BCM Building Materials and Construction Methods 1 — Questions and Answers
Question 1: The water-cement ratio (w/c ratio) in concrete mix design primarily affects:
- Compressive strength and durability of the hardened concrete (Correct answer)
- The color of the finished concrete surface
- Aggregate particle size distribution
- Reinforcing steel bond strength only
Correct answer: Compressive strength and durability of the hardened concrete
A lower w/c ratio produces stronger, more durable concrete by reducing porosity, while a higher ratio weakens the paste matrix.
Question 2: Tensile strength is a structural weakness of concrete, which is why:
- Steel reinforcing bars (rebar) are embedded in concrete to resist tension forces (Correct answer)
- Concrete is only used for compression members like columns
- Concrete footings are always thicker than slabs
- Post-tensioning is only used in bridge construction
Correct answer: Steel reinforcing bars (rebar) are embedded in concrete to resist tension forces
Concrete is strong in compression but weak in tension, so steel reinforcement is added to carry tensile stresses in beams, slabs, and other members.
Question 3: Which type of foundation is used when soil at shallow depths is too weak to support structural loads?
- Deep foundation (piles or caissons) (Correct answer)
- Spread footing
- Mat (raft) foundation
- Grade beam foundation
Correct answer: Deep foundation (piles or caissons)
Deep foundations transfer loads through weak upper soils to stronger bearing strata or bedrock at greater depths using piles or drilled shafts.
Question 4: CMU stands for which common masonry construction material?
- Concrete Masonry Unit (Correct answer)
- Composite Metal Unit
- Cured Mortar Unit
- Cast Material Underlayment
Correct answer: Concrete Masonry Unit
CMU (concrete masonry unit), commonly called a concrete block or cinder block, is a standard hollow or solid precast concrete building unit.
Question 5: In steel construction, the term 'wide flange' (W-shape) refers to:
- An I-shaped structural steel section with parallel flanges used for beams and columns (Correct answer)
- A bolted connection detail at column splices
- Steel decking used for composite floor systems
- A proprietary cold-formed steel framing system
Correct answer: An I-shaped structural steel section with parallel flanges used for beams and columns
Wide-flange sections are the most common structural steel shapes, characterized by their I-profile with flanges that are approximately the same width as the web depth.
Question 6: Vapor barriers in construction assemblies are installed to:
- Prevent moisture migration from humid areas into building assemblies where condensation could cause damage (Correct answer)
- Block UV radiation from degrading insulation materials
- Increase the fire resistance rating of wall assemblies
- Improve the acoustic performance of partition walls
Correct answer: Prevent moisture migration from humid areas into building assemblies where condensation could cause damage
Vapor barriers (or retarders) limit water vapor diffusion through building envelopes, preventing condensation within walls or roofs that could cause mold and decay.
BCM Building Materials and Construction Methods 1
The water-cement ratio (w/c ratio) in concrete mix design primarily affects: