1、Designation: C1552 14aStandard Practice forCapping Concrete Masonry Units, Related Units andMasonry Prisms for Compression Testing1This standard is issued under the fixed designation C1552; the number immediately following the designation indicates the year oforiginal adoption or, in the case of rev
2、ision, 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. Scope*1.1 This practice covers apparatus, materials, and proce-dures for capping concrete masonry units, rel
3、ated units, includ-ing coupons or other specimens obtained from such units, andmasonry prisms for compression testing.NOTE 1The testing laboratory performing these test methods shouldbe evaluated in accordance with Practice C1093.1.2 The values stated in inch-pound units are to be regardedas standar
4、d. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.3 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 stand
5、ard 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:2C140 Test Methods for Sampling and Testing ConcreteMasonry Units and Related UnitsC617 Practice for Capping Cylindrical Concret
6、e SpecimensC1093 Practice for Accreditation of Testing Agencies forMasonryC1232 Terminology of MasonryC1314 Test Method for Compressive Strength of MasonryPrisms3. Terminology3.1 Terminology defined in Terminology C1232 shall applyfor this practice.4. Significance and Use4.1 This practice describes
7、procedures for providing planesurfaces on the two bearing surfaces of units and prisms. Thepurpose of this standard is to provide consistent and standard-ized procedures for capping units and prisms for compressiontesting. The procedures are based on those contained (orpreviously contained) in Test
8、Methods C140, Practice C617,and Test Method C1314.NOTE 2Specimens capped using this practice will vary significantly insize and weight. Appropriate care and handling may differ based onspecimen size and weight. Provide care and handling as needed to providefor proper capping based on the physical ch
9、aracteristics of the specimenbeing capped.5. Apparatus5.1 Capping PlateIf used, the capping plate shall be madeof steel having a thickness of not less than 1 in. (25.4 mm), ora polished plate of granite or diabase at least 3 in. (76 mm)thick. The capping surface shall be plane within 0.002 in. in12
10、in. (0.05 mm in 300 mm) and shall be free of gouges,grooves, and indentations greater than 0.010 in. (0.25 mm)deep or greater than 0.05 in.2(32 mm2) in surface area. At thetime of capping, the capping surface shall be level within116in. (1.6 mm) over the length of the plate.5.1.1 Capping Wear PlateI
11、f used, the capping wear plateshall be placed directly on top of the capping plate and shallmeet the requirements of 5.2. At the time of capping, the wearplate surface shall be level within116 in. (1.6 mm) over thelength of the plate. Do not use a capping wear plate with sulfurcapping materials.NOTE
12、 3A capping wear plate has been found to reduce the potentialof damage to the capping plate. The capping wear plate is typically moreresistant to scratches and can be replaced at less cost than that required toresurface the capping plate. See Fig. 1 for a schematic of capping setupwhen using gypsum
13、cement materials.5.2 Casting PlateIf used, the casting plate shall be oftransparent glass with a thickness of not less than12 in. (13mm). The casting plate shall be plane within 0.002 in. in 12 in.(0.05 mm in 300 mm).6. Materials6.1 Capping Materials:6.1.1 High Strength Gypsum Cement Capping Materia
14、ls:1This practice is under the jurisdiction of ASTM Committee C15 on Manufac-tured Masonry Units and is the direct responsibility of Subcommittee C15.04 onResearch.Current edition approved Dec. 1, 2014. Published December 2014. Originallyapproved in 2002. Last previous edition approved in 2014 as C1
15、552 14. DOI:10.1520/C1552-14A.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.*A Summary of Changes section a
16、ppears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States16.1.1.1 In addition to the compressive strength testing re-quired in 6.2, qualification tests shall be made to determine theeffects of water-cement rati
17、o and age on compressive strength.Procedures used for preparing the high strength gypsumcement capping materials shall ensure that water-cement ratiosused for each batch provide the required strength.NOTE 4The water-gypsum cement ratio should typically be between0.26 and 0.30. Use of low water-gypsu
18、m cement ratios and vigorousmixing will usually permit development of 3500 psi (24.1 MPa) at ages ofone or two hours. Higher water-gypsum cement ratios extend workingtime, but reduce strength.6.1.1.2 Do not add fillers or extenders to the high strengthgypsum cement.NOTE 5Retarders extend working tim
