TESTS FOR AGGREGATES AND MINERAL FILLER SPECIFIC GRAVITY AND ABSORPTION TESTS OF COARSE AND FINE AGGREGATES FOR USE IN THE DESIGN OF ASPHALT CONCRETE MIXTURES. Reference - ASTM Designations; C 127 and C 128. A. Purpose: Determine the bulk, apparent, and effective specific gravities, and absorption of coarse and fine aggregates. Absorption is the process by which water is drawn into and tends to fill the permeable pores in a porous solid body. The effective specific gravity was determined since the absorption of asphalt cement is an important factor in asphalt mixtures. B. Equipment and Materials: Balance, wire basket, 500 ml. Flask, conical metal mold 1-1/2" in diameter at the top, 3" in diameter at the bottom, and 2-7/8" in height, metal tamping rod with a flat circular tamping face 1" in diameter, weighing 12 ounces, suitable balance and apparatus for suspending sample in water. 5 Kg. of coarse aggregates, where the nominal maximum size is 1-1/2 inches or less and all material is retained on the No. 4 sieve; 3 Kg. of fine aggregates, all particles passing the No. 4 sieve. C. Test Procedure: 1. Coarse Aggregate: a. Select by quartering or use of a sample splitter approximately 5 Kg. of aggregate. Reject all material passing a No. 4 sieve. b. Thoroughly wash the sample to remove all dust or other coatings from the particles. c. Dry the sample to a constant weight at a temperature of 100° to 1100C (212° to 2300F). Cool at room temperature for about 15 minutes and then immerse in water at room temperature for approximately 1/2 hour. d. Remove sample from water and wipe the particles until all surface films are removed. Weigh the sample in this saturated surface dry condition to the nearest 0.5 grams. e. Immediately after weighing, place the sample in a wire basket, suspend in water, and obtain the bouyant weight. f. Dry the sample to a constant weight at a temperature of 100° to 110°C(2120 to 2300F). Cool at room temperature for at least 1/2 hour and weigh. g. Computations A = weight of oven-dry sample in air, grams B = weight of saturated-surface-dry sample in air, grams C = weight of saturated sample in water, grams i) Bulk Specific Gravity = A B -C ii) Apparent Specific Gravity = A A -C iii) Absorption in Percent = (B-A) x 100 A 2. Fine Aggregate: a. Obtain by sample splitting or quartering 3,000 grams of aggregate, including equal quantities of all fractions. b. Dry to a constant weight at a temperature of 100° to HO0C (212° to 2300F) . c. Allow to cool and cover with water for about 1/2 hour. d. Remove excess water and spread on a flat surface. Expose to a gentle moving flame until test sample approaches a free-flowing condition. e. Place a portion of the fine aggregate sample loosely into the mold. Tamp lightly 25 times and lift the mold vertically. If surface moisture is present, the fine aggregate will maintain its molded share. Continue drying and testing until upon removal of the mold, the aggregate slumps slightly. This indicates that the saturated, surface-dry condition has been reached. f. Immediately introduce into the flask 500.0 grams of the fine aggregate. Fill the flask almost to capacity and eliminate the air bubbles by agitation. Determine the total weight of the flask, including the sample, and the water. g. Carefully remove the fine aggregate and dry to a constant weight at 100° to HO0C (212° to 2300F). Cool for at least 1/2 hour and weigh. h. Computations: A = weight of oven-dry sample in air, grams B = weight of pycnometer filled with water, grams C = weight of pycnometer with sample and water, grams i) Bulk Specific Gravity = A B + 500 - C ii) Apparent Specific Gravity = A B-CH-A iii) Absorption, Percent = (500 - A) x 100 A 3. Special Instructions: a. Determine the specific gravities for three samples of both the the coarse and fine aggregates. Test the fourth sample, if necessary, in order to obtain three sets of results that vary from each other by no more than 2%. If these precisions are not met, rerun the entire test. b. Effective Specific Gravity, determined in the design of asphalt concrete mixtures, should approximately equal Bulk Specific Gravity + Apparent Specific Gravity 2 Because of the greater viscosity of liquid asphalt cement in comparison to water, less of the aggregate voids are filled. For a more complete explanation see Equation 2 on page 155. D. Explanation of Computations and Data Sheets: 1. Computations: these were explained separately under Section C: Test Procedure, for both the coarse and fine aggregates. 