1、Designation: C 490/C 490M 08Standard Practice forUse of Apparatus for the Determination of Length Change ofHardened Cement Paste, Mortar, and Concrete1This standard is issued under the fixed designation C 490/C 490M; the number immediately following the designation indicates the yearof original adop
2、tion or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This practice covers the requirements for the apparatusand equipment us
3、ed to prepare specimens for the determinationof length change in hardened cement paste, mortar, andconcrete, the apparatus and equipment used for the determina-tion of these length changes, and the procedures for its use.1.2 Methods for the preparation and curing of test speci-mens, conditions of te
4、sting and curing, and detailed proceduresfor calculating and reporting test results are contained inapplicable test methods.1.3 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore,
5、eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.2. Referenced Documents2.1 ASTM Standards:2C511 Specification for Mixing Rooms, Moist Cabinets,Moist Rooms, and Water Storage Tanks Used in theTesting of Hydraulic
6、 Cements and ConcretesC 1005 Specification for Reference Masses and Devices forDetermining Mass and Volume for Use in the PhysicalTesting of Hydraulic Cements3. Terminology3.1 length changean increase or decrease in the lineardimension of a test specimen, measured along the longitudinalaxis, due to
7、causes other than applied load.4. Significance and Use4.1 This practice is intended to provide standard require-ments for apparatus common to many test methods used inconnection with cement and concrete and standardized proce-dures for its use. The detailed requirements as to materials,mixtures, spe
8、cimens, conditioning of specimens, number ofspecimens, ages at which measurements are to be made,interpretation of results, and precision and bias are left to bedealt with in specific test methods.5. Apparatus5.1 Reference Masses and Devices for Determining Massand Volume, shall conform to the requi
9、rements of SpecificationC 1005.5.2 Molds, shall have either one or two compartments andshall be constructed as shown in Fig. 1 or Fig. 2. Molds for testspecimens used in determining the length change of cementpastes and mortars shall provide for 25 by 25 by 285-mmprisms having a 250-mm gauge length,
10、 or for 1 by 1 by 1114in. prisms having a 10in. gauge length. Molds for testspecimens used in the length change of concretes shall providefor prisms of the desired cross section having a 10-in. or250-mm gauge length. In some routine tests, 25 by 25 by160-mm specimens with a gauge length of 125 mm, o
11、r 1 by 1by 614 in. specimens with a gauge length of 5-in. arepermitted, but in case of dispute, results obtained with speci-mens of 250-mm 10-in. gauge length shall govern.5.2.1 The gauge length shall be considered as the nominallength between the innermost ends of the gauge studs. Theparts of the m
12、olds shall be tight fitting and firmly held togetherwhen assembled, and their surfaces shall be smooth and free ofpits. The molds shall be made of steel or other hard metal notreadily attacked by the cement paste, mortar, or concrete. Thesides of the molds shall be sufficiently rigid to preventsprea
13、ding or warping. For the molds shown in Fig. 1, thetolerance on dimension A is 60.7 mm. For the molds shown inFig. 2, the tolerance on dimension A is 60.03 in.5.2.2 Each end plate of the mold shall be equipped to holdproperly in place, during the setting period, one of the gaugestuds shown in Fig. 1
14、 or Fig. 2. The gauge studs shall be ofAmerican Iron and Steel Institute (AISI)3Type 316 stainlesssteel or other corrosion-resistant metal of similar hardness.Gauge studs of Invar or similar metal shall be used when1This practice is under the jurisdiction ofASTM Committee C01 on Cement andis the dir
15、ect responsibility of Subcommittee C01.95 on Coordination of Standards.Current edition approved June 1, 2008. Published July 2008. Originally approvedin 1962. Last previous edition approved in 2007 as C 490 07.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Custo
16、mer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Details on this material are available from American Iron and Steel Institute(AISI), 1140 Connecticut Ave., NW, Suite 705, Washington, DC 20036, http:
17、/www.steel.org.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.specimens are tested at widely different temperatures. Toprevent restraint of the gauge studs before dem
18、olding of thespecimen, the device for holding the gauge studs in positionshall be so arranged that, if necessary, it can be partially orcompletely released after the compaction of the paste or mortarinto place in the mold. The gauge studs shall be set so that theirprincipal axes coincide with the pr
