1、Designation: C903 151Standard Practice forPreparing Refractory Specimens by Cold Gunning1This standard is issued under the fixed designation C903; 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 () indicates an editorial change since the last revision or reapproval.1NOTEEditorial changes were made throughout in April 2016.1. Scope1.1 This practice covers a procedure for preparing refractoryspecimens usually containin
3、g calcium aluminate cement withor without metal fibers by cold nozzle-mix gunning. Specimensprepared in accordance with this practice are intended for usein standard ASTM test methods required for evaluating gunnedmaterials.1.2 The values stated in inch-pound units are to be regardedas standard. The
4、 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 standard to
5、 establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C401 Classification of Alumina and Alumina-SilicateCastable RefractoriesC865 Practice for Firing Refractory Concrete Specimens3. Sign
6、ificance and Use3.1 The properties of refractories can be affected by theirmethod of installation. This practice attempts to minimize thevariables encountered during installation by pneumatic gun-ning.3.2 This practice provides parameters to produce gunnedspecimens for use in other ASTM test methods
7、.3.3 This practice may be used to produce specimens foracceptance testing, service evaluation, manufacturing control,and research and development.3.4 Differences between various kinds of equipment and thedifferences in procedures and operator techniques may result insignificant variations in the phy
8、sical properties of the gunnedspecimens. It is recommended that the same operator use thesame equipment to produce specimens for referee testingagreed to by the involved testing parties. The specific operatingparameters should be shown in the report.3.5 Although this practice is specifically designe
9、d for re-fractories containing calcium aluminate cement, it may be usedwith minor modifications for gun mixes containing other bondsystems.4. Apparatus4.1 Gun, pneumatic nozzle-mix. At least 50 ft (15.2 m) ofhose should be available. Acceptable nozzle diameters rangefrom 1 to 2 in. (25 to 51 mm).4.2
10、 Air Compressor, capable of delivering sufficient pres-sure and volume to adequately move refractory to the gun. Thecompressor should be able to supply at least 250 ft3(7 m3)/min.4.3 Forms, suitable nonabsorbent type, which will vary insize in accordance with the number and size of samples beingprep
11、ared, but are at minimum 12 by 12 by 4 in. (305 by 305 by100 mm). Forms should be sized to prevent rebound entrap-ment. The use of12 inch hardware cloth as sidewalls of theform allows most of the rebound to pass through.5. Procedure5.1 Store the refractory to be gunned at 70 to 85F (20 to27C) for 24
12、 h prior to gunning.5.2 Place the form against a rigid surface at an angle of 80to 90 to the horizontal.5.3 If recommended by the supplier, predampen the refrac-tory by mixing with potable water in a paddle mixer for 1 to 5min or follow manufacturers specific instructions. In general,regular (dense)
13、 refractories require 2 to 4 % of predampeningwater and lightweight (insulating) refractories require 5 to 8 %.NOTE 1Refractories that contain a high-purity cement may benefit by1This practice is under the jurisdiction ofASTM Committee C08 on Refractoriesand is the direct responsibility of Subcommit
14、tee C08.09 on Monolithics.Current edition approved Oct. 1, 2015. Published December 2015. Originallyapproved in 1979. Last previous edition approved in 2010 as C903 10. DOI:10.1520/C0903-15E01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at se
15、rviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1aging for 5 to 10 min after dampening before gunning.
16、This “agingprocedure should be used if gunning without it produces excessiverebound, dusting, or slumping.NOTE 2Treat refractories containing metal fibers in a normal manner.If metal fibers are to be added to the gunning material, add them to thepaddle mixer before any water is introduced. The amoun
17、t of fiber to beadded and the methods of reporting this amount shall be agreed upon bythe parties involved. To prevent clumping of the fibers they should beadded slowly through a suitable screen of12 in. mesh. Fibers larger than1 in. may require larger openings. If any predampening water is to beadd
18、ed, dry mix for two to three min before adding water.5.4 Gun the refractory into the form at a distance of 3 to 4ft (0.91 to 1.2 m) from gun nozzle. Hold the gun nozzle at 90to the form. Gunning pressures are suggested to be approxi-mately 40 psi (276 kPa) for regular-weight refractories andapproxim
19、ately 20 psi (138 kPa) for insulating refractories. Ifmore than 50 ft (15 m) of hose is used, it may be necessary toadd 5 psi (34 kPa) for each additional 50 ft. These conditionsand the amount of potable water used must be adjusted by thenozzleman for acceptable rebound. The gunning pattern in-volve
20、s moving the nozzle in a circular motion, back and forthacross the form, beginning at the bottom. Report any unusualdusting, slumping, or other unique characteristics of therefractory. The water, material, and environment temperatureshall also be reported.NOTE 3For referee tests all participating la
21、boratories should agree ona specific gun pressure and other test parameters to obtain reproducibleresults. Excessive air pressures and hose lengths may cause changes inproperties of the gunned refractory especially in properties of gunnedinsulating refractories.5.5 Trim the gunned surface approximat
22、ely parallel to theback of the form. See Practice C865 for procedures concerningthe measurement of specimens.5.6 Follow the recommended manufacturers curing instruc-tions. For calcium aluminate bonds, optimum curing tempera-ture is 90 to 95F (32 to 35C) for 24 + 0.5 h.5.7 Cut suitably sized laminati
23、on-free specimens from thecentral section. If excessive tearout of refractory grain occurswhile cutting, it may be necessary to dry the panel first beforecutting (ex. Low Cement Gun Mix). Cut specimen to excludethe portion nearest the backboard to eliminate trapped rebound.Identify the gunned face o
24、r gunning direction on each speci-men since it may influence the results of subsequent tests.5.8 Specimens prepared according to section 5.7 that will beused for further testing shall be placed in a 150F oven; holduntil all specimens have been inserted. Increase temperature ata rate of 50F/h (28C/h)
25、 maximum from 150F to between220 to 230F (105 to 100C) and hold for at least 15 h prior totesting or firing in a prescribed manner.5.9 Determine specific properties by selected test proce-dures.6. Report6.1 Report the following information:6.1.1 Specific predampening water content and type ofmixer,6
26、.1.2 Premix time,6.1.3 Temperature of the water, refractory, and environment,6.1.4 Aging time (if any),6.1.5 Type of gun, length and diameter of hose,6.1.6 Gunning pressure employed,6.1.7 Nozzle size and type,6.1.8 Size and type of form used,6.1.9 Type and amount (by weight or volume) of any metalfi
27、bers added prior to gunning, and6.1.10 Curing time, temperature and environment.6.2 The report may also specify the amount of rebound andany unusual gunning characteristics observed.6.3 The report may include any other parameters agreed toby the parties involved.7. Keywords7.1 gunning; predampening;
28、 rebound; specimensASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement
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