Designation: C1074 − 11Standard Practice forEstimating Concrete Strengthby the Maturity Method1This standard is issued under the fixed designation C1074; 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.1. Scope*1.1 This practice provides a procedure for estimating con-crete strength by means of the maturity method. The maturityindex is expressed 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 be estimated.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.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. (Warning—Freshhydraulic cementitious mixtures are caustic and may causechemical burns to skin and tissue upon prolonged exposure.2)2. Referenced Documents2.1 ASTM Standards:3C31/C31M Practice for Making and Curing Concrete TestSpecimens in the FieldC39/C39M Test Method for Compressive Strength of Cylin-drical Concrete SpecimensC78 Test Method for Flexural Strength of Concrete (UsingSimple Beam with Third-Point Loading)C109/C109M Test Method for Compressive Strength ofHydraulic Cement Mortars (Using 2-in. or [50-mm] CubeSpecimens)C192/C192M Practice for Making and Curing Concrete TestSpecimens in the LaboratoryC403/C403M Test Method for Time of Setting of ConcreteMixtures by Penetration ResistanceC511 Specification for Mixing Rooms, Moist Cabinets,Moist Rooms, and Water Storage Tanks Used in theTesting of Hydraulic Cements and ConcretesC684 Test Method for Making, Accelerated Curing, andTesting Concrete Compression Test Specimens (With-drawn 2012)4C803/C803M Test Method for Penetration Resistance ofHardened ConcreteC873/C873M Test Method for Compressive Strength ofConcrete Cylinders Cast in Place in Cylindrical MoldsC900 Test Method for Pullout Strength of Hardened Con-creteC918/C918M Test Method for Measuring Early-Age Com-pressive Strength and Projecting Later-Age Strength3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 datum temperature—the temperature that is subtractedfrom the measured concrete temperature for calculating thetemperature-time factor according to Eq 1.3.1.2 equivalent age—the 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 maturity—the extent of the development of a propertyof a cementitious mixture.3.1.3.1 Discussion—While the term is used usually to de-scribe 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.1This practice is under the jurisdiction of ASTM Committee C09 on Concreteand ConcreteAggregates and is the direct responsibility of Subcommittee C09.64 onNondestructive and In-Place Testing.Current edition approved June 15, 2011. Published July 2011. Originallyapproved in 1987. Last previous edition approved in 2010 as C1074 – 10a. DOI:10.1520/C1074-11.2Section on Safety Precautions, Manual of Aggregate and Concrete Testing,Annual Book of ASTM Standards, Vol 04.02.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at

[email protected] For Annual Book of ASTMStandards volume information, refer to the standard’s Document Summary page onthe ASTM website.4The last approved version of this historical standard is referenced onwww.astm.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 States13.1.4 maturity function—a 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 index—an indicator of maturity that is calcu-lated from the temperature history of the cementitious mixtureby using a maturity function.3.1.5.1 Discussion—The 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. Two widelyused maturity indexes are the temperature-time factor and theequivalent age.3.1.6 maturity method—a 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, 2, 3).53.1.7 strength-maturity relationship—an 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 factor—the maturity index com-puted according to Eq 1.4. 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 estimation 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 estimate 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 roadways to traffic.5.2 This practice can be used to estimate strength 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 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 using the appropriate maturity function for the particularconcrete mixture. Annex A1 provides a procedure for deter-mining experimentally the best parameters (datum temperatureor value of Q) for the maturity functions described in Section6.6. Maturity Functions6.1 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:M~t! 5(~Ta2 To! ∆t (1)where:M(t) = the temperature-time factor at age t, degree-days ordegree-hours,∆t = a time interval, days or hours,Ta= average concrete temperature during time interval,∆t, °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(e2QS1Ta21TsD∆ t (2)where:te= equivalent age at a specified temperature Ts, days or h,Q = activation energy divided by the gas constant, K,Ta= average temperature of concrete during time interval∆t,K,Ts= specified temperature, K, and∆t = time interval, days or h.NOTE 1—Temperature in kelvin (K) equals approximately temperature°C + 273 °C.6.4 Approximate values 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 A1.7. Apparatus7.1 A device is required to monitor and record the concretetemperature as a function of time and compute the maturityindex in accordance with Eq 1 or Eq 2.NOTE 2—Acceptable devices include commercial maturity instrumentsthat monitor temperature and compute and display either temperature-timefactor or equivalent age. Some commercial maturity instruments use fixedvalues of datum temperature or activation energy in evaluating thematurity index; thus the displayed maturity index may not be indicative ofthe true value for the concrete mixture being used. Refer to Appendix X1for information on correcting displayed time-temperature values foranother value of datum temperature. Equivalent-age values displayed by amaturity instrument cannot be adjusted for another activation energyvalue.7.2 Alternative devices include temperature sensors con-nected to data-loggers, or embedded digital devices that5The boldface numbers in parentheses refer to the list of references at the end ofthis practice.C1074 − 112measure, record, and store temperature data as a function oftime. The temperature data are used to calculate the maturityindex according to Eq 1 or Eq 2.7.3 The time interval between temperature measurementsshall be1⁄2 h or less for the first 48 h and1horless thereafter.The temperature recording device shall be accurate to within61 °C.8. Procedure to Develop Strength-Maturity Relationship8.1 Prepare at least 15 cylindrical specimens according toPractice C192/C192M . The mixture proportions and constitu-ents of the concrete shall be similar to those of the concretewhose strength will be estimated using 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. Immediately connect thesensors to maturity instruments or to temperature-recordingdevices such as data-loggers or strip-chart recorders.NOTE 3—A method to assist in the proper positioning of the sensor 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 toensure 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 C511.8.4 Unless specified otherwise, perform compression testsat ages of 1, 3, 7, 14, and 28 days in accordance with TestMethod C39/C39M. 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 the low test result.NOTE 4—For 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 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 Eq 1 or Eq 2. Unless specifiedotherwise, use a time interval (∆t)of1⁄2 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 5—Judgement should be used in selecting the initial timeintervals 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 strength 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 between compressivestrength and temperature-time factor, and Fig. 2 is an exampleof a relationship between compressive strength and equivalentage at 20 °C.NOTE 6—The strength-maturity relationship can also be established byusing regression analysis to determine a best-fit equation to the data.Possible 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 least 15 beamspecimens in accordance with Practice C192/C192M.Iftwobatches are needed to prepare the required number ofspecimens, cast an equal number of beams from each batch,and test one beam from each batch at the test ages given in 8.4.Embed temperature sensors in two specimens, one from eachbatch if two batches are made. Connect the sensors to maturityinstruments or temperature recording devices, and moist curethe specimens in a water bath or in a moist room meeting therequirements of Specification C511. Measure flexural strengthin accordance with Test Method C78 at time intervals 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 test 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.8.8 It is also permitted to develop a relationship betweencube strength of concrete and the maturity index. Follow theprocedure as given for cylinders except that the cubes shouldbe prepared and tested in accordance with the applicable testmethod. Insert temperature sensors at t