ASTM C1074-2004 Standard Practice for Estimating Concrete Strength by the Maturity Method《用老化法评估混凝土强度的标准规程》.pdf

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1、Designation: C 1074 04Standard Practice forEstimating Concrete Strengthby the Maturity Method1This standard is issued under the fixed designation C 1074; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A

2、number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This practice provides a procedure for estimating con-crete strength by means of the maturity method. The maturityindex is expressed

3、either in terms of the temperature-timefactor or in terms of the equivalent age at a specified tempera-ture.1.2 This practice requires establishing the strength-maturityrelationship of the concrete mixture in the laboratory andrecording the temperature history of the concrete for whichstrength is to

4、 be estimated.1.3 The values stated in SI units are to be regarded as thestandard.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 d

5、etermine the applica-bility of regulatory limitations prior to use. (WarningFreshhydraulic cementitious mixtures are caustic and may causechemical burns to skin and tissue upon prolonged exposure.2)2. Referenced Documents2.1 ASTM Standards:3C 39/C 39M Test Method for Compressive Strength of Cy-lindr

6、ical Concrete SpecimensC 78 Test Method for Flexural Strength of Concrete (UsingSimple Beam with Third-Point Loading)C 109/C 109M Test Method for Compressive Strength ofHydraulic Cement Mortars (Using 2-in. or 50-mm CubeSpecimens)C 192/C 192M Practice for Making and Curing ConcreteTest Specimens in

7、the LaboratoryC 403/C 403M Test Method for Time of Setting of ConcreteMixtures by Penetration ResistanceC 511 Specification for Mixing Rooms, Moist Cabinets,Moist Rooms, and Water Storage Tanks Used in theTesting of Hydraulic Cements and ConcretesC 684 Test Method for Making, Accelerated Curing, and

8、Testing of Concrete Compression Test SpecimensC 803/C 803M Test Method for Penetration Resistance ofHardened ConcreteC 873 Test Method for Compressive Strength of ConcreteCylinders Cast in Place in Cylindrical MoldsC 900 Test Method for Pullout Strength of Hardened Con-creteC 918 Test Method for Mea

9、suring Early-Age CompressiveStrength and Projecting Later-Age Strength3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 datum temperaturethe temperature that is subtractedfrom the measured concrete temperature for calculating thetemperature-time factor according to Eq 1.3.1.2 eq

10、uivalent agethe number of days or hours at aspecified temperature required to produce a maturity equal tothe maturity achieved by a curing period at temperaturesdifferent from the specified temperature.3.1.3 maturitythe extent of the development of a propertyof a cementitious mixture.3.1.3.1 Discuss

11、ionWhile the term is used usually todescribe the extent of relative strength development, it can alsobe applied to the evolution of other properties that aredependent on the chemical reactions that occur in a cementi-tious mixture. At any age, maturity depends on the curinghistory.3.1.4 maturity fun

12、ctiona mathematical expression thatuses the measured temperature history of a cementitiousmixture during the curing period to calculate an index that isindicative of the maturity at the end of that period. Refer toAppendix X1 for additional discussion of this term.3.1.5 maturity indexan indicator of

13、 maturity that is calcu-lated from the temperature history of the cementitious mixtureby using a maturity function.1This practice is under the jurisdiction of ASTM Committee C09 on Concreteand Concrete Aggregates and is the direct responsibility of Subcommittee C09.64 onNondestructive and In-Place T

14、esting.Current edition approved June 1, 2004. Published July 2004. Originally approvedin 1987. Last previous edition approved in 1998 as C 1074 98.2Section on Safety Precautions, Manual of Aggregate and Concrete Testing,Annual Book of ASTM Standards, Vol 04.02.3For referenced ASTM standards, visit t

15、he 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.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100

16、 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.5.1 DiscussionThe computed index is indicative ofmaturity provided there has been a sufficient supply of waterfor hydration or pozzolanic reaction of the cementitiousmaterials during the time used in the calculation

17、. Two widelyused maturity indexes are the temperature-time factor and theequivalent age.3.1.6 maturity methoda technique for estimating concretestrength that is based on the assumption that samples of a givenconcrete mixture attain equal strengths if they attain equalvalues of the maturity index (1,

18、 2, 3).43.1.7 strength-maturity relationshipan empirical relation-ship between compressive strength and maturity index that isobtained by testing specimens whose temperature history up tothe time of test has been recorded.3.1.8 temperature-time factorthe maturity index com-puted according to Eq 1.4.

19、 Summary of Practice4.1 A strength-maturity relationship is developed by labo-ratory tests on the concrete mixture to be used.4.2 The temperature history of the field concrete, for whichstrength is to be estimated, is recorded from the time ofconcrete placement to the time when the strength estimati

20、on isdesired.4.3 The recorded temperature history is used to calculate thematurity index of the field concrete.4.4 Using the calculated maturity index and the strength-maturity relationship, the strength of the field concrete isestimated.5. Significance and Use5.1 This practice can be used to estima

21、te the in-placestrength of concrete to allow the start of critical constructionactivities such as: (1) removal of formwork and reshoring; (2)post-tensioning of tendons; (3) termination of cold weatherprotection; and (4) opening of the roadways to traffic.5.2 This practice can be used to estimate str

22、ength oflaboratory specimens cured under non-standard temperatureconditions.5.3 The major limitations of the maturity method are: (1) theconcrete must be maintained in a condition that permits cementhydration; (2) the method does not take into account the effectsof early-age concrete temperature on

23、the long-term strength;and (3) the method needs to be supplemented by otherindications of the potential strength of the concrete mixture.5.4 The accuracy of the estimated strength depends, in part,on determining the appropriate maturity function for theparticular concrete mixture.6. Maturity Functio

24、ns6.1 There are two alternative functions for computing thematurity index from the measured temperature history of theconcrete.6.2 One maturity function is used to compute thetemperature-time factor as follows:Mt! 5 (Ta2 To! Dt (1)where:M(t) = the temperature-time factor at age t, degree-days ordegr

25、ee-hours,Dt = a time interval, days or hours,Ta= average concrete temperature during time interval,Dt, C, andTo= datum temperature, C.6.3 The other maturity function is used to compute equiva-lent age at a specified temperature as follows (4):te5 (e2QS1Ta21TsDD t (2)where:te= equivalent age at a spe

26、cified temperature Ts, days orh,Q = activation energy divided by the gas constant, K,Ta= average temperature of concrete during time intervalDt,K,Ts= specified temperature, K, andDt = time interval, days or h.NOTE 1Temperature in kelvin (K) equals approximately temperatureC + 273 C.6.4 Approximate v

27、alues of the datum temperature, To, andthe activation energy divided by the gas constant, Q, are givenin Appendix X1. Where maximum accuracy of strength esti-mation is desired, the appropriate values of Toor Q for aspecific concrete mixture are determined according to theprocedures given in Annex A1

28、.7. Apparatus7.1 A device is required to monitor and record the concretetemperature as a function of time. Acceptable devices includethermocouples or thermistors connected to strip-chart record-ers, or digital data-loggers, or embedded digital devices thatmeasure temperature and record and store the

29、 data. Therecording time interval shall be12 h or less for the first 48 h and1 h or less thereafter. The temperature recording device shall beaccurate to within 61 C.7.2 Alternative devices include commercial maturity instru-ments that automatically compute and display eithertemperature-time factor

30、or equivalent age.NOTE 2Commercial maturity instruments use specific values ofdatum temperature or activation energy in evaluating the maturity index;thus the displayed maturity index may not be indicative of the true valuefor the concrete mixture being used. Refer to Appendix X1 for informationon c

31、orrecting the displayed values.8. Procedure to Develop Strength-Maturity Relationship8.1 Prepare at least 15 cylindrical specimens according toPractice C 192/C 192M . The mixture proportions and con-stituents of the concrete shall be similar to those of the concretewhose strength will be estimated u

32、sing this practice. If twobatches are needed to prepare the required number of cylinders,cast an equal number of cylinders from each batch, and test onecylinder from each batch at the test ages given in 8.4.8.2 Embed temperature sensors to within 615 mm of thecenters of at least two specimens. Immed

33、iately connect the4The boldface numbers in parentheses refer to the list of references at the end ofthis practice.C1074042sensors to maturity instruments or to temperature-recordingdevices such as data-loggers or strip-chart recorders.NOTE 3A method to assist in the proper positioning of the sensor

