ACI Making and Curing Specimens Questions and Answers

Question 1

According to ASTM C31/C31M, what is the required temperature range for the initial curing of standard-cured concrete cylinders with a specified strength of less than 6000 psi (40 MPa)?

Accepted Answer

60°F to 80°F (16°C to 27°C)

Answer

ASTM C31/C31M specifies that for standard-cured specimens, the initial curing temperature must be maintained between 60°F and 80°F (16°C and 27°C). This ensures that the concrete gains strength in a controlled environment, providing an accurate measure for acceptance testing.

Question 2

A technician is preparing to cast 6x12-inch concrete cylinders. The concrete has a slump of 3 inches. Which of the following consolidation procedures is correct?

Accepted Answer

Fill the mold in three equal layers, rodding each layer 25 times.

Answer

For 6x12-inch cylinders, ASTM C31/C31M requires the mold to be filled in three approximately equal layers. Each layer must be rodded 25 times, penetrating the underlying layer by about 1 inch.

Question 3

Which of the following is an appropriate action immediately after molding and finishing a concrete test specimen?

Accepted Answer

Place the specimen in its initial curing location, protected from moisture loss and disturbance.

Answer

Immediately after molding, specimens must be moved to an initial curing environment that prevents moisture loss, maintains the specified temperature, and is free from vibrations or other disturbances that could affect the concrete's integrity.

Question 4

A field-cured specimen is primarily used to determine:

Accepted Answer

The in-place strength of the concrete in the structure.

Answer

Field-cured specimens are stored as close as possible to the actual structure and receive the same curing and protection. Their test results are used to estimate the in-place strength, which helps in determining when a structure can be put into service or when forms can be removed.

Question 5

When rodding the top layer of a concrete cylinder, the tamping rod should penetrate the underlying layer by approximately how much?

Accepted Answer

1 inch (25 mm)

Answer

To ensure proper consolidation and bonding between layers, ASTM C31/C31M requires the tamping rod to penetrate about 1 inch (25 mm) into the previously placed layer for all but the bottom layer.

ACI (American Concrete Institute Certification) Practice Test

ACI (American Concrete Institute Certification) Practice Test

ACI Making and Curing Specimens Questions and Answers