1、Designation: C 952 02e1Standard Test Method forBond Strength of Mortar to Masonry Units1This standard is issued under the fixed designation C 952; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number
2、in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.e1NOTEEditorial changes were made throughout in December 2003.1. Scope*1
3、.1 This test method provides two procedures for measuringbond strength of mortar to masonry units: a crossed brickcouplet tensile test for evaluating mortar-brick bond strengthand a stacked-bond, flexural test for evaluating mortar-concreteblock bond strength.1.2 This standard does not purport to ad
4、dress the safetyconcerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:C 67 Test Methods of Sam
5、pling and Testing Brick andStructural Clay Tile2C 90 Specification for Loadbearing Concrete MasonryUnits2C 129 Specification for Nonloadbearing Concrete MasonryUnits2C 140 Test Methods of Sampling and Testing ConcreteMasonry Units and Related Units2C 270 Specification for Mortar for Unit Masonry2C 7
6、80 Test Method for Preconstruction and ConstructionEvaluation of Mortars for Plain and Reinforced UnitMasonry2C 1072 Test Method for Measurement of Masonry FlexuralBond Strength2C 1357 Test Method for Evaluating Masonry BondStrength2C 1437 Test Method For Flow of Hydraulic Cement Mor-tar3E 518 Test
7、Methods for Flexural Bond Strength of Ma-sonry23. Significance and Use3.1 These procedures are useful for research into bondstrength of masonry. They are not intended to predict the bondstrength of commercial masonry construction. The bondstrength in commercially built structures is determined byman
8、y factors beyond the characteristics of mortar, masonryunits, and the procedures of this test method.NOTE 1The crossed-brick couplets method measures a direct tensilestrength of the bond between the mortar and masonry unit. It does notdetermine the flexural strength of the unit mortar assembly. Othe
9、r testmethods may be more appropriate for determining the flexural bondstrength between mortar and masonry units. These include, C 1072 TestMethod for Measurement of Masonry Flexural Bond Strength, C 1357Test Methods for Evaluating Masonry Bond Strength, and E 518 TestMethods for Flexural Bond Stren
10、gth of Masonry.PREPARATION AND TESTING OF FRESH MORTAR4. Preparation of Mortar4.1 Proportion mortar materials by weights equivalent tovolume proportions to be used in prism construction. Use unitweights for individual materials as given in Specification C270. Sand shall be permitted to be used in a
11、damp loosecondition, provided that moisture content of sand is determinedwith reference to the oven-dried condition and batch propor-tions are adjusted accordingly. Record weight of ingredients(including water) added to the batch of mortar.4.2 Mix mortar in a mechanical paddle-type mortar mixer.Time
12、 periods referenced below are measured from when waterand cementitious materials are combined.4.2.1 Add an estimated amount of water to the mortar toachieve the desired consistency (Note 2). Mix mortar for threeminutes and determine consistency. If the desired consistencyis specified by flow determi
13、ne it in accordance with TestMethod C 1437. If the desired consistency is specified as initialcone penetration, determine it in accordance with Test MethodC 780. Once consistency is recorded, return the material usedto measure the consistency to the mixer. If the consistency iswithin the desired ran
14、ge, continue mixing the batch for an1This test method is under the jurisdiction of ASTM Committee C15 onManufactured Masonry Units and is the direct responsibility of SubcommitteeC15.04 on Research. Committee E-6 maintains a continued interest in thesepractices and will make use of them in the futur
15、e.Current edition approved December 10, 2002. Published March 2003. Originallypublished as E 149 59 T. Redesignated C 952 76 in 1981. Last previous editionC 952 91 (1997).2Annual Book of ASTM Standards, Vol 04.05.3Annual Book of ASTM Standards, Vol 04.01.1*A Summary of Changes section appears at the
16、 end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.additional two minutes. If the consistency is less than thedesired range, add water to the batch and mix for one minuteand determine consistency. Once consistency i
17、s recorded,return the material used to measure consistency to the mixer. Ifthe consistency is within the desired range, continue mixing thebatch for one minute.NOTE 2Workable consistency of mortar for concrete masonry con-struction generally requires an initial cone penetration reading of 55 6 5mm o
18、r a flow of 125 6 5 %. Workable consistency of mortar for claymasonry construction generally requires an initial cone penetrationreading of 65 6 5 mm or a flow of 135 6 5 %. Optimum consistency fora specific mortar-unit combination may differ from these values.4.2.2 If after the one-time addition of