19、e for capping materials but theireffects on required water-cement ratio should be determined prior to use.NOTE 6See Appendix X1 for more information on high-strengthgypsum capping materials and product recommendations.6.1.2 Sulfur Capping Materials:6.1.2.1 Proprietary or laboratory prepared sulfur m
20、ixturesshall contain 40 to 60 % sulfur by weight, the remainder beingground fire clay or other suitable inert material passing a No.100 (150-m) sieve with or without a plasticizer.6.1.3 Use only capping materials identified in 6.1.1 and6.1.2. Do not use other capping materials.NOTE 7Examples of mate
21、rials that have been found to be unsuitablefor capping purposes include, but are not limited to: low-strength moldingplaster, plaster of paris, mixtures of plaster of paris and portland cement,and other cement-based materials.6.2 Compressive Strength of Capping MaterialsThe com-pressive strength of
22、the capping material shall be at least3500 psi (24.1 MPa) at an age of 2 h. The cube molds andmethods of preparing and testing the cubes shall be inaccordance with Practice C617. The capping material shall beplaced in the cube at capping consistency. Store the filledmolds in laboratory air. Remove c
23、ubes of sulfur material aftersolidification is complete and remove cubes of gypsum cementmaterial from the molds not more than 15 min prior to testing.Test cubes at an age of 2 h 6 10 min after completing thefilling of the molds.6.2.1 The strength of the capping material shall be deter-mined on rece
24、ipt of a new lot and at intervals not exceedingthree months. If a given test of the capping material fails toconform to the strength requirements, the package from whichthe material was sampled shall not be used unless twoadditional subsequent samples are taken from the same pack-age and both of the
25、se subsequent samples conform to thestrength requirements. If the strength tests from an individualpackage are inadequate, randomly obtain and test three addi-tional samples from the lot. These additional samples shall betaken from separate packages, if available. Unless these threesamples conform t
26、o the strength requirements, no part of the lotshall be used.7. Procedure7.1 Preparation of Specimens for CappingUse an abrasivestone to remove loose protrusions from the surfaces of thespecimens to be capped. Refer to the appropriate compressiontest method (Test Methods C140 or Test Method C1314) f
27、orother specimen preparation requirements.7.2 Capping Test SpecimensCap top and bottom bearingsurfaces of specimens by one of the methods in 7.2.1 or 7.2.2.Use alignment devices as needed to make sure the caps meetthe requirements of 7.4.NOTE 8Various alignment devices have been demonstrated to beef
28、fective. For capping with sulfur materials, which sets quickly, alignmentjigs make sure that the specimen is placed on the capping plate correctlyin the first motion. For capping with gypsum cement materials, levelsplaced across the top of specimen have proven to work well. Bullseyelevels work parti
29、cularly well with smaller specimens.7.2.1 Capping Using Gypsum Cement MaterialsSeeFig. 1 for capping setup. Spread the gypsum cement cappingmaterial evenly on the capping plate or capping wear plate thatFIG. 1 Gypsum Capping SchematicC1552 14a2has been lightly coated with oil or sprayed with a TFE-f
30、luorocarbon coating (Note 9). Bring the surface of the speci-men to be capped into contact with the capping material; firmlypress down the specimen with a single motion, holding it sothat its axis is at right angles to the capping surface to complywith the requirements of 7.4. Do not disturb the spe
31、cimen untilthe capping material has solidified.7.2.1.1 Alternative Capping Method Using Gypsum CementMaterialsSee Fig. 1 for capping setup. Spread the gypsumcement capping material evenly on the top surface of thespecimen. Bring the casting plate, which has been lightlycoated with oil or sprayed wit
32、h TFE-fluorocarbon coating(Note 9), into contact with the capping paste; firmly pressdown the plate with a single motion holding it so it is at rightangles to the specimen. Within 30 s, lightly adjust the plate toachieve a resulting cap that will comply with the requirementsof 7.4. Do not further di
33、sturb the specimen or casting plate untilthe capping material has solidified.NOTE 9The use of oil or TFE-fluorocarbon coatings on capping orcasting plates is not necessary if it is found that the plate and specimen canbe separated without damaging the cap.NOTE 10Generally, specimens can be removed f
34、rom capping orcasting plates after 30 min without damaging the cap. However, the lengthof time to assure setting of the cap will vary depending on a variety offactors such as the water-gypsum cement ratio used, environmentalconditions, the properties of the specimen being capped, and the tempera-tur
