1、Standard Method of Test for Uncompacted Void Content of Coarse Aggregate (As Influenced by Particle Shape, Surface Texture, and Grading) AASHTO Designation: T 326-05 (2013)1 American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 2
2、0001 TS-1c T 326-1 AASHTO Standard Method of Test for Uncompacted Void Content of Coarse Aggregate (As Influenced by Particle Shape, Surface Texture, and Grading) AASHTO Designation: T 326-05 (2013)11. SCOPE 1.1. This method describes the determination of the loose uncompacted void content of a samp
3、le of coarse aggregate. When measured on any aggregate of a known grading, void content provides an indication of the aggregates angularity, sphericity, and surface texture compared with other coarse aggregates tested in the same grading. 1.2. Three procedures are included for the measurement of voi
4、d content. Two use graded coarse aggregate (standard grading or as-received grading), and the other uses several individual size fractions for void content determinations: 1.2.1. Standard Graded Sample (Method A)This method uses a standard coarse aggregate grading that is obtained by combining indiv
5、idual sieve fractions from the maximum density curve drawn from the maximum coarse aggregate size. (See Section 8.) 1.2.2. Individual Size Fractions (Method B)This method uses each of three coarse aggregate size fractions: (a) 19 mm (3/4in.) to 12.5 mm (1/2in.); (b) 12.5 mm (1/2in.) to 9.5 mm (3/8in
6、.); and (c) 9.5 mm (3/8in.) to 4.75 mm (No. 4). For this method, each size is tested separately. 1.2.3. As-Received Grading (Method C)This method uses that portion of the coarse aggregate retained on the 4.75-mm (No. 4) sieve. 1.3. This standard may involve hazardous materials, operations, and equip
7、ment. 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 practices and determine the applicability of regulation limitations prior to its use. 2. REFER
8、ENCED DOCUMENTS 2.1. AASHTO Standards: M 231, Weighing Devices Used in the Testing of Materials T 2, Sampling of Aggregates T 11, Materials Finer Than 75-m (No. 200) Sieve in Mineral Aggregates by Washing T 19M/T 19, Bulk Density (“Unit Weight”) and Voids in Aggregate T 27, Sieve Analysis of Fine an
9、d Coarse Aggregates T 85, Specific Gravity and Absorption of Coarse Aggregate T 248, Reducing Samples of Aggregate to Testing Size 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1c T 326-2 AASHTO 3.
10、SUMMARY OF TEST METHODS 3.1. A calibrated cylindrical measure is filled with coarse aggregate of prescribed grading by allowing the sample to flow through a funnel from a fixed height into the measure. The coarse aggregate is struck off, and its mass is determined by weighing. Uncompacted void conte
11、nt is calculated as the difference between the volume of the cylindrical measure and the absolute volume of the coarse aggregate collected in the measure. Uncompacted void content is calculated using the bulk dry specific gravity of the coarse aggregate as received without special grading except as
12、noted in Section 4.3.1. Two runs are made on each sample and the results are averaged. 3.1.1. For a graded sample (Test Method A or C) the percent void content is determined directly, and the average value from two runs is reported. 3.1.2. For the individual size fractions (Test Method B), the mean
13、percent void content is calculated using the results from tests of each of the three individual size fractions. 4. SIGNIFICANCE AND USE 4.1. Methods A and B provide percent void content determined under standardized conditions, which depends on the particle shape and texture of a coarse aggregate. A
14、n increase in void content by these procedures indicates greater angularity, less sphericity, or rougher surface texture, or some combination of the three factors. A decrease in void content results is associated with more rounded, spherical, or smooth-surfaced coarse aggregates, or a combination of
15、 these factors. 4.2. Method C measures the uncompacted void content of the fraction retained on a 4.75-mm (No. 4) sieve of the as-received material. This void content depends on grading as well as particle shape and texture. 4.3. The void content determined on the standard graded sample (Method A) i
16、s not directly comparable with the average void content of the three individual size fractions from the same sample tested separately (Method B). A sample consisting of single-size particles will have a higher void content than a graded sample. Therefore, use either one method or the other as a comp
17、arative measure of shape and texture, and identify which method has been used to obtain the reported data. Method C does not provide an indication of shape and texture directly if the grading from sample to sample changes. 4.3.1. The bulk dry specific gravity of the coarse aggregate determined by T
