ACI Concrete Strength Testing Procedures Questions and Answers

Question 1

According to ASTM C39, what is the specified loading rate for applying a compressive force to a standard 6x12 inch concrete cylinder?

Accepted Answer

35 ± 7 psi/s

Answer

20 ± 5 psi/s

Answer

50 ± 10 psi/s

Answer

40 ± 8 psi/s

Question 2

A technician is preparing to perform a flexural strength test (Modulus of Rupture) on a concrete beam specimen in accordance with ASTM C78. Which of the following loading configurations is specified by this standard?

Accepted Answer

Third-point loading

Answer

Center-point loading

Answer

Cantilever loading

Answer

Uniformly distributed loading

Question 3

When making standard-cured test specimens in the field per ASTM C31, what is the primary purpose of this type of curing?

Accepted Answer

To check the adequacy of mixture proportions for strength and for acceptance testing.

Answer

To determine the earliest time for form removal.

Answer

To estimate the in-place strength of the concrete in the structure.

Answer

To evaluate the effectiveness of the curing methods used on the actual structure.

Question 4

A 4x8 inch concrete cylinder is being cast for strength testing. According to ASTM C31, how many layers should the concrete be placed in, and how many times should each layer be rodded?

Accepted Answer

2 layers, 25 times each

Answer

3 layers, 25 times each

Answer

2 layers, 50 times each

Answer

3 layers, 50 times each

Question 5

During the initial curing period for standard-cured concrete test cylinders on a job site, which of the following conditions is required by ASTM C31?

Accepted Answer

Specimens must be stored in an environment with a temperature between 60°F and 80°F and prevented from moisture loss.

Answer

Specimens must be stored in direct sunlight to accelerate hydration.

Answer

Specimens must be stored at a temperature between 40°F and 60°F.

Answer

Specimens should be left uncovered and exposed to the ambient job site conditions.

Question 6

Which of the following must be reported after performing a compressive strength test on a concrete cylinder according to ASTM C39?

Accepted Answer

The average measured diameter, maximum load, compressive strength, and type of fracture.

Answer

Only the maximum load applied and the calculated strength.

Answer

The cylinder's color and the time of day the test was performed.

Answer

The name of the technician and the brand of the compression machine.