2. Data Sheet: Specific Gravity Data Sheet, Page 16 - for both the fine and course aggregates the last value obtained in the laboratory will be A) the weight of the Oven Dry Sample. Once the saturated surface dry condition is obtained and weighed, value C) is determined which is in effect a measure of bouyancy. In the case of the coarse aggregate, C) is obtained directly. To get the value A), the aggregates are placed in an oven and dried to a constant weight. B, the saturated-surface-dry condition of the aggregates, is determined according to the procedures outlined in Section C.l.d. for coarse aggregates and Section C.2.e. for fine aggregates. The four values, bulk, apparent, and effective specific gravities and absorption are then computed for each sample. Based upon the results a decision needs to be made as whether or not to test the fourth sample for either or both of the aggregates. The final step is to determine the accepted results by averaging the values of those samples that fall within the guideline criteria as explained in Section C.3.a.. These values will then be used in the various mix design computations. It is for this reason that obtaining accurate specific gravities is so important. Do not hesitate to redo the entire procedure if the results are questionable. COARSE and FINE AGGREGATES SPECIFIC GRAVITY DATA SHEET ASTM Designations: C 127 and C 128 Coarse Aggregates - ASTM Designation: C 127 Passing Sieve & Sample Sample Sample Sample Retained on Sieve 1 2 3 4 A) Wt. Oven Dry Sample, gm. B) Wt. SSD Sample, gm. C)Wt. Saturated Sample in Water, gm. Bulk Specific Gravity Apparent Specific Gravity Effective Specific Gravity Absorption, % Average Values: Bulk Sp Gr. = ; Apparent Sp. Gr. = ; Effective Sp. Gr. = ; Absorption = Fine Aggregates - ASTM Designation: C 128 A) Wt. Oven Dry Sample, gm. B) Wt. Pycnometer+Water to Calibration Mark, gm. C) Pycnometer+Water+Sample to Calibration Mark, gm. Bulk Specific Gravity Apparent Specific Gravity Effective specific Gravity Absorption, % Average Values: Bulk Sp. Gr. Effective Sp. G = ; r. = Apparent ; Abso Sp. Gr. rption = = ; RESISTANCE to DEGRADATION of SMALL-SIZE COARSE AGGREGATE by ABRASION and IMPACT in the LOS ANGELES MACHINE Reference - ASTM Designation: C 131 A. Purpose: The test is to determine the ability of coarse aggregate smaller than 37.5mm (1-1/211) to resist abrasion, using the Los Angeles Testing Machine. B. Equipment and Materials: Los Angeles Testing Machine (details shown on the next page), sieves following specifications in ASTM Designation: E 11, abrasive charge in accordance with the table below, and test samples in accordance with the table below. C. Test Procedure: Select the proper amount of aggregate and abrasive charge in accordance with the following tables: Table of Abrasive Charge Grading Number of Spheres Weight of Charge in Grams A 12 5,000 ± 25 B 11 4,584 ± 25 C 8 3,330 ± 20 D 6 2,500 ± 15 The abrasive charge consists of steel spheres approximately 47.6mm (1-7/8") in diameter, each ball weighing between 390 and 445 grams. Table Showing the Grading of Test Samples Sieve Sizes from ASTM Weight of Indicated Size in Grams Designation: E 11 Aggregate Grading Passing Retained On A B C D 3 7.5mm(1.5")2 5.0mm(1") l,250±25 25.0mm(I")19.0mm(3/4") l,250±25 19.0mm(3/4")12.5mm(.5" l,250±25 2,500±10 12.5mm(1/2")9.5mm(3/8" l,250±25 2,500±10 9.5mm(3/8")6.3mm(1/4") 2,500±10 6.3mm(1/4") 4.75mm(#4) 2,500±10 4.75mm(#4) 2.36mm(#8) 5,000±10 Total 5,000±10 5,000±10 5,000±10 5,000±10 Test Procedure Continued: Place the test sample and the abrasive charge in the Los Angeles Abrasion Machine. The machine should rotate at a speed of 30 to 33 rpm for 500 revolutions. After the prescribed number of revolutions, the material shall be discharged from the machine. Separate the aggregates on a 1.7mm (No.12) sieve. Carefully weigh the material retained on the 1.7mm (No.12) sieve to the nearest whole gram. D. Explanation of Computations and Data Collection: 1. Calculate the difference between the original sample weight and that retained on the 1.7mm (No.12) sieve. Express that value as a percentage of the original sample weight. This value is considered as the percentage of