CCIL - Canadian Council of Independent Laboratories Advanced Aggregate Characterization Questions and Answers

Question 1

According to CSA A23.2-15A, what is the primary objective of conducting a petrographic analysis on a coarse aggregate sample?

Accepted Answer

To identify the mineralogical composition and physical characteristics of the rock types present.

Answer

CSA A23.2-15A outlines the procedure for the petrographic examination of aggregates. The primary purpose is to identify the constituent rock and mineral types, determine their physical and chemical characteristics, and detect the presence of potentially deleterious materials. This information is crucial for predicting the aggregate's performance in concrete or asphalt.

Question 2

A laboratory performs a Magnesium Sulfate Soundness test (CSA A23.2-9A) on a new source of coarse aggregate. The result is a weighted average mass loss of 15%, which exceeds the project specification limit of 12%. What does this high percentage loss primarily indicate about the aggregate?

Accepted Answer

The aggregate has poor resistance to weathering and is susceptible to degradation from freeze-thaw action.

Answer

The Magnesium Sulfate Soundness test is an accelerated weathering test designed to estimate an aggregate's resistance to degradation by natural freeze-thaw cycles. The sulfate solution crystallizes within the aggregate's pores, creating internal pressures that simulate ice formation. A high mass loss indicates the aggregate has a weak internal structure and is not durable against this type of weathering.

Question 3

A petrographic examination of a granite aggregate source reveals the presence of strained quartz and chert, which are known to be potentially alkali-silica reactive. To further quantify the risk of this aggregate causing deleterious expansion in concrete, which of the following tests would be most appropriate?

Accepted Answer

Accelerated Mortar Bar Test (CSA A23.2-14A).

Answer

The Accelerated Mortar Bar Test (referenced in CSA A23.2-14A for concrete prisms) is specifically designed to rapidly identify the potential for an aggregate to undergo deleterious expansion due to alkali-silica reaction (ASR). Mortar bars made with the aggregate are stored in a sodium hydroxide solution at an elevated temperature to accelerate the reaction, and their length change is measured over time.

Question 4

What property of a fine aggregate is primarily assessed by determining its uncompacted void content, as described in CSA A23.2-11A?

Accepted Answer

The particle shape, angularity, and surface texture.

Answer

The uncompacted void content test measures the void space in a loosely packed sample of fine aggregate. Aggregates that are more angular and have a rougher surface texture will not pack together as tightly, resulting in a higher uncompacted void content. This property is critical for predicting performance characteristics in asphalt and concrete mixes.

Question 5

The Micro-Deval abrasion test (CSA A23.2-29A) is performed on an aggregate sample to assess which of the following properties?

Accepted Answer

Hardness, toughness, and durability against abrasion and degradation.

Answer

The Micro-Deval test simulates the abrasive action and degradation that aggregates experience during processing, handling, and in-service use. It measures the mass loss of a sample after it has been tumbled with steel balls in the presence of water, which is an indicator of its resistance to abrasion and overall durability.

CCIL - Canadian Council of Independent Laboratories Practice Test

CCIL - Canadian Council of Independent Laboratories Practice Test

CCIL - Canadian Council of Independent Laboratories Advanced Aggregate Characterization Questions and Answers