18、85 is used in calculating the void content. The effectiveness of these methods of determining void content and its relationship to particle shape and texture depends on the bulk specific gravity of various size fractions being equal, or nearly so. The void content is actually a function of the volum
19、e of each size fraction. If the type of rock or mineral or its porosity varies markedly in any of the size fractions, it may be necessary to determine the specific gravity of the size fractions used in the test. 5. APPARATUS 5.1. Cylindrical MeasureA cylindrical metal measure shall be watertight, wi
20、th the top and bottom true and even, preferably machined to accurate dimensions on the inside and sufficiently rigid to retain its form under rough usage. The top rim shall be smooth and plane within 0.25 mm and shall be parallel to the bottom within 0.5 degrees. The inside diameter shall be 154 2 m
21、m and the inside height shall be 160 2 mm. See Figure 1 for nominal dimensions. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1c T 326-3 AASHTO Note: Figure is not to scale. Figure 1Test Apparatus 5
22、.2. FunnelThe lateral surface of the right frustum of a cone sloped 60 4 degrees from the horizontal with an opening of 105 2-mm diameter. The funnel section shall be a piece of metal, smooth on the inside. It shall have a volume of at least two times the volume of the cylindrical measure or shall b
23、e provided with a supplemental metal container to provide the required volume. (See Figure 1.) 5.3. Funnel StandA support capable of holding the funnel firmly in position with the axis of the funnel colinear (within a four degree angle and a displacement of 2 mm) with the axis of the cylindrical mea
24、sure. The funnel opening shall be 115 2 mm above the top of the cylinder. Aggregate Pan forparticle returnSpringHingeFunnel SectionHingeSpringCylindricalMeasure2.5min105 2mm154 2mm155 2mm2.5 mmmin(typ)5mm160 2mm115 2mm230 2mm45 2mm80mm60 4 2015 by the American Association of State Highway and Transp
25、ortation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1c T 326-4 AASHTO 5.4. Glass PlateA square glass plate approximately 170 mm by 170 mm with a minimum thickness of 4 mm used to calibrate the cylindrical measure. 5.5. PanA metal or glass pan of sufficient size to
26、 contain the funnel stand and to prevent loss of material. The purpose of the pan is to catch and retain aggregate particles that overflow the measure during filling and strike off. 5.6. Flat Metal StraightedgeA flat metal straightedge of 300 5 mm in length, 40 2 mm in width, and 3 mm in thickness i
27、s used to strike off the top of the container. 5.7. Scale or balance conforming to M 231 and capable of weighing the cylindrical measure and its contents. 6. SAMPLING 6.1. The samples used for this test shall be obtained using T 2 and T 248, or from sieve analysis samples used for T 27. For Methods
28、A and B, the sample is washed over a 75-m (No. 200) sieve in accordance with T 11 and then dried and sieved into separate size fractions according to T 27. Maintain the necessary size fractions obtained from one (or more) sieve analysis in a dry condition in separate containers for each size. For Me
29、thod C, dry and split the as-received sample in accordance with T 27 drying procedure. 7. CALIBRATION OF CYLINDRICAL MEASURE 7.1. Apply a light coat of grease to the top edge of the dry, empty cylindrical measure. Weigh the measure, grease, and glass plate. Fill the measure with freshly boiled, deio
30、nized water at a temperature of 18 to 24C. Record the temperature of the water. Place the glass plate on the measure, being sure that no air bubbles remain. Dry the outer surfaces of the measure and determine the combined mass of measure, glass plate, grease, and water by weighing. Following the fin
31、al weighing, remove the grease, and determine the mass of the clean, dry, empty measure for subsequent tests. 7.2. Calculate the volume of measure as follows: ( )1000V MD=(1) where: V = volume of cylinder, mL; M = net mass of water, g; and D = density of water (see Table 3 in T 19M/T 19 for density
32、at the temperature used), kg/m3. Determine the volume to the nearest 0.1 mL. 8. PREPARATION OF TEST SAMPLES 8.1. Method AStandard Graded Sampleweigh and combine the following quantities of coarse aggregate (based on the maximum size of the aggregate), which has been dried and sieved in accordance wi
33、th T 27. (See Table 1.) The total sample weight should be 5000 g 10 g. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1c T 326-5 AASHTO Table 1Standard Gradations for Method A Maximum Size of Aggrega
34、te Sieve Size (mm) Mass, g 19 mm 19 mm (3/4in.) to 12.5 mm (1/2in.) 12.5 mm (1/2in.) to 9.5 mm (3/8in.) 9.5 mm (3/8in.) to 4.75 mm (No. 4) 1740 1090 2170 12.5 mm 12.5 mm (1/2in.) to 9.5 mm (3/8in.) 9.5 mm (3/8in.) to 4.75 mm (No. 4) 1970 3030 8.2. Method BIndividual Size FractionsPrepare a separate
