ACI Aggregate Testing Technician (ATT) Certification Exam — Questions and Answers

Question 1: The Los Angeles abrasion loss is expressed as:

The difference in drum diameter before and after testing × 100
The mass passing the No. 12 sieve divided by original mass × 100 (Correct answer)
The mass of steel balls lost divided by original mass × 100
The mass retained on the No. 12 sieve divided by original mass × 100

Correct answer: The mass passing the No. 12 sieve divided by original mass × 100

LA abrasion loss (%) = (mass passing the No. 12 sieve ÷ original sample mass) × 100.

Question 2: The purpose of a sample splitter (riffle splitter) is to:

Measure the bulk specific gravity of the sample
Reduce a large sample to a smaller representative portion (Correct answer)
Increase the moisture content of the sample before testing
Separate fine aggregate from coarse aggregate by size

Correct answer: Reduce a large sample to a smaller representative portion

A riffle splitter divides a sample into two equal halves, allowing repeated halving to reach a target sample mass while maintaining representativeness.

Question 3: A technician collects only a single grab of material from the top of a stockpile and submits it as the field sample. This practice violates ASTM D75 primarily because:

Single grabs must be taken from the bottom, not the top
ASTM D75 prohibits manual sampling of stockpiles altogether
The mass of a single grab always exceeds the maximum allowed field sample size
A single grab cannot constitute a composite sample and the stockpile surface is subject to segregation (Correct answer)

Correct answer: A single grab cannot constitute a composite sample and the stockpile surface is subject to segregation

ASTM D75 requires composite samples formed from multiple increments; additionally, the stockpile surface is segregated and unrepresentative of the bulk material.

Question 4: When sampling from a stockpile, what is the most important principle to follow?

Collect only from the top of the pile.
Take the sample from near the edges only.
Collect from various depths and locations. (Correct answer)
Sample only dry areas.

Correct answer: Collect from various depths and locations.

Sampling from multiple locations and depths ensures the sample is representative of the entire stockpile.

Question 5: When performing the ASTM C117 wash test, how is the mass loss reported?

As the dry mass of particles collected on the No. 200 sieve
As a ratio of wet to dry mass
As volume of wash water used
As the percentage of material passing the No. 200 sieve by washing (Correct answer)

Correct answer: As the percentage of material passing the No. 200 sieve by washing

ASTM C117 results are reported as the percentage of material passing the No. 200 sieve by mass of the original dry sample.

Question 6: After determining the unit weight of aggregate, the technician wants to report void content but only has the bulk specific gravity on an SSD basis. What adjustment is needed?

No adjustment; SSD bulk specific gravity can be used directly in the voids formula
Use the apparent specific gravity instead of SSD
Convert SSD bulk specific gravity to OD bulk specific gravity by accounting for absorption (Correct answer)
Multiply SSD specific gravity by the water content to get OD specific gravity

Correct answer: Convert SSD bulk specific gravity to OD bulk specific gravity by accounting for absorption

ASTM C29 uses bulk dry (OD) specific gravity in the voids formula; the SSD value must be converted using the absorption to obtain the OD value.

Question 7: How many steel balls (charge) are used for ASTM C131 Grading A?

12 balls (Correct answer)
10 balls
8 balls
6 balls

Correct answer: 12 balls

Grading A in ASTM C131 requires a charge of 12 steel balls weighing 5,000 ± 25 g.

Question 8: When sampling from a flowing aggregate stream at a discharge point, when should increments be collected?

Only when flow rate is highest
After the stream has been running for at least 10 minutes
At random time intervals throughout the entire flow period (Correct answer)
Only at the beginning and end of the flow

Correct answer: At random time intervals throughout the entire flow period

Increments must be collected at random time intervals spanning the full duration of flow to ensure the composite sample represents all material discharged.

Question 9: What action should be taken if a field sample arrives at the laboratory with obvious segregation in the container?

Re-mix the entire container thoroughly before reducing the sample (Correct answer)
Use only the top half of the material
Return the sample to the source for resampling
Test the segregated portions separately and average the results

Correct answer: Re-mix the entire container thoroughly before reducing the sample

ASTM C702 requires thorough remixing before reduction to reintegrate any segregated particles and restore the sample's representativeness.

Question 10: When sampling aggregates from a conveyor belt, how many approximately equal increments must be taken to constitute one sample according to ASTM D75?

At least 10 increments
At least 5 increments
A single large scoop
At least 3 increments (Correct answer)

Correct answer: At least 3 increments

ASTM D75 requires a minimum of three approximately equal increments taken from the full cross-section of the belt to constitute a field sample.

Question 11: The 'increment' in ASTM D75 sampling terminology is defined as:

The total field sample minus rejected fines
Half the field sample after one quartering pass
A single portion of material collected in one sampling operation (Correct answer)
The final test portion weighed on a balance

Correct answer: A single portion of material collected in one sampling operation

An increment is a single portion of material collected at one time from one location; multiple increments are combined to form the composite sample.

Question 12: In ASTM C117 (material finer than No. 200), after washing the aggregate is dried to constant mass at what temperature?

200 ± 5°C
150 ± 5°C
110 ± 5°C (Correct answer)
60 ± 5°C

Correct answer: 110 ± 5°C

After washing, the aggregate is dried to constant mass at 110 ± 5°C in accordance with ASTM C117.

