1、Standard Method of Test for Total Evaporable Moisture Content of Aggregate by Drying AASHTO Designation: T 255-00 (2012)1ASTM Designation: C566-97(2004) American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-1c T 255-1 AA
2、SHTO Standard Method of Test for Total Evaporable Moisture Content of Aggregate by Drying AASHTO Designation: T 255-00 (2012)1ASTM Designation: C566-97(2004) 1. SCOPE 1.1. This test method covers the determination of the percentage of evaporable moisture in a sample of aggregate by drying both surfa
3、ce moisture and moisture in the pores of the aggregate. Some aggregate may contain water that is chemically combined with the minerals in the aggregate. Such water is not evaporable and is not included in the percentage determined by this test method. 1.2. The values stated in SI units are to be reg
4、arded as the standard. The values stated in parentheses are provided for information only. 1.3. This standard does not purport to address 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 prac
5、tices and determine the applicability of regulatory limitations prior to use. For specific precautionary statements, see Sections 5.3.1, 7.2.1, and 7.3.1. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: M 92, Wire-Cloth Sieves for Testing Purposes M 231, Weighing Devices Used in the Testing of Materi
6、als T 2, Sampling of Aggregates T 19M/T 19, Bulk Density (“Unit Weight”) and Voids in Aggregate T 84, Specific Gravity and Absorption of Fine Aggregate T 85, Specific Gravity and Absorption of Coarse Aggregate 2.2. ASTM Standards: C125, Standard Terminology Relating to Concrete and Concrete Aggregat
7、es C670, Standard Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials 3. TERMINOLOGY 3.1. DefinitionsFor definitions of terms used in this test method, refer to ASTM C125. 2015 by the American Association of State Highway and Transportation Officials.All
8、rights reserved. Duplication is a violation of applicable law.TS-1c T 255-2 AASHTO 4. SIGNIFICANCE AND USE 4.1. This test method is sufficiently accurate for usual purposes such as adjusting batch quantities of ingredients for concrete. It will generally measure the moisture in the test sample more
9、reliably than the sample can be made to represent the aggregate supply. In rare cases where aggregate itself is altered by heat, or where more refined measurement is required, the test should be conducted using a ventilated, controlled-temperature oven. 4.2. Large particles of coarse aggregate, espe
10、cially those larger than 50 mm (2 in.), will require greater time for the moisture to travel from the interior of the particle to the surface. The user of this test method should determine by trial if rapid drying methods provide sufficient accuracy for the intended use when drying large-size partic
11、les. 5. APPARATUS 5.1. BalanceThe balance shall have sufficient capacity, be readable to 0.1 percent of the sample mass, or better, and conform to the requirements of M 231. 5.2. Source of HeatA ventilated oven capable of maintaining the temperature surrounding the sample at 110 5C (230 9F). Where c
12、lose control of the temperature is not required (see Section 4.1), other suitable sources of heat may be used, such as an electric or gas hot plate, electric heat lamps, or a ventilated microwave oven. 5.3. Sample ContainerA container not affected by the heat, and of sufficient volume to contain the
13、 sample without danger of spilling, and of such shape that the depth of sample will not exceed one-fifth of the least lateral dimension. 5.3.1. PrecautionWhen a microwave oven is used, the container shall be nonmetallic. Note 1Except for testing large samples, an ordinary frying pan is suitable for
14、use with a hot plate, or any shallow flat-bottomed metal pan with heat lamps or oven. Note precaution in Section 5.3.1. 5.4. StirrerA metal spoon or spatula of convenient size. 6. SAMPLE 6.1. Sampling shall generally be accomplished in accordance with T 2, except the sample size may be as stated in
15、Table 1. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1c T 255-3 AASHTO Table 1Sample Size for Aggregate Nominal Maximum Size of Aggregate, mm (in.)aMass of Normal Weight Aggregate Sample, Min., kg
16、b4.75 (0.187) (No. 4) 0.5 9.5 (3/8) 1.5 12.5 (1/2) 2 19.0 (3/4) 3 25.0 (1) 4 37.5 (11/2) 6 50 (2) 8 63 (21/2) 10 75 (3) 13 90 (31/2) 16 100 (4) 25 150 (6) 50 a Based on sieves meeting M 92. b Determine the minimum sample mass for lightweight aggregate by multiplying the value listed by the dry-loose
17、 unit mass of the aggregate in kg/m3(determined using T 19M/T 19) and dividing by 1600. 6.2. Secure a sample of the aggregate representative of the moisture content in the supply being tested and having a mass not less than the amount listed in Table 1. Protect the sample against loss of moisture pr
18、ior to determining the mass. 7. PROCEDURE 7.1. Determine the mass of the sample to the nearest 0.1 percent. 7.2. Dry the sample thoroughly in the sample container by means of the selected source of heat, exercising care to avoid loss of any particles. Very rapid heating may cause some particles to e
