ASTM_C_78_C78M-18.pdf

C78/C78M-183.2.6 support block-component of the testing apparatus in5.1.1.1 The testing machine shall conform to the require-the shape of a portion of a cylinder that is used to provide aments of the sections on Basis of Verification,Corrections,andreaction to the force applied to the beam specimen.Time Interval Between Verifications of Practice E4.3.2.6.1 Discussion-If the testing apparatus applies force to5.1.1.2 Verify the accuracy of the testing machine in accor-the top of the beam,this block supports the beam.If the testingdance with Practice E4,except that the verified loading rangeapparatus applies force to the bottom of the beam,the supportshall be as required for flexural testing.Verification is required:block may be considered a reaction block because it provides(/)Within 13 months of the last verification,a line of reaction at the top of the beam and does not support(2)On original installation,the beam.(3)After relocation,3.2.7 testing machine-mechanical device for applying(4)After making repairs or adjustments that affect theforce to a specimen.operation of the force applying system or the values displayedon the load indicator,except for zero adjustments that com-4.Significance and Usepensate for the weight of loading or support blocks orspecimen,or both,or4.1 This test method is used to determine the flexural(5)Whenever there is reason to suspect the accuracy of thestrength of specimens prepared and cured in accordance withindicated forces.Test Methods C42/C42M or Practices C31/C31M or C192/C192M.Results are calculated and reported as the modulus of5.2 Flexural Testing Apparatus-The third point loadingrupture.For the same specimen size,the strength determinedmethod shall be used to determine the flexural strength ofwill vary if there are differences in specimen preparation,concrete.The loading blocks and support blocks shall becuring procedure,moisture condition at time of testing,anddesigned so that forces applied to the beam will be along lineswhether the beam was molded or sawed to size.perpendicular to the side faces of the beam and applied without4.2 The measured modulus of rupture generally increases aseccentricity.A diagram of the flexural testing apparatus isthe specimen size decreases.3.4.5shown in Fig.1.4.3 The results of this test method may be used to determineNorE 1-The flexural testing apparatus shown in Fig.I may be usedinverted.In this case,the loading blocks will be at the bottom of the beam,compliance with specifications or as a basis for mixturewhile the reaction blocks will be at the top of the beam.proportioning,evaluating uniformity of mixing,and checkingplacement operations by using sawed beams.It is used primar-5.2.1 The flexural testing apparatus shall be capable ofily in testing concrete for the construction of slabs andmaintaining the span length and distance between the lines ofpavements.loading withinl.0mm0.05in.】of the specified values.5.2.2 The ratio of the horizontal distance between the line of4.4 For identical test specimens,the modulus of ruptureapplication of the force and the line of the nearest reaction toobtained by this test method will,on average,be lower thanthat obtained by Test Method C293/C293M.the depth of the beam shall be 1.0+0.03.5.2.3 The loading blocks and support blocks shall not be5.Apparatusmore than 65 mm 2.50 in.high,measured from the center orthe axis of the ball or the axis of the rod and shall extend5.1 Testing Machine-Hand operated testing machines hav-entirely across or beyond the full width of the specimen.Eaching pumps that do not provide a continuous loading in onecase,the block surface in contact with the specimen shall notstroke are not permitted.Motorized pumps or hand operateddepart from a plane by more than 0.05 mm 0.002 in.and shallpositive displacement pumps having sufficient volume in onebe a portion of a cylinder,the axis of which is coincidental withcontinuous stroke to complete a test without requiring replen-either the axis of the rod or center of the ball,whichever theishment are permitted and shall be capable of applying loads atblock is pivoted upon.The angle subtended by the curveda uniform rate without shock or interruption.The testingsurface of each block shall be at least 0.80 rad 45.machine shall be equipped with a means of recording or5.2.4 At least every six months or as specified by theholding the peak value that will indicate the maximum load,towithin 1 accuracy,applied to the specimen during a test.manufacturer of the flexural testing apparatus,clean andlubricate metal-to-metal contact surfaces,such as interna5.1.1 Verification:concave surfaces and steel balls and rods of the loading blocksand support blocks(Fig.1).The lubricant shall be a petroleum-type oil,such as conventional motor oil,or as specified by the3 Tanesi,J:Ardani,A.Leavitt,J.Reducing the Specimen Size of ConcreteFlexural Strength Test(AASHTO T97)for Safety and Ease of Handling,Trans-manufacturer of the apparatus.portation Research Record:Journal of the Transportation Research Board,No.5.2.5 The support blocks shall be free to rotate.2342.Transportation Research Board of National Academies,Washington.D.C.5.2.6 The loading blocks and support blocks shall be2013.4 Carrasquillo.P.M.and Carrasquillo.R.LImproved Concrete Quality Controlmaintained in a vertical position and in contact with the rod orProcedures Using Third Point Loading,Research Report 119-/F,Project 3-9-87-ball by means of spring-loaded screws that hold them in1119,Center For Transportation Research,The University of Texas at Austin,contact with the rod or ball.The uppermost bearing plate andNovember 1987.Bazant,Z.and Novak,D.Proposal for Standard Test of Modulus of Rupturecenter point ball in Fig.I may be omitted if the testing machineof Concrete with its Size Dependence,ACI Materials Journal,January-Februaryhas a spherically seated bearing block,provided one rod and2001.one ball are used as pivots for the upper loading blocks.