Question 13: A technician notices that the total mass of all sieve fractions plus the pan is 2% less than the original sample mass. Per ASTM C136, this result is:

Unacceptable only if the sample mass exceeded 5 kg
Acceptable since ±2% tolerance is allowed
Acceptable if the loss is reported in the test results
Unacceptable; results should be discarded and the test repeated (Correct answer)

Correct answer: Unacceptable; results should be discarded and the test repeated

ASTM C136 requires that the total mass of all sieve fractions after sieving agree with the original mass to within 0.3%; a 2% discrepancy requires the test to be repeated.

Question 14: In aggregate quality evaluation, a fractured face count is most relevant for:

Organic impurity testing
Silt content determination
Coarse aggregate used in asphalt mixtures (Correct answer)
Fine aggregate gradation

Correct answer: Coarse aggregate used in asphalt mixtures

Fractured face counts are commonly specified for coarse aggregate in hot-mix asphalt to ensure adequate shear resistance and resistance to rutting.

Question 15: Which ASTM standard specifically governs the practice of reducing field samples of aggregate to testing size in the laboratory?

ASTM C127
ASTM C136
ASTM C702 (Correct answer)
ASTM D75

Correct answer: ASTM C702

ASTM C702 is the standard practice covering methods for reducing field samples of aggregate to testing size, including mechanical splitting and quartering.

Question 16: Which scenario would cause the LA abrasion loss to be artificially LOWER than the true value?

Failing to wash fines off the sample before testing (Correct answer)
Running the drum at a slightly higher speed than specified
Drying the sample to a higher temperature than specified
Using more steel balls than specified for the grading

Correct answer: Failing to wash fines off the sample before testing

If pre-existing fines are not washed off, they remain in the sample mass (denominator) without being lost, mathematically reducing the calculated percent loss.

Question 17: How is the percent passing a sieve calculated?

Sample weight times retained weight.
Retained weight minus sample weight.
Retained weight divided by sample weight.
Sample weight minus retained weight divided by total sample weight, times 100. (Correct answer)

Correct answer: Sample weight minus retained weight divided by total sample weight, times 100.

The percent passing is calculated by subtracting the cumulative retained weight from the total sample and dividing by the total, then multiplying by 100.

Question 18: In the ASTM C40 test, what solution is added to the sand sample before comparing to the color standard?

Sulfuric acid solution
Hydrochloric acid solution
3% sodium hydroxide (NaOH) solution (Correct answer)
Distilled water

Correct answer: 3% sodium hydroxide (NaOH) solution

A 3% sodium hydroxide (NaOH) solution is added to the sand and shaken, then allowed to stand before color comparison.

Question 19: An aggregate sample dries from field-moist to constant mass. The initial mass was 3,200 g and the oven-dry mass is 3,050 g. What is the total moisture content?

4.50%
4.92% (Correct answer)
4.69%
5.15%

Correct answer: 4.92%

Moisture content = (3200 − 3050) / 3050 × 100 = 150 / 3050 × 100 ≈ 4.92% per ASTM C566.

Question 20: How does risk management apply to daily practice in Unit Weight & Voids Testing for ACI Aggregate Testing Technician professionals?

By avoiding high-risk situations entirely
Through annual safety audits exclusively
Through proactive identification of potential hazards and implementation of preventive measures (Correct answer)
Only through responding to incidents after they occur

Correct answer: Through proactive identification of potential hazards and implementation of preventive measures

Effective risk management in Unit Weight & Voids Testing requires proactive hazard identification and preventive measures, not just reactive responses. This approach reduces incidents, improves outcomes, and protects both professionals and clients.

Question 21: ASTM C33 specifies gradation requirements for concrete aggregates. For coarse aggregate Size No. 57, the nominal size range is:

¾ in. to No. 8 (19.0 mm to 2.36 mm)
1 in. to No. 4 (25.0 mm to 4.75 mm) (Correct answer)
1½ in. to No. 4 (37.5 mm to 4.75 mm)
½ in. to No. 16 (12.5 mm to 1.18 mm)

Correct answer: 1 in. to No. 4 (25.0 mm to 4.75 mm)

ASTM C33 Size No. 57 coarse aggregate has a nominal size range of 1 in. to No. 4 (25.0 mm to 4.75 mm).

Question 22: During an LA abrasion test, the drum is accidentally stopped at 450 revolutions due to a power outage. The technician should:

Report the result as-is, noting the deviation in the test report
Discard the sample and start the test over with a fresh specimen (Correct answer)
Extrapolate the result to 500 revolutions mathematically
Complete the remaining 50 revolutions after power is restored

Correct answer: Discard the sample and start the test over with a fresh specimen

ASTM C131 requires exactly 500 revolutions; an incomplete run compromises the result and the test must be restarted with a fresh sample.

Question 23: How does risk management apply to daily practice in Organic Impurities Assessment for ACI Aggregate Testing Technician professionals?

Only through responding to incidents after they occur
Through annual safety audits exclusively
By avoiding high-risk situations entirely
Through proactive identification of potential hazards and implementation of preventive measures (Correct answer)

Correct answer: Through proactive identification of potential hazards and implementation of preventive measures

Effective risk management in Organic Impurities Assessment requires proactive hazard identification and preventive measures, not just reactive responses. This approach reduces incidents, improves outcomes, and protects both professionals and clients.

Question 24: A stockpile of coarse aggregate is sampled at three locations: top, middle, and side. Why are multiple locations sampled?

Because moisture is uniform in all stockpiles
To comply with aggregate gradation requirements
Because moisture content can vary significantly at different points in a stockpile (Correct answer)
To average out scale inaccuracies

Correct answer: Because moisture content can vary significantly at different points in a stockpile

Moisture tends to drain downward, making lower or interior portions of a stockpile wetter than the top or sides.

