ACI Concrete Strength Testing Technician Exam
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1. What is the primary purpose of a concrete compressive strength
test?
a) To measure water absorption
b) To determine slump
c) To determine the load-carrying capacity of hardened concrete
d) To evaluate air content
Rationale: The compressive strength test determines the concrete’s
ability to resist axial loads, which is critical for structural design and
safety.
2. When performing a compressive strength test, concrete
specimens are typically cured for how long before testing?
a) 1 day
b) 28 days
, c) 7 days
d) 90 days
Rationale: Standard curing for concrete compressive strength tests is
28 days, as this period generally allows concrete to reach near its
designed strength.
3. Which type of mold is most commonly used for preparing
concrete cylinders for strength testing?
a) Wooden cube molds
b) Steel cube molds
c) Steel or plastic cylindrical molds
d) Rubber molds
Rationale: Cylindrical molds, typically 6×12 in or 4×8 in, are standard
for compressive strength testing to ensure uniformity and
compatibility with testing machines.
4. What is the recommended procedure for compacting concrete in
a cylinder mold?
a) Allow concrete to settle on its own
b) Use a standard tamping rod in layers
c) Vibrate only the top layer
d) Tap the mold lightly once
,Rationale: Proper compaction in layers with a tamping rod ensures air
voids are minimized, giving accurate strength results.
5. According to ACI, the maximum allowable slump for structural
concrete is typically:
a) 1 inch
b) 2 inches
c) 4 inches
d) 6 inches
Rationale: Slump tests measure consistency, and most structural
concrete mixes are designed for a slump range of 3–4 inches to
balance workability and strength.
6. What is the standard diameter and height for a typical concrete
cylinder used in strength testing?
a) 4 in × 8 in
b) 6 in × 12 in
c) 6 in × 12 in (common) or 4 in × 8 in (for field tests)
d) 8 in × 16 in
Rationale: Standard sizes provide consistent results across
laboratories, with 6×12 in common for lab specimens and 4×8 in often
used in field testing.
, 7. How should concrete cylinders be capped before compression
testing?
a) With plastic wrap
b) With sulfur mortar or neoprene caps
c) No capping is needed
d) With a thin layer of concrete
Rationale: Capping ensures a smooth, level surface, which allows
uniform load distribution during compression testing.
8. What is the purpose of moist curing concrete cylinders?
a) To dry the concrete quickly
b) To prevent surface cracks
c) To allow hydration and gain strength
d) To increase slump
Rationale: Moist curing maintains the hydration process, which is
essential for concrete to reach its designed strength.
9. At what age is concrete typically first tested for strength if early
results are required?
a) 1 day
b) 3 days
c) 7 days
d) 14 days
Questions With Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A | Instant
Download Pdf
1. What is the primary purpose of a concrete compressive strength
test?
a) To measure water absorption
b) To determine slump
c) To determine the load-carrying capacity of hardened concrete
d) To evaluate air content
Rationale: The compressive strength test determines the concrete’s
ability to resist axial loads, which is critical for structural design and
safety.
2. When performing a compressive strength test, concrete
specimens are typically cured for how long before testing?
a) 1 day
b) 28 days
, c) 7 days
d) 90 days
Rationale: Standard curing for concrete compressive strength tests is
28 days, as this period generally allows concrete to reach near its
designed strength.
3. Which type of mold is most commonly used for preparing
concrete cylinders for strength testing?
a) Wooden cube molds
b) Steel cube molds
c) Steel or plastic cylindrical molds
d) Rubber molds
Rationale: Cylindrical molds, typically 6×12 in or 4×8 in, are standard
for compressive strength testing to ensure uniformity and
compatibility with testing machines.
4. What is the recommended procedure for compacting concrete in
a cylinder mold?
a) Allow concrete to settle on its own
b) Use a standard tamping rod in layers
c) Vibrate only the top layer
d) Tap the mold lightly once
,Rationale: Proper compaction in layers with a tamping rod ensures air
voids are minimized, giving accurate strength results.
5. According to ACI, the maximum allowable slump for structural
concrete is typically:
a) 1 inch
b) 2 inches
c) 4 inches
d) 6 inches
Rationale: Slump tests measure consistency, and most structural
concrete mixes are designed for a slump range of 3–4 inches to
balance workability and strength.
6. What is the standard diameter and height for a typical concrete
cylinder used in strength testing?
a) 4 in × 8 in
b) 6 in × 12 in
c) 6 in × 12 in (common) or 4 in × 8 in (for field tests)
d) 8 in × 16 in
Rationale: Standard sizes provide consistent results across
laboratories, with 6×12 in common for lab specimens and 4×8 in often
used in field testing.
, 7. How should concrete cylinders be capped before compression
testing?
a) With plastic wrap
b) With sulfur mortar or neoprene caps
c) No capping is needed
d) With a thin layer of concrete
Rationale: Capping ensures a smooth, level surface, which allows
uniform load distribution during compression testing.
8. What is the purpose of moist curing concrete cylinders?
a) To dry the concrete quickly
b) To prevent surface cracks
c) To allow hydration and gain strength
d) To increase slump
Rationale: Moist curing maintains the hydration process, which is
essential for concrete to reach its designed strength.
9. At what age is concrete typically first tested for strength if early
results are required?
a) 1 day
b) 3 days
c) 7 days
d) 14 days
