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.

According to ASTM C1260, an expansion of greater than 0.20% at 16 days indicates:

Answer: Potentially deleterious expansion requiring further testing or mitigation

ASTM C1260 classifies expansion exceeding 0.20% at 16 days as potentially deleterious, indicating the aggregate may cause harmful ASR in service.

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.

When performing the organic impurities test (ASTM C40), a color darker than the standard indicates:

Answer: The aggregate may be injurious and should be further tested

A color darker than the reference standard solution (Gardner Color Standard No. 11) suggests potentially harmful organic impurities requiring additional testing per ASTM C87.

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.

The soundness test for fine aggregate (ASTM C88) uses which reagents to assess durability?

Answer: Sodium sulfate or magnesium sulfate solution

ASTM C88 subjects aggregate to repeated immersion in sodium sulfate or magnesium sulfate solutions to simulate weathering and freeze-thaw effects.

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

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.

Which of the following best describes 'decanting' in the context of ASTM C117?

Answer: Pouring off the wash water carrying suspended fines over the nested sieves

Decanting means carefully pouring the turbid wash water (carrying suspended fines) over the No. 200 sieve while keeping the coarse aggregate in the container.

A technician notices that some aggregate particles broke along pre-existing cracks during the LA test. This outcome indicates:

Answer: The aggregate has inherent weaknesses, which is exactly what the test is designed to detect

Pre-existing fractures represent real aggregate weakness; detecting them is a valid purpose of the LA abrasion test.

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.

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

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%).

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.

For fine aggregate moisture testing, what is the minimum sample size recommended by ASTM C566?

Answer: 500 g

ASTM C566 recommends a minimum sample mass of 500 g for fine aggregate to ensure representative results.

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.

The bulk specific gravity (SSD basis) of fine aggregate is used primarily in concrete mix design to:

Answer: Calculate absolute volume of aggregate in a mix

SSD specific gravity allows the mix designer to calculate the absolute volume the aggregate occupies in a unit volume of concrete.