Testing Methods Flashcards

Per ASTM C143, how long should it take to raise the slump cone vertically after rodding?

Answer: 5 ± 2 seconds

ASTM C143 requires lifting the mold steadily in 5 ± 2 seconds without lateral or torsional motion.

Under ACI 318 for f'c ≤ 5000 psi, concrete strength is acceptable when the average of three consecutive tests ≥ f'c and no individual test falls below what value?

Answer: f'c - 500 psi

ACI 318 requires no single strength test to be more than 500 psi below f'c when f'c is 5000 psi or less.

Which method is appropriate for measuring the air content of fresh concrete made with lightweight aggregate?

Answer: Volumetric (roll-a-meter) method (ASTM C173)

The volumetric method is used for lightweight aggregate concrete because porous aggregates give erroneous pressure-meter readings.

In the splitting tensile test (ASTM C496), the tensile strength is calculated by which formula?

Answer: T = 2P / (πLD)

Splitting tensile strength equals 2P divided by π times the cylinder length times diameter.

What does the rebound hammer test (ASTM C805) primarily evaluate?

Answer: Surface hardness, used to assess uniformity and estimate strength

The rebound number reflects surface hardness and is used to assess uniformity, requiring correlation to estimate strength.

Per ACI 318, concrete in an area represented by core tests is considered structurally adequate when the average of three cores is at least what percentage of f'c, with no single core below 75%?

Answer: 85%

ACI 318 accepts cores averaging at least 85% of f'c with no single core less than 75% of f'c.

ASTM C78 determines concrete flexural strength (modulus of rupture) using which loading arrangement?

Answer: Third-point loading

ASTM C78 uses third-point loading, creating a constant-moment region in the middle third of the beam.