semplr.

Exams · Certifications · Licensing

NASCLA Commercial General Building Contractor — Practice Exam

Concrete: practice questions

Our NASCLA Commercial GC bank has 16 questions on this topic. Here are 5 of them with answers; the full mock exam draws from every topic, like the real one.

Start the free mock exam

Question 1

What is the nominal diameter of a #5 reinforcing bar?

  1. 5 inches
  2. 1/2 inch
  3. 5/8 inch
  4. 5/16 inch
Show the answer

C. 5/8 inch — Bar numbers are eighths of an inch for sizes #3 to #8.

Question 2

What causes plastic shrinkage cracking in a slab?

  1. Using a vapor retarder
  2. Rapid evaporation from the surface before the concrete sets
  3. Overloading the slab after a year
  4. Too much curing water applied too soon after finishing
Show the answer

B. Rapid evaporation from the surface before the concrete sets — Wind, heat and low humidity increase the risk.

Question 3

What is a cold joint?

  1. A joint filled with sealant
  2. A joint made in cold weather only
  3. A joint formed when fresh concrete is placed against concrete that has already set
  4. A joint cut into the slab after finishing to control where cracks form
Show the answer

C. A joint formed when fresh concrete is placed against concrete that has already set — Planned construction joints are prepared to bond and transfer load.

Question 4

Why is air-entraining admixture used in exterior concrete in cold climates?

  1. To change the color
  2. To speed up setting so finishing can start sooner on cold days
  3. To improve resistance to freeze-thaw damage
  4. To raise compressive strength
Show the answer

C. To improve resistance to freeze-thaw damage — Tiny air bubbles relieve pressure from freezing water.

Question 5

How does a faster rate of placement affect lateral pressure on wall forms?

  1. It increases the pressure
  2. It decreases the pressure
  3. It only matters for slabs
  4. It has no effect
Show the answer

A. It increases the pressure — Lower concrete temperature also raises form pressure.

More NASCLA Commercial GC topics