19、incipal axis of the testspecimen. For the molds shown in Fig. 1, gauge studs shallextend into the specimen 17.5 6 0.5 mm and the distancebetween the inner ends of the gauge studs shall be 250.0 6 2.5mm and 250 mm shall be considered the gauge length forcalculating length change. For the molds shown
20、in Fig. 2,gauge studs shall extend into the specimen 0.625 6 0.025 in.and the distance between the inner ends of the gauge studs shallbe 10.00 6 0.10 in. and 10 in. shall be considered the gaugelength for calculating length change.5.3 Length Comparator, for determining length change ofspecimens, sha
21、ll be designed to accommodate the size ofspecimen employed and to provide or permit a positive meansof contact with the gauge studs and the convenient and rapidobtaining of comparator readings (Note 1).5.3.1 The comparator for determining length changes ofspecimens produced in the molds shown in Fig
22、. 1 shall providea dial micrometer or other measuring device graduated to readin 0.002-mm units or less, accurate within 0.002 mm in any0.020-mm range, and within 0.004 mm in any 0.200-mmrange, and sufficient range (at least 8.0 mm) in the measuringdevice to allow for small variations in the actual
23、length ofvarious specimens. The terminals of the comparator shall beplane, polished and heat-treated. They shall be fitted withcollars held in place with set screws. The collars shall extend1.5 6 0.1 mm beyond the plane face of the terminal. Thecollars shall allow free rotation of the gauge stud tip
24、s that fitinside the collars and have an inside diameter no more than 0.5mm larger than the average diameter of that portion of thegauge stud tips that fit into the collars.NOTEDimension A to be specified by the purchaser.FIG. 1 Molds (SI Units)C 490/C 490M 082NOTE 1One type of instrument that has b
25、een found satisfactory foruse with small prisms is shown in Fig. 3. A horizontal comparator shouldbe used with prisms with a cross section greater than 9 in.2or 58 cm2.5.3.2 The comparator for determining length changes ofspecimens produced in the molds shown in Fig. 2 shall providea dial micrometer
26、 or other measuring device graduated to readin 0.0001-in. units, accurate within 0.0001 in. in any 0.0010-in.range, and within 0.0002 in. in any 0.0100-in. range, andsufficient range (at least 0.3 in.) in the measuring device toallow for small variations in the actual length of variousspecimens. The
27、 terminals of the comparator shall be plane,polished and heat-treated. They shall be fitted with collars heldin place with set screws. The collars shall extend 0.062 60.003 in. beyond the plane face of the terminal. The collarsshall allow free rotation of the gauge stud tips that fit inside thecolla
28、rs and have an inside diameter no more than 0.02 in. largerthan the average diameter of that portion of the gauge stud tipsthat fit into the collars.5.3.3 The design shall provide a means for checking themeasuring device against a reference bar at regular intervals.The reference bar shall have an ov
29、erall length of 295 6 3.0 mmor 170 6 3.0 mm 1158 618 in. or 658 618 in., whicheveris appropriate for the specimen in use. The bar shall be of asteel alloy having a coefficient of thermal expansion not greaterthan two millionths per degree Celsius. Each end of thereference bar shall be fitted with he
30、at treated, hardened, andpolished tips machined to the same shape as the contact end ofthe gauge studs used in test specimens. Except for the tips,which are attached after heat treatment, no part of the referencebar shall be heat treated. The central 100 mm 4 in. of thelength of the reference bar sh
31、all be covered by a rubber tubewith a wall at least 3 mm 18 in. thick to minimize the effectof temperature change during handling. The reference bar shallbe provided near one end with a positioning mark.NOTE 2Alloys such as invar lose their low coefficient of thermalexpansion properties when heat tr
32、eated.5.4 Check and document the bar mold dimensions, gaugestud projection into the mold interior, length comparator, andlength measuring device for conformance to the design anddimensional requirements of this specification at least every212 years.FIG. 2 Molds (Inch-Pound Units)C 490/C 490M 0836. P
33、rocedure6.1 Preparation of MoldsPrior to the molding of speci-mens, the outside joints of the mold and the contact lines of themold and base plate shall be sealed to prevent loss of mixingwater from a freshly molded specimen. Thinly cover theinterior surfaces of the mold with mineral oil. After this
