Concrete Flashcards

According to CSA A23.1, what is the minimum curing period for concrete exposed to freezing temperatures before it can be considered adequately cured?

Answer: 7 days at 10°C

CSA A23.1 requires concrete to be maintained at a minimum of 10°C for at least 7 days to achieve adequate early strength before exposure to freezing.

When performing a slump test per ASTM C143/CSA A23.2-5C, the concrete is rodded in how many layers?

Answer: 3 equal layers

The slump test requires filling the mold in 3 equal layers, each rodded 25 times with a tamping rod.

What does a bleeding rate in fresh concrete primarily indicate?

Answer: Excess mix water migrating to the surface

Bleeding occurs when excess mix water rises to the surface of fresh concrete due to settlement of heavier solids.

In CCIL concrete testing, what is the purpose of the air content test performed per ASTM C231?

Answer: Determining entrained and entrapped air in fresh concrete

ASTM C231 (pressure method) measures the air content of freshly mixed concrete to verify adequate air entrainment for freeze-thaw durability.

Which failure mode is expected during a standard compressive strength test of a properly made and tested concrete cylinder?

Answer: Diagonal shear cone fracture or columnar cracking with end cones

Acceptable failure patterns for concrete cylinders include diagonal shear cones, columnar cracks, or combinations; these indicate valid test results per ASTM C39.

What is the standard diameter-to-height ratio for a concrete test cylinder used in compressive strength testing?

Answer: 1:2

Standard concrete cylinders have a 1:2 diameter-to-height ratio (e.g., 100 mm × 200 mm or 150 mm × 300 mm) as required by ASTM C39.

When capping concrete cylinders with sulfur mortar per ASTM C617, the cap thickness should not exceed:

Answer: 6 mm

ASTM C617 limits sulfur mortar cap thickness to 6 mm (¼ inch) maximum to minimize eccentricity effects during loading.