The determinations that may be made from this procedure are identical to those made in AASHTO T 85 (Specific Gravity and Absorption of Coarse Aggregate).

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1SPECIFIC GRAVITY AND ABSORPTION OF FINE AGGREGATES AASHTO T 84 GLOSSARY Absorption: The increase in mass due to water in the pores of the material. Bulk Specific Gravity (also know n as Bulk Dry Specific Gravity): The ratio of the weight in air of a unit volume of aggregate at a stated temperature to the weight in air of an equal volume of gas-free distilled water at the stated temperature. Bulk SSD Specific Gravity: The ratio of the weight in ai r of a unit volume of aggregate, including the weight of water within the voids filled to the extent achieved by submerging in water for approximately 15 hours, to the weight in air of an equal volum e of gas-free distilled water at the stated temperature. Apparent Specific Gravity: The ratio of the weight in air of a unit volume of the impermeable portion of aggregate (does not include the permeable pores in aggregate) to the weight in air of an equal volume of gas-free distille d water at the stated temperature. SSD – Saturated, Surface Dry. The condition in which the aggregate has been soaked in water and has absorbed water into its pore spaces. The excess, free surface moisture has been removed so that the particles ar e still saturated, but th e surface of the particle is essentially dry. SCOPE Specific Gravity is the ratio of the weight of a given volume of aggregate to the weight of an equal volume of water. Water, at a temperatur e of 73.4°F (23°C) has a specific gravity of 1. Specific Gravity is important for several reasons. Some deleterious particles are lighter than the “good” aggregates. Tracking spec ific gravity can sometimes indi cate a change of material or possible contamination. Differences in specific gravity may be us ed to separate the deleterious particles from the good using a heavy media liquid. Specific gravity is critical information for the Hot Mix Asphalt Design Engineer. This value is used in calculating air voids, voids in minera l aggregate (VMA), and voids filled by asphalt (VFA). All are critical to a well performing and durable asphalt mix. Water absorption may also be an indicator of asphalt absorption. A hi ghly absorptive aggregate may result in a low durability asphalt mix. In Portland Cement Concrete the specific gravity of the aggregate is used in calculating the percentage of voids and the solid volume of aggreg ates in computations of yield. The absorption is important in determining the net water-cement ra tio in the concrete mix. Knowing the specific gravity of aggregates is also critical to th e construction of water filtration systems, slope stabilization projects, railway bedding and many other applications.

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2 This test method determines the sp ecific gravity of fine aggregates that have been soaked for a period of 15-19 hrs. The determinations that ma y be made from this pro cedure are identical to those made in AASHTO T 85 (Specific Gravit y and Absorption of Coarse Aggregate). SUMMARY OF TEST Apparatus Balance, conforming to the requirements of M 231, Class G2 Pycnometer, a flask or other suitable container into which the fine aggr egates may be readily introduced (Figure 1). Volume content for the container needs to be reproduced within ± 100 mm3. The volume of the container filled to the mark shall be at least 50 pe rcent greater than the space required to accommodate the test sample. Mold, metal in the form of a frustum of cone with acceptable dimensions of 40 ± 3 mm inside diameter at top, 90 ± 3 mm inside diameter at the bottom, and 75 ± 3 mm in height. The metal thickness is a minimum of 0.8 mm. Tamper, metal having a mass of 340 ± 15g and havi ng a flat circular tamping face of 25 ± 3 mm in diameter. Figure 1 Fine Aggregate Specific Gravity Apparatus Procedure 1. Thoroughly mix the sample and reduce th e sample to the required size in accordance with AASHTO T 248 (Reducing Fiel d samples of Aggregates to Test Size). The sample size for this pro cedure is approximately 1000g of material passing the No. 4 (4.75 mm) sieve. 2. Dry test samples to constant weight in an oven set at 230 ± 9°F (110 ± 5°C). Cool the sample at room temperature for 1 to 3 hours. After the cooling period, immerse the sand in water at room temp erature for a period of 15 to 19 hours.

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3 Instead of completely immersing the sand in water, AASHTO considers sand to be “soaked” if the sand is maintained at a moisture content of at least 6% for the prescribed period. This is the recommende d procedure to elim inate the need to decant excess water from the sand prior to testing. The decantation process is time consuming and difficult, since great care must be taken to avoid decanting some of the sample along with the wate r. Additionally, the sand will be much closer to the SSD condition when soaked at 6% moisture, whic h expedites the dry procedure. 3. Decant water from sample, avoiding loss of fines. Spread the sample on a flat, non-absorbent surface. Stir the sample occasionally to assist in homogeneous drying. A current of warm air may be used to assist drying procedures (Figure 2); however, fine particles may be lost with this procedure if not careful. Figure 2 A current of air being used to achieve SSD condition. 4. Determine the SSD condition of the sand using the Cone Test. Note: Throughout the process of drying in Step 3, test the sand for SSD condition using the cone method. Place the cone with the large diameter down on a glass plate. Fill cone to overflowing with dryi ng sand. Lightly tamp the fine aggregate into the mold with 25 light drops of the tamper (Figure 3). Each drop should start about 1/5 in. above the top surface of th e fine aggregate. Remove loose sand from base and carefully lift the mold ve rtically. If surface moisture is still present, the fine aggregate will retain th e molded shape. When the sand achieves an SSD condition, the sand will slump (Figure 4).

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4 Figure 3 Tamping sand using the cone method to determine SSD If on the first trial the sand slumps, mois ture must be re-added and the drying process repeated. Record the weight of the sand as SSD mass when the sand slumps to the nearest 0.1 g. Figure 4 Sand at SSD condition will slump once the cone is removed 5. Calibrate a specific gravity flask pycnom eter by filling with water at 73.4 ± 3°F (23 ± 1.7°C) to the calibration line. Reco rd this weight as the weight of the pycnometer filled with water to the nearest 0.1g. 6. Place the SSD sand into the pycnometer (Fi gure 5) and fill with water (set at 73.4 ± 3°F (23 ± 1.7°C)) to 90% of pycnometer capacity.

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5 Figure 5 Pouring sand into pycnometer once SSD is achieved Manually roll, invert, and agitate the pyc nometer to eliminate air bubbles (Figure 6). This procedure should be repeated several times to ensure that any entrapped air is eliminated. Agitation of the py cnometer does not have to be constant. Figure 6 Agitating the pycnometer

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6 7. Bring the pycnometer to the pycnometer calibrated capacity with additional water (Figure 7). Figure 7 Adding Water to Calibrated Capacity If bubbles prevent the proper filling of the pycnometer, adding a few drops of isopropyl alcohol is recomme nded to disperse the foam. Place the pycnometer in a water bath at the regulated temperat ure and allow the sample to equalize. 8. Determine the total weight of pycnomete r, specimen, and water. Record the weight to the nearest 0.1g as Weight of Pycnometer with sample and water. Calculations Determine calculations based on appropriate formula for desired result as follows: A. Bulk Specific Gravity (Gsb): The ratio of the weight in air of a unit volume of aggregate at a stated temperature to the weight in air of an equal volume of gas- free distilled water at a stated temperature. Gsb = A / (B-C) Where: A = Oven dry wt. B = SSD wt. C = Wt. in water B. Bulk SSD Specific Gravity (Gsb SSD): Th e ratio of the weight in air of a unit volume of aggregate, INCLUDING the weight of water within the voids filled to the extent achieved by submerging in water for approximately 15 hours, to the weight in air of an equal volume of gas-free distilled water at a stated temperature. Gsb SSD = B / (B-C)

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