ACI Concrete Field-Testing Technician Grade I Certification Exam Actual
Exam 2026/2027 | Complete Exam-Style Questions with Detailed Rationales |
Graded A+ Verified – Pass Guaranteed
Foundations of Representative Sampling and Field Procedures
Q1: You are assigned to sample concrete from a stationary mixer at a precast plant. According
to ASTM C172, what is the minimum number of portions you must collect to form a valid
composite sample?
A. One large grab sample from the center of the discharge.
B. Two or more portions taken at regular intervals during discharge. [CORRECT]
C. Three portions taken only from the beginning, middle, and end of the discharge.
D. Four portions scooped exclusively from the top surface of the truck bed.
Correct Answer: B
Rationale: This choice is correct because ASTM C172 requires two or more portions taken at
regular intervals to ensure the sample represents the entire batch. This matches the principle
that a single grab sample is highly susceptible to segregation and will not reflect the true mix
properties.
Q2: You are sampling concrete being placed by a continuous slipform paver on a highway
project, and the discharge is fast-moving and difficult to access. How should you obtain a
representative composite sample under these challenging conditions?
A. Wait until the paver stops and take a single grab sample from the center of the mat.
B. Pass a receptacle completely through the discharge stream at two or more regular intervals.
[CORRECT]
C. Scrape the top 2 inches of the placed concrete from the edge of the mat.
D. Collect the first and last portions of the paver's hopper discharge.
Correct Answer: B
Rationale: The best answer is to pass a receptacle completely through the discharge stream at
regular intervals, as this ensures all parts of the batch are represented. This aligns with ASTM
C172 guidelines for paving operations to avoid the segregation bias that occurs when sampling
only the edges or stopped material.
Q3: After obtaining the final portion of your composite sample, what is the maximum allowable
time to begin the slump, air content, and temperature tests?
A. 5 minutes
B. 10 minutes
C. 15 minutes [CORRECT]
D. 30 minutes
Correct Answer: C
, Rationale: This choice is correct because ASTM C172 specifies that these initial tests must
begin within 15 minutes of obtaining the final portion of the composite sample. This matches the
principle that concrete properties begin to change rapidly due to hydration and moisture loss if
testing is delayed.
Q4: While sampling from a revolving drum truck mixer, you notice the driver is discharging the
concrete very slowly. What is the most appropriate action to ensure a representative sample?
A. Take one large sample from the very end of the discharge to capture the final mix.
B. Collect two or more portions at regular intervals during the middle of the discharge.
[CORRECT]
C. Sample only from the top layer of the chute as it flows out.
D. Ask the driver to speed up the discharge to get it over with quickly.
Correct Answer: B
Rationale: The best answer is to collect two or more portions at regular intervals during the
middle of the discharge. This aligns with ASTM C172, which dictates discarding the first and last
portions and sampling the middle to avoid materials that may have segregated or washed out.
Q5: Why does ASTM C172 require discarding the first and last portions of a concrete discharge
before collecting the composite sample?
A. The first and last portions are typically too cold to test accurately.
B. These portions are most likely to contain segregated aggregate or washed-out cement paste.
[CORRECT]
C. The equipment used for the first and last portions is usually contaminated.
D. The slump is always zero in the first and last portions of any mix.
Correct Answer: B
Rationale: This choice is correct because the initial and final discharge materials are highly
prone to segregation and mortar washout. This matches the principle that a representative
sample must reflect the homogeneous middle of the batch, not the extremes of the discharge
cycle.
Q6: You need to sample concrete from a conveyor belt placing operation. Which technique will
yield a compliant composite sample?
A. Stopping the belt and shoveling concrete from the top surface.
B. Using a sampling plate to catch the full cross-section of the discharge stream at two or more
intervals. [CORRECT]
C. Scooping concrete from the spillage that has fallen onto the ground beside the belt.
D. Taking a single sample from the tail end of the belt discharge.
Correct Answer: B
Rationale: The best answer is using a sampling plate to catch the full cross-section of the
discharge stream. This aligns with ASTM C172, which requires capturing the entire material
profile at regular intervals to prevent the loss of fine materials or coarse aggregate that would
skew the sample.
