1、Designation: C 862 02 (Reapproved 2008)Standard Practice forPreparing Refractory Concrete Specimens by Casting1This standard is issued under the fixed designation C 862; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l
2、ast revision. A number 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.1. Scope1.1 This practice covers the mixing, cast
3、ing and curing ofmonolithic refractory concrete specimens for use in furthertesting. It does not apply to monolithic castable refractoriesintended primarily for gunning applications.1.2 The values given in inch-pound units are to be regardedas the standard. The values given in parentheses are forinf
4、ormation only.1.3 Various specimen sizes are required for specific testmethods. Refer to these test methods to determine the size andnumber of specimens, which will be required from the sample.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. I
5、t is theresponsibility of the user of this standard 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:2C 133 Test Methods for Cold Crushing Strength and Modu-lus of Rupture of Refrac
6、toriesC 192/C 192M Practice for Making and Curing ConcreteTest Specimens in the Laboratory3. Significance and Use3.1 This practice is used to standardize mixing, moldconditions, placement and curing of refractory concrete speci-mens to be used for testing and evaluation under other testmethods.3.2 T
7、his practice standardizes laboratory conditions forproducing refractory concrete specimens to minimizelaboratory-to-laboratory variation and does not attempt toduplicate the conditions of field installations.3.3 This practice can be used for the preparation of speci-mens used in referee testing.4. A
8、pparatus and Conditions4.1 Laboratory ConditionsThe laboratory ambient shouldbe controlled between 70 and 80F (20 and 27C) and from 40to 60 % relative humidity for preconditioning materials andequipment, batching and mixing casting test specimens, strip-ping molds, and testing specimens. Report labo
9、ratory tempera-ture and relative humidity with physical test results if otherthan specified.4.2 BalancesAppropriately sized scales having a sensitiv-ity of 0.2 % of the related batch size.4.3 Castable MixersAn electrically operated mechanicalmixer3(Fig. 1) may be used for preparing castable batches
10、forcasting specimens.A2-ft3(56.6-dm3) mixing bowl or a 212-ft3(70.8-dm3) concrete mixer has sufficient capacity to mix about1ft3of refractory castable. The smallest batches required forcasting 1-in. (25-mm) square bars can be mixed in a 0.10-ft3(2.83-dm3) bowl available with bench mixers. Size mixin
11、gbowl to contain from 50 to 75 % volume loading with the drybatch.NOTE 1Castable water requirement variation becomes more signifi-cant as dry volume loadings drop below 40 % because the water requiredto wet the bowl surfaces changes more rapidly with decreasing volumeloadings.4.4 Gang MoldsMetal, tw
12、o or more sets, as shown inFigs. 2 and 3, for casting specimens to the size required forspecific physical property testing (see Note 8). The front plateof the mold illustrated is held in place by quick-release clamps(50-lbf (222-N) pull exerted by each clamp) that permitemptying the mold by releasin
13、g the clamps and tapping the left1This practice is under the jurisdiction of ASTM Committee C08 onRefractories , and is the direct responsibility of Subcommittee C08.09 on Mono-lithics.Current edition approved March 1, 2008. Published March 2008. Originallyapproved in 1977. Last previous edition app
14、roved in 2002 as C 862 02.2For 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.3Mixers having various capacities a
15、re available from the Hobart ManufacturingCo., Troy, OH and have been found to be suitable for this purpose.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.end of the front plate, thereby parting all of the separator platesand loosen
16、ing the cast-test specimens.44.4.1 As an alternative design for 1 in. (25-mm) square bars,individual molds may be constructed out of 16-gage (1.588-mm) stainless-steel sheet and ganged in groups of five with alarge rubber band on a glass base-plate.4.4.2 There are commercially available molds from c
17、on-crete testing suppliers and other sources. Molds may bereusable or for single use. Molds must be water tight, rigid, andremovable.4.5 CalipersSuitable for measuring internal longitudinalmold dimensions and subsequent specimen length size to thenearest 0.01 in. (0.25 mm).4.6 Mold LubricantEither p
18、araffin or silicone-based oilscan be used as a release or parting agent for coating molds.Other mold lubricants such as vegetable oils and petroleum-based oils can be used.4.7 Strike-Off Bar20-in. (510-mm) length of steel barstock, 112 by316 in. (38 by 5 mm).4.8 ThermometerDigital or dial-type, meta
