AASHTO R 60-2012 Standard Practice for Sampling Freshly Mixed Concrete.pdf

1、Standard Practice for Sampling Freshly Mixed Concrete AASHTO Designation: R 60-12 (2016) Release: Group 1 (April 2016) ASTM Designation: C172-10 American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-3b R 60-1 AASHTO Stan

2、dard Practice for Sampling Freshly Mixed Concrete AASHTO Designation: R 60-12 (2016) Release: Group 1 (April 2016) ASTM Designation: C172-10 1. SCOPE 1.1. This method covers the procedures for obtaining representative samples of fresh concrete as delivered to the project site and on which tests are

3、to be performed to determine compliance with quality requirements of the specifications under which the concrete is furnished (Note 1). The method includes sampling from stationary, paving, and truck mixers and from agitating and nonagitating equipment used to transport central mixed concrete. 1.2.

4、The values stated in SI units are to be regarded as the standard. The inch-pound equivalents of metric units may be approximate. Note 1Combined samples are required by this method, unless specifically excepted by procedures governing the tests to be performed, such as tests to determine uniformity o

5、f consistency and mixer efficiency. Procedures used to select the specific test batches are not described in this method, but it is recommended that random sampling be used to determine overall specification compliance. 1.3. This practice also covers the procedures to be used for preparing a sample

6、of concrete for further testing where it is desirable or necessary to remove the aggregate larger than a designated size. This removal of larger aggregate particles is preferably accomplished by wet-sieving. 1.4. The text of this standard references notes and footnotes that provide explanatory mater

7、ial and shall not be considered as requirements of the practice. 1.5. This standard does not purport to address of all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the

8、 applicability of regulatory limitations prior to use. WarningFresh hydraulic cementitious mixtures are caustic and may cause chemical burns to skin and tissue upon prolonged exposure. 2. REFERENCED DOCUMENT 2.1. AASHTO Standard: M 92, Wire-Cloth Sieves for Testing Purposes 3. SIGNIFICANCE AND USE 3

9、.1. This practice is intended to provide standard requirements and procedures for sampling freshly mixed concrete from different containers used in the production or transportation of concrete. The detailed requirements as to materials, mixtures, air content, temperature, number of specimens, slump,

10、 interpretation of results, and precision and bias are described in specific test methods. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b R 60-2 AASHTO 4. SAMPLING 4.1. The elapsed time shall not

11、exceed 15 min between obtaining the first and final portions of the composite sample. 4.1.1. Transport the individual samples to the place where fresh concrete tests are to be performed or where test specimens are to be molded. They shall then be combined and remixed with a shovel in the minimum amo

12、unt necessary to ensure uniformity and compliance with the minimum time limits specified in Section 4.1.2. 4.1.2. Start tests for slump, temperatures, and air content within 5 min after obtaining the final portion of the composite sample. Complete these tests quickly. Start molding specimens for str

13、ength tests within 15 min after fabricating the composite sample. Quickly obtain and use the sample and protect the sample from the sun, wind, and other sources of rapid evaporation and from contamination. 5. PROCEDURE 5.1. Size of SampleMake the samples to be used for strength tests a minimum of 28

14、 L (1 ft3). Smaller samples are not prohibited for routine air content and slump tests and the size shall be dictated by the maximum aggregate size. 5.2. The procedures used in sampling shall include the use of every precaution that will assist in obtaining samples that are truly representative of t

15、he nature and condition of concrete sampled as follows: Note 2Sampling should normally be performed as the concrete is delivered from the mixer to the conveying vehicle used to transport the concrete to the forms; however, specifications may require other points of sampling, such as at the discharge

16、 of a concrete pump. 5.2.1. Note 3As routine air content and slump tests are not readily adaptable to sampling the concrete at two or more regularly spaced intervals during discharge of the middle portion of the batch as specified in this method, the sample for air content, slump, and temperature ma

17、y be taken after at least 0.20 m3(0.25 yd3) of concrete has been discharged. 5.2.2. Sampling from Stationary Mixers, Except Paving MixersSample the concrete by collecting two or more portions taken at regularly spaced intervals during discharge of the middle of the batch. Obtain these portions withi

18、n the time limit specified in Section 4. Combine the portions into one sample for testing purposes. Do not obtain portions of the composite sample from the very first or last part of the batch discharge (Note 4). Perform sampling by passing a receptacle completely through the discharge stream or by

19、completely diverting the discharge into a sample container. If discharge of the concrete is too rapid to divert the complete discharge stream, discharge the concrete into a container or transportation unit sufficiently large to accommodate the entire batch and then accomplish the sampling in the sam