35、5000-g sample of coarse aggregate, dried and sieved in accordance with T 27, for each of the following size fractions (see Table 2): Table 2Size Fractions for Method B Sieve Size (mm) Mass, g 19 mm (3/4in.) to 12.5 mm (1/2in.) 12.5 mm (1/2in.) to 9.5 mm (3/8in.) 9.5 mm (3/8in.) to 4.75 mm (No. 4) 50
36、00 5000 5000 8.3. Method CAs-Received GradingPass the sample (dried in accordance with T 27) over a 4.75-mm (No. 4) sieve. Obtain a 5000 g 10-g sample of the material. The tolerance on each of the amounts in Table 2 is 10 g. Do not mix these samples together. Each size is tested separately. 8.4. Spe
37、cific Gravity of Coarse AggregateIf the bulk dry specific gravity of coarse aggregate from the source is unknown, determine it on the plus 4.75-mm (No. 4) sample according to T 85. 9. PROCEDURE 9.1. Mix each sample until it appears to be homogeneous. Center the cylindrical measure under the funnel s
38、ection as shown in Figure 1. Close the doors at the bottom of the funnel section and latch them shut. Pour the test sample into the funnel section. Hold the doors shut with one finger and open the latch on the doors. Remove the finger from the doors, allowing the doors to swing open and the aggregat
39、e to fall freely into the cylindrical measure. Note 1A latch may be placed on the doors for the convenience of the operator or the operator may hold the doors closed with a finger during the filling of the funnel section, in which case the latch on the doors would not be necessary. 9.2. After the fu
40、nnel empties, strike off excess heaped aggregate from the cylindrical measure. Until this operation is complete, exercise care to avoid vibration or any disturbance that could cause compaction of the coarse aggregate in the cylindrical measure. Remove any aggregate that may have fallen on the outsid
41、e of the container and determine the mass of the cylindrical measure and contents to the nearest 0.1 g. Retain all aggregate particles for a second test run. 9.3. Recombine the sample from the retaining pan and cylindrical measure and repeat the procedure. The results of two runs are averaged. (See
42、Section 10.) 9.4. Record the mass of the empty measure. Also, for each run, record the mass of the measure and coarse aggregate. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1c T 326-6 AASHTO 10. C
43、ALCULATION 10.1. Calculate uncompacted voids for each determination as follows: ( )100V FGUV= /(2) where: V = volume of cylindrical measure, mL; F = net mass, g, of coarse aggregate in measure (gross mass minus the mass of the empty measure); G = bulk dry specific gravity of coarse aggregate; and U
44、= uncompacted voids, percent, in the material. 10.2. For the standard graded sample (Method A), calculate the average uncompacted voids for the two determinations and report the result as Us. 10.3. For the individual size fractions (Method B), calculate: 10.3.1. First, the average uncompacted voids
45、for the determination made on each of the three size-fraction samples: U1= uncompacted voids, 19 mm (3/4in.) to 12.5 mm (1/2in.), percent; U2= uncompacted voids, 12.5 mm (1/2in.) to 9.5 mm (3/8in.), percent; and U3= uncompacted voids, 9.5 mm (3/8in.) to 4.75 mm (No. 4), percent. 10.3.2. Second, the
46、mean uncompacted voids (Um) including the results for all three sizes: 1233mU (U U U )/= + (3) 10.4. For the as-received grading (Method C), calculate the average uncompacted voids for the two determinations and report the results as UR. 11. REPORT 11.1. For the standard graded sample (Method A), re
47、port the following: 11.1.1. The uncompacted voids (Us) in percent to the nearest one tenth of a percent; and 11.1.2. The specific gravity value used in the calculation. 11.2. For the individual size fractions (Method B), report the following percent voids to the nearest one tenth of a percent: 11.2.
48、1. Uncompacted voids for size fraction: 11.2.1.1. 19 mm (3/4in.) to 12.5 mm (1/2in.) (U1); 11.2.1.2. 12.5 mm (1/2in.) to 9.5 mm (3/8in.) (U2); and 11.2.1.3. 9.5 mm (3/8in.) to 4.75 mm (No. 4) (U3). 11.2.2. Mean uncompacted voids (Um): 2015 by the American Association of State Highway and Transportat
49、ion Officials.All rights reserved. Duplication is a violation of applicable law.TS-1c T 326-7 AASHTO 11.2.3. Specific gravity value(s) used in the calculations, and whether the specific gravity value(s) were determined on a graded sample or the individual size fractions used in the test. 11.3. For the as-received sample (Method C), report the following: 11.3.1. The uncompacted voids (UR) in percent to the nearest one tenth of a percent; and 11.3.2. The specific gravity value used in the calculation. 12. PRECISION
