ATT Sieve Analysis & Gradation 3 — Questions and Answers
Question 1: 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:
- 1 kg (2.2 lb)
- 5 kg (11 lb)
- 15 kg (33 lb) (Correct answer)
- 25 kg (55 lb)
Correct 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.
Question 2: On a gradation chart, a well-graded aggregate will appear as:
- A nearly vertical line
- A relatively smooth S-shaped curve spanning a wide range of sizes (Correct answer)
- A nearly horizontal line
- A curve with one or more flat sections
Correct 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.
Question 3: When combining two aggregate stockpiles to achieve a desired gradation, the method used to calculate the blend proportions is called:
- Fineness modulus blending
- The diagonal method or trial-and-error blending (Correct answer)
- Maximum density theory
- Sieve ratio analysis
Correct 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.
Question 4: The percent retained on a given sieve is calculated by dividing the mass retained on that sieve by:
- The mass retained on the next larger sieve
- The total original dry sample mass (Correct answer)
- The mass passing that sieve
- The combined mass of all sieves below it
Correct 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.
Question 5: ASTM C33 specifies gradation requirements for concrete aggregates. For coarse aggregate Size No. 57, the nominal size range is:
- 1½ in. to No. 4 (37.5 mm to 4.75 mm)
- 1 in. to No. 4 (25.0 mm to 4.75 mm) (Correct answer)
- ¾ in. to No. 8 (19.0 mm to 2.36 mm)
- ½ in. to No. 16 (12.5 mm to 1.18 mm)
Correct 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).
Question 6: During a mechanical sieve shaker operation per ASTM C136, the recommended shaking duration is:
- 1 to 2 minutes
- 5 to 10 minutes
- 15 minutes
- Until no further separation is observed, typically verified manually (Correct answer)
Correct 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.
Question 7: If the cumulative percent passing values sum to exactly 100% at each sieve from top to bottom, this indicates:
- A calculation error in the sieve analysis
- The material is uniformly graded
- Normal results — cumulative percent passing always totals 100% at the finest sieve (Correct answer)
- The sample had no oversize material
Correct 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.
ATT Sieve Analysis & Gradation 3
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: