1、Designation: C1761/C1761M 15Standard Specification forLightweight Aggregate for Internal Curing of Concrete1This standard is issued under the fixed designation C1761/C1761M; the number immediately following the designation indicates theyear of original adoption or, in the case of revision, the year
2、of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This specification covers lightweight aggregate intendedto provide water for internal curing of concrete. It inclu
3、des testmethods for determining the absorption and desorption prop-erties of lightweight aggregate.NOTE 1Internal curing provides an additional source of water tosustain hydration and substantially reduce the early-age autogenousshrinkage and self-desiccation that can be significant contributors toe
4、arly-age cracking. Appendix X1 provides guidance on calculating thequantity of lightweight aggregate for internal curing.1.2 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, eac
5、hsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformance.Some values have only SI units because the inch-poundequivalents are not used in practice.NOTE 2Sieve size is identified by its standard designation in Speci-fication E11. The alterna
6、tive designation given in parentheses is forinformation only and does not represent a different standard sieve size.1.3 The text of this specification references notes andfootnotes that provide explanatory material. These notes andfootnotes (excluding those in tables and figures) shall not beconside
7、red as requirements of the standard.1.4 This specification 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
8、 limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C29/C29M Test Method for Bulk Density (“Unit Weight”)and Voids in AggregateC40 Test Method for Organic Impurities in Fine Aggregatesfor ConcreteC87 Test Method for Effect of Organic Impurities in FineAggregate on Strength of Mortar
9、C114 Test Methods for Chemical Analysis of HydraulicCementC125 Terminology Relating to Concrete and Concrete Ag-gregatesC128 Test Method for Relative Density (Specific Gravity)and Absorption of Fine AggregateC136 Test Method for Sieve Analysis of Fine and CoarseAggregatesC142 Test Method for Clay Lu
10、mps and Friable Particles inAggregatesC330/C330M Specification for Lightweight Aggregates forStructural ConcreteC641 Test Method for Iron Staining Materials in Light-weight Concrete AggregatesC702 Practice for Reducing Samples ofAggregate to TestingSizeC1498 Test Method for Hygroscopic Sorption Isot
11、herms ofBuilding MaterialsC1608 Test Method for Chemical Shrinkage of HydraulicCement PasteC1698 Test Method for Autogenous Strain of Cement Pasteand MortarD75 Practice for Sampling AggregatesE11 Specification for Woven Wire Test Sieve Cloth and TestSieves3. Terminology3.1 Definitions:3.1.1 For defi
12、nitions of terms used in this practice, refer toTerminology C125.3.2 Definitions of Terms Specific to This Standard:3.2.1 absorption, A72,nof lightweight aggregate, the in-crease in mass of a specimen of oven-dry lightweight aggregatedue to water penetrating into the permeable pores of theparticles
13、after being submerged for 72 h, expressed as percent-age of oven-dry mass.3.2.2 autogenous shrinkage, nreduction in volume due tochemical shrinkage of a sealed cementitious mixture, notsubjected to external forces and under constant temperature,measured from the time of final setting.1This specifica
14、tion is under the jurisdiction of ASTM Committee C09 onConcrete and Concrete Aggregates and is the direct responsibility of SubcommitteeC09.21 on Lightweight Aggregates and Concrete.Current edition approved April 1, 2015. Published May 2015. Originallyapproved in 2012. Last previous edition approved
15、 in 2013 as C1761/C1761M 13b.DOI: 10.1520/C1761_C1761M-15.2For 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.*A
16、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 States13.2.2.1 DiscussionThe chemical shrinkage leads to emp-tying of the internal pores (see self-desiccation) that causes theform
17、ation of menisci in the partially water-filled pores. Themenisci in turn give rise to internal tensile stresses that causebulk shrinkage. While autogenous shrinkage is due to thechemical shrinkage, the magnitude of autogenous shrinkage isless than the chemical shrinkage after setting occurs, because
18、the aggregate particles and the hydrated cement paste networkrestrain the shrinkage. The restraint may in turn lead tocracking.3.2.3 chemical shrinkage, nthe reduction in volume ofcementitious paste that occurs during hydration because thehydration products occupy less volume than the volumeoccupied
