AASHTO T 248-2014 Standard Method of Test for Reducing Samples of Aggregate to Testing Size.pdf

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1、Standard Method of Test for Reducing Samples of Aggregate to Testing Size AASHTO Designation: T 248-141ASTM Designation: C 702/C 702M-11 American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-1c T 248-1 AASHTO Standard Me

2、thod of Test for Reducing Samples of Aggregate to Testing Size AASHTO Designation: T 248-141ASTM Designation: C 702/C 702M-11 1. SCOPE 1.1. These methods cover the reduction of large samples of aggregate to the appropriate size for testing, employing techniques that are intended to minimize variatio

3、ns in measured characteristics between the test samples so selected and the large sample. 1.2. The values stated in SI units are to be regarded as the standard. 1.3. This standard does not purport to address the safety concerns associated with its use. It is the responsibility of the user of this st

4、andard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: T 2, Sampling of Aggregates T 84, Specific Gravity and Absorption of Fine Aggregate 2.2. ASTM Standard: C 125, Standard T

5、erminology Relating to Concrete and Concrete Aggregates 3. TERMINOLOGY 3.1. definitionsthe terms used in this standard are defined in ASTM C 125. 4. SIGNIFICANCE AND USE 4.1. Specifications for aggregates require sampling portions of the material for testing. Other factors being equal, larger sample

6、s will tend to be more representative of the total supply. The methods described in this standard provide for reducing the large sample obtained in the field or produced in the laboratory to a convenient size for conducting a number of tests to describe the material and measure its quality. These me

7、thods are conducted in such a manner that the smaller test sample portion will be representative of the larger sample and, thus, of the total supply. The individual test methods provide for minimum masses of material to be tested. 4.2. Under certain circumstances, reduction in size of the large samp

8、le prior to testing is not recommended. Substantial differences between the selected test samples sometimes cannot be avoided, as for example, in the case of an aggregate having relatively few large-sized particles in 2014 by the American Association of State Highway and Transportation Officials.All

9、 rights reserved. Duplication is a violation of applicable law.TS-1c T 248-2 AASHTO the sample. The laws of chance dictate that these few particles may be unequally distributed among the reduced-size test samples. Similarly, if the test sample is being examined for certain contaminants occurring as

10、a few discrete fragments in only small percentages, caution should be used in interpreting results from the reduced-size test sample. Chance inclusion or exclusion of only one or two particles in the selected test sample may importantly influence interpretation of the characteristics of the original

11、 sample. In these cases, the entire original sample should be tested. 4.3. Failure to carefully follow the procedures in these methods could result in providing a nonrepresentative sample to be used in subsequent testing. 5. SELECTION OF METHOD 5.1. Fine AggregateSamples of fine aggregate that are d

12、rier than the saturated surface-dry condition (Note 1) shall be reduced in size by a mechanical splitter according to Method A. Samples having free moisture on the particle surfaces may be reduced in size by quartering according to Method B, or by treating as a miniature stockpile as described in Me

13、thod C. 5.1.1. If the use of Method B or Method C is desired, and the sample does not have free moisture on the particle surfaces, the sample may be moistened to achieve this condition, thoroughly mixed, and then the sample reduction performed. Note 1The method of determining the saturated surface-d

14、ry condition is described in T 84. As a quick approximation, if the fine aggregate will retain its shape when molded in the hand, it may be considered to be wetter than saturated surface-dry. 5.1.2. If use of Method A is desired and the sample has free moisture on the particle surfaces, the entire s

15、ample may be dried to at least the surface-dry condition, using temperatures that do not exceed those specified for any of the tests contemplated, and then the sample reduction performed. Alternatively, if the moist sample is very large, a preliminary split may be made using a mechanical splitter ha

16、ving wide chute openings 38 mm (11/2in.) or more to reduce the sample to not less than 5000 g. The portion so obtained is then dried, and reduction to test sample size is completed using Method A. 5.2. Coarse AggregatesReduce the sample using a mechanical splitter in accordance with Method A (prefer

