Average for a Characteristic of aLot or Process1This test method is under the jurisdiction of ASTM Committee D30 onComposite

14、Materials and is the direct responsibility of Subcommittee D30.10 onComposites for Civil Structures.Current edition approved Aug. 1, 2017. Published September 2017. DOI:10.1520/D7958_D7958M-17.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United

15、StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to

16、 Trade (TBT) Committee.1E251 Test Methods for Performance Characteristics of Me-tallic Bonded Resistance Strain GagesE456 Terminology Relating to Quality and Statistics3. Terminology3.1 Terminology D3878 defines terms relating to high-modulus fibers and their composites. Terminology D883 de-fines te

17、rms relating to plastics. Terminology E6 defines termsrelating to mechanical testing. Terminology C125 defines termsrelating to concrete. Terminology E456 and Practice E122define terms relating to statistics. In the event of a conflictbetween terms, Terminology D3878 shall have precedenceover the ot

18、her standards.3.2 Definitions:3.2.1 detach, vThe FRP system pulling off of or breakingaway from the concrete substrate. Detachment may result fromcohesive failure in the FRP laminate, adhesive or substrateconcrete or from adhesive failure between any components ofthe FRP system. Detachment correspon

19、ds to the peak forcecarried by the FRP.3.3 Symbols:3.3.1 Alower bound rate coefficient: A = 0.50 MPa/min72 psi/min3.3.2 Bupper bound rate coefficient: A = 0.69 MPa/min100 psi/min3.3.3 Cresultant force of compression block3.3.4 bwidth of test beam3.3.5 CVsample coefficient of variation3.3.6 doverall

20、depth of test beam3.3.7 Ecmodulus of elasticity of concrete3.3.8 Echordtensile chord modulus of elasticity of FRP(D3039)3.3.9 fccompressive strength of concrete (C39/C39M)3.3.10 Fmaximum force in FRP3.3.11 hthickness of FRP (D3039)3.3.12 K*FRP tensile stiffness per unit width (D7565)3.3.13 nnumber o

21、f specimens3.3.14 Pmaximum applied force indicated by testing ma-chine3.3.15 rrepeatability limit, the value below which theabsolute difference between two individual test results obtainedunder repeatability conditions may be expected to occur with aprobability of approximately 0.95 (95 %)3.3.16 rPr

22、ate of application of load P, N/min lbf/min3.3.17 Sn-1sample standard deviation3.3.18 Sbonded length of FRP3.3.19 wbonded width of FRP3.3.20 xsample mean3.3.21 ximeasured or derived property3.3.22 ratio of neutral axis depth measured from com-pression face of specimen to overall depth of specimen3.3

23、.23 ratio of axial stiffness of FRP to that of concretespecimen3.3.24 strain at debonding recorded from strain gage4. Summary of Test Method4.1 This test is conducted by loading simply supportedconcrete beam specimens having a load located at the center ofthe beam span to failure. The beams are rein

24、forced on theirsoffit (tension face) with bonded FRP reinforcement. Thespecimen configuration and testing procedures are similar tothose used to determine modulus of rupture of concrete (seeTest Method C78).5. Significance and Use5.1 This test method serves as a means for uniformlypreparing and test

25、ing standard specimens suitable for beingsubject to environmental conditioning and subsequently usedFIG. 1 Schematic of Suitable Apparatus for Flexure Test by a Single Load at the Center of the Span. All Parts of Apparatus are Made ofSteel.D7958/D7958M 172to evaluate FRP-bonded-to-concrete system pe

26、rformance, andevaluating and reporting the results.5.2 This test method is intended for use in the laboratory.5.3 The comparison of results from this test method con-ducted on identical specimens subject to different environmen-tal conditioning protocols can be used to evaluate the effects ofenviron

27、mental exposure on the bond performance of FRPsystems.6. Interferences6.1 Material and Specimen PreparationNon-uniformFRP or FRP-to-substrate adhesive thickness can affect anindividual test result. Variation in FRP or adhesive thicknessbetween specimens can cause biased or scattered test results.6.2

28、 Specimen DimensionsThis method calculates a valueof maximum force resisted by the FRP system, as such, resultsare dependent on the specimen dimensions. Values calculatedusing specimens having different dimensions should not becompared.6.3 FRP ReinforcementUse of excessive FRPreinforcement, sufficie

29、nt to cause a diagonal shear failure modein the concrete beam (as shown in Fig. 3(c), results in aninvalid test.6.4 FRP ReinforcementUse of very flexurally stiff FRPreinforcement, sufficient to cause a debonding failure at thetermination of the FRP, results in an invalid test.6.5 Concrete Strength a

30、nd Modulus of ElasticityVariationdue to aging and/or conditioning affects the concrete strengthand modulus which may affect the assumed distribution ofstress in the cross section which affects Calculation Method 2.6.6 Calculation MethodIt is known that calculation meth-ods 1 and 2 will yield differe

31、nt results. Method 1 relies on ameasured value of stiffness per unit width obtained fromanother specimen using Test Method D7565 or D3039. Method2 relies on a number of geometric and material simplifications.Method 2 is intended for use when direct strain measurementsare not possible. Values calcula