19、l, with a rangefrom 0 to 180F (18 to 80C).4.9 TimerSignal-type, for periods up to 5 min. (A stopwatch may be used.)4.10 Trowels6 in. pointing and 2 by 6 in. (51 by 152 mm)square, and a 10-in. (254-mm) stainless-steel spatula.4.11 OvenFor curing and drying, preferably forced draftrather than natural
20、convection, with a capacity to hold aminimum of one sample group of specimens (12 by 12 by 12in.) (30 by 30 by 30-mm.).4.12 Heavy Rubber GlovesFor castables containing metalfibers.4.13 ScoopFor transferring the castable from the mixer tothe mold more easily.4.14 Vibration TableFor use in 6.4.2.54.15
21、 Sample SplittersThe sample splitter opening shall bea minimum of 3 times the maximum grain size.4.16 Mixing BoxBox of suitable size and strength to handmix lightweight castable. Inside surface of box should not bewater absorbent. Fig. 4 is a possible solution.4.17 HoeHand-held hoe for mixing lightw
22、eight castable.4.18 Humidity CabinetA cabinet capable maintaining arelative humidity of greater then 95 % within 90-95F (32-35C) is optional.5. Sampling5.1 Asufficient amount of dry castable should be batched tooverfill the gang molds by at least a 10 %. This shouldeliminate the use of both trailing
23、s and scrapings of wetcastable.5.2 At the time of use, the dry sample should be between 70and 80F (20 and 27C). Measure the temperature (Note 2)byinserting the full length of the thermometer stem into thematerial until the reading is constant. Record and report withphysical test results.4A list of m
24、aterials and notes on construction of the 9-in. (230 mm) straight-brick gang molds are available at a nominal charge from the Orton RefractoryResearch Center, Westerville, Ohio.5While there is no current specification for vibration table, ASTM C08recognizes that the frequency and amplitude of the vi
25、bration table can affect thedegree of consolidation of the sample. Current practice is to use an electric vibrationtable, which at least has a generally fixed frequency by the electric motor and theACcurrent.FIG. 1 Five Quart Hobart MixerFIG. 2 Five-Brick Gang Mold for Castable RefractoriesC 862 02
26、(2008)2NOTE 2It is recommended that in referee tests involving more thanone laboratory, the temperature of the dry refractory concrete mix andmixing water be within the specified range, in all laboratories.Metric Equivalentsin.mm1320.818353243165146516838101213916145816111617in.mm7822131630112382126
27、525867331681410241211492301434375NOTE 1Sizes other than 9-in. straights commonly used for physical testing are: 212 by 412 by 412 in.(65by114by114mm);2by2by7or9in. (51 by 51 by 178 or 230 mm); 112 by 112 by 412 in. (38 by 38 by 114 mm); or 1 by 1 by 6 or 7 in. (25 by 25 by 152 or 178 mm). Dimensions
28、are in inches.FIG. 3 Detail Drawing for Gang MoldNOTE 1Dimensions are in inches.FIG. 4 Mixing BoxC 862 02 (2008)35.3 The contents of the container should be thoroughlymixed dry prior to water addition. When less than a full bag isrequired, reduce the contents of the sample container with asample spl
29、itter to obtain a representative sample of the desiredsize. Take precautions to prevent segregation.NOTE 3When the castable mix consists of more than one bag orcontainer, the contents should be combined and mixed thoroughly beforebeing quartered.6. Molding Test Specimens6.1 Water AdditionDetermine t
30、he amount of water to beused in the mix for casting test specimens in accordance withthe manufacturers or referees recommendations. Use potablewater (Note 4) having temperature between 70 and 80F (20and 27C). Report the temperature with any physical testresults. Measure the water addition to the nea
31、rest 0.1 % byweight.NOTE 4Potable water is used only if soluble constituents do not affectcastable properties significantly. However, filtered, deionized, or distilledwater is preferred and should be sufficient and used in referee tests.6.2 Mechanical MixingAdd the weighed batch to anappropriately s
32、ized drum or paddle castable mixer (4.3). If drybatch has not been pre-mixed, dry mix for 1 min at slow speed.Operate the mixer at slow speed and add the required water tothe mix within 1 min. Part of the water may be added to themixer first, if the mix is already homogenous and dry mixing isnot nec
33、essary. Continue to mix at slow speed for a total time of3 to 5 min after water addition (Notes 5 and 6) or according tomanufacturers recommendations.NOTE 5For drum mixers, select the speed of rotation and drum angleto provide a cascading effect. For paddle type, a paddle speed should beselected to
34、provide good mix agitation without throwing the batch out ofthe mixing zone.NOTE 6Batches should be homogeneous after mixing. Fast-settingmixes are normally mixed within 3 min. to provide adequate time forcasting sound specimens. Lightweight castables and others may requirethe full 5 min. to reach h
