Aggregates for Concrete and Asphaltic Mixes

Moisture Content and Specific Gravity (for Fine Aggregate)

1. Obtain approximately 1 kg air-dry fine aggregate (sand) and place it in a flat metal pan. The sand should have been dried in an oven at temperatures above 220°F for at least 24 hours to evaporate all water.
2. Bring the fine aggregate to the SSD condition by sprinkling a few drops of water on the air-dry sand and thoroughly mixing.
3. Hold a conical mold firmly on the flat metal pan with the large diameter down.
4. Place a portion of the sand loosely in the mold by filling it to the point of overflow, then heap additional sand above the top of the mold.
5. Lightly tamp the sand into the mold with 25 light drops of the tamping rod. Start each drop about 0.2 in. above the top of the sand. Permit the rod to fall freely on each drop. Adjust the starting height to the new surface elevation after each drop and distribute the drops evenly over the surface.
6. Clean loose sand from around the base and remove the mold by lifting it vertically. When the sand slumps slightly it indicates that it has reached a saturated surface dry condition. If the cone retains its mold shape, the sand is still in a wet condition and the process needs to be repeated using less water. This is a trial-and-error procedure.
7. Take approximately 400 g of the SSD aggregate. Record exact weight of SSD sample (D).
8. Fill a flask with 500 mL water and record the weight of water and the flask in grams (B). The water temperature should be about 73 ± 3^oF (23 ± 1.5^oC).
9. Empty the water from the flask and add the entire SSD sand sample to the flask. Fill the flask with water to about 1/2 in. above the aggregate. Apply vacuum and rolling action to eliminate the air entrapped in the aggregate. This action will take at least 5 minutes.
10. Fill the flask with water up to 500 mL mark. Record the total weight (in grams) of the flask plus the water plus the aggregate (C).
11. Calculate the Bulk Specific Gravity (SSD) based on the weights B, C, D, and compare the calculated value with the typical value to ensure that the data obtained is accurate.
12. Pour the entire contents of the flask into a pan and place it in oven. Additional tap water may be used as necessary to wash all the aggregate out of the flask. After 24 hours, return and measure the weight of the oven-dry aggregate (A).

Sieve Analysis (for Fine Aggregate)

1. Obtain the proper weight of dry aggregate. For fine aggregate, use about 400 grams.
2. Assemble 8" diameter size sieves in the following order: #4, #8, #16, #30, #50, #100, pan.
3. Place the aggregates in the top of the sieve stack and cover with the lid. Properly secure the sieves in the mechanical shaker and turn on the shaker for five minutes.
4. Weigh the materials that are retained on each of the sieves, including the weight retained on the pan, and record on the data sheet. If the sum of these weights is not within 0.1% times the number of sieves used (0.6%) of the original sample weight, the procedure should be repeated. Otherwise, use the sum of the weight retained in the pan to calculate the percentage retained on each sieve.
5. Compute the cumulative percentage retained on and the percentage passing each sieve. Plot the gradation curves for the fine aggregates from the experiment on the gradation chart as shown below in the example plot below.
6. Compute the Fineness Modulus for the fine aggregate.