COE CRD-C 55-92-1992 HANDBOOK FOR CONCRETE AND CEMENT TEST METHOD FOR WITHIN-BATCH UNIFORMITY OF FRESHLY MIXED CONCRETE《新拌混凝土批次内均质性混凝土和水泥测试方法手册》.pdf

1、(Issued 1 Sep. 1992)CRD-C 55-92C 55Test Method for Within-Batch Uniformity of Freshly Mixed Concrete1. Scope1.1 This standard gives procedures for estimatingthe uniformity of distribution of constituents within abatch of freshly mixed hydraulic-cement concrete.These data, together with limits based

2、on their use, mayprovide requirements for uniformity as this should beachieved when a satisfactory mixer mixes a batch ofconcrete for an appropriate length of time.1.2 The procedures given in this standard are sim-ilar to but different from those given in CRD-C 31. Theprimary difference is that this

3、 standard requires estima-tion of uniformity based on three samples rather thantwo samples from a single batch of mixed concrete.2. Applicable Documents2.1 Corps of Engineers StandardsCRD-C 4 Method of Sampling Freshly MixedConcrete (ASTM C 172)CRD-C 5 Test Method for Slump of PortlandCement Concret

4、e (ASTM C 143)CRD-C 7 Test Method for Unit Weight, Yield,and Air Content (Gravimetric) of Concrete (ASTM C138)CRD-C 8 Test Method for Air Content ofFreshly Mixed Concrete by the Volumetric Method(ASTM C 173)CRD-C 10 Practice for Making and CuringConcrete Test Specimens in the Laboratory (ASTM C192)C

5、RD-C 11 Practice for Making and CuringConcrete Test Specimens in the Field (ASTM C 31)CRD-C 14 Test Method for CompressiveStrength of Cylindrical Concrete Specimens (ASTM C39)CRD-C 31 Specification for Ready-MixedConcrete (ASTM C 94)CRD-C 41 Test Method for Air Content ofFreshly Mixed Concrete by th

6、e Pressure Method(ASTM C 231)CRD-C 75 Test Method for Unit Weight ofStructural Lightweight Concrete (ASTM C 567)CRD-C 97 Method of Making, AcceleratedCuring, and Testing of Concrete Compression TestSpecimens (ASTM C 684)CRD-C 102 Specification for Wire-ClothSieves for Testing Purposes (ASTM E 11)CRD

7、-C 113 Test Method for Total MoistureContent of Aggregate by Drying (ASTM C 566)3. Significance and Use3.1 This test method is used primarily to provide abasis for establishing the minimum time of mixing re-quired to produce a batch of concrete from given mate-rials and proportions in a given concre

8、te mixer withadequate uniformity of distribution of constituents inthe batch. The performance of a given concrete mixeras used for mixing a given batch of concrete for a givenmixing time may be evaluated from the information cal-culated from the results of tests made using this method.Requirements f

9、or satisfactory performance of a mixerwith respect to uniformity should be given in the appli-cable specification.3.2 Since the sequence of method of charging themixer will have an important effect on the uniformity ofthe concrete, it follows that the results obtained by theuse of this standard not

10、only measure effects of themixer itself and the mixing time, but also those of themanner in which the mixer was charged.4. Apparatus and Materials4.1 The apparatus and materials shall consist ofthe following:4.1.1 Scales or Balances. - Scales andbalances having capacities of 1000 lb (453.59 kg). 2 k

11、g,and 500 g with an accuracy of 0.1 percent of the testload at any point within the range of use for this test,and meeting the requirements for sensitivity andtolerances prescribed in CRD-C 10.4.1.2 Drying Apparatus. - A hot platecapable of heating to at least 110 C, a drying pan, and aspatula; or a

12、 suitable microwave oven with oven glasscontainers. A suitable microwave oven is one that iscapable of drying six 500-g samples of mortar of 0.6water-cement ratio (by mass) to constant mass in a timeperiod of not more than 48 min. Constant mass isachieved when the mass of a sample does not change by

13、more than 0.2 percent of the original mass onProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-C 55 (Issued 1 Sep. 1992)2 CRD-C 55-92successive determinations of mass. The apparatusdescribed in CRD-C 113 is satisfactory.4.1.3 Sieving Apparatus. - A mec

14、hanicalsieve shaker and sieves for sieving the concrete. Theapparatus described in CRD-C 4 has been foundsatisfactory. The sieves shall conform to therequirements of CRD-C 102.4.2 In addition, the apparatus and materials re-quired to perform such of the tests listed underapplicable documents as may

15、be specified for the partic-ular testing to be done, shall be provided.5. Samples5.1 Any quantity of concrete, such as a batch thathas been mixed in a given mixer for a given length oftime, shall be sampled in accordance with the applicableprovisions of CRD-C 4, in such a manner as to obtainthree sa

