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 Fineness Modulus (FM) is an index of the fineness of an aggregate. For fine aggregate (sand), CSA A23.1 typically requires the FM to be between 2.3 and 3.1. An FM of 3.4 is higher than this range, indicating that the sand is relatively coarse.

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

If finer particles from a previous test are already in the lower sieves, the mass of material collected on these finer sieves during the test will be artificially high. This leads to a calculation that shows more material passing through the upper sieves and being retained on the lower ones than is actually present in the sample, thus increasing the percent passing for those finer sieves.

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

A well-graded aggregate has a good representation of all particle sizes from coarse to fine. This distribution allows the finer particles to fill the voids between the larger particles, resulting in a dense, strong, and economical concrete mix with minimal paste requirement.

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

Deleterious substances are contaminants that can harm the properties of concrete. Clay lumps and coatings are specifically identified as deleterious because they can interfere with the bond between the aggregate surface and the cement paste, leading to reduced strength and durability.

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

In the context of the Flat and Elongated Particles test, the ratio (e.g., 3:1, 5:1) defines the dimensional criteria for a particle to be classified as flat or elongated. For example, a particle is considered elongated if its length is more than three times its width, and flat if its width is more than three times its thickness.

CCIL - Canadian Council of Independent Laboratories Practice Test

CCIL - Canadian Council of Independent Laboratories Practice Test

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