Hot Mix Asphalt Field Density Testing Flashcards

What is the primary laboratory use of a pavement core extracted from a compacted HMA mat?

Answer: To determine bulk specific gravity for in-place density calculation

Extracted cores are tested for bulk specific gravity (ASTM D2726), which is then compared to MTD to calculate percent compaction and verify compliance with density specifications.

Which ASTM standard is used to determine the bulk specific gravity of non-absorptive compacted HMA specimens (cores)?

Answer: ASTM D2726

ASTM D2726 (Bulk Specific Gravity and Density of Non-Absorptive Compacted Bituminous Mixtures) is the standard procedure applied to dense-graded HMA cores using the saturated surface-dry method.

In HMA quality acceptance specifications, what is a 'lot'?

Answer: A defined quantity of pavement production used as the statistical unit for acceptance decisions

A lot is a defined quantity of production — typically by area, tonnage, or linear distance — that serves as the statistical sampling unit for making pass/fail acceptance decisions.

What does PWL stand for in statistical HMA density acceptance specifications?

Answer: Percent Within Limits

PWL (Percent Within Limits) is a statistical measure estimating what percentage of a production lot falls between the lower and upper specification limits for a quality characteristic such as density.

If the bulk specific gravity of a core is 2.350 and the maximum theoretical density is 2.500, what is the percent compaction?

Answer: 94.0%

Percent compaction = (bulk specific gravity / MTD) × 100 = (2.350 / 2.500) × 100 = 94.0%.

Why is a correction factor (bias correction) applied when comparing nuclear gauge readings to core density values?

Answer: To account for systematic differences between nuclear gauge readings and laboratory bulk specific gravity results

Nuclear gauges and laboratory core tests measure density by fundamentally different physics, which can produce consistent systematic offsets; a correlation correction aligns gauge readings with core-based acceptance criteria.

What is the appropriate action when a nuclear density gauge fails to produce a standard count within acceptable control limits?

Answer: Remove the gauge from service until it is inspected, recalibrated, or repaired

A gauge failing standard count checks may have instrument malfunction, source decay, or contamination; it must be taken out of service to prevent erroneous density data from being used in acceptance decisions.