1. A technician arrives at a jobsite and needs a representative sample of concrete from a
truck mixer for temperature testing. What must be done first?
a) Take concrete from the very first discharge
b) Take concrete only from the top of the mixer
c) Obtain a composite sample by collecting portions at regularly spaced intervals during
discharge
d) Use only the last portion of the batch
Rationale: ASTM C172 requires composite samples from middle discharge portions taken at
regular intervals within 15 minutes, avoiding first and last material.
2. During a slump test on plastic concrete with aggregate smaller than 1.5 inches, what is
the correct number of rodding strokes per layer?
a) 15 strokes
b) 20 strokes
c) 25 strokes
d) 30 strokes
Rationale: ASTM C143 specifies 25 strokes per layer for the slump cone, with each stroke
penetrating the layer below.
3. A field technician is measuring the temperature of fresh concrete. How deep must the
sensing portion of the device be submerged?
a) 1 inch
b) 2 inches
c) 3 inches
d) 4 inches
Rationale: ASTM C1064 requires at least 3 inches of concrete cover in all directions around
the temperature probe.
,4. What is the standard diameter and height of a cylinder mold for compressive strength
testing when the nominal maximum aggregate size is less than 2 inches?
a) 4 x 8 in
b) 6 x 12 in
c) 8 x 16 in
d) 10 x 20 in
Rationale: The standard 6x12 inch cylinder is required unless otherwise specified, per ASTM
C31.
5. A concrete sample has a slump of 2 inches. Which consolidation method should be used
for the unit weight measure?
a) Rodding only
b) Vibration only
c) Either rodding or vibration
d) No consolidation needed
Rationale: ASTM C138 allows either rodding or vibration for slumps between 1 and 3 inches.
6. During air content testing by the pressure method (Type B), after consolidating the
concrete, what must be done before closing the cover?
a) Add water to the bowl
b) Strike off the concrete surface evenly
c) Shake the bowl vigorously
d) Wait 10 minutes
Rationale: Proper strike-off ensures the bowl is correctly filled to the rim before attaching the
cover assembly.
7. A technician is sampling from a paving mixer. From how many different portions of the
pile must samples be taken to form a composite?
a) Two
b) Three
c) Four
d) Five
Rationale: ASTM C172 requires at least five different portions from the discharged pile to
form a representative composite sample.
,8. What is the maximum allowable time between obtaining the first and final portions of a
composite concrete sample?
a) 5 minutes
b) 10 minutes
c) 15 minutes
d) 20 minutes
Rationale: ASTM C172 states 15 minutes maximum elapsed time for collecting composite
sample portions.
9. A technician sees water rising to the surface of freshly placed concrete after rodding. This
indicates:
a) Normal bleeding
b) Over-rodding or over-vibration
c) Low water content
d) Cold concrete
Rationale: Excessive rodding can cause segregation and bleeding, leading to a non-
representative sample.
10. Which ASTM standard covers the practice for making and curing concrete test
specimens in the field?
a) ASTM C143
b) ASTM C172
c) ASTM C31
d) ASTM C138
*Rationale: ASTM C31/C31M is the standard practice for field curing, protection, and
transport of specimens.*
11. A technician is testing concrete with a slump of 4 inches. Which consolidation method is
required for the air content pressure method bowl?
a) Vibration
b) Rodding
c) Spading
d) Tapping only
Rationale: ASTM C231 requires rodding for slump >3 inches, vibration only for slump <1 inch.
, 12. What is the required frequency of an internal vibrator used for consolidating concrete
test specimens?
a) At least 5000 vpm
b) At least 7000 vpm
c) At least 9000 vpm
d) At least 11000 vpm
Rationale: ASTM C31 specifies minimum 9000 vibrations per minute when operating in
concrete.
13. A technician reads the air content on a pressure meter. Where should the liquid level be
in the neck of the meter?
a) At the very top
b) At the very bottom
c) At the zero mark or initial pressure line
d) Anywhere is fine
Rationale: The liquid level indicates the initial pressure setting; proper reading requires it at
the calibrated mark.
14. When using a tamping rod for a 6-inch diameter cylinder, what are the required rod
dimensions?
a) 3/8 inch dia x 12 inch length
b) 5/8 inch dia x 20 inch length
c) 5/8 inch dia x 26 inch length
d) 1 inch dia x 24 inch length
*Rationale: For a 6-inch cylinder, rod diameter = 5/8 inch, length = 20 inches, per ASTM
C31.*
15. A composite sample is required for strength tests. What is the minimum sample size
when the maximum aggregate size is 1.5 inches?
a) 0.5 ft³
b) 1 ft³ (28 L)
c) 1.5 ft³
d) 2 ft³
Rationale: ASTM C172 requires at least 28 L or 1 ft³ for strength test specimens.
truck mixer for temperature testing. What must be done first?
a) Take concrete from the very first discharge
b) Take concrete only from the top of the mixer
c) Obtain a composite sample by collecting portions at regularly spaced intervals during
discharge
d) Use only the last portion of the batch
Rationale: ASTM C172 requires composite samples from middle discharge portions taken at
regular intervals within 15 minutes, avoiding first and last material.