17、red method) or by quartering in accordance with Method B. The miniature stockpile Method C is not permitted for coarse aggregates or mixtures of coarse and fine aggregates. 5.3. Combined Coarse and Fine AggregateSamples that are in a dry condition may be reduced in size by either Method A or Method

18、B. Samples having free moisture on the particle surfaces may be reduced in size by quartering according to Method B. When Method A is desired and the sample is damp or shows free water, dry the sample until it appears dry or until clumps can be easily broken by hand (Note 2). Dry the entire sample t

19、o this condition, using temperatures that do not exceed those specified for any of the tests contemplated, and then reduce the sample. The miniature stockpile Method C is not permitted for combined aggregates. Note 2The “dryness” of the sample can be tested by tightly squeezing a small portion of th

20、e sample in the palm of the hand. If the cast crumbles readily, the correct moisture range has been obtained. 6. SAMPLING 6.1. The samples of aggregate obtained in the field shall be taken in accordance with T 2, or as required by individual test methods. When tests for sieve analysis only are conte

21、mplated, the size of field sample listed in T 2 is usually adequate. When additional tests are to be conducted, the 2014 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1c T 248-3 AASHTO user shall determi

22、ne that the initial size of the field sample is adequate to accomplish all intended tests. Similar procedures shall be used for aggregate produced in the laboratory. METHOD AMECHANICAL SPLITTER 7. APPARATUS 7.1. Sample SplitterSample splitters shall have an even number of equal width chutes, but not

23、 less than a total of eight for coarse aggregate, or 12 for fine aggregate, which discharge alternatively to each side of the splitter. For coarse aggregate and mixed aggregate, the minimum width of the individual chutes shall be approximately 50 percent larger than the largest particles in the samp

24、le to be split (Note 3). For dry fine aggregate in which the entire sample will pass the 9.5-mm (3/8-in.) sieve, the minimum width of the individual chutes shall be at least 50 percent larger than the largest particles in the sample and the maximum width shall be 19 mm (3/4in.). The splitter shall b

25、e equipped with two receptacles to hold the two halves of the sample following splitting. It shall also be equipped with a hopper or straightedged pan, which has a width equal to or slightly less than the overall width of the assembly of chutes, by which the sample may be fed at a controlled rate to

26、 the chutes. The splitter and accessory equipment shall be so designed that the sample will flow smoothly without restriction or loss of material (see Figure 1). Note: (a) may be constructed as either closed or open type. Closed type is preferred. Figure 1Sample Splitters (Riffles) Note 3Mechanical

27、splitters are commonly available in sizes adequate for coarse aggregate having the largest particle not over 37.5 mm (11/2in.). Feed ChuteAt Least EightOpeningsRiffle Sample Splitter(a) Large Sample Splitter for Coarse AggregateRolled Edges(b) Small Sample Splitters for Fine AggregateAt Least Twelve

28、Openings 2014 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1c T 248-4 AASHTO 8. PROCEDURE 8.1. Place the original sample in the hopper or pan and uniformly distribute it from edge to edge, so that when

29、it is introduced into the chutes, approximately equal amounts will flow through each chute. The rate at which the sample is introduced shall be such as to allow free flowing through the chutes into the receptacles below. 8.2. Reintroduce the portion of the sample in one of the receptacles into the s

30、plitter as many times as necessary to reduce the sample to the size specified for the intended test. The portion of the material collected in the other receptacle may be reserved for reduction in size for other tests. METHOD BQUARTERING 9. APPARATUS 9.1. Apparatus shall consist of a straightedge; st

31、raightedged scoop, shovel or trowel; a broom or brush; and a canvas blanket or tear-resistant tarp approximately 2 by 2.5 m (6 by 8 ft). 10. PROCEDURE 10.1. Use either the procedure described in Section 10.1.1 or 10.1.2, or a combination of both. 10.1.1. Place the original sample on a hard, clean, l