Question 25: Which ASTM standard governs the specific gravity and absorption of fine aggregate?

ASTM C128 (Correct answer)
ASTM C29
ASTM C127
ASTM C566

Correct answer: ASTM C128

ASTM C128 covers specific gravity and absorption of fine aggregate, while ASTM C127 covers coarse aggregate.

Question 26: Per ASTM C117, what must be done with any material retained on the No. 200 sieve after washing?

Weighed and recorded as the fine material mass
Discarded as it is considered contamination
Returned to the main sample before oven drying (Correct answer)
Reported separately as a clay fraction

Correct answer: Returned to the main sample before oven drying

Material retained on the No. 200 sieve during washing must be returned to the main sample so that the total post-wash dry mass accurately represents all particles coarser than 75 µm.

Question 27: If a technician uses the jigging method instead of rodding for fine aggregate, what effect does this typically have?

Jigging is required for fine aggregate with moisture content above 5%
Results may be slightly different but both are acceptable methods under ASTM C29 (Correct answer)
Results are invalid because jigging is only for coarse aggregate
Jigging always produces higher unit weights than rodding

Correct answer: Results may be slightly different but both are acceptable methods under ASTM C29

ASTM C29 permits both rodding and jigging; either method is acceptable and results may differ slightly but remain valid.

Question 28: Per ASTM C33, what is the maximum allowable material finer than No. 200 sieve in fine aggregate for concrete subject to surface wear?

2.0%
1.0%
3.0% (Correct answer)
5.0%

Correct answer: 3.0%

ASTM C33 limits material finer than No. 200 in fine aggregate to 3.0% for concrete subject to abrasion.

Question 29: Why is it important to remove entrapped air bubbles from the pycnometer during fine aggregate specific gravity testing?

Bubbles cause the pycnometer to overflow before reading
Trapped air inflates the measured water volume, causing an artificially low specific gravity result (Correct answer)
Air increases the SSD moisture content value
Trapped air increases aggregate mass on the balance

Correct answer: Trapped air inflates the measured water volume, causing an artificially low specific gravity result

Air bubbles occupy volume in the pycnometer and are counted as water, making the displaced water volume appear larger and yielding a falsely low specific gravity.

Question 30: What is the purpose of recording the tare (container) mass before and after drying during a moisture content test?

To verify the balance is functioning correctly
To determine the density of the container material
To confirm the aggregate did not absorb moisture from the container
To subtract the container mass and calculate the actual aggregate and water masses (Correct answer)

Correct answer: To subtract the container mass and calculate the actual aggregate and water masses

The tare mass of the container must be subtracted from total masses so that only the aggregate's wet and dry masses are used in the moisture calculation.

Question 31: How long must the sand and sodium hydroxide mixture stand before the color comparison is made in ASTM C40?

72 hours
15 minutes
1 hour
24 hours (Correct answer)

Correct answer: 24 hours

The mixture must stand for 24 hours before the color of the solution is compared to the organic plate reference standard.

Question 32: Which ASTM standard covers the test method for clay lumps and friable particles in aggregates?

ASTM C117
ASTM C142 (Correct answer)
ASTM C131
ASTM C136

Correct answer: ASTM C142

ASTM C142 is the standard test method for clay lumps and friable particles in aggregates.

Question 33: What is the purpose of washing aggregate over a No. 200 (75 µm) sieve per ASTM C117?

To remove material finer than 75 µm including clay and silt coatings (Correct answer)
To separate fine and coarse aggregate
To determine organic content
To measure moisture content

Correct answer: To remove material finer than 75 µm including clay and silt coatings

ASTM C117 washing removes clay, silt, and fine dust coatings finer than 75 µm that could weaken the paste-aggregate bond.

Question 34: How does risk management apply to daily practice in Los Angeles Abrasion Testing for ACI Aggregate Testing Technician professionals?

Through proactive identification of potential hazards and implementation of preventive measures (Correct answer)
Only through responding to incidents after they occur
By avoiding high-risk situations entirely
Through annual safety audits exclusively

Correct answer: Through proactive identification of potential hazards and implementation of preventive measures

Effective risk management in Los Angeles Abrasion Testing requires proactive hazard identification and preventive measures, not just reactive responses. This approach reduces incidents, improves outcomes, and protects both professionals and clients.

Question 35: According to ASTM C33, the maximum allowable clay lumps and friable particles in fine aggregate for concrete is:

2.0%
1.0%
5.0%
3.0% (Correct answer)

Correct answer: 3.0%

ASTM C33 limits clay lumps and friable particles in fine aggregate to a maximum of 3.0% by mass.

Question 36: Which sieve size represents the boundary between fine and coarse aggregate per ASTM C33?

No. 4 (4.75 mm) (Correct answer)
3/8 in. (9.5 mm)
No. 8 (2.36 mm)
No. 16 (1.18 mm)

Correct answer: No. 4 (4.75 mm)

The No. 4 (4.75 mm) sieve is the dividing line: material retained on the No. 4 is classified as coarse aggregate, and material passing is classified as fine aggregate.

Question 37: When testing for lightweight pieces per ASTM C123, the test result is expressed as:

Percentage by mass of lightweight pieces (Correct answer)
Percentage by volume
Number of particles per kilogram
Parts per million

Correct answer: Percentage by mass of lightweight pieces

ASTM C123 results are reported as the percentage by mass of lightweight pieces in the aggregate sample.

Question 38: During aggregate moisture testing, why is the sample cooled in a covered container before the final mass is taken?

