Concrete Contractor Exam Questions
And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the main ingredient in concrete that gives it compressive
strength?
a) Sand
b) Cement
c) Gravel
d) Water
Rationale: Cement is the binding material in concrete that reacts with water
(hydration) to give concrete its compressive strength.
2. Which type of cement is typically used for general construction?
a) Rapid-hardening cement
b) Ordinary Portland Cement (OPC)
c) Sulfate-resisting cement
d) White cement
Rationale: Ordinary Portland Cement is commonly used for general
concrete construction due to its balanced strength and setting characteristics.
3. What is the primary function of water in a concrete mix?
a) Fill voids
b) Hydrate cement and enable workability
c) Increase density
d) Prevent cracks
,Rationale: Water hydrates the cement, initiating the chemical reaction that
allows concrete to harden and also provides workability for placing and
finishing.
4. In concrete mix design, which factor primarily affects workability?
a) Cement type
b) Water-cement ratio
c) Aggregate size
d) Curing time
Rationale: Workability is mainly influenced by the water-cement ratio; too
little water makes concrete stiff, too much reduces strength.
5. What is the typical curing period for ordinary concrete to achieve most
of its strength?
a) 3 days
b) 7 days
c) 28 days
d) 90 days
Rationale: Concrete gains most of its compressive strength within 28 days
when properly cured.
6. Which aggregate size is preferred for reinforced concrete beams and
slabs?
a) 5–10 mm
b) 20 mm maximum
c) 40–50 mm
d) 60 mm minimum
Rationale: Maximum aggregate size should be small enough to allow proper
placement and bonding around reinforcement.
7. What is the purpose of adding air-entraining admixtures in concrete?
a) Increase density
b) Improve freeze-thaw resistance
c) Speed up setting
d) Reduce curing time
, Rationale: Air-entraining admixtures create microscopic air bubbles,
improving resistance to freezing and thawing cycles.
8. How is the slump test used in concrete construction?
a) To measure workability
b) To determine compressive strength
c) To measure water content
d) To assess curing quality
Rationale: The slump test assesses concrete consistency and workability at
the point of placement.
9. Which method is commonly used to compact concrete in forms?
a) Hand rubbing
b) Tamping only
c) Vibration
d) Spraying water
Rationale: Vibrators remove air pockets and ensure concrete fully surrounds
reinforcement, improving strength and durability.
10. What is the recommended minimum concrete cover for
reinforcement in normal exposure conditions?
a) 10 mm
b) 25 mm
c) 50 mm
d) 75 mm
Rationale: Adequate cover protects steel from corrosion and fire and
ensures proper bonding with concrete.
11. Which of the following is a sign of insufficient curing?
a) Smooth surface
b) Surface cracking and reduced strength
c) Hard concrete
d) Uniform color
Rationale: Insufficient curing leads to rapid moisture loss, causing cracking
and lower strength.
And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the main ingredient in concrete that gives it compressive
strength?
a) Sand
b) Cement
c) Gravel
d) Water
Rationale: Cement is the binding material in concrete that reacts with water
(hydration) to give concrete its compressive strength.
2. Which type of cement is typically used for general construction?
a) Rapid-hardening cement
b) Ordinary Portland Cement (OPC)
c) Sulfate-resisting cement
d) White cement
Rationale: Ordinary Portland Cement is commonly used for general
concrete construction due to its balanced strength and setting characteristics.
3. What is the primary function of water in a concrete mix?
a) Fill voids
b) Hydrate cement and enable workability
c) Increase density
d) Prevent cracks
,Rationale: Water hydrates the cement, initiating the chemical reaction that
allows concrete to harden and also provides workability for placing and
finishing.
4. In concrete mix design, which factor primarily affects workability?
a) Cement type
b) Water-cement ratio
c) Aggregate size
d) Curing time
Rationale: Workability is mainly influenced by the water-cement ratio; too
little water makes concrete stiff, too much reduces strength.
5. What is the typical curing period for ordinary concrete to achieve most
of its strength?
a) 3 days
b) 7 days
c) 28 days
d) 90 days
Rationale: Concrete gains most of its compressive strength within 28 days
when properly cured.
6. Which aggregate size is preferred for reinforced concrete beams and
slabs?
a) 5–10 mm
b) 20 mm maximum
c) 40–50 mm
d) 60 mm minimum
Rationale: Maximum aggregate size should be small enough to allow proper
placement and bonding around reinforcement.
7. What is the purpose of adding air-entraining admixtures in concrete?
a) Increase density
b) Improve freeze-thaw resistance
c) Speed up setting
d) Reduce curing time
, Rationale: Air-entraining admixtures create microscopic air bubbles,
improving resistance to freezing and thawing cycles.
8. How is the slump test used in concrete construction?
a) To measure workability
b) To determine compressive strength
c) To measure water content
d) To assess curing quality
Rationale: The slump test assesses concrete consistency and workability at
the point of placement.
9. Which method is commonly used to compact concrete in forms?
a) Hand rubbing
b) Tamping only
c) Vibration
d) Spraying water
Rationale: Vibrators remove air pockets and ensure concrete fully surrounds
reinforcement, improving strength and durability.
10. What is the recommended minimum concrete cover for
reinforcement in normal exposure conditions?
a) 10 mm
b) 25 mm
c) 50 mm
d) 75 mm
Rationale: Adequate cover protects steel from corrosion and fire and
ensures proper bonding with concrete.
11. Which of the following is a sign of insufficient curing?
a) Smooth surface
b) Surface cracking and reduced strength
c) Hard concrete
d) Uniform color
Rationale: Insufficient curing leads to rapid moisture loss, causing cracking
and lower strength.
