1、Designation: C490/C490M 111C490/C490M 17Standard Practice forUse of Apparatus for the Determination of Length Change ofHardened Cement Paste, Mortar, and Concrete1This standard is issued under the fixed designation C490/C490M; the number immediately following the designation indicates the yearof ori
2、ginal adoption 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 NOTEEditorial corrections were made in April 2014.1. Scope*1.1 This prac
3、tice covers the requirements for the apparatus and equipment used to prepare specimens for the determination oflength change in hardened cement paste, mortar, and concrete, the apparatus and equipment used for the determination of theselength changes, and the procedures for its use.1.2 Methods for t
4、he preparation and curing of test specimens, conditions of testing and curing, and detailed procedures forcalculating and reporting test results are contained in applicable test methods.1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values
5、 stated in eachsystem may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from thetwo systems may result in non-conformance with the standard.2. Referenced Documents2.1 ASTM Standards:2C219 Terminology Relating to Hydraulic CementC511 Speci
6、fication for Mixing Rooms, Moist Cabinets, Moist Rooms, and Water Storage Tanks Used in the Testing of HydraulicCements and ConcretesC1005 Specification for Reference Masses and Devices for Determining Mass and Volume for Use in the Physical Testing ofHydraulic Cements3. Terminology3.1 length change
7、Definitions: an increase or decrease in the linear dimension of a test specimen, measured along thelongitudinal axis, due to causes other than applied load.3.1.1 For definitions of terms used in this test method, refer to Terminology C219.4. Significance and Use4.1 This practice is intended to provi
8、de standard requirements for apparatus common to many test methods used in connectionwith cement and concrete and standardized procedures for its use. The detailed requirements as to materials, mixtures, specimens,conditioning of specimens, number of specimens, ages at which measurements are to be m
9、ade, interpretation of results, andprecision and bias are left to be dealt with in specific test methods.5. Apparatus5.1 Reference Masses and Devices for Determining Mass and Volume, shall conform to the requirements of SpecificationC1005.5.2 Molds, shall have either one or two compartments and shal
10、l be constructed as shown in Fig. 1 or Fig. 2. Molds for testspecimens used in determining the length change of cement pastes and mortars shall provide for 25 by 25 by 285-mm prismshaving a 250-mm gauge length, or for 1 by 1 by 1114 in. -in. prisms having a 10in. gauge length. Molds for test specime
11、ns used1 This practice is under the jurisdiction of ASTM Committee C01 on Cement and is the direct responsibility of Subcommittee C01.95 on Coordination of Standards.Current edition approved Oct. 1, 2011March 15, 2017. Published November 2011March 2017. Originally approved in 1962. Last previous edi
12、tion approved in 20102011as C490/C490MC490/C490M 11110 DOI: 10.1520/C0490_C0490M-11E01.10.1520/C0490_C0490M-17.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the st
13、andards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accura
14、tely, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor D
15、rive, PO Box C700, West Conshohocken, PA 19428-2959. United States1in the length change of concretes shall provide for prisms of the desired cross section having a 10-in. or 250-mm gauge length.In some routine tests, 25 by 25 by 160-mm specimens with a gauge length of 125 mm, or 1 by 1 by 614 in. -i
16、n. specimens witha gauge length of 5-in. are permitted, but in case of dispute, results obtained with specimens of 250-mm 10-in. gauge length shallgovern.5.2.1 The gauge length shall be considered as the nominal length between the innermost ends of the gauge studs. The parts ofthe molds shall be tig
17、ht fitting and firmly held together when assembled, and their surfaces shall be smooth and free of pits. Themolds shall be made of steel or other hard metal not readily attacked by the cement paste, mortar, or concrete. The sides of themolds shall be sufficiently rigid to prevent spreading or warpin
18、g. For the molds shown in Fig. 1, the tolerance on dimension A is60.7 mm. For the molds shown in Fig. 2, the tolerance on dimension A is 60.03 in.5.2.2 Each end plate of the mold shall be equipped to hold properly in place, during the setting period, one of the gauge studsshown in Fig. 1 or Fig. 2.