Exam 2026/2027 | Complete Exam-Style Questions with Detailed Rationales |
Graded A+ Verified – Pass Guaranteed
Foundations of Representative Sampling and Field Procedures
Q1: You are assigned to sample concrete from a stationary mixer at a precast plant. According
to ASTM C172, what is the minimum number of portions you must collect to form a valid
composite sample?
A. One large grab sample from the center of the discharge.
B. Two or more portions taken at regular intervals during discharge. [CORRECT]
C. Three portions taken only from the beginning, middle, and end of the discharge.
D. Four portions scooped exclusively from the top surface of the truck bed.
Correct Answer: B
Rationale: This choice is correct because ASTM C172 requires two or more portions taken at
regular intervals to ensure the sample represents the entire batch. This matches the principle
that a single grab sample is highly susceptible to segregation and will not reflect the true mix
properties.
Q2: You are sampling concrete being placed by a continuous slipform paver on a highway
project, and the discharge is fast-moving and difficult to access. How should you obtain a
representative composite sample under these challenging conditions?
A. Wait until the paver stops and take a single grab sample from the center of the mat.
B. Pass a receptacle completely through the discharge stream at two or more regular intervals.
[CORRECT]
C. Scrape the top 2 inches of the placed concrete from the edge of the mat.
D. Collect the first and last portions of the paver's hopper discharge.
Correct Answer: B
Rationale: The best answer is to pass a receptacle completely through the discharge stream at
regular intervals, as this ensures all parts of the batch are represented. This aligns with ASTM
C172 guidelines for paving operations to avoid the segregation bias that occurs when sampling
only the edges or stopped material.
Q3: After obtaining the final portion of your composite sample, what is the maximum allowable
time to begin the slump, air content, and temperature tests?
A. 5 minutes
B. 10 minutes
C. 15 minutes [CORRECT]
D. 30 minutes
Correct Answer: C
, Rationale: This choice is correct because ASTM C172 specifies that these initial tests must
begin within 15 minutes of obtaining the final portion of the composite sample. This matches the
principle that concrete properties begin to change rapidly due to hydration and moisture loss if
testing is delayed.
Q4: While sampling from a revolving drum truck mixer, you notice the driver is discharging the
concrete very slowly. What is the most appropriate action to ensure a representative sample?
A. Take one large sample from the very end of the discharge to capture the final mix.
B. Collect two or more portions at regular intervals during the middle of the discharge.
[CORRECT]
C. Sample only from the top layer of the chute as it flows out.
D. Ask the driver to speed up the discharge to get it over with quickly.
Correct Answer: B
Rationale: The best answer is to collect two or more portions at regular intervals during the
middle of the discharge. This aligns with ASTM C172, which dictates discarding the first and last
portions and sampling the middle to avoid materials that may have segregated or washed out.
Q5: Why does ASTM C172 require discarding the first and last portions of a concrete discharge
before collecting the composite sample?
A. The first and last portions are typically too cold to test accurately.
B. These portions are most likely to contain segregated aggregate or washed-out cement paste.
[CORRECT]
C. The equipment used for the first and last portions is usually contaminated.
D. The slump is always zero in the first and last portions of any mix.
Correct Answer: B
Rationale: This choice is correct because the initial and final discharge materials are highly
prone to segregation and mortar washout. This matches the principle that a representative
sample must reflect the homogeneous middle of the batch, not the extremes of the discharge
cycle.
Q6: You need to sample concrete from a conveyor belt placing operation. Which technique will
yield a compliant composite sample?
A. Stopping the belt and shoveling concrete from the top surface.
B. Using a sampling plate to catch the full cross-section of the discharge stream at two or more
intervals. [CORRECT]
C. Scooping concrete from the spillage that has fallen onto the ground beside the belt.
D. Taking a single sample from the tail end of the belt discharge.
Correct Answer: B
Rationale: The best answer is using a sampling plate to catch the full cross-section of the
discharge stream. This aligns with ASTM C172, which requires capturing the entire material
profile at regular intervals to prevent the loss of fine materials or coarse aggregate that would
skew the sample.
