Aggregate Gradation and Properties Flashcards

What does 'bulk specific gravity (SSD)' mean in the context of aggregate testing?

Answer: The ratio of the SSD mass to the mass of an equal volume of water including permeable pores

Bulk specific gravity (SSD) is the ratio of the saturated surface-dry mass of aggregate to the mass of an equal volume of water, including the volume of permeable pores.

What is the flat and elongated particle ratio used to assess?

Answer: Aggregate particle shape and potential for crushing under load

Flat and elongated particles are more susceptible to breaking under compaction loads, and their ratio is measured to assess aggregate durability and compactability in pavement construction.

Which ASTM test method is used to determine the unit weight and voids in aggregate?

Answer: ASTM C29

ASTM C29 covers the standard test method for bulk density (unit weight) and voids in aggregate using rodding, jigging, or shoveling procedures.

What is the purpose of the aggregate soundness test (ASTM C88)?

Answer: To evaluate the resistance of aggregate to weathering by freeze-thaw or wetting-drying cycles

The soundness test uses sodium or magnesium sulfate solution to simulate weathering and assess whether aggregate will deteriorate when exposed to freeze-thaw cycling in service.

Which aggregate property most directly affects the workability and water demand of a concrete mix?

Answer: Aggregate gradation and particle shape

Aggregate gradation and particle shape directly influence void content in the mix; gap-graded or angular aggregates increase void content and water demand, reducing workability.

What does the 'percent crushed faces' or 'crushed content' test measure?

Answer: The proportion of aggregate particles with one or more mechanically fractured faces

Crushed face content measures the percentage of aggregate particles that have at least one fractured face created by mechanical crushing, which improves interlock and stability in pavement layers.

When conducting sieve analysis, what is the maximum allowable mass retained on any single sieve to avoid overloading?

Answer: It depends on the sieve diameter and opening size as specified by ASTM C136

ASTM C136 specifies maximum mass retained per sieve based on sieve diameter and opening size; overloading a sieve can cause particles to be retained that should pass, skewing results.