To prevent condensation from forming on the balance pan
To ensure the aggregate returns to its original size before weighing
To allow moisture to redistribute evenly through the sample
To prevent the hot aggregate from damaging the balance and to avoid convection air currents affecting the reading (Correct answer)

Correct answer: To prevent the hot aggregate from damaging the balance and to avoid convection air currents affecting the reading

Hot samples can create convection currents that affect balance readings and may damage sensitive balances; covering prevents moisture re-absorption during cooling.

Question 39: Which of the following aggregate conditions will cause the concrete batch to have LESS water than designed if no moisture adjustment is made?

Aggregate with zero absorption capacity
Aggregate that is drier than SSD (partially absorbing) (Correct answer)
Saturated surface-dry aggregate
Aggregate with total moisture content greater than absorption

Correct answer: Aggregate that is drier than SSD (partially absorbing)

When aggregate is below SSD condition, it will absorb water from the mix, effectively removing water from the batch and reducing the actual water-cement ratio.

Question 40: According to ASTM D75, what is the minimum number of increments required to constitute a field sample of aggregate from a conveyor belt?

10 increments taken at regular intervals
2 increments taken from the head and tail of the belt
5 increments taken at random intervals
3 increments taken at random intervals (Correct answer)

Correct answer: 3 increments taken at random intervals

ASTM D75 requires a minimum of 3 increments taken at random intervals to form a representative field sample from a conveyor belt.

Question 41: Why is it important that the No. 200 sieve used in ASTM C117 be inspected and cleaned before each test?

To prevent blinding from previous tests from reducing the effective opening size (Correct answer)
To verify the frame serial number matches the laboratory record
To remove residual oven heat that could crack the wire cloth
To ensure the sieve weighs the same as during calibration

Correct answer: To prevent blinding from previous tests from reducing the effective opening size

Clay or fines from previous tests can blind (plug) the sieve openings, causing fines to be retained rather than passing, leading to an underestimate of percent finer.

Question 42: If a technician accidentally loses some washed aggregate down the drain before drying, how does this error affect the calculated percent passing No. 200?

It increases the calculated percent finer than No. 200 (Correct answer)
It decreases the calculated percent finer than No. 200
It causes the test to be invalid and must be repeated with a new sample
It has no effect because the fines are already accounted for

Correct answer: It increases the calculated percent finer than No. 200

Losing coarse material reduces the post-wash dry mass B, making (A − B) larger, which inflates the calculated percent finer than No. 200.

Question 43: An aggregate has a sodium sulfate soundness loss of 8% and an LA abrasion loss of 42%. Which test result is most likely to cause rejection for use in bridge deck concrete?

The sodium sulfate loss, which exceeds typical 5% limits for severe exposure
Both results are within acceptable limits for bridge deck concrete
The LA abrasion loss, which exceeds typical 40% limits for bridge decks (Correct answer)
Neither result alone is sufficient for rejection without absorption data

Correct answer: The LA abrasion loss, which exceeds typical 40% limits for bridge decks

Bridge deck specifications often limit LA abrasion loss to 40%, so a 42% result would cause rejection, while 8% sodium sulfate loss is within the typical 12% coarse aggregate limit.

Question 44: In Aggregate Sampling & Reduction, what is the FIRST step a ATT professional should take when encountering a new case or situation?

Conduct a comprehensive assessment and gather all relevant information (Correct answer)
Implement an immediate solution based on past experience
Document the situation and wait for further instructions
Consult with a supervisor before taking any action

Correct answer: Conduct a comprehensive assessment and gather all relevant information

In Aggregate Sampling & Reduction, a thorough initial assessment ensures all relevant factors are identified before deciding on an appropriate course of action. This systematic approach is fundamental to ACI Aggregate Testing Technician practice.

Question 45: An aggregate is described as 'uniformly graded' or 'single-sized.' This means it will produce concrete with:

Good workability with minimum water demand
Higher strength and lower permeability
Higher void content requiring more paste to fill (Correct answer)
Lower shrinkage and improved durability

Correct answer: Higher void content requiring more paste to fill

Uniformly graded aggregate has particles of similar size, resulting in high void content that requires more cement paste to fill, increasing cost and potentially increasing shrinkage.

Question 46: When performing the bulk density (unit weight) test per ASTM C29 on fine aggregate using rodding, how many layers are used?

1 layer, rodded 75 times
3 layers, each rodded 25 times (Correct answer)
5 layers, each rodded 10 times
2 layers, each rodded 50 times

Correct answer: 3 layers, each rodded 25 times

ASTM C29 rodding procedure uses three equal layers, each consolidated by 25 strokes of the tamping rod.

Question 47: The 'percent passing' and 'percent retained' for any given sieve should always:

Sum to the fineness modulus value
Both equal 50% for a well-graded aggregate
Equal the cumulative retained on that sieve
Sum to 100% for that sieve (Correct answer)

Correct answer: Sum to 100% for that sieve

For any sieve, percent passing + percent retained = 100%, since all material either passes or is retained on each sieve.

Question 48: Which ASTM standard governs the determination of the amount of material finer than the No. 200 (75-μm) sieve by washing?

ASTM C535
ASTM C117 (Correct answer)
ASTM C136
ASTM C702

Correct answer: ASTM C117

ASTM C117 covers the test method for material finer than 75 μm (No. 200) in mineral aggregates by washing, complementing the dry sieve analysis of ASTM C136.

Question 49: Which ASTM standard is used to determine lightweight pieces in aggregate (such as coal and lignite)?

ASTM C123 (Correct answer)
ASTM C127
ASTM C40
ASTM C142

Correct answer: ASTM C123

ASTM C123 is the standard test method for lightweight pieces in aggregate, used to identify coal, lignite, and other low-density particles.

