ACI CONCRETE STRENGTH TESTING
TECHNICIAN EXAM QUESTIONS AND
CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2026 Q&A
| INSTANT DOWNLOAD PDF
1. What is the primary purpose of curing concrete?
A) Strength development
B) Color enhancement
C) Reducing density
D) Increasing permeability
Rationale: Proper curing ensures hydration of cement, leading to
continued strength gain.
2. The standard test method for compressive strength of cylindrical concrete
specimens is ASTM:
A) C39
B) C39/C39M
C) C31
D) C143
Rationale: ASTM C39/C39M covers compressive strength testing of
concrete cylinders.
3. When molding concrete cylinders, consolidation should be done by:
A) Brushing
B) Tamping or vibrating
C) Spraying water
D) Letting concrete self-level
Rationale: Consolidation removes entrapped air and ensures adequate
compaction.
,4. Slump test is used to measure:
A) Temperature
B) Consistency
C) Air content
D) Strength
Rationale: Slump indicates workability and consistency of fresh concrete.
5. A concrete slump decrease indicates:
A) Increased workability
B) Decreased workability
C) Increased temperature
D) More air
Rationale: A lower slump reflects stiffer, less workable concrete.
6. The air content of fresh concrete can be measured by:
A) Slump test
B) Pressure method
C) Compressive test
D) Cylinder molding
Rationale: Pressure method (ASTM C231) is a common air content test.
7. The size of a standard concrete cylinder for strength testing is:
A) 3 × 6 in.
B) 4 × 8 in.
C) 6 × 12 in.
D) 2 × 4 in.
Rationale: 4 × 8 in. cylinders are standard for strength testing.
8. The temperature of freshly mixed concrete should be tested because:
A) It affects curing rate
B) It affects strength development
C) It affects slump
D) It affects only color
Rationale: Temperature impacts hydration and strength gain.
9. The initial setting time refers to:
A) Beginning of stiffening
B) Final set
, C) Hardness
D) Failure under load
Rationale: Initial set is when concrete starts losing plasticity.
10.Concrete should be transported and placed in a manner that:
A) Minimizes segregation
B) Ensures uniformity
C) Prevents premature stiffening
D) All of the above
Rationale: Good practices maintain mix quality until placement.
11.A standard slump cone height is:
A) 6 in.
B) 12 in.
C) 8 in.
D) 10 in.
Rationale: The slump cone is 12 in. tall for standard tests.
12.Over-vibration of concrete can lead to:
A) Higher air content
B) Segregation
C) Higher slump
D) Lower density only
Rationale: Excessive vibration can separate paste from aggregates.
13.The compressive strength of concrete is usually reported in:
A) psi
B) MPa or psi
C) ft-lb
D) kJ
Rationale: Strength is commonly stated in pressure units.
14.Curing concrete at too high a temperature may:
A) Improve workability
B) Reduce ultimate strength
C) Increase air content
D) Increase slump
TECHNICIAN EXAM QUESTIONS AND
CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2026 Q&A
| INSTANT DOWNLOAD PDF
1. What is the primary purpose of curing concrete?
A) Strength development
B) Color enhancement
C) Reducing density
D) Increasing permeability
Rationale: Proper curing ensures hydration of cement, leading to
continued strength gain.
2. The standard test method for compressive strength of cylindrical concrete
specimens is ASTM:
A) C39
B) C39/C39M
C) C31
D) C143
Rationale: ASTM C39/C39M covers compressive strength testing of
concrete cylinders.
3. When molding concrete cylinders, consolidation should be done by:
A) Brushing
B) Tamping or vibrating
C) Spraying water
D) Letting concrete self-level
Rationale: Consolidation removes entrapped air and ensures adequate
compaction.
,4. Slump test is used to measure:
A) Temperature
B) Consistency
C) Air content
D) Strength
Rationale: Slump indicates workability and consistency of fresh concrete.
5. A concrete slump decrease indicates:
A) Increased workability
B) Decreased workability
C) Increased temperature
D) More air
Rationale: A lower slump reflects stiffer, less workable concrete.
6. The air content of fresh concrete can be measured by:
A) Slump test
B) Pressure method
C) Compressive test
D) Cylinder molding
Rationale: Pressure method (ASTM C231) is a common air content test.
7. The size of a standard concrete cylinder for strength testing is:
A) 3 × 6 in.
B) 4 × 8 in.
C) 6 × 12 in.
D) 2 × 4 in.
Rationale: 4 × 8 in. cylinders are standard for strength testing.
8. The temperature of freshly mixed concrete should be tested because:
A) It affects curing rate
B) It affects strength development
C) It affects slump
D) It affects only color
Rationale: Temperature impacts hydration and strength gain.
9. The initial setting time refers to:
A) Beginning of stiffening
B) Final set
, C) Hardness
D) Failure under load
Rationale: Initial set is when concrete starts losing plasticity.
10.Concrete should be transported and placed in a manner that:
A) Minimizes segregation
B) Ensures uniformity
C) Prevents premature stiffening
D) All of the above
Rationale: Good practices maintain mix quality until placement.
11.A standard slump cone height is:
A) 6 in.
B) 12 in.
C) 8 in.
D) 10 in.
Rationale: The slump cone is 12 in. tall for standard tests.
12.Over-vibration of concrete can lead to:
A) Higher air content
B) Segregation
C) Higher slump
D) Lower density only
Rationale: Excessive vibration can separate paste from aggregates.
13.The compressive strength of concrete is usually reported in:
A) psi
B) MPa or psi
C) ft-lb
D) kJ
Rationale: Strength is commonly stated in pressure units.
14.Curing concrete at too high a temperature may:
A) Improve workability
B) Reduce ultimate strength
C) Increase air content
D) Increase slump