19、 originally by the water and unhydrated cementitiousmaterials.3.2.4 density (OD), nof lightweight aggregate, the mass ofoven-dry lightweight aggregate particles per unit volume ofaggregate particles, where the volume includes the permeableand impermeable pores within the particles but does notinclud
20、e the voids between the particles.3.2.5 desorption (D), nof lightweight aggregate, the de-crease in mass of lightweight aggregate originally containingabsorbed water due to water leaving the permeable pores as theaggregate attains moisture equilibrium with the surroundingenvironment maintained at co
21、nstant temperature and a relativehumidity less than 100 %, and expressed as a percentage of the72-h absorption.3.2.6 internal curing, nsupplying water within a cemen-titious mixture using pre-wetted lightweight aggregate, or othermaterials that readily release water from within the particles,thereby
22、 mitigating self-desiccation and sustaining hydration.3.2.7 oven-dry (OD), adjrelated to lightweight aggregateparticles, the condition in which the specimen of lightweightaggregate has been dried by heating in an oven at 110 6 5C230 6 10 F for sufficient time to reach a constant mass.3.2.8 relative
23、density, (OD), nof lightweight aggregate,the ratio of the density (OD) of the lightweight aggregate to thedensity of water at a stated temperature.3.2.9 wetted surface-dry (WSD), adjrelated to lightweightaggregate particles, the condition in which the permeablepores of lightweight aggregate particle
24、s are filled with water, tothe extent achieved by submerging an oven-dry specimen for72 h, and the surfaces of the particles are dry.3.2.10 self-desiccation, nreduction in the internal relativehumidity of a sealed cementitious mixture, due to chemicalshrinkage, that may reduce the rate of hydration
25、or stophydration.3.3 Symbols:A72= the 72-h absorption, expressed as a percentage of theoven-dry mass.D = the desorption, expressed as a percentage of the A72absorption.GOD= relative density (oven-dry) of lightweight aggregate.GODN= relative density (oven-dry) of normal weight aggre-gate.MLWA= calcul
26、ated mass of oven-dry lightweight aggregateneeded for internal curing per unit volume of concrete,kg/m3lb yd3.MNWA= mass of normal weight aggregate in oven-dry con-dition to be removed, kg/m3lb yd3.MOD= mass of lightweight aggregate specimen in oven-drycondition, g.MPS= mass of pycnometer containing
27、 lightweight aggregatespecimen and filled with water, g.MPW= mass of pycnometer filled with water, g.MSD= mass of lightweight aggregate specimen in wettedsurface-dry condition, g.M94= equilibrium mass of aggregate originally in wettedsurface-dry condition and subsequently stored at 94 % relativehumi
28、dity, g.Cf= cementitious materials content of concrete mixture,kg/m3lb yd3.CS = chemical shrinkage of cementitious material, expressedas kg water/kg of cement lb/lb (see Note 3).S = degree of saturation of lightweight aggregate relative towetted surface-dry condition (0 to 1.0).w/cm = water-cementit
29、ious materials ratio, kg/kg lb/lb.max= maximum potential degree of hydration of cementi-tious materials expressed as a decimal fraction (0 to 1.0).WLWA= mass of water released by lightweight aggregate ingoing from the wetted surface-dry condition to the equilibriummass at a relative humidity of 94 %
30、, expressed as a fraction ofthe oven-dry mass.NOTE 3Chemical shrinkage is measured in units of volume of waterper unit mass of cement. In using the value of chemical shrinkage tocalculate the required amount of lightweight aggregate for internal curing,the volume of water is converted to the mass of
31、 water. Hence chemicalshrinkage is expressed as mass of water per unit mass of cement.4. Ordering Information4.1 The direct purchaser of lightweight aggregate for inter-nal curing shall include the following information in thepurchase order as applicable.4.1.1 Reference to this specification, as Spe
32、cificationC1761.4.1.2 Whether the order is for fine aggregate, coarseaggregate, or combined fine and coarse aggregate.4.1.3 Quantity in metric tons tons or cubic meters cubicyards.4.1.4 If the order is for coarse aggregate or combined fineand coarse aggregate, provide the nominal size designation as
33、given in Table 1 or alternative grading as agreed between thepurchaser and aggregate supplier.4.1.5 Whether certification shall be furnished indicating thatthe material was sampled and tested in accordance with thisspecification and found to meet the requirements.4.1.6 Whether a report of the result
34、s of aggregate tests shallbe furnished.4.1.7 Whether the results of tests of concrete properties arerequired.4.1.8 Any exceptions or additions to this specification.C1761/C1761M 1525. Materials and Manufacture5.1 Two general types of lightweight aggregate are coveredby this specification, as follows
