Strength Testing Technician Certification

American Concrete Institute (ACI) Concrete Strength Testing Technician Certification Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of the ACI Concrete Strength Testing

Technician certification?

a) To design concrete mixtures

b) To ensure accurate field placement of concrete

c) To verify competence in testing hardened concrete specimens for

compressive and flexural strength

d) To oversee all concrete construction activities

Rationale: The certification ensures that technicians can accurately

prepare, cure, and test concrete specimens to determine compressive and flexural strengths according to ASTM standards.

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• According to ASTM C39, what type of load should be applied to the

specimen during testing?

a) Impact load

b) Continuous and without shock

c) Stepwise load

d) Cyclic load

Rationale: ASTM C39 specifies that load should be applied continuously

without shock at a constant rate until failure occurs.

• What is the standard specimen size for compressive strength testing in

ASTM C39?

• 6 x 12 inches (150 x 300 mm) cylinder
• 4 x 8 inches (100 x 200 mm) cylinder
• 3 x 6 inches (75 x 150 mm) cylinder
• 8 x 16 inches (200 x 400 mm) cylinder

Rationale: The standard specimen size used in compressive strength testing

is a 6 x 12-inch cylinder.

• Which ASTM standard covers the making and curing of concrete test

specimens in the field?

a) ASTM C39

b) ASTM C31

c) ASTM C617 2 / 4

d) ASTM C78

Rationale: ASTM C31 details the procedures for making and curing

concrete specimens under field conditions.

• What is the minimum curing time for standard strength test specimens

before testing?

• 3 days
• 7 days
• 28 days
• 56 days

Rationale: The standard curing period for determining concrete

compressive strength is 28 days.

• How should freshly molded concrete cylinders be stored for the first 24

hours according to ASTM C31?

a) In open air

b) In a moist environment between 16–27°C (60–80°F)

c) In an oven

d) In freezing conditions

Rationale: Cylinders must be stored in a moist environment within the

temperature range specified to ensure proper initial curing.

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• According to ASTM C617, sulfur capping compound must have a

compressive strength at least:

• 3,000 psi (20 MPa)
• 5,000 psi (35 MPa)

c) Equal to or greater than the expected strength of the concrete specimen

• 10,000 psi (70 MPa)

Rationale: The capping compound should be strong enough not to fail

before the concrete specimen does.

• Which standard covers the capping of cylindrical concrete specimens?

a) ASTM C39

b) ASTM C617

c) ASTM C31

d) ASTM C78

Rationale: ASTM C617 describes the proper capping procedures for

concrete cylinders before testing.

9. The primary function of capping concrete cylinders is to:

a) Decorate the ends

b) Ensure plane, parallel surfaces for load application

c) Seal the cylinder

d) Reduce weight

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