32、ted using Method 1 are notcomparable to values calculated using Method 2.7. Apparatus7.1 The testing machine used shall conform to the require-ments of the sections on Basis of Verification, Corrections, andTime Interval Between Verifications of Practices E4. Hand-operated testing machines having pu

33、mps that do not provide acontinuous loading in one stroke are not permitted. Motorizedpumps or hand-operated positive displacement pumps havingsufficient volume in one continuous stroke to complete a testwithout requiring replenishment are permitted and shall becapable of applying loads at a uniform

34、 rate without shock orinterruption.7.2 Loading ApparatusWith the exception that the beamtest is conducted with a single load at the center of the beam,rather than two loads at the third-points, the loading apparatusshall be the same as that used for Test Method C78.7.2.1 The center-point loading met

35、hod shall be used inmaking beam tests employing bearing blocks that will ensurethat forces applied to the beam will be perpendicular to the faceof the specimen and applied without eccentricity. A diagram ofan apparatus that accomplishes this purpose is shown in Fig. 1.7.2.2 All apparatus for making

36、flexure tests shall be capableof maintaining the specified span length and distances betweenload-applying blocks and support blocks constant within61.0 mm 60.05 in.7.2.3 The ratio of the horizontal distance between the pointof application of the load and the point of application of thenearest reacti

37、on to the depth of the beam shall be 1.5 6 0.03.7.2.4 If an apparatus similar to that illustrated in Fig. 1 isused: the force-applying and support blocks shall not be morethan 64 mm 2.50 in. nor less than 25 mm 1 in. high,measured from the center or the axis of pivot, and shouldextend entirely acros

38、s or beyond the full width of the specimen.Each case-hardened bearing surface in contact with the speci-men shall not depart from a plane by more than 0.05 mm0.002 in. and shall be a portion of a cylinder, the axis ofFIG. 2 Specimen Dimensions and Details of Bonded FRP SystemFIG. 3 Failure Modes for

39、 Beam TestD7958/D7958M 173which is coincidental with either the axis of the rod or centerof the ball, whichever the block is pivoted upon. The anglesubtended by the curved surface of each block shall be at least45. The force-applying and support blocks shall be maintainedin a vertical position and i

40、n contact with the rod or ball bymeans of spring-loaded screws that hold them in contact withthe pivot rod or ball. The uppermost bearing plate and centerpoint ball in Fig. 1 may be omitted when a spherically seatedbearing block is used.7.3 Bonded Resistance Strain GagesFRP strain data, ifrequired f

41、or Calculation Method 1, shall be determined bymeans of a bonded electrical resistance strain gage. Strain gageselection is a compromise based on the type of FRP materialbeing tested. An active gage length of 6 mm 0.25 in. isrecommended for most materials. Active gage lengths shouldnot be less than

42、3 mm 0.125 in. Gage calibration certificationshall comply with Test Methods E251. When testing wovenfabric composites, gage selection should consider the use of anactive gage length that is at least as great as the characteristicrepeating unit of the weave.7.3.1 Bonded strain gages should be applied

43、 followingenvironmental conditioning so as not to be affected by theconditioning. In some cases, bonding following environmentalconditioning will not be possible; in these cases CalculationMethod 2 may be used.NOTE 1Guidelines on the use of strain gages on FRP composites areprovided in Test Method D

44、3039.7.4 MicrometersMicrometers used to determine specimendimensions shall use a suitable size diameter ball-interface onirregular surfaces and a flat anvil interface on machined edgesor very-smooth tooled surfaces. For typical specimengeometries, the accuracy of the instruments shall be suitablefor

45、 reading to within 1 % of the intended measurement. The useof alternative measurement devices is permitted if agreed to bythe test requestor and reported by the testing laboratory.8. Test Specimen and Sampling8.1 The concrete test specimen shall conform to all require-ments of Test Method C42/C42M o

46、r Practices C31/C31M orC192/C192M applicable to beam specimens and shall have atest span within 2% of three times its depth as tested. The sidesof the specimen shall be at right angles with the top andbottom. All surfaces shall be smooth and free of scars,indentations, holes, or inscribed identifica

47、tion marks.8.1.1 The depth of the test specimen, d, shall be 102 mm4.0 in. or 152 mm 6.0 in.8.2 Cast Specimens (Practices C31/C31M or C192/C192M)Cast specimen concrete mixture shall meet thefollowing requirements:8.2.1 AggregatesAggregates shall conform to Specifica-tion C33/C33M, and the maximum ag

48、gregate size shall be 9.5or 12.7 mm 38 or12 in.8.2.2 CementUse Type I/II portland cement conforming toSpecification C150/C150M. The concrete mixture shall notinclude any other cementitious materials (for example, slag, flyash, silica fume, or limestone powder) or chemical admixtures(for example, air

49、-entraining agents, water reducers, high-rangewater reducers, shrinkage-compensating admixtures, corrosioninhibitors, set retarders, and set accelerators) unless the evalu-ation of these is an objective of the test program.8.2.3 Concrete StrengthCylinders should be cast andtested in accordance with Practice C31/C31M and Test MethodC39/C39M. The 28-day compressive strength of the cylindersshall fall between 46 to 60 MPa 6500 to 8500 psi.8.2.4 CuringCure cylinders and beam specimens for 28days