35、omogeneity.NOTE 7Although brick sized shapes may be cut with a diamond sawto obtain a specific size, it is preferable to fabricate the desired shape. Thesmallest mold dimension should be a minimum of three times the largestaggregate diameter, as specified in Practice C 192/C 192M. In some cases,when
36、 smaller specimens are required and grain sizing does not allow forsmaller castings, cut specimens may be used.6.3 Manual MixingManual mixing may be necessary forlightweight mixes having friable aggregate which may bebroken by mechanical mixing. Place the weighed dry batch inthe mixing box and all o
37、f the required water. Mix by cuttinginto the material with the hoe, pulling it upward and forward,and continue until all the batch is piled at the end of the box.Then, standing at the opposite end, work the batch forward inthe same manner, but by hoeing slices 2 to 3 in. (51 to 76 mm)thick, frequent
38、ly pressing the mix with the back of the hoe.Continue the mixing in a rapid and intensive manner until thebatch is homogeneous in appearance, but for a period notexceeding 3 to 5 min.6.4 Molding Test Specimens6.4.1 Obtain Initial Cast LengthPrior to filling each mold,use the calipers to obtain a mea
39、surement of the internal lengthto the nearest 0.01 in. (0.3 mm). Record this value to providethe basis for determining linear change of cured, dried, andfired specimens.6.4.2 Fill MoldsAfter the 3 to 5 min. mixing has beenaccomplished, start the timer and begin filling the molds. Usea scoop for cutt
40、ing into the batch to get a good section and halffill the mold cavity. Consolidate the material in the molds byspading at close intervals with a square trowel or spatula heldvertically, and with the blade turned to form an angle of 45with the side of the mold. Spade along the length and thenreverse
41、the 45 angle for the next pass along the mold. Fill themolds with an excess of the mix and repeat the trowel spading.Use the strike-off bar with a sawing motion to remove theexcess mix, then smooth the exposed surface with a minimumamount of troweling (Note 8). Complete the operation of fillingthe m
42、olds within 5 min. or at a rate of 1 min. per test specimen.Mechanical vibration should not be used unless specified bythe manufacturer. Vibrate at a consistent amplitude and fre-quency.NOTE 8The cited procedure is applicable when filling deep molds,that is, brick molds as shown in Fig. 2 or larger.
43、 Hand placement of thecastable can be used to fill and consolidate the material in shallow molds(normally 2 in. (50 mm) deep or less). Appropriate spading with thespatula should be used with the finger tamping to ensure consolidation ofthe material into the mold comers. Self flowing castables will n
44、ot requirespading, but will simply be poured into place.6.5 Curing Test Specimens6.5.1 Immediately after forming test specimens, enclose orcover them with an impervious membrane to prevent waterevaporation.6.5.2 Store the molded cast specimens at a temperature from60 to 90F (15.6 to 32.2C) for 24 6
45、0.5 h (Notes 9 and 10).Use of an impervious membrane is not required if a humiditycabinet capable of maintaining a relative humidity of 95 % orgreater is used. The chamber should be large enough to permitfree air circulation to remove heat developed during hydration.A forced-draft chamber is preferr
46、ed to natural convection forcirculation and a volume of free space equal to that of thespecimens and mold being tested should be considered mini-mal.NOTE 9The CAH10,C2AH8,C3AH6, and AH3hydrates (abbreviatedcompounds:C=CaO,A=AL2O3,H=H20) are generally the dominantproducts of hydration in this tempera
47、ture range. The hydration reactionmay cause the internal temperature to increase above the chambertemperatures, particularly with larger specimens. Useful information canbe obtained by casting thermocouples in the center of specimens so thatthe maximum temperature achieved during curing can be measu
48、red.NOTE 10The hydrate composition of the specimen will depend on thecuring temperature. For this reason, the curing temperature is a determin-ing variable in the development of green strength. Any comparison orreferee testing must call out a specific temperature 6 2F. Testing hasshown for conventio
49、nal castables that the highest fired strengths areachievable when curing at 90-95F (32.2 to 35.0C). A current commonpractice in industry is to cure at 66-70F (18.9 to 21.1 C).6.5.3 Remove specimens to be tested for cured propertiesfrom the chamber and evaluate upon removing the molds, orreturn to the curing chamber until tested, but for no longer than24.5 h total curing time.NOTE 11Caution: If test specimens are removed from the molds inC 862 02 (2008)4less than the specified time of 24 6 0.5 h,