wear. 2. There are no special data sheets. Simply follow the instuctions in the Procedure for Data Collection. Figure 3 - Los Angeles Testing Machine Copyright ASTM. Reprinted with permission. SIEVE ANALYSIS OF FINE AND COARSE AGGREGATES Reference - ASTM Designation; C 136 and MATERIAL FINER THAN #200 by WASHING Reference - ASTM Designation: C 117 A. Purpose: Determination of the particle size distribution of fine and coarse aggregates by sieving. B. Equipment and Materials: Balance, sensitive to within 0.1 per cent of the weight of the sample to be tested; standard sieves for grading of fine agregates - No. 4, 8, 16, 30, 50, & 100; standard sieves for grading coarse aggregates 2, 1-1/2, 1, 3/4, and 3/8 inch, plus a No. 4 sieve; fine (0.5 kg) and coarse (2 to 20 kg depending upon maximum size from 3/8" to 2") aggregate samples. C. Test Procedure: 1. Samples - Use dry aggregates from the specific gravity and absorption tests of coarse and fine aggregates. 2. Continue the sieving until not more than 1% by weight of the residue passes any sieve during 1 minute. 3. For the wet analysis procedure (ASTM C 117), after weighing the dry aggregates, cover with water, agitate, and pour off the wash water containing suspended particles. Repeat until the wash water is clear. Dry the aggregates a second time at 110°±5° C (230°±9°F) and weigh. D. Explanation of Computations and Data Sheets: 1. Computations: On page 20, Sieve Analysis for Fine and Coarse Aggregate, calculate percentages on the basis of the total weight of the sample. Compute the per cent of material retained on each sieve and the per cent of material finer than for each sieve size for both the coarse and the fine aggregates. Follow the procedure at the bottom of the table on page 21 for the determination of all minus #200 mineral aggregates by the wet analysis. Plot the results on the Gradation Charts, Page 22 which is a semilog scale and/or Page 23 which are the sieve sizes raised to the 0.45 power. Both graphs are commonly used to help select the best aggregate blend. On both graphs the ordinate is the total percent by weight passing a given size on an arithmetic scale. If you are blending an asphalt concrete mix design from several aggregate sources, compute the combined gradation by following the form on Page 24. The 0.45 exponent FHWA graph is very convenient for determining the maximum density line and then adjusting the aggregate gradation accordingly. The maximum density lines can easily be obtained by drawing a straight line from the origin at the lower left hand corner to the 100 percent passing point of the maximum nominal size aggregate. Plot the midband gradation line on this graph. It is generally considered best when this gradation line is parallel to the maximum density line and a few percentages above or below it in order for the asphalt mix to have sufficient air voids. VMA increases as the gradation line moves away from the maximum density line. A poor aggregate gradation will adversely affect almost all the critical properties of a hot mixed asphalt concrete. 2. Data Sheets: for dry Sieve Analysis for Fine and Coarse Aggre- gate use the data sheet below; for the wet sieve analysis use the data sheet on Page 21; Gradation Charts, Pages 22 and 23; and Aggregate Blend Design for Bituminous Paving Mixtures, Page 24. SIEVE ANALYSIS for FINE and COARSE AGGREGATE (ASTM C 136) DRY SIEVE ANALYSIS Sample Number Sample Number Sieve Weight % Re- % Sieze Weight % Re- % Size Retain- tained Pass- Size Retain- tained Pass- ed (gm) ing ed (gm) ing 2 2 1 1/2 1 1/2 1 1 3/4 3/4 1/2 1/2 3/8 3/8 4 4 8 8 16 16 30 30 50 50 100 100 200 200 -200 -200 Total Total SIEVE ANALYSIS for FINE and COARSE AGGREGATE (ASTM C 136) and MINERAL AGGREGATES by WASHING (ASTM C 117) WASH and DRY SIEVE ANALYSIS Sample Number Sample Number Sieve Weight % Re- % Sieze Weight % Re- % Size Retain- tained Pass- Size Retain- tained Pass- ed (gm) ing ed (gm) ing 2 2 1 1/2 1 1/2 1 1 3/4 3/4 1/2 1/2 3/8 3/8 4 4 8 8 16 16 30 30 50 50 100 100 200 200 -200 -200 Total Total a. Wt. of Sample, grains - a. Wt. of Sample, grams - b. Wt. of Sample after b. Wt. of Sample after Washing, grams Washing, grams c. Loss in Washing, c. Loss in Washing, (a - b) , grams (a - b), grams d. -200 from Dry Sieve, d. -200 from Dry Sieve, grams grams Total-200, (c+d), grams - Total-200, (c+d), grams -