35、:5.1.1 Aggregates produced by expanding, pelletizing, orsintering products such as blast-furnace slag, clay, diatomite,fly ash, shale, or slate, and5.1.2 Aggregate prepared by processing natural materials,such as pumice, scoria, and tuff.5.2 The aggregate shall be composed predominately oflightweigh
36、t-cellular and granular inorganic materials.6. Chemical Requirements6.1 Organic ImpuritiesTest Method C40. Lightweightaggregate shall not produce a color darker than the standardcolor solution, unless it is demonstrated that when the aggre-gate is tested for the effect of organic impurities on stren
37、gth ofmortar, the relative strength at 7 days, determined in accor-dance with Test Method C87, is not less than 95 %.6.2 StainingTest Method C641. Lightweight aggregateshall produce a stain index of less than 60. Lightweightaggregate producing a stain index of 60 or higher shall besubject to rejecti
38、on if the deposited stain is found uponchemical analysis to contain an iron content, expressed asFe2O3, equal to or greater than 1.5 mg/200 g of sample.6.2.1 Loss on IgnitionTest Method C114. The loss onignition of lightweight aggregates shall not exceed 5 %.NOTE 4Some aggregate may contain carbonat
39、es or water of hydrationthat contribute to loss on ignition but may not affect the quality of theproduct. Therefore, when evaluating an aggregate, consideration should begiven to the material characteristics that cause the ignition loss.7. Physical Properties7.1 Clay Lumps and Friable ParticlesTest
40、Method C142.The total amount of clay lumps and friable particles shall notexceed 2 % by dry mass.7.2 GradingTest Method C136 as modified in Specifica-tion C330/C330M. The grading shall conform to the require-ments shown in Table 1 or established by mutual agreementbetween interested parties.NOTE 5In
41、 general, a volume of lightweight aggregate (fine or acombination of coarse and fine) for internal curing will replace an equalvolume of normal weight aggregate in an existing conventional concretemixture. The grading of the lightweight aggregate can be chosen to closelymatch the existing grading of
42、 the normal weight aggregates, or to fill in agap in the existing normal weight aggregate grading, such as using amid-range size lightweight aggregate to enhance the gradation of agap-graded mixture (1).37.2.1 Uniformity of GradingFor continuing shipments offine aggregate from a given source, the fi
43、neness modulus shallnot vary more than 7 % from the base fineness modulus. Thebase fineness modulus shall be that value that is typical of thesource. The purchaser has the authority to approve a change inthe base fineness modulus. For coarse aggregate and combinedfine and coarse aggregate, the unifo
44、rmity of grading require-ments of Specification C330/C330M shall apply.7.3 Bulk DensityTest Method C29/C29M. The dry bulkdensity using the shoveling method of compaction shallconform to the requirements of Table 2 using a 14 L 12 ft3measure.7.4 Water AbsorptionThe lightweight aggregate shallhave a 7
45、2-h absorption not less than 5 % when tested inaccordance with Section 10.7.5 Desorption PropertiesThe lightweight aggregate shallrelease at least 85 % of its absorbed water at 94 % relativehumidity when tested in accordance with Section 11.8. Sampling8.1 Sample lightweight aggregates in accordance
46、with Prac-tice D75.8.2 Reduce sample to test sizes in accordance with PracticeC702.3The boldface numbers in parentheses refer to the list of references at the end ofthis standard.TABLE 1 Grading RequirementsNominal Size DesignationPercentages (Mass) Passing Sieves Having Square Openings25.0 mm(1 in.
47、)19.0 mm(34 in.)12.5 mm(12 in.)9.5 mm(38 in.)4.75 mm(No. 4)2.36 mm(No. 8)1.18 mm(No. 160)300 m(No. 50)150 m(No. 100)75 mA(No. 200)Fine aggregate:4.75 mm to 0 (No. 4 to 0) . . . . . . . . . 100 85100 . . . 4080 1035 525 . . .Coarse aggregate:25.0 to 4.75 mm (1 in. to No. 4) 95100 . . . 2560 . . . 010
48、 . . . . . . . . . . . . 01019.0to4.75mm(34 in. to No.4) 100 90100 . . . 1050 015 . . . . . . . . . . . . 01012.5to4.75mm(12 in. to No. 4) . . . 100 90100 4080 540 020 010 . . . . . . 0109.5to2.36mm(38 in. to No. 8) . . . . . . 100 80100 540 020 010 . . . . . . 010Combined fine and coarse aggregate:
49、12.5mmto0(12 in. to 0) . . . 100 95100 . . . 5080 . . . . . . 520 215 0109.5mmto0(38 in. to 0) . . . . . . 100 90100 6590 3565 . . . 1025 515 010AThe surfaces of pyro-processed lightweight aggregate particles finer than the 75 m (No. 200) sieve are not deleterious and may be moderately pozzolanic.TABLE 2 Maximum Dry Loose Bulk DensitySize DesignationMaximum Densitykg/m3lb ft3Fine aggregate 1120 70Coarse aggregate 880 55Combined fine and coarseaggregate1040 65C1761/C1761M 1539.
