CCIL - Canadian Council of Independent Laboratories Concrete Compressive Strength Testing Questions and Answers

Question 1

A technician tests a standard 100 mm x 200 mm concrete cylinder and applies the load much faster than the rate specified in CSA A23.2-9C.
What is the most likely effect on the measured compressive strength?

Accepted Answer

The measured strength will be artificially high.

Answer

The measured strength will be artificially low.

Answer

The loading rate has no significant effect on the final strength.

Answer

The cylinder will most likely exhibit a columnar fracture.

Question 2

According to CSA A23.2-9C, what is the primary purpose of capping concrete cylinders with sulphur mortar or using unbonded neoprene pads before testing?

Accepted Answer

To ensure the load is applied uniformly over the entire cross-section.

Answer

To protect the testing machine platens from damage.

Answer

To increase the overall strength of the cylinder.

Answer

To absorb moisture from the cylinder ends before testing.

Question 3

As per CSA A23.2-9C, what is the required moisture condition of a standard-cured concrete cylinder immediately before compressive strength testing?

Accepted Answer

It must be tested in a moist condition, immediately after removal from curing.

Answer

It must be submerged in lime-saturated water until the moment of testing.

Answer

It must be allowed to air-dry for at least 4 hours to remove surface water.

Answer

It must be dried to a constant mass in an oven at 110 °C.

Question 4

A technician needs to test a cored concrete specimen with a diameter of 100 mm and a length of 175 mm. According to CSA A23.2-14C, what must be done before reporting the final compressive strength?

Accepted Answer

The calculated compressive strength must be multiplied by a correction factor.

Answer

The result must be discarded as the L/D ratio is outside the acceptable range.

Answer

The test should be performed at a slower loading rate to compensate.

Answer

The core must be trimmed to a length of 200 mm before testing.

Question 5

After testing a concrete cylinder, a technician observes a fracture pattern that consists of well-formed cones on both ends of the specimen. According to CSA A23.2-9C and referenced standards like ASTM C39, what does this type of fracture typically indicate?

Accepted Answer

A valid and acceptable test result.

Answer

The concrete had insufficient air entrainment.

Answer

The cylinder was not properly centered in the machine.

Answer

The loading rate was applied too slowly.

Question 6

What is the critical function of the spherically seated bearing block (upper platen) in a concrete compression testing machine?

Accepted Answer

To allow the block to tilt and align itself with the top surface of the specimen.

Answer

To apply the load at the precise rate specified by the standard.

Answer

To absorb the shock of the cylinder fracturing, protecting the load cell.

Answer

To measure the diameter of the concrete cylinder automatically.