CMA Construction Materials & Methods 2 — Questions and Answers
Question 1: Which type of concrete admixture is used to reduce the water-cement ratio while maintaining workability?
- Air-entraining agent
- Superplasticizer (Correct answer)
- Accelerating admixture
- Fly ash pozzolan
Correct answer: Superplasticizer
Superplasticizers (high-range water reducers) significantly reduce water demand while maintaining or improving concrete workability.
Question 2: What is the primary purpose of a vapor retarder placed below a concrete slab-on-grade?
- To prevent radon gas infiltration
- To limit moisture migration from soil into the slab (Correct answer)
- To improve thermal insulation
- To reduce frost heave
Correct answer: To limit moisture migration from soil into the slab
A vapor retarder beneath a slab-on-grade prevents ground moisture from migrating upward through the concrete, protecting floor coverings and interior conditions.
Question 3: Glulam (glued laminated timber) beams are manufactured using which bonding agent?
- Epoxy resin
- Phenol-resorcinol or melamine-urea formaldehyde adhesive (Correct answer)
- Polyurethane foam
- Portland cement paste
Correct answer: Phenol-resorcinol or melamine-urea formaldehyde adhesive
Glulam beams use structural adhesives such as phenol-resorcinol formaldehyde (PRF) or melamine-urea formaldehyde (MUF) to bond laminations.
Question 4: In masonry construction, what does the term 'efflorescence' describe?
- Cracking caused by thermal expansion
- White salt deposits that migrate to the surface (Correct answer)
- Spalling due to freeze-thaw cycles
- Staining from iron oxide in brick
Correct answer: White salt deposits that migrate to the surface
Efflorescence is the white crystalline deposit formed when water-soluble salts migrate to the masonry surface and crystallize upon evaporation.
Question 5: Which steel section shape provides the most efficient resistance to bending about its strong axis?
- Square HSS (hollow structural section)
- Round pipe section
- Wide-flange (W-shape) section (Correct answer)
- Angle (L-shape) section
Correct answer: Wide-flange (W-shape) section
Wide-flange sections concentrate material in the flanges, maximizing the moment of inertia about the strong axis for efficient bending resistance.
Question 6: What is the principal advantage of using insulated concrete forms (ICF) in residential construction?
- They eliminate the need for reinforcing steel
- They provide integrated formwork and continuous thermal insulation (Correct answer)
- They reduce concrete curing time by 50%
- They allow concrete placement at below-freezing temperatures without heating
Correct answer: They provide integrated formwork and continuous thermal insulation
ICF systems serve as stay-in-place formwork while providing continuous rigid foam insulation on both faces of the concrete wall.
Question 7: Which roofing membrane system relies on the weight of ballast to resist wind uplift rather than adhesive or mechanical fasteners?
- Fully adhered TPO system
- Mechanically fastened EPDM system
- Ballasted single-ply system (Correct answer)
- Torch-applied modified bitumen system
Correct answer: Ballasted single-ply system
Ballasted single-ply roofing systems use river-washed stone or concrete pavers to hold the membrane in place against wind uplift forces.
CMA Construction Materials & Methods 2
Which type of concrete admixture is used to reduce the water-cement ratio while maintaining workability?