20、e manner as given above. Take care not to restrict the flow of concrete from the mixer, container, or transportation unit so as to cause segregation. These requirements apply to both tilting and nontilting mixers. Note 4No sample should be taken before 10 percent or after 90 percent of the batch has

21、 been discharged. Due to the difficulty of determining the actual quantity of concrete discharged, the intent is to provide samples that are representative of widely separated portions but not the beginning and end of the load. 5.2.3. Sampling from Paving MixersSample the concrete after the contents

22、 of the paving mixer have been discharged. Obtain samples from at least five different portions of the pile and then combine 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b R 60-3 AASHTO them into

23、one sample for test purposes. Avoid contamination with subgrade material or prolonged contact with an absorptive subgrade. To preclude contamination or absorption by the subgrade, sample the concrete by placing three shallow containers on the subgrade and discharging the concrete across the containe

24、rs. Combine the samples into one sample for test purposes. The containers shall be of a size sufficient to provide a composite sample size that is in agreement with the maximum aggregate size. Note 5In some instances, the containers may have to be supported above the subgrade to prevent displacement

25、 during discharge. 5.2.4. Sampling from Revolving Drum Truck Mixers or AgitatorsSample the concrete by collecting two or more portions taken at regularly spaced intervals during discharge of the middle portion of the batch. Take the samples so obtained within the time limit specified in Section 4 an

26、d combine them into one sample for test purposes. In any case do not obtain samples until after all of the water and any admixtures have been added to the mixer; also do not obtain samples from the very first or last portions of the batch discharge (Note 4). Sample by repeatedly passing a receptacle

27、 through the entire discharge stream or by completely diverting the discharge into a sample container. Regulate the rate of discharge of the batch by the rate of revolution of the drum and not by the size of the gate opening. 5.2.5. Sampling from Open-Top Truck Mixers, Agitators, Nonagitating Equipm

28、ent, or Other Types of Top ContainersTake samples by whichever of the procedures described in Sections 5.2.1, 5.2.2, or 5.2.3 is most applicable under the given conditions. 6. ADDITIONAL PROCEDURE FOR LARGE, MAXIMUM-SIZE AGGREGATE CONCRETE 6.1. When the concrete contains aggregate larger than that a

29、ppropriate for the size of the molds or equipment to be used, wet-sieve the sample as described below except perform density (unit weight) tests for use in yield computations on the full mix. Note 6The effect of wet-sieving on the test results should be considered. For example, wet-sieving concrete

30、causes the loss of a small amount of air due to additional handling. The air content of the wet-sieved fraction of concrete is greater than that of the total concrete because the larger size aggregate that is removed does not contain air. The apparent strength of wet-sieved concrete in smaller speci

31、mens is usually greater than that of the total concrete in larger appropriate size specimens. The effect of these differences may need to be considered or determined by supplementary testing for quality control or test result evaluation purposes. 6.2. Definition: 6.2.1. Wet-Sieving Concretethe proce

32、ss of removing aggregate larger than a designated size from the fresh concrete by sieving it on a sieve of the designated size. 6.3. Apparatus: 6.3.1. Sievesas designated, conforming to M 92. 6.3.2. Receptaclea container of suitable size having a nonabsorbent surface. 6.3.3. Wet-Sieving EquipmentEqu

33、ipment for wet-sieving concrete shall be a sieve, as noted in Section 6.3.1, of suitable size and conveniently arranged and supported so that one can shake it rapidly by either hand or mechanical means. Generally, a horizontal back-and-forth motion is preferred. The equipment shall be capable of rap

34、idly and effectively removing the designated size of aggregate. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b R 60-4 AASHTO 6.3.4. Hand ToolsShovels, hand scoops, plastering trowels, and rubber g

35、loves, as required. 6.4. Procedure: 6.4.1. Wet-SievingAfter sampling the concrete, pass the concrete over the designated sieve and remove and discard the aggregate retained. This shall be done before remixing. Shake or vibrate the sieve by hand or mechanical means until no undersize material remains

36、 on the sieve. Mortar adhering to the aggregate retained on the sieve shall not be wiped from it before it is discarded. Place only enough concrete on the sieve at any one time so that, after sieving, the thickness of the layer of retained aggregate is not more than one particle thick. The concrete

37、that passes the sieve shall fall into a batch pan of suitable size that has been dampened before use or onto a clean, moist, nonabsorbent surface. Scrape any mortar adhering to the sides of the wet-sieving equipment into the batch. After removing the larger aggregate particles by wet-sieving, remix

38、the batch with a shovel in the minimum amount necessary to ensure uniformity and proceed testing immediately. 7. KEYWORDS 7.1. Air content; batch; composite sample; concrete; slump; temperature; wet-sieving. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.