19、 water the consistencyis not in the desired range, discard the batch.4.2.3 If the measured consistency exceeds the desired rangeat any time, discard the batch.4.3 Immediately after mixing the mortar, determine itsinitial cone penetration in accordance with Test Method C 780.Determine the cone penetr
20、ation of the mortar every 15 6 5minutes. If the cone penetration is less than 80 % of its initialvalue, discard the remaining portion of the mortar withoutconstructing additional mortar joints.PREPARATION AND TESTING OF BOND STRENGTHTEST SPECIMENS5. Apparatus5.1 MiscellaneousBrass-covered mortar boa
21、rd 18 in. (457mm) square, an 11-in. (279-mm) long masons trowel, labora-tory trowel with straight edges, short handled spoon or scoopof14-cup (0.5-dm3) capacity, steel straightedge 10 in. (254mm) long, metal mold12 in. (13 mm) deep with 358-in.(92-mm) square opening beveled to slope of 0.08 (total 0
22、.04),splash board (Fig. 1) with handle 20 in. (508 mm) long and 3in. (76 mm) wide.5.2 Drop Hammer for crossed-brick couplets (Fig. 2, Table1).5.3 Drop Hammer for block assemblies (Fig. 3).5.4 Loading Jigs for crossed-brick couplets (Fig. 4).5.5 Frames (Fig. 5) for testing block assemblies: upperfram
23、e fitted with ball bearing mounted 10 in. (254 mm) fromvertical axis of specimen for eccentric application of verticalload. .5.6 Torque Wrench.6. Crossed-Brick Couplets6.1 BrickTest specimens consisting of crossed-brick cou-plets may be used to determine:6.1.1 Bond between specified brick and a spec
24、ified mortar,6.1.2 Relative bond between different brick and a specifiedmortar, or6.1.3 Relative bond between a specified brick and differentmortars.6.1.4 In each case, the initial rate of absorption of the brickshall be determined in accordance with Test Methods C 67. Thebrick used for couplets sha
25、ll include the full range of absorp-tion rates acceptable under the specifications.6.2 Construction of Test Specimens:6.2.1 Center the mold on the lower brick of the couplet andlightly mix a small quantity of mortar on the board by turningover with the spoon.6.2.2 Half-fill the mold by sharply dashi
26、ng into each cornerand the center of the mold a small quantity of mortar from thehalf-filled spoon. Note the time at start of a 1-min interval.Apply additional mortar by heaping loosely with the spoonabove the top of the mold. Strike off excess mortar with thestraightedge, starting on a diagonal acr
27、oss the mold andworking first to one corner and then to the opposite corner ofthe mold. Remove the mold from the mortar bed.6.2.3 At the end of the 1-min time interval, place the upperbrick on the mortar bed in a crosswise direction to the lowerbrick. Place the frame of the hammer on the top brick w
28、ith theweight of the hammer held in the other hand. Drop the hammerin a frame a distance of 112 in. (38 mm).6.2.4 Measure and record the extrusion of the mortar on thetop surface of the lower brick. Cut away extruded mortar fromall four edges of the mortar bed.6.3 CuringPromptly enclose the test spe
29、cimen within anairtight covering. Keep covered for 7 days. Remove the coverand store until tested. Unless otherwise specified, the specimenshall be stored in laboratory air at a relative humidity of at least50 %.6.4 TestingCenter the specimen between the upper andlower tripods and place in the testi
30、ng machine as shown in Fig.6. Load the specimen at the rate of 600 lb (2.7 kN)/min or ata rate sufficient to cause failure in 1 to 2 min. Note and recordmaximum load and type of failure.NOTE 3The method of making the specimens typically produces afailure of the joint at the top of the mortar bed.FIG
31、. 1 Splash BoardC95202e12NOTE 4Reproducibility of test results may be improved by theinsertion of strips of high-density insulation board interlayers between thetest specimen and test apparatus.6.5 CalculationCalculate the maximum tensile bondstrength as follows:Tensile bond strength, T, psi or N/m2
32、! 5 A/B (1)where:A = total applied load, lbf (or N), andB = cross-sectional area in bond, in.2(or m2).7. Concrete Masonry Unit Assemblies7.1 Concrete Masonry UnitsConcrete masonry units usedin test specimens shall conform to Specification C 90 or C 129.The moisture content of the concrete masonry un
33、its shall be asspecified. In the absence of any other specified moisturecontent, the concrete masonry units shall be conditioned tohave a moisture content of between 25 % and 35 % of totalabsorption, as determined in accordance with Test MethodsC 140.7.2 Construction of Test Specimens:FIG. 2 Drop Ha
34、mmer for Cross-Brick CoupletsTABLE 1 Metric Equivalents for Figs. 2, 3, 4, 5, and 6Inch-Pound Metric Inch-Pound Metric Inch-Pound Metric1/16 in. 1.6 mm 134 in. 44 mm 5 in. 127 mm18 in. 3 mm 178 in. 48 mm 514 in. 133 mm3/16 in. 4.7 mm 2 in. 51 mm 534 in. 146 mm14 in. 6.4 mm 218 in. 54 mm 6 in. 152 mm