34、is toinsert a small diameter rigid rod into the center of the freshly madecylinder. The rod will push aside any interfering aggregate particles. Therod is removed and the sensor is inserted into the cylinder. The side of thecylinder mold should be tapped with a rubber mallet or the tamping rod toens

35、ure that the concrete comes into contact with the sensor.8.3 Moist cure the specimens in a water bath or in a moistroom meeting the requirements of Specification C 511.8.4 Unless specified otherwise, perform compression testsat ages of 1, 3, 7, 14, and 28 days in accordance with TestMethod C 39/C 39

36、M. Test two specimens at each age andcompute the average strength. If the range of compressivestrength of the two specimens exceeds 10 % of their averagestrength, test another cylinder and compute the average of thethree tests. If a low test result is due to an obviously defectivespecimen, discard t

37、he low test result.NOTE 4For concrete mixtures with rapid strength development, orwhen strength estimates are to be made at low values of maturity index,tests should begin as soon as practicable. Subsequent tests should bescheduled to result in approximately equal increments of strength gainbetween

38、test ages. At least five test ages should be used.8.5 At each test age, record the average maturity index forthe instrumented specimens.8.5.1 If maturity instruments are used, record the average ofthe displayed values.8.5.2 If temperature recorders are used, evaluate the matu-rity index according to

39、 Eq 1 or Eq 2. Unless specifiedotherwise, use a time interval (Dt)of12 h or less for the first 48h of the temperature record. Longer time intervals are permit-ted for the relatively constant portion of the subsequenttemperature record.NOTE 5Judgement should be used in selecting the initial timeinter

40、vals to record temperature in mixtures that result in rapid changes inearly-age temperature due to rapid hydration. Appendix X2 gives anexample of how to evaluate the temperature-time factor or equivalent agefrom the recorded temperature history of the concrete.8.6 Plot the average compressive stren

41、gth as a function ofthe average value of the maturity index. Draw a best-fit curvethrough the data. The resulting curve is the strength-maturityrelationship to be used for estimating the strength of theconcrete mixture cured under other temperature conditions.Fig. 1 is an example of a relationship b

42、etween compressivestrength and temperature-time factor, and Fig. 2 is an exampleof a relationship between compressive strength and equivalentage at 20 C.NOTE 6The strength-maturity relationship can also be established byusing regression analysis to determine a best-fit equation to the data.Possible

43、equations that have been found to be suitable for this purposemay be found in Ref. (3). A popular equation is to express strength as alinear function of the logarithm of the maturity index (see Fig. 3).8.7 When specified, a flexural strength versus maturityindex relationship is permitted. Prepare at

44、 least 15 beamspecimens in accordance with Practice C 192/C 192M. If twobatches are needed to prepare the required number of speci-mens, cast an equal number of beams from each batch, and testone beam from each batch at the test ages given in 8.4. Embedtemperature sensors in two specimens, one from

45、each batch iftwo batches are made. Connect the sensors to maturity instru-ments or temperature recording devices, and moist cure thespecimens in a water bath or in a moist room meeting therequirements of Specification C 511. Measure flexural strengthin accordance with Test Method C 78 at time interv

46、als of 1, 3,7, 14 and 28 days, or as specified otherwise (See Note 4). Testtwo specimens at each age and compute the average strength.If the range of flexural strength of the two specimens exceeds15 % of their average strength, test another beam and computethe average of the three tests. If a low te

47、st result is due to anobviously defective specimen, discard the low test result. Usethe same procedures as in 8.5 and 8.6 to develop the flexuralstrength-maturity relationship.9. Procedure to Estimate In-Place Strength9.1 As soon as is practicable after concrete placement,embed temperature sensors i

48、nto the fresh concrete. When usingthis practice to allow critical construction operations to begin,FIG. 1 Example of a Relationship Between Compressive Strengthand Temperature-Time FactorFIG. 2 Example of a Relationship Between Compressive Strengthand Equivalent Age at 20 CC1074043install sensors at

49、 locations in the structure that are critical interms of exposure conditions and structural requirements.NOTE 7In building construction, exposed portions of slabs andslab-column connections are typically critical locations. The advice of theEngineer should be sought for critical locations in the particular structureunder construction.9.2 Connect the sensors to maturity instruments ortemperature-recording devices and activate the recording de-vices as soon as is practicable. Use the same value of datumtemperature or activation energy, whichever is applicab