34、operation, set the gauge studs, taking care to keep them clean,and free of oil, grease, and foreign matter.6.2 Use of Reference BarPlace the reference bar in theinstrument in the same position each time a comparator readingis taken. Check the dial gauge setting of the measuring deviceby use of the r
35、eference bar at least at the beginning and end ofthe readings made within a half day when the apparatus is keptin a room maintained at constant temperature. Check it moreoften when kept in a room where the temperature is notconstant.NOTE 3The equation given in the section on calculation of lengthcha
36、nge contemplates that a comparator reading for the reference bar willbe recorded each time the reference bar is used and a difference calculatedfor each test specimen reading. Alternatively, the dial gauge setting can bereset, if necessary, to its original setting with the reference bar in placeeach
37、 time the reference bar is read. Doing so simplifies the calculation oflength change by canceling the comparator reading of the reference barfrom the values of Lxand Li. If this procedure is used, care should be takento ensure that the dial set screw is tightened adequately each time the dialis rese
38、t.6.3 Obtaining Comparator ReadingsRotate specimensslowly in the measuring instrument while the comparatorreading is being taken. Record the minimum reading of the dialif the rotation causes a change in the dial reading. Placespecimens in the instrument with the same end up each time acomparator rea
39、ding is taken.6.3.1 Obtaining Comparator Readings of Specimens StoredMoistClean the hole in the base of the comparator into whichthe gauge stud on the lower end of the bar fits (this hole tendsto collect water and sand and should be cleaned after everyreading). Read and record the comparator indicat
40、ion of thelength of the reference bar. Take one bar out of immersion, blotthe pins, put the bar in the comparator, read, and record theindication. Return the bar to immersion and clean the hole inthe base of the comparator. Take out the second bar and treat itin a like manner. Return the second bar
41、to immersion, recordthe reading, and clean the hole in the base of the comparator.Continue the procedure until all bars have been read, returnedto immersion, and the readings recorded, cleaning the hole inthe bottom of the comparator each time. After reading the lastbar, clean the hole in the compar
42、ator base and read and recordthe reference-bar indication. Blot only around the pins (Note4).NOTE 4The purpose of the minimal blotting of the pins and noblotting of the bars is to avoid drying and shrinkage of the bars. It has beenobserved that if the pins are blotted, and the bar placed in the comp
43、aratorand the dial read, and the bar is then wiped gently with a dry cloth, the barwill shrink measurably. Therefore, drying should be minimized.7. Calculation of Length Change7.1 Calculate the length change at any age as follows:L 5Lx2 Li!G3 100where:L = change in length at x age, %,Lx= comparator
44、reading of specimen at x age minuscomparator reading of reference bar at x age; inmillimetres when using Fig. 1 apparatus, in incheswhen using Fig. 2 apparatus,Li= initial comparator reading of specimen minus com-parator reading of reference bar at that same time; inmillimetres when using Fig. 1 app
45、aratus, in incheswhen using Fig. 2 apparatus, andG = nominal gauge length, 250 mm when using Fig. 1apparatus, 10 in. when using Fig. 2 apparatus.7.2 Calculate length change values for each specimen to thenearest 0.001 % and report averages to the nearest 0.01 %.8. Temperature, Humidity, and Time8.1
46、Molding RoomThe temperature of the molding roomand dry materials shall be maintained between 23.0 6 4 C.The relative humidity shall be not less than 50 %. Thetemperature of the mixing water shall be 23.0 6 2.0 C.8.2 Moist Storage FacilityThe temperature and humidityof the air in the moist storage fa
47、cility shall conform to therequirements of Specification C511.8.3 TimeComparator readings shall be taken at specifiedtime intervals or ages. All intervals and ages shall be metwithin 62%.FIG. 3 Type of Suitable Apparatus for Measurement of LengthChangesC 490/C 490M 0849. Keywords9.1 cement paste; co
48、mparator; concrete; length change ap-paratus; molds; mortarSUMMARY OF CHANGESCommittee C01 has identified the location of selected changes to this practice since the last issue, C 490 07,that may impact the use of this practice. (Approved June 1, 2008)(1) Editorially changed the designation to dual
49、editorially toagree with the units statement in the Scope.(2) Revised 5.3.1 and 5.3.2.Committee C01 has identified the location of selected changes to this practice since the last issue, C 490 04,that may impact the use of this practice. (Approved June 1, 2007)(1) Added new paragraph 5.4.ASTM 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
