ATT Soundness & Durability Testing 2 — Questions and Answers
Question 1: In the sodium sulfate soundness test (ASTM C88), what is the required soaking temperature of the solution?
- 18 ± 1°C (64 ± 2°F) (Correct answer)
- 23 ± 1°C (73 ± 2°F)
- 10 ± 1°C (50 ± 2°F)
- 30 ± 1°C (86 ± 2°F)
Correct answer: 18 ± 1°C (64 ± 2°F)
ASTM C88 requires the sodium sulfate solution to be maintained at 18 ± 1°C (64 ± 2°F) during the soaking period.
Question 2: How many cycles of immersion and drying are typically specified in the ASTM C88 soundness test?
- 3 cycles
- 5 cycles (Correct answer)
- 10 cycles
- 7 cycles
Correct answer: 5 cycles
ASTM C88 specifies 5 cycles of alternating immersion in sulfate solution and oven drying.
Question 3: When calculating the weighted percent loss in the sulfate soundness test, what information is used as the weighting factor?
- The particle density of each fraction
- The percent retained on each sieve before testing (Correct answer)
- The absorption capacity of each fraction
- The original total sample mass
Correct answer: The percent retained on each sieve before testing
The weighted percent loss uses the percentage of material originally retained on each sieve as the weighting factor for each size fraction's loss.
Question 4: Which of the following best describes why magnesium sulfate is sometimes used instead of sodium sulfate in ASTM C88?
- It produces more consistent results on carbonate aggregates
- It is less expensive and easier to prepare
- It provides a more severe test with higher percent losses (Correct answer)
- It is safer to handle and dispose of
Correct answer: It provides a more severe test with higher percent losses
Magnesium sulfate produces higher percent losses and is considered a more severe soundness test than sodium sulfate.
Question 5: After the final drying cycle in ASTM C88, aggregate particles are washed over a sieve that is what fraction of the original test sieve size?
- One-quarter of the original sieve opening
- Three-quarters of the original sieve opening
- One-half of the original sieve opening (Correct answer)
- Equal to the original sieve opening
Correct answer: One-half of the original sieve opening
Particles are washed over a sieve with an opening one-half the size of the sieve on which they were originally retained to determine loss.
Question 6: A coarse aggregate soundness result of 18% loss using sodium sulfate would be classified as:
- Well within typical acceptance limits for most applications
- Exceeding the typical AASHTO limit of 12% for sodium sulfate (Correct answer)
- Within AASHTO limits but failing ASTM limits
- Acceptable only if magnesium sulfate was used instead
Correct answer: Exceeding the typical AASHTO limit of 12% for sodium sulfate
AASHTO typically specifies a maximum sodium sulfate soundness loss of 12% for coarse aggregate, so 18% would exceed this limit.
Question 7: What is the purpose of allowing the sodium sulfate solution to rest for at least 48 hours before use in ASTM C88?
- To allow impurities to settle out of solution
- To ensure the solution reaches saturation equilibrium at the test temperature (Correct answer)
- To prevent exothermic reactions during testing
- To allow dissolved gases to escape
Correct answer: To ensure the solution reaches saturation equilibrium at the test temperature
The rest period ensures the sodium sulfate solution reaches saturation equilibrium at the specified test temperature of 18°C, which is critical for consistent crystallization pressure.
ATT Soundness & Durability Testing 2
In the sodium sulfate soundness test (ASTM C88), what is the required soaking temperature of the solution?