35、38 in. 9.5 mm 214 in. 57 mm 614 159 mm7/16 in. 11 mm 238 in. 61 mm 712 in. 190 mm12 in. 12.7 mm 212 in. 64 mm 8 in. 203 mm58 in. 15.8 mm 258 in. 67 mm 812 in. 216 mm34 in. 19 mm 3 in. 76 mm 934 in. 248 mm7/8 in. 22 mm 318 in. 79 mm 1034 in. 273 mm1 in. 25 mm 314 in. 82 mm 16 in. 406 mm118 in. 28 mm
36、312 in. 89 mm 1612 in. 419 mm1316 in. 30 mm 358 in. 92 mm 1834 in. 476 mm114 in. 32 mm 334 in. 95 mm 28 in. 711 mm138 in. 35 mm 4 in. 102 mm 2 lb 0.9 kg112 in. 38 mm 434 in. 121 mm 3.5 lb 1.6 kgC95202e137.2.1 Position the bottom concrete masonry unit of theassembly on a metal pallet with the thickes
37、t part of the faceshells upwards. Lightly turn over and remix the mortar on theboard with a masons trowel.7.2.2 With a masons trowel and technique, apply mortar tothe top of the face shell that will be in the compressive face ofthe specimen, when tested. The amount of mortar applied shallbe sufficie
38、nt to produce a bed joint of the desired thickness inthe finished specimen (Note 5). In the absence of any specifiedthickness, the bed joints in the finished specimen shall be of anominal38-in. (9.5-mm) thickness.NOTE 5The consistency of the mortar, when made, and the amount ofwater used in the mort
39、ar shall have been adjusted to meet the requirementsfor the proper joint thickness of concrete masonry unit assemblies.7.2.3 Hold the splash board along the top of the oppositeface shell (the shell that will be in the tensile face of thespecimen) and with the masons trowel lightly loaded, sharplydas
40、h a thin bed of mortar on the top of this shell as shown inFig. 7. Remove the splash board. Note the time for the start ofa 1-min interval. Load the trowel and build up the mortar bedby gently rolling or dropping a sufficient amount of additionalmortar.7.2.4 At the end of the 1-min time interval, pi
41、ck up and levelthe upper concrete masonry unit of the assembly on the mortarbeds by bringing the concrete masonry unit downward andforward to one end of the lower masonry unit. The upperconcrete masonry unit shall be placed with the thin edge of theface shells in the mortar.7.2.5 Immediately positio
42、n the drop hammer frame at thecenter of the upper masonry unit, holding the weight of thehammer in the other hand. Drop the hammer in the tubularframe a distance of 4 in. (102 mm). Remove the drop hammer.No further adjustment of the top masonry unit on its bed shallbe made.7.2.6 Measure and record t
43、he extrusion of mortar from thefaces of the specimen. Cut extruded mortar away with themasons trowel. Tool the joints with a rounded iron.7.3 CuringPromptly enclose the specimen in an airtightcovering. Keep covered for 7 days. Remove the cover and storeuntil tested. Unless otherwise specified, the s
44、pecimen shall bestored in laboratory air at a relative humidity of at least 50 %.7.4 TestingClamp the specimen in the lower and uppertest frames by tightening the screws of the test frames with atorque wrench (see Fig. 8). Center the ball bearing on the uppertest frame in the testing machine. Apply
45、a vertical load to thespecimen at the rate of 600 lbf (2.7 kN)/min or at a ratesufficient to cause failure in 1 to 2 min.FIG. 3 Drop Hammer for Concrete Block AssembliesC95202e14FIG. 4 Loading Jigs for Crossed-Brick CoupletsFIG. 5 Frames for Testing Concrete Block AssembliesC95202e15FIG. 5 Frames fo
46、r Testing Concrete Block Assemblies (continued)FIG. 6 Crossed-Brick Test Assembly Positioned in Testing MachineC95202e167.5 CalculationCalculate the maximum flexural bondstrength of the section for the gross and the net section of thespecimen, taken normal to the face shells, as follows:fg5 xPc/Ig!
47、2 P/Ag! (2)fn5 xPc/In! 2 P/An!where:fg= flexural bond stress on gross area, psi (or N/m2)fn= flexural bond stress on net area, psi (or N/m2),x = lever arm of load about vertical axis of specimen, in.(or m),P = applied load, lbf (or N),c = distance from neutral axis to face of specimen, in. (orm),Ig=
48、 moment of inertia of gross section, in.4(or m4),In= moment of inertia of net section, in.4(or m4),b = length of masonry unit, in. (or m),d = width of masonry unit, in. (or m),FIG. 7 Preparing Concrete Block Test AssemblyFIG. 8 Concrete Block Test Assembly Positioned in Testing MachineC95202e17t = m
49、inimum thickness of face shell, in. (or m),Ag= gross area of section = bd, in.2(or m2), andAn= net area of section = 2bt, in.2(or m2).8. Precision and Bias8.1 Variability is a characteristic of tensile and flexural bondstresses. Round robin testing has not been performed on thesemethods. Coefficients of variation of 15 to 35 % are common-place in published investigations using the methods of thisstandard.9. Keywords9.1 bond; concrete masonry unit; crossed brick couplet;mortar; masonrySUMMARY OF CHANGESCommittee C 12
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