Exam Questions and Answers Best rated A

Nevada Concrete Contractor (C-5) Contractor Practice Exam Questions and Answers Best rated A+ Guaranteed Success Latest Update

• What is the primary purpose of reinforcing steel (rebar) in concrete?
• Reduce shrinkage cracking
• Increase tensile strength [ANSWER]
• Accelerate curing time
• Improve concrete workability

Rationale: Concrete is strong in compression but weak in tension. Rebar adds tensile strength, helping concrete resist bending and cracking.

• What is the minimum compressive strength of concrete required for residential footings

per typical building codes?

• 1,500 psi
• 2,500 psi
• 3,000 psi [ANSWER]
• 4,000 psi

Rationale: Most building codes require concrete footings to have at least 3,000 psi compressive strength at 28 days to ensure structural safety.

• Which admixture is used to slow down the setting time of concrete in hot weather?
• Accelerators
• Retarders [ANSWER]
• Water reducers
• Air-entraining agents

Rationale: Retarders slow the hydration process of cement, giving workers more time to place and finish concrete in hot conditions.

• What is the recommended slump range for concrete used in standard slabs?
• 0–2 inches
• 2–3 inches 1 / 4

• 3–4 inches [ANSWER]
• 5–6 inches

Rationale: A 3–4 inch slump ensures sufficient workability without excessive water, maintaining strength and durability.

• When constructing concrete forms, what is the minimum clearance required between the

form and the finished grade for footings?

• 1 inch
• 3 inches [ANSWER]
• 6 inches
• 12 inches

Rationale: Adequate clearance ensures proper concrete consolidation and prevents weak spots at the edges of footings.

• What is the primary function of an air-entraining agent in concrete?
• Increase compressive strength
• Accelerate setting time
• Improve freeze-thaw durability [ANSWER]
• Reduce curing time

Rationale: Air-entraining agents create tiny air bubbles in concrete, which allow space for water to expand during freezing, reducing cracking.

• Which type of cement is typically used for most general construction concrete in

Nevada?

• Type I
• Type II
• Type III
• Type I/II [ANSWER]

Rationale: Type I/II Portland cement is suitable for most general concrete work and provides moderate sulfate resistance, appropriate for Nevada’s conditions.

• When pouring a concrete slab over soil, what is the recommended minimum thickness of

compacted gravel base?

• 2 inches 2 / 4

• 3 inches
• 4 inches [ANSWER]
• 6 inches

Rationale: A 4-inch gravel base provides proper drainage and prevents settlement, helping maintain slab integrity.

• What is the correct water-to-cement ratio for high-strength concrete?

A. 0.60–0.70

B. 0.50–0.60

C. 0.40–0.50 [ANSWER]

D. 0.30–0.40

Rationale: Lower water-to-cement ratios (0.40–0.50) produce stronger, denser concrete while minimizing shrinkage and cracking.

• What tool is used to consolidate freshly placed concrete in forms?
• Trowel
• Vibrator [ANSWER]
• Float
• Screed

Rationale: Vibrators remove air pockets and ensure proper consolidation of concrete around reinforcement and formwork.

• Which of the following curing methods helps maintain moisture in freshly poured

concrete?

• Saw cutting
• Power troweling
• Wet burlap covering [ANSWER]
• Accelerating admixtures

Rationale: Wet coverings prevent water loss, ensuring proper hydration and strength development.

• When is it recommended to saw-cut control joints in a slab?
• Immediately after finishing
• After 1 week 3 / 4

• Within 12–24 hours after finishing [ANSWER]
• After 1 month

Rationale: Early saw-cutting controls cracking caused by shrinkage, without compromising structural integrity.

• What is the primary hazard associated with wet concrete for workers?
• Chemical burns
• Slip and fall
• Both A and B [ANSWER]
• None of the above

Rationale: Wet concrete is caustic and can cause chemical burns; it is also slippery, posing a risk of falls.

• What is the minimum concrete cover over rebar for exterior slabs exposed to weather?
• 1 inch
• 1.5 inches
• 2 inches [ANSWER]
• 3 inches

Rationale: Adequate cover protects rebar from corrosion due to moisture and environmental exposure.

• Which type of joint allows for movement due to thermal expansion in concrete

pavements?

• Construction joint
• Expansion joint [ANSWER]
• Contraction joint
• Isolation joint

Rationale: Expansion joints accommodate concrete expansion and prevent cracking under temperature changes.

• How often should concrete test cylinders be taken for compressive strength

verification?

• Once per project
• Once per month
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