CCIL - Canadian Council of Independent Laboratories Aggregate Gradation and Properties Questions and Answers

Question 1

A laboratory technician performs a sieve analysis on a fine aggregate sample.
The results show a Fineness Modulus (FM) of 3.4.
According to CSA A23.1, what does this value indicate about the aggregate?

Accepted Answer

The aggregate is coarser than the typical acceptable range for fine aggregate.

Answer

The aggregate is well-graded and suitable for most concrete mixes.

Answer

The aggregate is very fine and may increase water demand in a concrete mix.

Answer

The aggregate has a high percentage of deleterious materials.

Question 2

During a sieve analysis of a coarse aggregate sample according to CSA A23.2-2A, the technician fails to ensure the sieves are clean before starting the test. Some finer particles from a previous test are present in the lower sieves. How would this MOST likely affect the calculated results for the current sample?

Accepted Answer

It would falsely increase the calculated percentage passing the finer sieves.

Answer

It would artificially increase the percentage of material retained on the coarser sieves.

Answer

It would have no significant effect on the overall gradation curve.

Answer

It would lead to a lower calculated total sample mass.

Question 3

A concrete mix design requires a well-graded aggregate. Which of the following descriptions best characterizes a well-graded aggregate?

Accepted Answer

An aggregate containing a wide and continuous distribution of particle sizes.

Answer

An aggregate with most particles of a similar size, creating high void content.

Answer

An aggregate where specific intermediate particle sizes are absent.

Answer

An aggregate composed exclusively of fine sand and dust.

Question 4

According to CSA A23.1, which of the following is considered a deleterious substance that could negatively impact the bond between cement paste and aggregate if present in excessive amounts?

Accepted Answer

Clay lumps or coatings on the aggregate particles.

Answer

Hard, angular crushed rock particles.

Answer

Silica fume used as a supplementary cementing material.

Answer

Well-rounded natural gravel particles.

Question 5

A technician is preparing a coarse aggregate sample for a Flat and Elongated Particles test (CSA A23.2-13A). The specification requires testing particles using a 3:1 ratio. What does this ratio represent?

Accepted Answer

The ratio of the aggregate's length to its width, or width to its thickness.

Answer

The ratio of the sample mass to the required water content.

Answer

The maximum allowable percentage of flat and elongated particles in the sample.

Answer

The minimum number of particles that must be tested from three different sieve sizes.

Question 6

In a sieve analysis performed according to CSA A23.2-2A, the sum of the masses retained on all the sieves plus the pan is found to be 0.8% less than the initial dry mass of the sample. What is the most likely cause of this discrepancy?

Accepted Answer

Loss of fine dust particles during the sieving operation.

Answer

The use of an incorrect number of sieves for the test.

Answer

Overloading the sieves with too much material.

Answer

Calculation error when determining cumulative percent retained.