Mixed Deck — All ATT Topics Flashcards

Which ASTM standard governs the Organic Impurities in Fine Aggregates for Concrete test?

Answer: ASTM C40

ASTM C40 is the standard test method for organic impurities in fine aggregates for concrete.

When sampling freshly mixed concrete at a job site for aggregate content verification, which standard governs obtaining the composite sample of fresh concrete?

Answer: ASTM C172

ASTM C172 covers sampling freshly mixed concrete, from which aggregate-related tests such as unit weight and air content are then performed.

What is the significance of the 'increment' in aggregate sampling terminology?

Answer: A single portion of material collected in one operation that is combined with others to form the field sample

An increment is one individual scoop or cut of material; multiple increments are combined to create the composite field sample used for testing.

When determining fine aggregate specific gravity by ASTM C128, the pycnometer is filled with water to what level after adding the aggregate?

Answer: The calibration mark on the neck

The pycnometer is filled to its calibration mark to ensure a known, reproducible water volume.

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

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.

How should a field sample be reduced to testing size?

Answer: Using a mechanical splitter or quartering method.

Mechanical splitting or quartering methods must be used to reduce the sample without bias.

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

Answer: Metal cone and tamping rod

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

What is the minimum sample mass recommended for a field sample of 37.5 mm (1.5 in.) nominal maximum size coarse aggregate per ASTM D75?

Answer: Approximately 100 kg (220 lb)

ASTM D75 Table 1 specifies approximately 100 kg for 37.5 mm NMAS to ensure enough material is available for all required tests after reduction.

Which test best evaluates the presence of plastic fines (clay minerals) in fine aggregate that could reduce concrete durability?

Answer: Sand equivalent test (ASTM D2419)

The sand equivalent test (ASTM D2419) is specifically designed to measure the relative proportion of clay-like plastic fines in fine aggregate.

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

Answer: 110 ± 5°C

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

When the field sample size exceeds what is needed but the technician has no mechanical splitter available, ASTM C702 recommends which alternative reduction method?

Answer: Use the quartering method as an approved alternative to mechanical splitting

ASTM C702 explicitly recognizes quartering as an approved alternative when mechanical splitters are unavailable, provided the procedure is followed correctly.

Which environmental condition is most likely to affect the moisture content of a field sample between collection and testing?

Answer: Prolonged exposure to direct sunlight or wind in an open container

Open exposure to sun and wind causes evaporative drying that alters moisture content, potentially affecting absorption and unit weight tests.

When sampling from a truck or rail car, at how many approximately equal depth-interval locations across the load should increments be taken?

Answer: At least three locations across the load

ASTM D75 recommends collecting increments from at least three locations across the load at approximately equal depth intervals to account for variation within the unit.

What concentration of NaOH solution is used in the ASTM C40 organic impurities test?

Answer: 3% by weight

ASTM C40 specifies a 3% sodium hydroxide (NaOH) solution by weight for detecting organic impurities in fine aggregate.

Aggregate sampling plans should be developed with input from which parties?

Answer: All parties involved in the project including purchaser, producer, and testing laboratory

ASTM D75 recommends that sampling plans be developed cooperatively among all stakeholders to ensure the plan meets project acceptance requirements.

The percentage of material finer than the No. 200 sieve by washing is calculated using which formula?

Answer: (A − B) / A × 100

The formula (A − B) / A × 100 gives the percent passing No. 200, where A is the original dry mass and B is the dry mass after washing.

How does risk management apply to daily practice in Soundness & Durability Testing for ACI Aggregate Testing Technician professionals?

Answer: Through proactive identification of potential hazards and implementation of preventive measures

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

Which of the following aggregate sampling locations is generally considered the MOST representative of the material going into a pavement?

Answer: From the discharge end of the cold feed conveyor belt

The cold feed conveyor belt captures aggregate in motion before it enters the dryer, giving a representative cross-section of the material actually being fed into production.

What sieve size is used to separate the material retained for the clay lumps test in coarse aggregate per ASTM C142?

Answer: No. 4 (4.75 mm)

For coarse aggregate, ASTM C142 testing uses material retained on the No. 4 (4.75 mm) sieve.

What documentation practice is considered essential in Aggregate Sampling & Reduction within the ACI Aggregate Testing Technician field?

Answer: Recording actions, observations, and outcomes in real-time or as close to the event as possible

Real-time or near-real-time documentation in Aggregate Sampling & Reduction ensures accuracy, provides a contemporaneous record, and is considered the gold standard for professional accountability and legal defensibility.