ASCE Structural Engineering and Materials 3

Question 1

Per ACI 318, what is the minimum specified cover for cast-in-place concrete cast against and permanently exposed to earth?

Accepted Answer

3 in.

Answer

ACI 318 requires 3 in. of cover for concrete cast directly against earth.

Question 2

At what age is the specified compressive strength f'c of concrete normally determined?

Accepted Answer

28 days

Answer

f'c is based on cylinder tests at 28 days unless the contract specifies another age.

Question 3

The slump test (ASTM C143) is mainly used to measure which property of fresh concrete?

Accepted Answer

Workability/consistency

Answer

Slump measures the consistency, or workability, of fresh concrete.

Question 4

In the ACI rectangular stress block, what is β1 for concrete with f'c ≤ 4,000 psi?

Accepted Answer

0.85

Answer

β1 = 0.85 for f'c up to 4,000 psi and drops by 0.05 per 1,000 psi above that, down to a minimum of 0.65.

Question 5

All else equal, what is the main effect of raising the water-cement ratio of a concrete mix?

Accepted Answer

Lower strength and durability

Answer

Per Abrams' law, a higher w/c ratio adds porosity, which lowers strength and durability.

ASCE - American Society of Civil Engineers Certification Practice Test