32、evel surface where there will be neither loss of material nor the accidental addition of foreign material. Mix the material by turning the entire sample over at least three times until the material is thoroughly mixed. With the last turning, form the entire sample into a conical pile by depositing i

33、ndividual lifts on top of the preceding lift. Carefully flatten the conical pile to a uniform thickness and diameter by pressing down the apex with a shovel or trowel so that each quarter sector of the resulting pile will contain the material originally in it. The diameter should be approximately fo

34、ur to eight times the thickness. Divide the flattened mass into four equal quarters with a shovel or trowel and remove two diagonally opposite quarters, including all fine material, and brush the cleared spaces clean. The two unused quarters may be set aside for later use or testing, if desired. Suc

35、cessively mix and quarter the remaining material until the sample is reduced to the desired size (see Figure 2). 10.1.2. As an alternative to the procedure in Section 10.1.1 or when the floor surface is uneven, the field sample may be placed on a canvas blanket or tear-resistant tarp and mixed with

36、a shovel or trowel as described in Section 10.1.1, leaving the sample in a conical pile. As an alternative to mixing with the shovel or trowel, lift each corner of the blanket or tarp and pull it over the sample toward the diagonally opposite corner, causing the material to be rolled. After the mate

37、rial has been rolled a sufficient number of times (a minimum of four times), so that it is thoroughly mixed, pull each corner of the blanket or tarp toward the center of the pile so the material will be left in a conical pile. Flatten the pile as described in Section 10.1.1. Divide the sample as des

38、cribed in Section 10.1.1, or insert a stick or pipe beneath the blanket or tarp and under the center of the pile, then lift both ends of the stick, dividing the sample into two equal parts. Remove the stick, leaving a fold of the blanket between the divided portions. Insert the stick under the cente

39、r of the pile at right angles to the first division and again lift both ends of the stick, dividing the sample into four equal parts. Remove two diagonally opposite quarters, being careful to clean the fines from the blanket or tarp. The two unused quarters may be set aside for later use or testing,

40、 if desired. Successively mix and quarter the remaining material until the sample is reduced to the desired size (see Figure 3). 2014 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1c T 248-5 AASHTO Figur

41、e 2Quartering on a Hard, Clean, Level Surface Figure 3Quartering on a Canvas Blanket or Tear-Resistant Tarp Cone Sample on Hard,Clean SurfaceMix by FormingNew ConeQuarter after Flattening ConeSample Divided into Quarters Retain Opposite QuartersReject the Other Two QuartersMix by Rolling on Blanket

42、Form Cone after Mixing Quarter after Flattening ConeSample Divided into Quarters Retain Opposite QuartersReject the Other Two Quarters 2014 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1c T 248-6 AASHTO

43、 METHOD CMINIATURE STOCKPILE SAMPLING (DAMP FINE AGGREGATE ONLY) 11. APPARATUS 11.1. Apparatus shall consist of a straightedge; straightedged scoop, shovel, or trowel for mixing the aggregate; and either a small sampling thief, small scoop, or spoon for sampling. 12. PROCEDURE 12.1. Place the origin

44、al sample of damp fine aggregate on a hard, clean, level surface where there will be neither loss of material nor the accidental addition of foreign material. Mix the material by turning the entire sample over at least three times until the material is thoroughly mixed. With the last turning, form t

45、he entire sample into a conical pile by depositing individual lifts on top of the preceding lift. If desired, the conical pile may be flattened to a uniform thickness and diameter by pressing the apex with a shovel or trowel so that each quarter sector of the resulting pile will contain the material

46、 originally in it. Obtain a sample for each test by selecting at least five increments of material at random locations from the miniature stockpile, using any of the sampling devices described in Section 11.1. 1 Technically equivalent but not identical to ASTM C 702/C 702M-11. 2014 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.