1、Designation: C 862 02Standard 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 last revision. A nu
2、mber 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, casting and curing ofm
3、onolithic 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 forinformation only.1.3
4、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. It is theresponsibi
5、lity 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:C 133 Test Methods for Cold Crushing Strength and Modu-lus of Rupture of Refractories2C 192 Practi
6、ce for Making and Curing Concrete Test Speci-mens in the Laboratory33. 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 This practice standardi
7、zes 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. Apparatus and Condition
8、s4.1 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 laboratory tempera-ture an
9、d 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 mechanicalmixer4(Fig. 1) may be used for preparing castable batches forcasting specimens.
10、A 2-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 mixingbowl to contain fro
11、m 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, two or more sets, as s
12、hown 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 releasing the clamps and tap
13、ping the leftend of the front plate, thereby parting all of the separator platesand loosening the cast-test specimens.51This practice is under the jurisdiction ofASTM Committee C08 on Refractories, and is the direct responsibility of Subcommittee C08.09 on Monolithic Refracto-ries.Current edition ap
14、proved Nov 10, 2002. Published June 2003. Originallyapproved in 1977. Last previous edition approved in 2001 as C 862 01.2Annual Book of ASTM Standards, Vol 15.01.3Annual Book of ASTM Standards, Vol 04.02.4Mixers having various capacities are available from the Hobart ManufacturingCo., Troy, OH and
15、have been found to be suitable for this purpose.5A list of materials 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C7
16、00, West Conshohocken, PA 19428-2959, United States.4.4.1 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
17、 available molds from con-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
18、 Mold LubricantEither paraffin 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 ThermometerDig
19、ital or dial-type, metal, 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 dr
20、aftrather than natural 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 Tabl
21、eFor use in 6.4.2.64.15 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-hel
22、d hoe for mixing lightweight 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 t
23、he use of both trailings 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 te
24、st results.NOTE 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.5.3 The contents of the container should be thoroughlymixed dry prior to water addition. W
25、hen less than a full bag isrequired, reduce the contents of the sample container with asample splitter to obtain a representative sample of the desiredsize. Take precautions to prevent segregation.6While there is no current specification for vibration table, ASTM C08recognizes that the frequency and
26、 amplitude of the vibration 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 R
27、efractoriesC862022NOTE 3When the castable mix consists of more than one bag orMetric Equivalentsin.mm1320.818353243165146516838101213916145816111617in.mm7822131630112382126525867331681410241211492301434375NOTE 1Sizes other than 9-in. straights commonly used for physical testing are: 212 by 412 by 41
28、2 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). Dimensionsare in inches.FIG. 3 Detail Drawing for Gang MoldNOTE 1Dimensions are in inches.FIG. 4 Mixing BoxC862023container, the contents
29、should be combined and mixed thoroughly beforebeing quartered.6. Molding Test Specimens6.1 Water AdditionDetermine the 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
30、 70 and 80F (20and 27C). Report the temperature with any physical testresults. Measure the water addition to the nearest 0.1 % byweight.NOTE 4Potable water is used only if soluble constituents do not affectcastable properties significantly. However, filtered, deionized, or distilledwater is preferre
31、d and should be sufficient and used in referee tests.6.2 Mechanical MixingAdd the weighed batch to anappropriately sized 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 withi
32、n 1 min. Part of the water may be added to themixer first, if the mix is already homogenous and dry mixing isnot necessary. 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
33、speed of rotation and drum angleto provide a cascading effect. For paddle type, a paddle speed should beselected to 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 prov
34、ide adequate time forcasting sound specimens. Lightweight castables and others may requirethe full 5 min. to reach homogeneity.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
35、be a minimum of three times the largestaggregate diameter, as specified in Practice C 192. In some cases, whensmaller specimens are required and grain sizing does not allow for smallercastings, cut specimens may be used.6.3 Manual MixingManual mixing may be necessary forlightweight mixes having fria
36、ble aggregate which may bebroken by mechanical mixing. Place the weighed dry batch inthe mixing box and all of 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 opposit
37、e end, work the batch forward inthe same manner, but by hoeing slices 2 to 3 in. (51 to 76 mm)thick, frequently 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 Mold
38、ing Test Specimens6.4.1 Obtain Initial Cast LengthPrior to filling each mold,use the calipers to obtain a measurement 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
39、the 3 to 5 min. mixing has beenaccomplished, start the timer and begin filling the molds. Usea scoop for cutting 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 w
40、ith the blade turned to form an angle of 45with the side of the mold. Spade along the length and thenreverse 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
41、smooth the exposed surface with a minimumamount of troweling (Note 8). Complete the operation of fillingthe molds 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
42、8The cited procedure is applicable when filling deep molds,that is, brick molds as shown in Fig. 2 or larger. 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
43、the finger tamping to ensure consolidation ofthe material into the mold comers. Self flowing castables will not 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 wa
44、terevaporation.6.5.2 Store the molded cast specimens at a temperature from60 to 90F (15.6 to 32.2C) for 24 6 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 eno
45、ugh to permitfree air circulation to remove heat developed during hydration.A forced-draft chamber is preferred 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 AH3hydrat
46、es (abbreviatedcompounds:C=CaO,A=AL2O3,H=H20) are generally the dominantproducts of hydration in this temperature range. The hydration reactionmay cause the internal temperature to increase above the chambertemperatures, particularly with larger specimens. Useful information canbe obtained by castin
47、g thermocouples in the center of specimens so thatthe maximum temperature achieved during curing can be measured.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 strengt
48、h. Any comparison orreferee testing must call out a specific temperature 6 2F. Testing hasshown for conventional 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 spe
49、cimens 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 inless than the specified time of 24 6 0.5 h, structural damage to the testspecimens may occur.7. Test Methods7.1 Following the mold curing, remove specimens sched-uled for dried and fired properties from the mold. Measure andrecord the length of the cured s
