CCIL Concrete Compressive Strength Testing 5 — Questions and Answers
Question 1: Which standard governs the use of unbonded neoprene pad caps for compression testing of concrete cylinders?
- ASTM C617
- ASTM C1231 (Correct answer)
- ASTM C803
- ASTM C805
Correct answer: ASTM C1231
ASTM C1231 covers unbonded neoprene pad capping systems as an alternative to the bonded capping methods in ASTM C617.
Question 2: A technician discovers that a concrete cylinder was stored at 35°C (95°F) for the first 48 hours after casting. What is the most likely impact on 28-day strength?
- Higher 28-day strength due to accelerated early hydration
- Lower 28-day strength due to disruption of normal hydration reactions (Correct answer)
- No impact because early temperature does not affect long-term strength
- Higher 28-day strength due to increased calcium silicate hydrate production
Correct answer: Lower 28-day strength due to disruption of normal hydration reactions
Excessive early curing temperatures accelerate early strength gain but disrupt normal hydration, resulting in lower long-term (28-day) strength.
Question 3: What is the minimum capacity verification frequency required for compression testing machines used in accredited laboratories per CCIL requirements?
- Every 6 months or after any repairs (Correct answer)
- Every 12 months
- Every 24 months
- Every 36 months
Correct answer: Every 6 months or after any repairs
CCIL and ASTM E4 require verification of compression machine accuracy at least every 12 months, but CCIL accreditation often mandates verification every 6 months or after repairs.
Question 4: What minimum concrete compressive strength range is required before neoprene pad caps per ASTM C1231 are considered acceptable for use?
- Greater than 7 MPa (1,000 psi)
- Greater than 10 MPa (1,450 psi) (Correct answer)
- Greater than 14 MPa (2,000 psi)
- Greater than 17 MPa (2,500 psi)
Correct answer: Greater than 10 MPa (1,450 psi)
ASTM C1231 specifies that unbonded neoprene pads are appropriate for concrete with compressive strengths between 10 MPa and 50 MPa (1,450 to 7,250 psi).
Question 5: When must a fresh concrete cylinder be moved to standard moist curing after initial field curing per ASTM C31?
- Within 4 hours of casting
- Within 8 hours of casting
- Within 24 hours of casting (Correct answer)
- Within 48 hours of casting
Correct answer: Within 24 hours of casting
ASTM C31 requires cylinders to be transported to the standard curing environment within 48 hours, but they must not be moved during the first 24 hours to avoid early-age disturbance.
Question 6: In a CCIL-accredited concrete testing lab, which proficiency testing program is used to assess technician and laboratory performance for compressive strength testing?
- AASHTO re:source Proficiency Sample Program (PSP)
- ASTM Cement and Concrete Reference Laboratory (CCRL)
- Both CCRL and AASHTO PSP programs are accepted (Correct answer)
- NIST Standard Reference Material (SRM) program only
Correct answer: Both CCRL and AASHTO PSP programs are accepted
CCIL accreditation accepts participation in both the CCRL and AASHTO re:source PSP programs as evidence of laboratory proficiency for concrete compressive strength testing.
Question 7: What is the primary purpose of grinding or lapping the ends of a concrete cylinder rather than using capping materials?
- To reduce test preparation time compared to capping
- To achieve superior planeness and perpendicularity without introducing additional materials (Correct answer)
- To allow testing at ages earlier than 24 hours
- To increase measured compressive strength above actual values
Correct answer: To achieve superior planeness and perpendicularity without introducing additional materials
Grinding or lapping produces extremely flat and perpendicular ends, eliminating the potential for capping material variability to influence test results.
CCIL Concrete Compressive Strength Testing 5
Which standard governs the use of unbonded neoprene pad caps for compression testing of concrete cylinders?