35、e of the mix water.7.2.2 Capping Using Sulfur Capping Materials:7.2.2.1 (WarningHydrogen sulfide gas is often producedduring capping when sulfur capping material is contaminatedwith organic materials such as paraffin or oil. The gas iscolorless and has a notoriously bad odor of rotten eggs;however,
36、the odor is not a reliable warning sign, since thesensitivity to the odor disappears rapidly on exposure. Highconcentrations are lethal and less concentrated dosages mayproduce nausea, stomach distress, dizziness, headache, orirritation of the eyes. For this and other safety reasons, locatethe cappi
37、ng station in a well-ventilated area and the melting potunder a hood with an exhaust fan.)7.2.2.2 (WarningSulfur capping materials are used in ahot, molten state. Adequate protection is required to preventcontact with eyes, hands and other parts of the body.)7.2.2.3 Heat the sulfur mixture in a ther
38、mostatically con-trolled heating pot to a temperature of 265 to 290F (129 to143C) to maintain fluidity after contact with the cappingsurface. Verify sulfur capping material temperature using anall-metal thermometer placed at the center of the mass. Verifytemperature at hourly intervals during cappin
39、g operations.7.2.2.4 Empty the pot and recharge with fresh materialsperiodically to ensure that the oldest material in the pot has notbeen used more than five times. Fresh sulfur capping materialshall be dry at the time it is placed in the pot as dampness maycause foaming. Keep water away from the m
40、olten sulfurcapping material for the same reason.7.2.2.5 Warm the capping plate before use to slow the rateof hardening of the molten sulfur capping material and topermit the production of thin caps. Lightly oil the surface of thecapping plate (Note 9) and stir the molten sulfur cappingmaterial imme
41、diately prior to pouring each cap.7.2.2.6 Form a rectangular mold on the capping plate whosedimensions are approximately12 in. (13 mm) greater than theoverall dimensions of the specimen. The mold must besufficiently rigid to not move or deflect during the cappingoperation, and large enough to accomm
42、odate the specimen tobe capped and the sulfur capping material without overflow.(See Note 11.) Fill the mold to a depth of14 in. (6 mm) withthe hot sulfur compound. Bring the surface of the specimen tobe capped quickly into contact with the liquid, holding thespecimen so that its axis is at right an
43、gles to the surface of thecapping liquid to achieve a resulting cap that will comply withthe requirements of 7.4.NOTE 11The use of four 1-in. square steel bars has been found to beadequate for forming this capping mold.7.2.2.7 Do not disturb the specimen until the sulfur com-pound has solidified and
44、 cooled.7.3 Once the caps have solidified and, in the case of sulfurcapping materials, cooled, separate the specimen from thecapping or casting plates in such manner as to prevent damageto the caps and specimens.7.4 Caps shall be perpendicular within 0.08 in. in 8 in.(2 mm in 200 mm) to the vertical
45、 axis of the specimen. Forspecimens up to 12 in. in length, the surfaces of the caps shallbe plane within 0.002 in. in 12 in. (0.05 mm in 300 mm). Forspecimens greater than 12 in. in length, the surfaces of the capsshall be in plane within 0.002 in. in any 12 in. (0.05 mm in300 mm) span.7.5 The aver
46、age thickness of the cap shall not exceed18 in.(3 mm).7.6 Do not patch caps. Remove imperfect caps and replacewith new ones. Do not test the specimens until the cap hasachieved the desired strength based on qualification testing.Cap age shall be at least two hours.7.7 Capping Verifications:7.7.1 Dur
47、ing each day of capping operations, verify theplaneness of both caps prior to compression testing on at leastone randomly selected specimen. Verify by making a minimumof four measurements in two different orientations on each capto ensure that the surface of the caps do not depart from a planeby mor
48、e than 0.002 in. in 12 in. (0.05 mm in 300 mm).7.7.2 During each day of capping operations, verify theperpendicularity of both caps prior to compression testing on atleast one randomly selected specimen. Verify by making aminimum of one check against each face for both caps toensure that the caps ar
49、e perpendicular within 0.08 in. in 8 in.(2 mm in 200 mm).7.7.3 Record the results of these verifications in the qualitycontrol documentation of the laboratory. At a minimum, therecords shall include date(s) of verifications, person(s) per-forming the verifications, and whether or not the caps complywith the planeness and perpendicularity requirements.NOTE 12One method of verifying planeness is with a straightedge andfeeler gauge. The straightedge is placed on the cap of the unit, and a checkis made to see if the feeler gauge can fit between the cap and
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