Question 50: Chert with a bulk specific gravity less than 2.40 is considered a deleterious substance in coarse aggregate because:

It reduces water demand
It accelerates cement hydration
It increases workability too much
It has poor freeze-thaw durability and causes pop-outs (Correct answer)

Correct answer: It has poor freeze-thaw durability and causes pop-outs

Low-density chert absorbs water and deteriorates rapidly during freeze-thaw cycles, causing surface pop-outs in concrete.

Question 51: What is the PRIMARY purpose of continuing education requirements in Unit Weight & Voids Testing for ATT professionals?

Maintaining current knowledge and competency as the field evolves (Correct answer)
Fulfilling mandatory regulatory requirements only
Networking with other professionals in the field
Earning additional credentials for career advancement

Correct answer: Maintaining current knowledge and competency as the field evolves

Continuing education in Unit Weight & Voids Testing ensures professionals maintain current knowledge and skills as standards, technologies, and best practices evolve in the ACI Aggregate Testing Technician field.

Question 52: Soft particles in coarse aggregate are a concern primarily because they:

Can crush under load and create voids that weaken concrete (Correct answer)
Reduce bleeding in fresh concrete
Increase the air content
Improve freeze-thaw resistance

Correct answer: Can crush under load and create voids that weaken concrete

Soft particles crush under compressive loads, creating voids and weak zones that significantly reduce concrete strength and durability.

Question 53: Which condition makes it necessary to increase the number of increments when sampling from a conveyor belt?

When the aggregate is fine-grained only
When the belt is moving slowly
When ambient temperature is above 90°F
When the material shows high variability or segregation (Correct answer)

Correct answer: When the material shows high variability or segregation

Higher material variability requires more increments to achieve a composite sample that adequately represents the aggregate being sampled.

Question 54: For ASTM C40 (organic impurities), the sodium hydroxide solution used has a concentration of:

3% NaOH by mass (Correct answer)
1% NaOH by mass
10% NaOH by mass
5% NaOH by mass

Correct answer: 3% NaOH by mass

ASTM C40 specifies a 3% sodium hydroxide (NaOH) solution by mass to extract organic compounds from the aggregate for color comparison.

Question 55: If the original oven-dry mass of a fine aggregate sample is 498 g and the oven-dry mass after washing is 485 g, what is the percentage of material finer than the No. 200 sieve?

2.6% (Correct answer)
2.0%
2.8%
3.2%

Correct answer: 2.6%

(498 − 485) / 498 × 100 = 13/498 × 100 = 2.61%, which rounds to 2.6%.

Question 56: The shelf (lifter) inside the LA abrasion machine drum is positioned:

On the outside of the drum parallel to the axis
Bolted to the drum door as a removable insert
Projecting inward along the full length of the drum (Correct answer)
At a 45-degree angle to redirect aggregate flow

Correct answer: Projecting inward along the full length of the drum

The shelf projects inward along the full interior length of the drum to lift and tumble the charge during rotation.

Question 57: Compared to base course aggregate, the maximum allowable LA abrasion loss for aggregate used in concrete wearing slabs is typically:

Higher, because concrete provides extra protection
Not specified, because slump controls concrete durability
The same, because ASTM C131 applies uniformly
Lower, because surface aggregate must resist traffic wear directly (Correct answer)

Correct answer: Lower, because surface aggregate must resist traffic wear directly

Wearing surfaces demand harder, more abrasion-resistant aggregate, so specifications set lower maximum LA loss values (often ≤30–40%).

Question 58: When performing a sieve analysis, material is found between two nested sieves after shaking. The technician should:

Report it as a separate fraction
Discard the material between sieves
Add it to the finer sieve's retained mass (Correct answer)
Add it to the coarser sieve's retained mass

Correct answer: Add it to the finer sieve's retained mass

Material found between sieve frames (pan leakage or inter-sieve particles) is added to the next finer sieve, as it passed the coarser sieve but did not reach the finer sieve.

Question 59: Apparent specific gravity of an aggregate is generally _ than bulk specific gravity because it excludes _ pores.

Lower; permeable
Higher; impermeable
Higher; permeable (Correct answer)
Lower; impermeable

Correct answer: Higher; permeable

Apparent specific gravity is higher than bulk because it excludes the volume of water-permeable pores, using only the solid impermeable volume in the denominator.

Question 60: In the clay lumps and friable particles test (ASTM C142), the sample is soaked in water for a period of:

48 hours minimum
24 ± 4 hours (Correct answer)
1 to 4 hours
12 ± 1 hours

Correct answer: 24 ± 4 hours

ASTM C142 requires soaking the sample in water for 24 ± 4 hours before attempting to break particles with the fingers.

Question 61: ASTM C123 is used to determine the percentage of which material in fine aggregate?

Lightweight pieces (Correct answer)
Clay lumps
Chert particles
Organic matter

Correct answer: Lightweight pieces

ASTM C123 uses a heavy liquid (such as zinc chloride solution) to float and separate lightweight pieces from the aggregate.

Question 62: The percent retained on a given sieve is calculated by dividing the mass retained on that sieve by:

The combined mass of all sieves below it
The mass passing that sieve
The total original dry sample mass (Correct answer)
The mass retained on the next larger sieve

Correct answer: The total original dry sample mass

Percent retained = (mass retained on sieve / total original dry sample mass) × 100, using the total original sample as the denominator.

Question 63: Which ASTM standard covers the determination of bulk density of aggregates?