2. During a slump test on plastic concrete with aggregate smaller than 1.5 inches, what is
the correct number of rodding strokes per layer?
a) 15 strokes
b) 20 strokes
c) 25 strokes
d) 30 strokes
Rationale: ASTM C143 specifies 25 strokes per layer for the slump cone, with each stroke
penetrating the layer below.
3. A field technician is measuring the temperature of fresh concrete. How deep must the
sensing portion of the device be submerged?
a) 1 inch
b) 2 inches
c) 3 inches
d) 4 inches
Rationale: ASTM C1064 requires at least 3 inches of concrete cover in all directions around
the temperature probe.
,4. What is the standard diameter and height of a cylinder mold for compressive strength
testing when the nominal maximum aggregate size is less than 2 inches?
a) 4 x 8 in
b) 6 x 12 in
c) 8 x 16 in
d) 10 x 20 in
Rationale: The standard 6x12 inch cylinder is required unless otherwise specified, per ASTM
C31.
5. A concrete sample has a slump of 2 inches. Which consolidation method should be used
for the unit weight measure?
a) Rodding only
b) Vibration only
c) Either rodding or vibration
d) No consolidation needed
Rationale: ASTM C138 allows either rodding or vibration for slumps between 1 and 3 inches.
6. During air content testing by the pressure method (Type B), after consolidating the
concrete, what must be done before closing the cover?
a) Add water to the bowl
b) Strike off the concrete surface evenly
c) Shake the bowl vigorously
d) Wait 10 minutes
Rationale: Proper strike-off ensures the bowl is correctly filled to the rim before attaching the
cover assembly.
7. A technician is sampling from a paving mixer. From how many different portions of the
pile must samples be taken to form a composite?
a) Two
b) Three
c) Four
d) Five
Rationale: ASTM C172 requires at least five different portions from the discharged pile to
form a representative composite sample.
,8. What is the maximum allowable time between obtaining the first and final portions of a
composite concrete sample?
a) 5 minutes
b) 10 minutes
c) 15 minutes
d) 20 minutes
Rationale: ASTM C172 states 15 minutes maximum elapsed time for collecting composite
sample portions.
9. A technician sees water rising to the surface of freshly placed concrete after rodding. This
indicates:
a) Normal bleeding
b) Over-rodding or over-vibration
c) Low water content
d) Cold concrete
Rationale: Excessive rodding can cause segregation and bleeding, leading to a non-
representative sample.
10. Which ASTM standard covers the practice for making and curing concrete test
specimens in the field?
a) ASTM C143
b) ASTM C172
c) ASTM C31
d) ASTM C138
*Rationale: ASTM C31/C31M is the standard practice for field curing, protection, and
transport of specimens.*
11. A technician is testing concrete with a slump of 4 inches. Which consolidation method is
required for the air content pressure method bowl?
a) Vibration
b) Rodding
c) Spading
d) Tapping only
Rationale: ASTM C231 requires rodding for slump >3 inches, vibration only for slump <1 inch.
, 12. What is the required frequency of an internal vibrator used for consolidating concrete
test specimens?
a) At least 5000 vpm
b) At least 7000 vpm
c) At least 9000 vpm
d) At least 11000 vpm
Rationale: ASTM C31 specifies minimum 9000 vibrations per minute when operating in
concrete.
13. A technician reads the air content on a pressure meter. Where should the liquid level be
in the neck of the meter?
a) At the very top
b) At the very bottom
c) At the zero mark or initial pressure line
d) Anywhere is fine
Rationale: The liquid level indicates the initial pressure setting; proper reading requires it at
the calibrated mark.
14. When using a tamping rod for a 6-inch diameter cylinder, what are the required rod
dimensions?
a) 3/8 inch dia x 12 inch length
b) 5/8 inch dia x 20 inch length
c) 5/8 inch dia x 26 inch length
d) 1 inch dia x 24 inch length
*Rationale: For a 6-inch cylinder, rod diameter = 5/8 inch, length = 20 inches, per ASTM
C31.*
15. A composite sample is required for strength tests. What is the minimum sample size
when the maximum aggregate size is 1.5 inches?
a) 0.5 ft³
b) 1 ft³ (28 L)
c) 1.5 ft³
d) 2 ft³
Rationale: ASTM C172 requires at least 28 L or 1 ft³ for strength test specimens.
