AR CC Concrete Contractor
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Section 1: Concrete Materials and Properties
1. What is the primary function of Portland cement in a concrete
mixture?
A. To provide reinforcement against tensile stress
B. To act as a waterproofing membrane
C. To bind the aggregates together through hydration
,D. To prevent all shrinkage during curing
Rationale: Portland cement reacts chemically with water through
hydration, producing compounds that bind sand and coarse aggregates
into a hardened mass. Cement provides the binding matrix, while
reinforcement, proper mix proportions, and curing contribute to the
concrete's overall performance. Cement alone does not eliminate
shrinkage or make concrete completely waterproof.
2. Which material is commonly used as fine aggregate in concrete?
A. Crushed reinforcing steel
B. Natural sand or manufactured sand
C. Large river cobbles
D. Portland cement clinker
Rationale: Fine aggregate generally consists of sand-sized particles that
fill spaces between coarse aggregate particles and contribute to
workability and strength. Manufactured sand can also be used when it
meets applicable grading and quality requirements. Proper aggregate
grading helps reduce voids and excessive paste demand.
3. What is the primary purpose of coarse aggregate in concrete?
A. To accelerate cement hydration
,B. To replace all cement paste
C. To eliminate the need for water
D. To provide bulk and contribute to dimensional stability and
strength
Rationale: Coarse aggregate makes up a substantial portion of
concrete's volume. It provides bulk, contributes to mechanical
performance, and can reduce the amount of cement paste needed for a
given concrete volume. Aggregate size, shape, grading, and quality
influence workability, strength, and durability.
4. What does the water-cement ratio represent?
A. The weight of aggregate divided by the weight of cement
B. The total concrete volume divided by the water volume
C. The weight of mixing water divided by the weight of cementitious
material, when expressed as a water-cementitious ratio
D. The volume of cement divided by the volume of sand
Rationale: The water-cement ratio is calculated by dividing the weight
of mixing water by the weight of cement. When supplementary
cementitious materials are included in the denominator, the term
water-cementitious materials ratio (w/cm) is used. This ratio
, significantly affects strength, permeability, and durability when the
other mix variables are appropriately controlled.
5. What is the likely effect of adding excessive water to a concrete
mixture?
A. Increased compressive strength in every situation
B. Complete elimination of segregation
C. Reduced strength and increased permeability
D. Elimination of the need for curing
Rationale: Excess water increases the amount of water that is not
required for cement hydration and can leave capillary pores as the
concrete hardens. This often reduces compressive strength and
increases permeability and drying shrinkage. Excessive water can also
cause bleeding, segregation, and finishing problems.
6. What is the main purpose of an air-entraining admixture in
concrete?
A. To replace coarse aggregate
B. To eliminate cement hydration
C. To create microscopic air bubbles that improve resistance to
freezing and thawing
Exam Questions and Correct
Answers (Verified Answers)
Plus Rationale 2027 Q&A|
Instant Download Pdf
Section 1: Concrete Materials and Properties
1. What is the primary function of Portland cement in a concrete
mixture?
A. To provide reinforcement against tensile stress
B. To act as a waterproofing membrane
C. To bind the aggregates together through hydration
,D. To prevent all shrinkage during curing
Rationale: Portland cement reacts chemically with water through
hydration, producing compounds that bind sand and coarse aggregates
into a hardened mass. Cement provides the binding matrix, while
reinforcement, proper mix proportions, and curing contribute to the
concrete's overall performance. Cement alone does not eliminate
shrinkage or make concrete completely waterproof.
2. Which material is commonly used as fine aggregate in concrete?
A. Crushed reinforcing steel
B. Natural sand or manufactured sand
C. Large river cobbles
D. Portland cement clinker
Rationale: Fine aggregate generally consists of sand-sized particles that
fill spaces between coarse aggregate particles and contribute to
workability and strength. Manufactured sand can also be used when it
meets applicable grading and quality requirements. Proper aggregate
grading helps reduce voids and excessive paste demand.
3. What is the primary purpose of coarse aggregate in concrete?
A. To accelerate cement hydration
,B. To replace all cement paste
C. To eliminate the need for water
D. To provide bulk and contribute to dimensional stability and
strength
Rationale: Coarse aggregate makes up a substantial portion of
concrete's volume. It provides bulk, contributes to mechanical
performance, and can reduce the amount of cement paste needed for a
given concrete volume. Aggregate size, shape, grading, and quality
influence workability, strength, and durability.
4. What does the water-cement ratio represent?
A. The weight of aggregate divided by the weight of cement
B. The total concrete volume divided by the water volume
C. The weight of mixing water divided by the weight of cementitious
material, when expressed as a water-cementitious ratio
D. The volume of cement divided by the volume of sand
Rationale: The water-cement ratio is calculated by dividing the weight
of mixing water by the weight of cement. When supplementary
cementitious materials are included in the denominator, the term
water-cementitious materials ratio (w/cm) is used. This ratio
, significantly affects strength, permeability, and durability when the
other mix variables are appropriately controlled.
5. What is the likely effect of adding excessive water to a concrete
mixture?
A. Increased compressive strength in every situation
B. Complete elimination of segregation
C. Reduced strength and increased permeability
D. Elimination of the need for curing
Rationale: Excess water increases the amount of water that is not
required for cement hydration and can leave capillary pores as the
concrete hardens. This often reduces compressive strength and
increases permeability and drying shrinkage. Excessive water can also
cause bleeding, segregation, and finishing problems.
6. What is the main purpose of an air-entraining admixture in
concrete?
A. To replace coarse aggregate
B. To eliminate cement hydration
C. To create microscopic air bubbles that improve resistance to
freezing and thawing