ASTM C40
ASTM C117
ASTM C128
ASTM C29 (Correct answer)

Correct answer: ASTM C29

ASTM C29 is the recognized method for measuring the bulk density and void content of aggregates.

Question 64: After the LA abrasion test, the aggregate and charge are separated using a sieve with an opening size of:

No. 16 (1.18 mm)
No. 12 (1.70 mm) (Correct answer)
No. 8 (2.36 mm)
No. 4 (4.75 mm)

Correct answer: No. 12 (1.70 mm)

The material is removed from the machine and sieved over a No. 12 (1.70 mm) sieve to determine loss.

Question 65: Per ASTM C702, when using the quartering method, after how many completed quartering cycles is the sample typically considered reduced to testing size?

Exactly three cycles for coarse and two for fine aggregate
Always exactly one cycle regardless of starting mass
A maximum of two cycles is permitted to avoid bias
As many cycles as needed until the remaining mass meets the minimum test requirement (Correct answer)

Correct answer: As many cycles as needed until the remaining mass meets the minimum test requirement

Quartering cycles are repeated until the retained portion reaches the minimum required test sample mass; there is no fixed number of cycles specified.

Question 66: The nominal maximum size of an aggregate is defined as:

The smallest sieve that retains any material
The largest sieve opening where more than 15% is retained
The largest sieve opening through which 100% of the aggregate passes
The sieve size one step larger than the first sieve to retain more than 10% (Correct answer)

Correct answer: The sieve size one step larger than the first sieve to retain more than 10%

Nominal maximum size is the smallest sieve opening through which the entire amount of aggregate is permitted to pass, which is one sieve size larger than the maximum size.

Question 67: What is the diameter of the tamping rod specified in ASTM C29?

10 mm (3/8 in)
25 mm (1 in)
20 mm (3/4 in)
16 mm (5/8 in) (Correct answer)

Correct answer: 16 mm (5/8 in)

ASTM C29 specifies a smooth, straight steel tamping rod 16 mm (5/8 in) in diameter and approximately 600 mm (24 in) in length.

Question 68: The inside diameter of the Los Angeles abrasion machine drum is approximately:

610 mm (24 in.)
711 mm (28 in.) (Correct answer)
508 mm (20 in.)
457 mm (18 in.)

Correct answer: 711 mm (28 in.)

The LA machine drum has an inside diameter of 711 mm (28 in.) and an inside length of 508 mm (20 in.).

Question 69: Why is it important to sample aggregate from a moving conveyor belt rather than from a stationary pile whenever possible?

Moving belt samples capture the full cross-section of material flow, reducing segregation bias (Correct answer)
Belt sampling is faster and requires less equipment
Stationary piles are restricted areas under OSHA regulations
Belt samples have higher moisture content, making them easier to handle

Correct answer: Moving belt samples capture the full cross-section of material flow, reducing segregation bias

Sampling from a moving belt captures the complete cross-section of aggregate being conveyed, avoiding the segregation bias inherent in stockpile sampling.

Question 70: Which of the following is NOT classified as a deleterious substance in aggregates per ASTM C33?

Chert of low specific gravity
Clay lumps
Coal and lignite
Well-graded crushed granite (Correct answer)

Correct answer: Well-graded crushed granite

Well-graded crushed granite is a sound, durable aggregate material and is not classified as a deleterious substance.

Question 71: When a conflict arises between standard procedures and a unique situation in Moisture Content Testing, what should a ATT professional prioritize?

Safety and ethical obligations while seeking expert consultation (Correct answer)
The most cost-effective solution available
The preference of the client or stakeholder
Strict adherence to written procedures without exception

Correct answer: Safety and ethical obligations while seeking expert consultation

Safety and ethics always take priority in Moisture Content Testing. When standard procedures don't adequately address a unique situation, consulting with experienced colleagues or supervisors ensures both safety and professional standards are maintained.

Question 72: For aggregate sampled from flowing streams (chutes or discharge points), the preferred device to collect the full width of material flow is:

A full-width sampling frame or pan that intercepts the entire stream (Correct answer)
A hand scoop inserted at the edge of the stream
A core barrel driven vertically into the stream
A flat-bladed shovel

Correct answer: A full-width sampling frame or pan that intercepts the entire stream

A sampling device that spans the full width of the flowing stream ensures all particle sizes are captured without size-biased collection.

Question 73: When using the ASTM C136 sieve analysis, the percent passing each sieve is calculated based on:

The SSD sample mass before drying
The mass remaining after washing through the No. 200 sieve
The total original dry sample mass before washing (Correct answer)
The mass of the largest sieve fraction only

Correct answer: The total original dry sample mass before washing

All percentages in ASTM C136 are calculated as a proportion of the total original dry sample mass, ensuring mass balance is verified.

Question 74: Which of the following applications is MOST sensitive to aggregate LA abrasion loss?

Embankment fill material
Granular sub-base fill
Concrete pavement wearing course (Correct answer)
Bedding sand for utilities

Correct answer: Concrete pavement wearing course

Concrete pavement wearing courses experience direct traffic abrasion, making aggregate hardness critical and LA loss limits most restrictive.

Question 75: Under ASTM C87, what minimum strength ratio (suspect mortar vs. clean mortar) is typically required for aggregate acceptance?

95%
100%
85% (Correct answer)
75%

Correct answer: 85%

ASTM C87 requires the suspect aggregate mortar to achieve at least 95% of the strength of the control mortar made with Ottawa sand for acceptance.

Question 76: Which deleterious substance in aggregate is most likely to cause unsightly staining and pop-outs in hardened concrete?

