ACI Concrete Strength Testing Technician
Certification Exam Questions And Answers
Plus Rationales | Qs & Ans 2026 | Instant Pdf
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This exam covers the procedures for making, curing, and testing
concrete specimens (cylinders and beams) in accordance with ASTM C31,
C39, C78, C1231, C617, and related standards. Each question includes a
verified rationale.
1. What is the primary purpose of ASTM C31?
A) Compressive strength testing of cylinders
B) Making and curing concrete test specimens in the field
C) Flexural strength testing of beams
D) Slump test
Answer: B
Rationale: ASTM C31 covers procedures for field fabrication and initial
curing of concrete specimens.
2. According to ASTM C31, the initial curing temperature for
cylinders (first 48 hours) shall be maintained between:
,A) 40–60°F (4–16°C)
B) 60–80°F (16–27°C)
C) 70–90°F (21–32°C)
D) 80–100°F (27–38°C)
Answer: B
Rationale: Initial cure requires 60–80°F (16–27°C) and protection from
moisture loss.
3. The maximum time allowed between obtaining a concrete sample
and beginning to make test specimens is:
A) 5 minutes
B) 10 minutes
C) 15 minutes
D) 30 minutes
Answer: C
Rationale: ASTM C172 requires that all fresh concrete testing and
specimen fabrication begin within 15 minutes of sampling.
4. For a 6 x 12 inch (150 x 300 mm) cylinder, the number of rodding
strokes per layer is:
A) 15
,B) 25
C) 35
D) 50
Answer: B
Rationale: ASTM C31 specifies 25 strokes per layer for 6-inch (150 mm)
diameter cylinders.
5. For a 4 x 8 inch (100 x 200 mm) cylinder, the number of rodding
strokes per layer is:
A) 15
B) 25
C) 35
D) 50
Answer: A
Rationale: 15 strokes per layer for 4-inch (100 mm) diameter cylinders.
6. When using a vibrating device to consolidate concrete in a
cylinder, the cylinder should be filled in how many equal layers?
A) 1 layer
B) 2 equal layers
, C) 3 equal layers
D) 4 layers
Answer: B
Rationale: When vibrating, fill the mold in two equal layers.
7. The rod used for consolidating concrete (rodding) shall have a
diameter of:
A) 1/4 in. (6 mm) for all molds
B) 5/8 in. (16 mm) for 6-inch molds; 1/2 in. (12.5 mm) for 4-inch molds
C) 1/2 in. for all
D) 3/4 in. for all
Answer: B
Rationale: Rod size is proportional to mold diameter to ensure proper
consolidation.
8. After casting, cylinders shall remain in the molds for an initial
curing period of:
A) 12 hours
B) 24 ± 8 hours (typically 24 hours)
C) 48 hours
D) 7 days
Certification Exam Questions And Answers
Plus Rationales | Qs & Ans 2026 | Instant Pdf
Download
This exam covers the procedures for making, curing, and testing
concrete specimens (cylinders and beams) in accordance with ASTM C31,
C39, C78, C1231, C617, and related standards. Each question includes a
verified rationale.
1. What is the primary purpose of ASTM C31?
A) Compressive strength testing of cylinders
B) Making and curing concrete test specimens in the field
C) Flexural strength testing of beams
D) Slump test
Answer: B
Rationale: ASTM C31 covers procedures for field fabrication and initial
curing of concrete specimens.
2. According to ASTM C31, the initial curing temperature for
cylinders (first 48 hours) shall be maintained between:
,A) 40–60°F (4–16°C)
B) 60–80°F (16–27°C)
C) 70–90°F (21–32°C)
D) 80–100°F (27–38°C)
Answer: B
Rationale: Initial cure requires 60–80°F (16–27°C) and protection from
moisture loss.
3. The maximum time allowed between obtaining a concrete sample
and beginning to make test specimens is:
A) 5 minutes
B) 10 minutes
C) 15 minutes
D) 30 minutes
Answer: C
Rationale: ASTM C172 requires that all fresh concrete testing and
specimen fabrication begin within 15 minutes of sampling.
4. For a 6 x 12 inch (150 x 300 mm) cylinder, the number of rodding
strokes per layer is:
A) 15
,B) 25
C) 35
D) 50
Answer: B
Rationale: ASTM C31 specifies 25 strokes per layer for 6-inch (150 mm)
diameter cylinders.
5. For a 4 x 8 inch (100 x 200 mm) cylinder, the number of rodding
strokes per layer is:
A) 15
B) 25
C) 35
D) 50
Answer: A
Rationale: 15 strokes per layer for 4-inch (100 mm) diameter cylinders.
6. When using a vibrating device to consolidate concrete in a
cylinder, the cylinder should be filled in how many equal layers?
A) 1 layer
B) 2 equal layers
, C) 3 equal layers
D) 4 layers
Answer: B
Rationale: When vibrating, fill the mold in two equal layers.
7. The rod used for consolidating concrete (rodding) shall have a
diameter of:
A) 1/4 in. (6 mm) for all molds
B) 5/8 in. (16 mm) for 6-inch molds; 1/2 in. (12.5 mm) for 4-inch molds
C) 1/2 in. for all
D) 3/4 in. for all
Answer: B
Rationale: Rod size is proportional to mold diameter to ensure proper
consolidation.
8. After casting, cylinders shall remain in the molds for an initial
curing period of:
A) 12 hours
B) 24 ± 8 hours (typically 24 hours)
C) 48 hours
D) 7 days
