Aggregates Flashcards
Main uses for aggregates
underlying materials for foundations and pavements, riprap for erosion protection, and ingridients in portland cement and concrete
Aggregate Sources
Natural Sand, gravel pits, and quarries
Rocks forming from volcanic action
igneous
rocks forming from inorganic remains of marine animals, or disintegrated in existing rock
sedimentary rocks
aggregate material retained on a sieve with 4.75 mm openings
coarse
aggregate material passing through a 4.75 mm sieve
fine
largest sieve size that allows all aggregates to pass
max aggregate size
the first sieve to retain some aggregate, usually less than 10%
Max nominal Size
What aggregates give strength and stability of asphalt?
angular and rough
What aggregate gives workability of concrete?
Smooth and round
texture and angularity indicates what?
fractured faces
How are fine aggregates analyzed?
determining the uncompacted void content of a sample of aggregates
What test helps evaluating the load resistance damage?
LA Abrasion test
If there is negative free moisture in aggregates
aggregates will absorb water
If there is positive free moisture in aggregates
aggregates will release water
Specific gravity
mass of solid/mass of water
Apparent Specific Gravity (Gsa)
Dry Weight/(Volume not accesible to water*62.4)
Bulk Specific Gravity (Gsb)
Dry weight/(total volume)*62.4
Bulk specific gravity, saturated surface dry
SSD Weight/Total particle volume*62.4
What is Gsb,ssd used for ?
concrete mix design
the weight of aggregate required to fill a “unit” volume. Typical units are cubic meters and cubic feet
Bulk unit weight
Strength of concrete cannot exceed strength of aggregates
true
typical compressive strength for aggregates
5000-50000 psi
has a good mix of all particles sizes which means the aggregates use most of the volume and less cement and asphalt is used
high density gradation (well-graded)
all the same size
one size gradation (uniform)
missing some sizes
gap-graded
missing small aggregates which fill holes between larger ones
open graded
a measure of the gradation fineness, used for concrete mix design
fineness modulus
What sieves are not included in fineness modulus?
2.00 and 0.075 mm