19、xplode, resulting in loss of particles. Use a controlled temperature oven when excessive heat may alter the character of the aggregate, or where more precise measurement is required. If a source of heat other than the controlled temperature oven is used, stir the sample during drying to accelerate t
20、he operation and avoid localized overheating. When using a microwave oven, stirring of the sample is optional. 7.2.1. Caution: When using a microwave oven, occasionally minerals are present in aggregates that may cause the material to overheat and explode. If this occurs, it can damage the microwave
21、 oven. 7.3. When a hot plate is used, drying can be expedited by the following procedure. Add sufficient anhydrous denatured alcohol to cover the moist sample. Stir and allow suspended material to settle. Decant as much of the alcohol as possible without losing any of the sample. Ignite the remainin
22、g alcohol and allow it to burn off during drying over the hot plate. 7.3.1. Warning: Exercise care to control the ignition operation to prevent injury or damage from the burning alcohol. 7.4. The sample is thoroughly dry when further heating causes, or would cause, less than 0.1 percent additional l
23、oss in mass. 7.5. Determine the mass of the dried sample to the nearest 0.1 percent after it has cooled sufficiently not to damage the balance. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1c T 255
24、-4 AASHTO 8. CALCULATION 8.1. Calculate total evaporable moisture content as follows: ( )100p WDD= (1) where: p = total evaporable moisture content of sample, percent; W = mass of original sample, g; and D = mass of dried sample, g. 8.2. Surface moisture content is equal to the difference between th
25、e total evaporable moisture content and the absorption, with all values based on the mass of a dry sample. Absorption may be determined in accordance with T 85, Test for Specific Gravity and Absorption of Coarse Aggregate, or T 84, Test for Specific Gravity and Absorption of Fine Aggregate. 9. PRECI
26、SION AND BIAS 9.1. Precision: 9.1.1. The within-laboratory single-operator standard deviation for moisture content of aggregates has been found to be 0.28 percent (Note 2). Therefore, results of two properly conducted tests by the same operator in the same laboratory on the same type of aggregate sa
27、mple should not differ by more than 0.79 percent (Note 2) from each other. 9.1.2. The between-laboratory standard deviation for moisture content of aggregates has been found to be 0.28 percent (Note 2). Therefore, results of properly conducted tests from two laboratories on the same aggregate sample
28、 should not differ by more than 0.79 percent (Note 2) from each other. 9.1.3. Test data used to derive the above precision indices were obtained from samples dried to a constant mass in a drying oven maintained at 110 5C. When other drying procedures are used, the precision of the results may be sig
29、nificantly different than that indicated above. Note 2These numbers represent, respectively, the 1s and d2s limits as described in ASTM C670. 9.2. Bias: 9.2.1. When experimental results are compared with known values from accurately compounded specimens, the following has been derived. 9.2.1.1. The
30、bias of moisture tests on one aggregate material has been found to have a mean of +0.06 percent. The bias of individual test values from the same aggregate material has been found with 95 percent confidence to lie between 0.07 percent and +0.20 percent. 9.2.1.2. The bias of moisture tests on a secon
31、d aggregate material has been found to have a mean of less than +0.01 percent. The bias of individual test values from the same aggregate material has been found with 95 percent confidence to lie between 0.14 percent and +0.14 percent. 9.2.1.3. The bias of moisture tests overall on both aggregate ma
32、terials has been found to have a mean of +0.03 percent. The bias of individual test values overall from both aggregate materials has been found with 95 percent confidence to lie between 0.12 percent and +0.18 percent. 2015 by the American Association of State Highway and Transportation Officials.All
33、 rights reserved. Duplication is a violation of applicable law.TS-1c T 255-5 AASHTO 9.2.2. Test data used to derive the above bias statement were obtained from samples dried to a constant mass in a drying oven maintained at 110 5C. When other drying procedures are used, the bias of the results may b
34、e significantly different than that indicated above. Note 3These precision and bias statements were derived from aggregate moisture data provided by 17 laboratories participating in the SHRP Soil Moisture Proficiency Sample Program, which is fully described in the National Research Council Report SH
35、RP-P-619. The samples tested that relate to these statements were well-graded mixtures of fine and coarse aggregate with moisture contents ranging from air dry to saturated surface-dry. 10. KEYWORDS 10.1. Aggregate; drying; moisture content. 1 This method is technically equivalent with ASTM C566-97(2004), except for the balance statement in Section 5.1. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