Well-graded limestone fines
Crushed glass
Rounded quartz particles
Coal and lignite particles (Correct answer)

Correct answer: Coal and lignite particles

Coal and lignite particles can expand, cause pop-outs, and produce dark staining on the surface of hardened concrete.

Question 77: A technician performing the LA abrasion test washes and dries the test sample before testing. The drying temperature should be:

60 ± 3°C (140 ± 5°F)
110 ± 5°C (230 ± 9°F) (Correct answer)
175 ± 5°C (347 ± 9°F)
150 ± 5°C (302 ± 9°F)

Correct answer: 110 ± 5°C (230 ± 9°F)

The sample must be dried to constant mass at 110 ± 5°C (230 ± 9°F) before testing per ASTM C131.

Question 78: If a coarse aggregate sample has an original dry mass of 5,000 g, and after washing and drying the mass is 4,925 g, what is the percent passing the No. 200 sieve by washing?

1.52%
2.00%
0.75%
1.50% (Correct answer)

Correct answer: 1.50%

Percent passing No. 200 = ((5000 - 4925) / 5000) × 100 = (75/5000) × 100 = 1.50%.

Question 79: According to ASTM C136, the minimum sample mass for sieve analysis of a coarse aggregate with a nominal maximum size of 1½ in. (37.5 mm) is approximately:

25 kg (55 lb)
1 kg (2.2 lb)
5 kg (11 lb)
15 kg (33 lb) (Correct answer)

Correct answer: 15 kg (33 lb)

ASTM C136 Table 2 requires approximately 15 kg for nominal maximum size of 37.5 mm (1½ in.) to ensure a representative sample.

Question 80: For coarse aggregate gradation testing, ASTM C136 requires that the sample be reduced to the proper test size using which method?

Mechanical splitter or quartering per ASTM C702 (Correct answer)
Quartering by hand on the floor
Random grab samples from the stockpile
Selecting the top layer of the sample container

Correct answer: Mechanical splitter or quartering per ASTM C702

ASTM C702 covers methods for reducing field samples of aggregate to testing size, using a mechanical splitter or the quartering method to ensure representative subsamples.

Question 81: A recycled concrete aggregate (RCA) source is suspected to have high abrasion loss. Which grading would most likely be selected for an LA abrasion test if the RCA is all passing 3/4 in. (19 mm) and retained on No. 4 (4.75 mm)?

Grading A
Grading D
Grading C (Correct answer)
Grading B

Correct answer: Grading C

Grading C covers material passing 3/8 in. and retained on No. 4, while Grading B covers 3/4–3/8 in.; for material all passing 3/4 in. and retained on No. 4, the composite falls under Grading C.

Question 82: For a concrete batch that calls for 175 kg of mix water, and the fine aggregate contributes 12 kg of free moisture while the coarse aggregate contributes 5 kg, how much water should be added at the mixer?

192 kg
170 kg
175 kg
158 kg (Correct answer)

Correct answer: 158 kg

Batch water = 175 − 12 − 5 = 158 kg, because the aggregate's free moisture replaces that amount of added water.

Question 83: Aggregate from a stockpile exposed to rain is tested and shows 5.2% total moisture with an absorption of 1.8%. What surface moisture correction should be applied to the mix water for 500 lb of aggregate (OD basis)?

Reduce mix water by 9 lb
Reduce mix water by 17 lb (Correct answer)
Increase mix water by 17 lb
No adjustment needed

Correct answer: Reduce mix water by 17 lb

Free moisture = 5.2% − 1.8% = 3.4%; water contributed = 0.034 × 500 = 17 lb; this free water reduces the required mix water addition by 17 lb.

Question 84: After mechanical splitting of an aggregate sample, the technician notices one half is significantly heavier than the other. What is the most likely cause?

The splitter chutes were of unequal width or material bridged during splitting (Correct answer)
One half contained more elongated particles
The aggregate was too dry to split evenly
The aggregate has two different specific gravities

Correct answer: The splitter chutes were of unequal width or material bridged during splitting

Unequal chute widths or bridging during mechanical splitting are the most common causes of uneven mass distribution between the two halves.

Question 85: Many highway specifications require that coarse aggregate for base course have an LA abrasion loss no greater than:

15%
50% (Correct answer)
65%
25%

Correct answer: 50%

A maximum LA abrasion loss of 50% is a common specification limit for coarse aggregate used in base course applications.

Question 86: A sieve is considered overloaded during a sieve analysis when:

More than 5% of the sample is retained on one sieve
The mass of material retained exceeds the limits specified in ASTM C136 for that sieve size (Correct answer)
The sieve frame bends under the weight of the material
Any single layer of particles covers more than 50% of the sieve area

Correct answer: The mass of material retained exceeds the limits specified in ASTM C136 for that sieve size

ASTM C136 specifies maximum mass limits per unit area for each sieve size; exceeding these limits causes particles to stack and prevents accurate separation.

Question 87: During the ASTM C88 soundness test, how many cycles of immersion and drying are typically performed?

3 cycles
7 cycles
5 cycles (Correct answer)
10 cycles

Correct answer: 5 cycles

The standard soundness test procedure performs 5 cycles of immersion in sulfate solution followed by oven drying.

Question 88: Which ASTM standard provides the primary guidance for sampling aggregates from various sources including stockpiles, conveyor belts, and transportation units?

ASTM C702
ASTM C136
ASTM C535
ASTM D75 (Correct answer)

Correct answer: ASTM D75

ASTM D75 is the standard practice for sampling aggregates and covers procedures for obtaining samples from stockpiles, flowing streams, trucks, rail cars, and barges.