16、mples which represent separately each of thethree thirds of the quantity being investigated. In thecase of a batch that has been mixed, these three samplesshall represent the first, middle, and last third of thebatch as it is discharged from the mixer. If the batch issampled as it is discharged, the

17、 mixer shall be dis-charged using normal procedures (not in increments). Ifthe device used for sampling concrete for other tests isnot adaptable for obtaining three samples as describedabove, during discharge of the mixer, samples may beobtained as the concrete is discharged from the wet-batch hoppe

18、r, or especially in the case of turbine mix-ers, they may be taken from the mixer drum at thirdpoints in the batch. In the event that the samples aretaken from the wet-batch hopper, care should be takento insure that the hopper is empty when the batch is dis-charged into the hopper and that no concr

19、ete is added tothe hopper until the sampling is complete.5.2 The very first and very last concrete to be dis-charged should not be sampled; specifically, the threesamples shall be taken as nearly as possible from withinvolumes making up each of three different fifths of thebatch as visualized from b

20、eginning to end of dischargeas illustrated in Fig. 1.5.3 The sample size shall be as follows:Maximum Nominal ApproximateSize of Concrete Size of Each ofAggregate Three Samplesmm in. cu ft m 319.0 3/4 2.00 0.05737.5 1-1/2 2.25 0.06475 3 3.50 0.099150 6 5.00 0.1426. Sample Preparation6.1 Preliminary S

21、ieving. For concrete mixturescontaining aggregate larger than 37.5 mm (1-1/2 in.),perform a preliminary mechanical sieving with enoughmaterials of each sample in order to obtain approxi-mately 180 lb (82 kg) of material passing the 37.5-mm(1-1/2 in.) sieve for use in determining the slump, unitweigh

22、t of air-free mortar, water content, and moldingspecimens for compressive strength test. Discard thosematerials retaining on the 37.5-mm (1-1/2 in.) sieve.The remaining materials in each sample shall be usedLASTMATERIALDISCHARGEDFIRSTPERCENTAGE OF DISCHARGE MATERIALDISCHARGEDFig. 1. Hypothetical dis

23、tribution linearly of a batch or other volume of concrete to be sampled for uniformity,indicating (by cross hatching) zones to be avoided and (by numerals) zones within which the three samples areto be taken.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IH

24、S-,-,-(Issued 1 Sep. 1992)CRD-C 55-92C 553for the determination of percentage of coarse aggregatein accordance with paragraph 12.1. Do not include anyportions that have been removed during the preliminarymechanical sieving. For concrete mixtures containingno aggregate particles that would be retaine

25、d on the37.5-mm (1-1/2 in.) sieve, preliminary mechanical siev-ing is not needed.termine the air content on the same sample using theprocedure given in CRD-C 41. Wash the entire air-content test sample over a 4.75-mm (No. 4) sieve, andobtain the saturated surface-dry mass of the retained ag-gregate.

26、10.2 The unit weight of air-free mortar is calcu-lated as follows:6.2 Take approximately 25 lb (or 11 kg) of theconcrete containing no aggregate particles that would beretained on the 37.5-mm (1-1/2-in.) sieve, representingeach of the three samples of the mixture, and mechani-cally sieve each over a

27、 dampened 4.75-mm (No. 4)sieve for 5 min. Use the material passing the 4.75-mm(No. 4) sieve for water content test.where6.3 In both of the sieving operations, use coarsersieves above the test sieve to prevent overloading. Con-duct the sampling and testing of the three samples in asshort a time as po

28、ssible, since the results are signifi-cantly affected by the time of testing.7. Regular Testing7.1 Regular testing will include slump, air content,compressive strength, unit weight of air-free mortar,water content, and percentage of coarse aggregate.M = unit weight of air-free mortar, lb/cu ft (kg/m

29、 3 ).b = mass of concrete sample, lb (kg),c = saturated surface-dry mass of aggregate re-tained on the 4.75-mm (No. 4) sieve, lb (kg),V = volume of air-content test container, cu ft (m 3 ),A = air content of sample test, %,G = specific gravity of the coarse aggregate, andW = unit weight of water, 62

30、.3 lb/ft 3 (998 kg/m 3 ).8. Slump8.1 Material from each of the three samples shallbe tested for slump using CRD-C 5.10.3 If the concrete is structural lightweight con-crete, unit weight shall be determined by CRD-C 75 andair content by CRD-C 8.9. Compressive Strength 11. Water Content9.1 Material fr

