CCIL Concrete Compressive Strength Testing 3

Question 1

Which ASTM standard governs the practice of making and curing concrete test specimens in the field?

Accepted Answer

ASTM C31

Answer

ASTM C31 covers the standard practice for making and curing concrete test specimens in the field.

Question 2

What is the minimum inside diameter of a mold used to cast a cylindrical concrete specimen per ASTM C31?

Accepted Answer

At least 3.0 times the maximum aggregate size

Answer

ASTM C31 requires mold diameter to be at least 3 times the nominal maximum size of coarse aggregate in the concrete.

Question 3

During compression testing, which specimen condition is most likely to cause a significant reduction in measured compressive strength?

Accepted Answer

Specimen with a concave end surface

Answer

A concave end surface causes stress concentration at the edges rather than uniform load distribution, significantly reducing measured strength.

Question 4

What is the acceptable length-to-diameter (L/D) ratio range for a cylinder to be tested without applying a correction factor per ASTM C39?

Accepted Answer

1.75 to 2.25

Answer

ASTM C39 states no correction factor is needed when the L/D ratio is between 1.75 and 2.25 for standard cylinders.

Question 5

What action should be taken when the L/D ratio of a concrete cylinder is less than 1.75?

Accepted Answer

Apply a correction factor from the ASTM C39 table to the measured strength

Answer

ASTM C39 provides correction factors for cylinders with L/D ratios between 1.00 and 1.74 to normalize results to standard geometry.

CCIL - Canadian Council of Independent Laboratories Practice Test