Question 89: What is the maximum allowable lightweight pieces (coal and lignite) in fine aggregate per ASTM C33 for concrete subject to surface wear?

2.0%
1.5%
0.5% (Correct answer)
1.0%

Correct answer: 0.5%

For fine aggregate in concrete subject to surface wear, ASTM C33 limits lightweight pieces (coal and lignite) to 0.5% by mass.

Question 90: After collecting a field sample, what information must be recorded as a minimum on the sample identification tag?

Sample ID, material description, source location, date and time, and sampler's name (Correct answer)
Weight of the sample and sieve size only
Only the date and material type
Project number and the testing laboratory name only

Correct answer: Sample ID, material description, source location, date and time, and sampler's name

Complete identification including source, time, date, and sampler ensures traceability and allows results to be linked back to a specific lot of material.

Question 91: When sampling aggregate from a barge or ship hold, what is the recommended approach if material cannot be sampled from a flowing stream?

Sample from multiple locations within the hold at varying depths (Correct answer)
Sample only after the barge is partially unloaded
Take one sample from each corner of the hold
Sample only from the center of the hold at surface level

Correct answer: Sample from multiple locations within the hold at varying depths

Multiple sampling locations at varying depths within the hold help account for segregation caused by loading and settling during transport.

Question 92: For fine aggregate, what instrument is typically used to determine when SSD condition is achieved in ASTM C128?

Nuclear moisture gauge
Hydrometer
Metal cone and tamping rod (Correct answer)
Proctor compaction mold

Correct answer: Metal cone and tamping rod

ASTM C128 uses the cone test — the fine aggregate slumps when surface moisture is gone, indicating SSD condition.

Question 93: An aggregate sample has an original dry mass of 5,000 g. After the LA abrasion test, 4,150 g is retained on the No. 12 sieve. What is the percent loss?

15%
17% (Correct answer)
21%
19%

Correct answer: 17%

Loss = (5,000 − 4,150) ÷ 5,000 × 100 = 850 ÷ 5,000 × 100 = 17%.

Question 94: In Los Angeles Abrasion Testing, what is the FIRST step a ATT professional should take when encountering a new case or situation?

Consult with a supervisor before taking any action
Document the situation and wait for further instructions
Implement an immediate solution based on past experience
Conduct a comprehensive assessment and gather all relevant information (Correct answer)

Correct answer: Conduct a comprehensive assessment and gather all relevant information

In Los Angeles Abrasion Testing, a thorough initial assessment ensures all relevant factors are identified before deciding on an appropriate course of action. This systematic approach is fundamental to ACI Aggregate Testing Technician practice.

Question 95: In ASTM C123, lightweight particles are separated from aggregate by:

Heating to 100°C and measuring mass loss
Magnetic separation
Immersion in a heavy liquid of specified density (Correct answer)
Acid dissolution

Correct answer: Immersion in a heavy liquid of specified density

ASTM C123 uses a heavy liquid (such as zinc chloride solution) with a specific gravity between 1.95 and 2.0 to float out lightweight particles.

Question 96: When sampling aggregate from a flowing discharge stream, increments should be collected:

Only during the first 10% and last 10% of the discharge
Only during peak flow velocity to capture the finest particles
From the fastest-moving center of the stream only
At regular time intervals throughout the entire discharge period (Correct answer)

Correct answer: At regular time intervals throughout the entire discharge period

Collecting increments at regular intervals throughout the entire discharge period ensures that material from all phases of the discharge is represented in the composite sample.

Question 97: Per ASTM C702, which reduction method is NOT recommended for fine aggregate because it can introduce segregation errors?

Mechanical splitter method
Incremental belt sampling
Quartering method
Miniature stockpile method (Correct answer)

Correct answer: Miniature stockpile method

The miniature stockpile method is not recommended for fine aggregate because fine particles can segregate when formed into a small conical pile.

Question 98: Which of the following would cause absorption results to be artificially LOW when testing coarse aggregate?

Soaking the aggregate for only 12 hours instead of 24 hours
Over-drying the aggregate surface so some evaporation of pore water occurs (Correct answer)
Using water that is slightly warmer than 23°C
Failing to agitate the water during soaking

Correct answer: Over-drying the aggregate surface so some evaporation of pore water occurs

If the aggregate is over-dried beyond SSD, some absorbed pore water evaporates, resulting in a lower measured SSD mass and artificially low absorption.

Question 99: When performing a washed sieve analysis per ASTM C117, after washing the sample over the No. 200 sieve, the material retained must be:

Dried at room temperature for 24 hours
Dried in a microwave oven
Dried to constant mass in an oven at 230±9°F (110±5°C) (Correct answer)
Air-dried and immediately weighed

Correct answer: Dried to constant mass in an oven at 230±9°F (110±5°C)

After washing, the retained material is oven-dried to constant mass at 110±5°C (230±9°F) before performing the dry sieve analysis.

Question 100: Which condition best describes 'friable particles' as tested in ASTM C142?

Particles that float in sodium sulfate solution
Particles that crumble when squeezed between thumb and forefinger while wet (Correct answer)
Particles smaller than the No. 200 sieve
Particles that are lighter than water

Correct answer: Particles that crumble when squeezed between thumb and forefinger while wet

Friable particles are those that disintegrate under modest hand pressure when wetted, as defined in ASTM C142.

ACI Aggregate Testing Technician (ATT) Certification Exam

The ACI Aggregate Testing Technician certification validates competency in performing ASTM and AASHTO aggregate sampling, gradation, and physical property tests on fine and coarse aggregates used in concrete and construction materials.

100

Questions

120 min

Time Limit

70%

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