CCIL Concrete 5

Question 1

What is the primary function of a plasticizer (water reducer) admixture in concrete?

Accepted Answer

Reduce the water requirement while maintaining workability

Answer

Water-reducing admixtures (plasticizers) allow a reduction in mixing water while maintaining equivalent workability, thereby improving strength and reducing w/cm.

Question 2

Concrete affected by delayed ettringite formation (DEF) typically shows damage that:

Accepted Answer

Manifests years after placement as internal expansion and cracking

Answer

DEF is a long-term durability issue where ettringite forms within hardened concrete years after curing, causing internal expansion and cracking.

Question 3

The initial set of concrete is defined as the point at which penetration resistance reaches:

Accepted Answer

500 psi (3.5 MPa)

Answer

Per ASTM C403, initial set corresponds to a penetration resistance of 500 psi (3.5 MPa), while final set corresponds to 4000 psi (27.6 MPa).

Question 4

What does the term 'carbonation depth' in concrete indicate in a durability assessment?

Accepted Answer

Depth to which atmospheric CO₂ has reduced the concrete's pH

Answer

Carbonation occurs when CO₂ reacts with calcium hydroxide in cement paste, reducing pH from ~13 to ~9 and potentially depassivating reinforcing steel.

Question 5

In accelerated curing of concrete specimens using warm water or steam, which property may be adversely affected?

Accepted Answer

Long-term strength compared to moist-cured specimens

Answer

Accelerated curing boosts early strength but can reduce long-term strength compared to standard moist-cured specimens due to less uniform microstructure development.

CCIL - Canadian Council of Independent Laboratories Practice Test

CCIL - Canadian Council of Independent Laboratories Practice Test

CCIL Concrete 5