Lecture 29 Flashcards
(14 cards)
Aggregates Definition
Aggregates are materials that have been
specifically sorted or processed to
achieve given properties.
Used in base/subbase courses, shoulders
What are the 2 Aggregate Source
Natural
Manufactured Sources
5 steps to prepare aggregate
excavating
transportation
crushing
sizing
Washing
poor stockpiling causes
segragation
Why is sampling important
To evaluate the potential quality of a proposed aggregate source
To determine compliance with project specification requirements
Cleanliness
Limits must be placed on the amount of foreign
or deleterious substances in the aggregate
– Vegetation
– Shale
– Soft particles
– Clay lumps
– Clay coatings on coarse aggregates
what does particle shape influence
workability and compaction
aggregate source properties
Toughness
Soundness
Deleterious materials
aggregate consensus properties
Coarse aggregate angularity
Fine aggregate angularity
Flat, elongated particles
Clay content (or Sand
Equivalent)
aggregate should be hard enough to resist crushing and degrading from
manufacturing,
stockpiling,
production
compaction of mix
placing
percent weight for hard, igneous rocks for LA abrasion
10
percent weight for soft lime-stones and sandstones rocks for LA abrasion
60
aggregates must be resistant to breakdown from
weathering (wetting/drying,
freezing/thawing)
what isn’t an a problem for bituminous mixes and why
aggregates are heated. Hence no moisture.
Freezing/thawing not a problem
