Construction Concrete and Masonry 3

Question 1

What is 'efflorescence' on masonry walls?

Accepted Answer

White salt deposits on the masonry surface caused by water migration

Answer

Efflorescence is a white powdery deposit on masonry surfaces caused by water-soluble salts being carried to the surface and left behind as the water evaporates.

Question 2

What type of footing is typically used for a single column load?

Accepted Answer

Spread (pad) footing

Answer

A spread footing (also called a pad footing) is an isolated square or rectangular footing designed to distribute a single column load to the soil.

Question 3

What is the purpose of a 'vapor barrier' under a concrete slab on grade?

Accepted Answer

To prevent ground moisture from migrating up through the slab

Answer

A vapor barrier (typically polyethylene sheeting) is placed under slabs on grade to prevent ground moisture from rising through the concrete and damaging flooring above.

Question 4

What is 'cold joint' in concrete construction?

Accepted Answer

A joint between two separate concrete pours where the first set before the second was placed

Answer

A cold joint forms when fresh concrete is placed against previously hardened concrete, creating a plane of weakness due to poor bond at the interface.

Question 5

Which test is used to measure the compressive strength of hardened concrete cylinders?

Accepted Answer

Cylinder compression test (ASTM C39)

Answer

ASTM C39 is the standard test method for compressive strength of cylindrical concrete specimens, typically 4×8 or 6×12 inch cylinders tested at 28 days.

Construction Practice Test

Construction Practice Test

Construction Concrete and Masonry 3