AR MC Masonry Contractor
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Section 1: Masonry Materials and Properties
Question 1
Which ingredient in Portland cement is primarily responsible for
contributing to early strength development during hydration?
A. Gypsum
B. Tricalcium silicate (C₃S)
,C. Tricalcium aluminate (C₃A)
D. Calcium sulfate
Rationale: Tricalcium silicate reacts relatively rapidly with water and
produces calcium silicate hydrate (C-S-H), which is the primary strength-
producing product of cement hydration. It contributes significantly to
early strength, particularly during the first week. Gypsum primarily
regulates setting time, while tricalcium aluminate contributes to early
heat generation and setting reactions.
Question 2
What is the primary purpose of adding hydrated lime to masonry
mortar?
A. To eliminate the need for cement
B. To increase the mortar's compressive strength without affecting
workability
C. To improve workability, water retention, and bond characteristics
D. To prevent all water penetration through masonry walls
Rationale: Hydrated lime improves mortar plasticity, making it easier to
spread and tool. It also improves water retention, which helps prevent
the mortar from losing moisture too quickly to absorbent masonry units.
,These characteristics can improve bond development and workability.
Lime does not eliminate the need for cement in cement-lime mortar or
make a wall completely waterproof.
Question 3
Which ASTM specification covers hollow and solid loadbearing concrete
masonry units?
A. ASTM C90
B. ASTM C150
C. ASTM C144
D. ASTM C90
Rationale: ASTM C90 establishes requirements for loadbearing concrete
masonry units, including applicable physical properties and dimensional
tolerances. ASTM C150 addresses Portland cement, while ASTM C144
addresses aggregate for masonry mortar. ASTM C90 is therefore the
relevant specification for loadbearing concrete masonry units.
Question 4
What is the principal purpose of using masonry sand that meets the
applicable grading requirements?
A. To eliminate the need for water in mortar
, B. To produce workable mortar with appropriate strength and volume
stability
C. To make mortar set immediately
D. To prevent all shrinkage in the masonry wall
Rationale: Properly graded masonry sand provides a suitable particle-
size distribution for workability, cohesion, and consistent mortar
performance. Poorly graded or contaminated sand can increase water
demand, impair bond, and contribute to inconsistent mortar properties.
No aggregate grading can eliminate all shrinkage or remove the need
for proper mixing and curing.
Question 5
Which material is commonly used as a reinforcement within concrete
masonry unit walls to improve tensile resistance?
A. Roofing felt
B. Gypsum board
C. Steel reinforcing bars
D. Plastic vapor barrier
Rationale: Steel reinforcing bars are commonly placed in grouted
masonry cells or bond beams to resist tensile forces and help the
Exam Questions and Correct
Answers (Verified Answers)
Plus Rationale 2027 Q&A|
Instant Download Pdf
Section 1: Masonry Materials and Properties
Question 1
Which ingredient in Portland cement is primarily responsible for
contributing to early strength development during hydration?
A. Gypsum
B. Tricalcium silicate (C₃S)
,C. Tricalcium aluminate (C₃A)
D. Calcium sulfate
Rationale: Tricalcium silicate reacts relatively rapidly with water and
produces calcium silicate hydrate (C-S-H), which is the primary strength-
producing product of cement hydration. It contributes significantly to
early strength, particularly during the first week. Gypsum primarily
regulates setting time, while tricalcium aluminate contributes to early
heat generation and setting reactions.
Question 2
What is the primary purpose of adding hydrated lime to masonry
mortar?
A. To eliminate the need for cement
B. To increase the mortar's compressive strength without affecting
workability
C. To improve workability, water retention, and bond characteristics
D. To prevent all water penetration through masonry walls
Rationale: Hydrated lime improves mortar plasticity, making it easier to
spread and tool. It also improves water retention, which helps prevent
the mortar from losing moisture too quickly to absorbent masonry units.
,These characteristics can improve bond development and workability.
Lime does not eliminate the need for cement in cement-lime mortar or
make a wall completely waterproof.
Question 3
Which ASTM specification covers hollow and solid loadbearing concrete
masonry units?
A. ASTM C90
B. ASTM C150
C. ASTM C144
D. ASTM C90
Rationale: ASTM C90 establishes requirements for loadbearing concrete
masonry units, including applicable physical properties and dimensional
tolerances. ASTM C150 addresses Portland cement, while ASTM C144
addresses aggregate for masonry mortar. ASTM C90 is therefore the
relevant specification for loadbearing concrete masonry units.
Question 4
What is the principal purpose of using masonry sand that meets the
applicable grading requirements?
A. To eliminate the need for water in mortar
, B. To produce workable mortar with appropriate strength and volume
stability
C. To make mortar set immediately
D. To prevent all shrinkage in the masonry wall
Rationale: Properly graded masonry sand provides a suitable particle-
size distribution for workability, cohesion, and consistent mortar
performance. Poorly graded or contaminated sand can increase water
demand, impair bond, and contribute to inconsistent mortar properties.
No aggregate grading can eliminate all shrinkage or remove the need
for proper mixing and curing.
Question 5
Which material is commonly used as a reinforcement within concrete
masonry unit walls to improve tensile resistance?
A. Roofing felt
B. Gypsum board
C. Steel reinforcing bars
D. Plastic vapor barrier
Rationale: Steel reinforcing bars are commonly placed in grouted
masonry cells or bond beams to resist tensile forces and help the