31、om each of the three samples shallbe used to make three compressive strength specimensaccording to the applicable portions of CRD-C 11 orCRD-C 10 depending on whether the work is beingdone in the field or in the laboratory. The specimensshall be tested for compressive strength at the age of 7days ac

32、cording to CRD-C 14. They may be cured ac-cording to the warm water method in CRD-C 97, if re-sults are needed quickly.11.1 Using that portion of the mixture passing the4.75-mm (No. 4) sieve for each of the three samples,weigh out two 500-g fractions into pans and dry on thehot plate for at least 15

33、 min until constant mass isachieved, being careful to prevent any loss of solid ma-terial from the pans during drying; or weigh out two500-g fractions into oven glass containers and dry in themicrowave oven until constant mass is achieved.9.2 The compressive strength of each specimenand the average

34、strength of the three specimens fromeach sample shall be calculated.11.2 Upon completion of the drying, again weighthe samples to the nearest 0.1 g and determine the watercontents by the following formula:10. Unit Weight of Air-Free Mortar10.1 The unit weight of air-free mortar is deter-mined on the

35、 portion of each of the three samples pass-ing the 37.5-mm (1-1/2-in.) sieve. First, consolidate theconcrete in the air-content test container and obtain themass for that volume according to CRD-C 7. Then de-where:P = water content of sample, %, andW = mass of dried sample, g.Provided by IHSNot for

36、ResaleNo reproduction or networking permitted without license from IHS-,-,-C 55 (Issued 1 Sep. 1992)4 CRD-C 55-9211.3 The average water content of the two deter-minations for each of the three samples shall becalculated.12. Percentage of Coarse Aggregate in Sample12.1 Weigh each of the three samples

37、 remainingfor determining the percentage of coarse aggregate andwash the materials over a 4.75-mm (No. 4) sieve to ob-tain the total saturated surface-dry weight of the mate-rial retained on the 4.75-mm (No. 4) sieve.12.2 For concrete containing large aggregate itmay be desirable, after the total ma

38、ss retained on the4.75-mm (No. 4) sieve has been obtained, to sieve theretained material over the 37.5-mm (1-1/2-in.) and 75-mm (3-in.) sieves to obtain further information concern-ing the distribution of the coarse aggregate for each ofthe three samples.12.3 The percentage of coarse aggregate retai

39、nedon each of these sieves is obtained by dividing the satu-rated surface-dry mass of the material retained on eachsieve by the mass of the original sample of the freshlymixed concrete as obtained from the mixer discharge, asfollows:whereP = (c/b) x 100P = mass % of coarse aggregate in concrete,c =

40、saturated surface-dry-mass in lb (kg) of aggre-gate retained on the 4.75-mm (No. 4) sieve, re-sulting from washing all material finer thanthis sieve from the fresh concrete, andb = mass of sample of fresh concrete, lb (kg)13. Abbreviated Testing13.1 Abbreviated testing consists of the determi-nation

41、 of coarse-aggregate content, compressivestrength, and unit weight of air-free mortar as describedabove.14. Report14.1 In preparing the report on evaluation of theperformance of the mixer under test, the results for eachof the three samples for each batch and mixing timeshould be reported and the di

42、fference between the high-est and lowest of the values for each determination (Fig.2) reported. These values for the three batches mixed atthe designated or selected mixing time shall also be re-ported (Fig. 3).14.2 The report shall include the following (ex-cept that a report of abbreviated testing

43、 will not includeresults of tests not part of such testing).14.2.1 Name of manufacturer of mixer.14.2.2 Type and capacity of mixer.14.2.3 Mixing time for each batch of concretetested.14.2.4 Complete data concerning the mixtureproportions, including materials used and mass of eachingredient in the ba

44、tch: slump, air content, and unitweight results for each of the three samples.14.2.5 Mass of each of the three concrete testsamples from each batch tested.14.2.6 Water content of each mortar specimenand average water content of two specimens to thenearest 0.1 percent by mass for each of the three te

45、stsamples.14.2.7 The unit weight of air-free mortar tothe nearest 0.1 lb/ft 3 (1.6 kg/m 3 ) for each of the threetest samples.14.2.8 Total amount of coarse aggregate to thenearest 0.1 percent by mass for each of the three testsamples.14.2.9 Compressive strength of each specimenand the average compre

46、ssive strength of threespecimens from each of the three test samples.14.2.10 The range of the three values for thethree samples for each batch. Range is the numericaldifference between the highest value and the lowestvalue obtained from the different portions of a batch ofconcrete being evaluated fo

47、r uniformity.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-(Issued 1 Sep. 1992) C 55CRD-C 55-92 5Fig. 2. Test results for one batch.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-C 55 (Issued 1 Sep. 1992)6 CRD-C 55-92Fig. 3. Test results for three batches.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-