Contractor Exam Questions And

CA D06 Concrete-Related Services Contractor Exam Questions And Correct Answers (Verified Answers) Plus Rationale2026 Q&A| Instant Download Pdf

• Which of the following is the main ingredient in concrete that provides

compressive strength?

• Water
• Cement
• Sand
• Gravel

Rationale: Cement is the binding material in concrete that hardens

and gains strength, providing compressive strength.

• What is the primary purpose of reinforcing steel (rebar) in concrete?
• Reduce shrinkage
• Provide tensile strength
• Increase workability
• Accelerate curing

Rationale: Concrete is strong in compression but weak in tension;

rebar provides tensile strength.

• Which type of cement is typically used for high-strength concrete?
• Type I
• Type II
• Type III
• Type IV

Rationale: Type III cement is high early-strength cement suitable for

high-strength concrete applications. 1 / 3

• The slump test measures what property of fresh concrete?
• Compressive strength
• Workability
• Setting time
• Water-cement ratio

Rationale: The slump test evaluates the consistency and workability

of fresh concrete.

• What is the recommended water-cement ratio for most structural

concrete?

A. 0.3–0.4

B. 0.45–0.6

C. 0.7–0.8

D. 0.2–0.3

Rationale: A water-cement ratio of 0.45–0.6 ensures proper

hydration and strength development.

• Which aggregate size is generally used for reinforced concrete slabs?
• 1–5 mm
• 5–10 mm
• 10–20 mm
• 20–40 mm

Rationale: Medium-sized aggregates (10–20 mm) are commonly used

in slabs for strength and workability.

• What is the main purpose of curing concrete?
• Reduce workability
• Accelerate drying
• Maintain moisture for hydration
• Increase slump

Rationale: Curing maintains moisture and temperature to allow

cement hydration, which increases strength and durability.

• How long is concrete typically cured to reach its design strength?
• 3 days
• 7 days
• 28 days
• 90 days

Rationale: Concrete reaches approximately 90% of its design

strength at 28 days under normal curing conditions. 2 / 3

• Which of the following admixtures is used to reduce water content and

increase workability?

• Air-entraining agent
• Plasticizer
• Retarder
• Accelerator

Rationale: Plasticizers reduce water demand while maintaining

workability.

10. Air-entraining agents in concrete are primarily used to:

• Increase strength
• Improve freeze-thaw resistance
• Accelerate setting
• Reduce water-cement ratio

Rationale: Air-entraining agents create microscopic air bubbles that

help resist freeze-thaw damage.

• Which test measures the compressive strength of concrete?
• Slump test
• Cylinder or cube crushing test
• Flow table test
• Tensile test

Rationale: Cylinders or cubes are cast and tested to determine the

compressive strength of concrete.

• What is the typical size of concrete cylinders used for standard

strength testing?

• 75 × 150 mm
• 100 × 200 mm
• 150 × 300 mm
• 200 × 400 mm

Rationale: 150 mm diameter × 300 mm height cylinders are standard

for strength testing.

• When concrete is poured in hot weather, which of the following

precautions is recommended?

• Increase water content
• Use retarding admixtures and keep it shaded
• Decrease curing
• Use smaller aggregates
• / 3