ATT Moisture Content Testing 2 — Questions and Answers
Question 1: When drying aggregate in an oven for moisture content determination, what is the required drying temperature per ASTM C566?
- 100 ± 5°C (212 ± 9°F)
- 110 ± 5°C (230 ± 9°F) (Correct answer)
- 125 ± 5°C (257 ± 9°F)
- 90 ± 5°C (194 ± 9°F)
Correct answer: 110 ± 5°C (230 ± 9°F)
ASTM C566 specifies a drying temperature of 110 ± 5°C (230 ± 9°F) to evaporate free moisture without decomposing the aggregate.
Question 2: Total moisture content of aggregate is defined as:
- Only the surface moisture on aggregate particles
- The moisture in excess of the saturated surface-dry condition
- The sum of absorbed moisture and surface moisture (Correct answer)
- Only the moisture inside the aggregate pores
Correct answer: The sum of absorbed moisture and surface moisture
Total moisture content includes both the absorbed moisture within pores and the free (surface) moisture on the outside of particles.
Question 3: A coarse aggregate sample has a wet mass of 2,050 g and an oven-dry mass of 2,000 g. What is the moisture content?
- 2.5% (Correct answer)
- 2.0%
- 2.44%
- 0.05%
Correct answer: 2.5%
Moisture content = (2,050 − 2,000) / 2,000 × 100 = 50 / 2,000 × 100 = 2.5%.
Question 4: Which of the following conditions describes aggregate that has no surface moisture but has absorbed water filling its permeable pores?
- Oven-dry (OD)
- Air-dry (AD)
- Saturated surface-dry (SSD) (Correct answer)
- Wet or moist
Correct answer: Saturated surface-dry (SSD)
Saturated surface-dry (SSD) aggregate has all internal pores filled with water but no free water on the surface.
Question 5: Why is it important to seal or cover the aggregate sample tightly immediately after sampling for moisture content?
- To prevent contamination from dust
- To prevent evaporation of moisture before testing (Correct answer)
- To keep the sample at a constant temperature
- To prevent oxidation of the aggregate surface
Correct answer: To prevent evaporation of moisture before testing
Moisture can evaporate quickly from a sample, causing erroneously low moisture content readings if the sample is not sealed promptly.
Question 6: For fine aggregate moisture testing, what is the minimum sample size recommended by ASTM C566?
- 500 g (Correct answer)
- 1,500 g
- 250 g
- 2,000 g
Correct answer: 500 g
ASTM C566 recommends a minimum sample mass of 500 g for fine aggregate to ensure representative results.
Question 7: In hot weather conditions on a job site, aggregate moisture content can change rapidly. What is the BEST practice to account for this?
- Test moisture once in the morning and apply that value all day
- Increase batch water and ignore moisture fluctuations
- Test moisture content at frequent intervals throughout the day (Correct answer)
- Use a fixed moisture factor based on historical averages
Correct answer: Test moisture content at frequent intervals throughout the day
Hot and dry conditions can cause rapid moisture loss from aggregate stockpiles, so frequent testing ensures accurate water-cement ratio control.
ATT Moisture Content Testing 2
When drying aggregate in an oven for moisture content determination, what is the required drying temperature per ASTM C566?