Sieve Analysis & Gradation Flashcards
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According to ASTM C136, the minimum sample mass for sieve analysis of a coarse aggregate with a nominal maximum size of 1½ in. (37.5 mm) is approximately:
Answer: 15 kg (33 lb)
ASTM C136 Table 2 requires approximately 15 kg for nominal maximum size of 37.5 mm (1½ in.) to ensure a representative sample.
On a gradation chart, a well-graded aggregate will appear as:
Answer: A relatively smooth S-shaped curve spanning a wide range of sizes
A well-graded aggregate has particles distributed across a wide range of sizes, producing a smooth S-shaped curve on a percent-passing gradation chart.
When combining two aggregate stockpiles to achieve a desired gradation, the method used to calculate the blend proportions is called:
Answer: The diagonal method or trial-and-error blending
Aggregate blending typically uses the diagonal method (graphical) or trial-and-error calculations to determine proportions that meet specification gradation limits.
The percent retained on a given sieve is calculated by dividing the mass retained on that sieve by:
Answer: The total original dry sample mass
Percent retained = (mass retained on sieve / total original dry sample mass) × 100, using the total original sample as the denominator.
ASTM C33 specifies gradation requirements for concrete aggregates. For coarse aggregate Size No. 57, the nominal size range is:
Answer: 1 in. to No. 4 (25.0 mm to 4.75 mm)
ASTM C33 Size No. 57 coarse aggregate has a nominal size range of 1 in. to No. 4 (25.0 mm to 4.75 mm).
During a mechanical sieve shaker operation per ASTM C136, the recommended shaking duration is:
Answer: Until no further separation is observed, typically verified manually
ASTM C136 requires sieving until no more than 1% of the residue on any sieve passes during 1 minute of hand sieving, regardless of shaker time used.
If the cumulative percent passing values sum to exactly 100% at each sieve from top to bottom, this indicates:
Answer: Normal results — cumulative percent passing always totals 100% at the finest sieve
In a correctly computed sieve analysis, 100% of the sample passes through the top (largest) sieve conceptually, and the cumulative percent passing the finest sieve should equal 100% minus the percent retained on the pan.