19、The gauge studs shall be of American Iron and Steel Institute (AISI)3 Type 316 stainless steel or othercorrosion-resistant metal of similar hardness. Gauge studs of Invar or similar metal shall be used when specimens are tested atwidely different temperatures. To prevent restraint of the gauge studs
20、 before demolding of the specimen, the device for holdingthe gauge studs in position shall be so arranged that, if necessary, it can be partially or completely released after the compactionof the paste or mortar into place in the mold. The gauge studs shall be set so that their principal axes coinci
21、de with the principalaxis of the test specimen. For the molds shown in Fig. 1, gauge studs shall extend into the specimen 17.5 6 0.5 mm and thedistance between the inner ends of the gauge studs shall be 250.0 6 2.5 mm 2.5 mm and 250 mm shall be considered the gauge3 Details on this material are avai
22、lable fromAmerican Iron and Steel Institute (AISI), 1140 ConnecticutAve., NW, Suite 705, Washington, DC 20036, http:/www.steel.org.NOTE 1Dimension A to be specified by the purchaser.FIG. 1 Molds (SI Units)C490/C490M 172length for calculating length change. For the molds shown in Fig. 2, gauge studs
23、shall extend into the specimen 0.625 6 0.025in. and the distance between the inner ends of the gauge studs shall be 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 of specimens, shall be designed to ac
24、commodate the size of specimenemployed and to provide or permit a positive means of contact with the gauge studs and the convenient and rapid obtaining ofcomparator readings (Note 1).5.3.1 The comparator for determining length changes of specimens produced in the molds shown in Fig. 1 shall provide
25、a dialmicrometer or other measuring device graduated to read in 0.002-mm units or less, accurate within 0.002 mm in any 0.020-mmrange, and within 0.004 mm in any 0.200-mm range, and sufficient range (at least 8.0 mm) in the measuring device to allow forsmall variations in the actual length of variou
26、s specimens. The terminals of the comparator shall be plane, polished andheat-treated. They shall be fitted with collars held in place with set screws. The collars shall extend 1.5 6 0.1 mm beyond the planeface of the terminal. The collars shall allow free rotation of the gauge stud tips that fit in
27、side the collars and have an inside diameterno more than 0.5 mm 0.5 mm larger than the average diameter of that portion of the gauge stud tips that fit into the collars.NOTE 1One type of instrument that has been found satisfactory for use with small prisms is shown in Fig. 3.Ahorizontal comparator s
28、hould be usedwith prisms with a cross section greater than 9 in.2 or 58 cm2.5.3.2 The comparator for determining length changes of specimens produced in the molds shown in Fig. 2 shall provide a dialmicrometer or other measuring device graduated to read in 0.0001-in. units, accurate within 0.0001 in
29、. in any 0.0010-in. range,and within 0.0002 in. in any 0.0100-in. range, and sufficient range (at least 0.3 in.) in the measuring device to allow for smallvariations in the actual length of various specimens.The terminals of the comparator shall be plane, polished and heat-treated.Theyshall be fitte
30、d with collars held in place with set screws. The collars shall extend 0.062 6 0.003 in. beyond the plane face of theFIG. 2 Molds (Inch-Pound Units)C490/C490M 173terminal. The collars shall allow free rotation of the gauge stud tips that fit inside the collars and have an inside diameter no morethan
31、 0.02 in. larger than the average diameter of that portion of the gauge stud tips that fit into the collars.5.3.3 The design shall provide a means for checking the measuring device against a reference bar at regular intervals.5.4 Reference Bar, shall have an overall length of 295 6 3.0 mm 3.0 mm or
32、170 6 3.0 mm 11 58 6 18 in. or 6 58 6 18 in.,whichever is appropriate for the specimen in use. The bar shall be of a steel alloy having a coefficient of thermal expansion notgreater than two millionths per degree Celsius. Each end of the reference bar shall be fitted with heat treated, hardened, and
33、polished tips machined to the same shape as the contact end of the gauge studs used in test specimens. That portion of the bar thatextends into the comparators collar shall have a diameter of 6 6 0.25 mm 0.250 6 0.010 in., and the length of that portion shallextend beyond the depth of the collar. Ex
34、cept for the tips, which are attached after heat treatment, no part of the reference bar shallbe heat treated (Note 2). The central 100 mm 100 mm 4 in. of the length of the reference bar shall be covered by a rubber tubewith a wall at least 3 mm 18 in. thick to minimize the effect of temperature cha
35、nge during handling. The reference bar shall beprovided near one end with a positioning mark.NOTE 2Alloys such as invar lose their low coefficient of thermal expansion properties when heat treated.5.5 Check and document the bar mold dimensions, gauge stud projection into the mold interior, length co
36、mparator, and lengthmeasuring device for conformance to the design and dimensional requirements of this specification at least every 212 years.6. Procedure6.1 Preparation of MoldsPrior to the molding of specimens, the outside joints of the mold and the contact lines of the moldand base plate shall b
37、e sealed to prevent loss of mixing water from a freshly molded specimen. Thinly cover the interior surfacesof the mold with mineral oil. After this operation, set the gauge studs, taking care to keep them clean, and free of oil, grease, andforeign matter.6.2 Use of Reference BarFor each reference re
38、ading taken, place the reference bar into the comparator with the positioningmark in the same orientation. With the bar in the comparator, rotate it slowly through at least one complete revolution while thegauge reading is being taken. Record the minimum (shortest) gauge reading (Note 3). Monitor an
39、d record the room temperaturein which the comparator is used. Use the reference bar when the temperature difference is more than 61.0 C 61.0C of theprevious use of the comparator apparatus, and at least at the beginning and end of the specimen readings made within a half day.FIG. 3 Type of Suitable
40、Apparatus for Measurement of Length ChangesC490/C490M 174NOTE 3The reference bar is used in the comparator to correct for changes occurring to the comparator apparatus and gauge that affect length readings.The reference bar is always placed in the same orientation in the comparator apparatus to mini
41、mize changes in reading due to differences in contactsurfaces. Frequent use of the reference bar can result in significant wear of the tips, which affects the indicated length of the bar.Appropriate steps shouldbe taken to monitor reference bar condition and replace as needed.NOTE 4The equation give
42、n in the section on calculation of length change contemplates that a comparator reading for the reference bar will berecorded each time the reference bar is used and a difference calculated for each test specimen reading. Alternatively, the dial gauge setting can be reset,if necessary, to its origin
43、al setting with the reference bar in place each time the reference bar is read. Doing so simplifies the calculation of length changeby canceling the comparator reading of the reference bar from the values of Lx and Li. If this procedure is used, care should be taken to ensure that thedial set screw
44、is tightened adequately each time the dial is reset.6.3 Obtaining Comparator ReadingsRotate specimens slowly in the measuring instrument while the comparator reading isbeing taken. Record the minimum reading of the dial if the rotation causes a change in the dial reading. Place specimens in theinstr
45、ument with the same end up each time a comparator reading is taken.6.3.1 Obtaining Comparator Readings of Specimens Stored MoistClean the hole in the base of the comparator into which thegauge stud on the lower end of the bar fits before and after every reading. Read and record the comparator indica
46、tion of the lengthof the reference bar and temperature of the room in which the comparator is being used (Note 4). Take one bar out of immersion,blot only around the pins, put the bar in the comparator, read, and record the indication (Note 5). Return the bar to immersion. Takeout the second bar and
47、 treat it in a like manner. Return the second bar to immersion and record the reading. Continue the procedureuntil all bars have been read, returned to immersion, and the readings recorded. After reading the last bar, read and record thereference-bar indication and temperature of the room in which t
48、he comparator was used. Compare the two reference bar readings.If the difference in the reference bar readings is greater than 0.010 mm 0.0004 in, 0.0004 in., then use the average of thebeginning and ending values for the Lx and Li factors in the formula in the calculations section. Otherwise use th
49、e beginningreading only.NOTE 5The purpose of the minimal blotting of the pins and no blotting of the bars is to avoid drying and shrinkage of the bars. It has been observedthat if the pins are blotted, and the bar placed in the comparator and the dial read, and the bar is then wiped gently with a dry cloth, the bar will shrinkmeasurably. Therefore, drying should be minimized.7. Calculation of Length Change7.1 Calculate the length change at any age as follows:L 5Lx 2L i!G 3100where:L = change in length at x age, %,Lx = comparator re
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