Construction Materials & Methods Flashcards

What is the primary purpose of using a vapor barrier in a concrete slab-on-grade?

Answer: To prevent moisture migration from the subgrade into the slab

A vapor barrier (polyethylene sheet) prevents soil moisture from wicking upward through the concrete slab, protecting flooring systems and interior finishes.

Which masonry unit classification indicates the highest structural quality per ASTM C90?

Answer: Grade N

ASTM C90 Grade N concrete masonry units are intended for general use including above- and below-grade applications exposed to moisture and weather.

In structural steel fabrication, what does the term 'mill scale' refer to?

Answer: Iron oxide layer formed on hot-rolled steel during manufacturing

Mill scale is a flaky iron oxide layer that forms on the surface of hot-rolled steel during the manufacturing process and must be removed before painting.

What concrete admixture type is used to reduce the water content required to achieve a given slump?

Answer: Water reducer (plasticizer)

Water-reducing admixtures (plasticizers) allow the same workability to be achieved with less water, improving the water-to-cement ratio and concrete strength.

When inspecting reinforcing steel, 'No. 5 bar' refers to a rebar with a nominal diameter of:

Answer: 5/8 inch

Rebar bar numbers correspond to the nominal diameter in eighths of an inch, so a No. 5 bar has a nominal diameter of 5/8 inch.

Which type of Portland cement is specifically designed for use in environments with high sulfate exposure?

Answer: Type V

Type V Portland cement has a very low tricalcium aluminate (C3A) content, making it highly resistant to sulfate attack from soil and groundwater.

What is the standard curing period recommended for normal-strength Portland cement concrete to achieve adequate strength?

Answer: 28 days

Portland cement concrete is conventionally tested and specified to reach its design compressive strength at 28 days of moist curing.