GCC Materials & Equipment Knowledge 2 — Questions and Answers
Question 1: What is the minimum compressive strength of concrete typically specified for residential foundation footings?
- 2,000 psi
- 2,500 psi
- 3,000 psi (Correct answer)
- 4,000 psi
Correct answer: 3,000 psi
3,000 psi is the standard minimum compressive strength specified for residential foundation concrete per most building codes.
Question 2: Which type of lumber grading system is used for structural applications in the US?
- Aesthetic grading
- Visual and machine stress-rated (MSR) grading (Correct answer)
- Density grading
- Color grading
Correct answer: Visual and machine stress-rated (MSR) grading
Visual and machine stress-rated (MSR) grading systems are used to classify lumber for structural applications based on strength properties.
Question 3: What does the R-value of insulation measure?
- Moisture resistance
- Fire resistance rating
- Thermal resistance to heat flow (Correct answer)
- Sound transmission coefficient
Correct answer: Thermal resistance to heat flow
R-value measures the thermal resistance of insulation material — the higher the R-value, the greater the resistance to heat flow.
Question 4: A contractor needs to select rebar for a concrete beam. Grade 60 rebar has a minimum yield strength of:
- 40,000 psi
- 50,000 psi
- 60,000 psi (Correct answer)
- 75,000 psi
Correct answer: 60,000 psi
Grade 60 rebar has a minimum yield strength of 60,000 psi, which is the most commonly used grade in structural concrete.
Question 5: What is the primary advantage of using engineered lumber (LVL) over dimensional lumber for long-span beams?
- Lower material cost
- Greater dimensional stability and higher strength-to-weight ratio (Correct answer)
- Faster installation time
- Better fire resistance
Correct answer: Greater dimensional stability and higher strength-to-weight ratio
LVL (Laminated Veneer Lumber) offers greater dimensional stability and a higher strength-to-weight ratio compared to sawn lumber, making it ideal for long spans.
Question 6: Which ASTM standard governs the specification for Portland cement?
- ASTM A36
- ASTM C150 (Correct answer)
- ASTM D1586
- ASTM E119
Correct answer: ASTM C150
ASTM C150 is the standard specification for Portland cement, defining its chemical and physical requirements.
Question 7: What is the water-to-cement (w/c) ratio's primary effect on concrete?
- It controls workability only, with no effect on strength
- Lower w/c ratios produce stronger, more durable concrete (Correct answer)
- Higher w/c ratios produce stronger concrete
- W/c ratio only affects curing time
Correct answer: Lower w/c ratios produce stronger, more durable concrete
A lower water-to-cement ratio results in stronger, more durable concrete because excess water creates voids as it evaporates.
GCC Materials & Equipment Knowledge 2
What is the minimum compressive strength of concrete typically specified for residential foundation footings?