ASTM_C_426_-_16.pdf

Designation:C42616Standard Test Method forLinear Drying Shrinkage of Concrete Masonry Units1This standard is issued under the fixed designation C426;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope*1.1 This test method covers a routine standardized proce-dure for determining the linear drying shrinkage of concretemasonry units or related concrete units under specified accel-erated drying conditions.1.2 The text of this test method references notes andfootnotes that provide explanatory material.These notes andfootnotes(excluding those in tables and figures)shall not beconsidered as requirements of the standard.1.3 The values stated in inch-pound units are to be regardedas standard.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.4 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 establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2C490 Practice for Use ofApparatus for the Determination ofLength Change of Hardened Cement Paste,Mortar,andConcreteC1093 Practice for Accreditation of Testing Agencies forMasonryC1232 Terminology of Masonry2.2 ANSI Standard:B94.11M1993 Twist Drills33.Terminology3.1 Terminology defined in Terminology C1232 shall applyfor this test method.3.2 Definitions of Terms Specific to This Standard:3.2.1 linear drying shrinkage,nin this test method,thechange in linear dimension of the test specimen due to dryingfrom a saturated condition to an equilibrium weight and lengthunder specified accelerated drying conditions.4.Significance and Use4.1 This test method is intended to evaluate the dryingshrinkage characteristics of a given unit.The results of thislaboratory method are considered in determining concretemasonry crack control provisions.NOTE1The testing laboratory performing this test method should beevaluated in accordance with Practice C1093.5.Apparatus5.1 Strain GaugeThe instruments for measuring lineardrying shrinkage shall be so designed as to permit or providethe conditions described in 5.1.1 through 5.1.5.NOTE2Strain gauges may be obtained with various gauge lengths.The 10-in.(254-mm)gauge length is recommended for use with regularconcrete masonry units,however,particular sizes of products may requireother lengths.The length of the shrinkage specimen shall not be less thanrequired for a minimum gauge length(distance between gauge plugs)of6 in.(152.4 mm).5.1.1 A means of positive contact with the specimen thatwill ensure reproducible measurements of length.5.1.2 Means for precise measurement,consisting of a dialmicrometer or other measuring device graduated to read in0.0001-in.(0.0025-mm)units,and accurate within 0.0001 in.(0.0025 mm)in any 0.0010-in.(0.025-mm)range,and within0.0002 in.(0.0050-mm)in any 0.0100-in.(0.254-mm)range.5.1.3 Sufficient range to allow for small variations in thegauge lengths.NOTE3If the shrinkage reference points are set carefully to position,a dial micrometer with a travel of 0.2 or 0.3 in.(5.1 or 7.6 mm)providesample range in the instrument.5.1.4 Means for checking the strain gauge at regular inter-vals against a standard reference bar.The standard referencebar shall be protected from air currents by placing it inside a1This test method is under the jurisdiction of ASTM Committee C15 onManufactured Masonry Units and is the direct responsibility of SubcommitteeC15.03 on Concrete Masonry Units and Related Units.Current edition approved June 1,2016.Published July 2016.Originally approvedin 1958.Last previous edition approved in 2015 as C426 151.DOI:10.1520/C0426-16.2For 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.3Available from American National Standards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036,http:/www.ansi.org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 wooden box which should be closed except when the straingauge is being checked against it.NOTE4A standard reference bar shall be furnished by the manufac-turer of the instrument.A standard bar of ordinary steel is satisfactory,butcorrections must be made for variations in its length due to temperaturechanges.When a more nearly constant datum