Aggregates Flashcards
(24 cards)
nominal maximum agg size
immediate smaller than the smallest sieve which all agg passed
Agg grading characteristics
; maximum agg size
; packing efficiency: how dense the agg will be
Fuller Eqn
; max density
; minimize voids
Fuller curve
; max density
; minimize voids
round agg
+ easy to compact, packing efficiency good
+ lower interlocking work ability
smooth agg
+ lower inter particle friction, workability
- lower strength and lower bond to cement
air dry
; porosity is partially filled
SSD
; saturated surface dry
; pores filled with water
Absorption Capacity
From oven dry to SSD
Absorption Capacity
From oven dry to SSD
Effective Absorption
From air dry to SSD
Moisture content
= Absorption Capacity - Effective Absorption
porosity
; generally low porosity is desirable
As porosity increase
- strength decreases
- permeability increases
- durability decreases
- abrasion resistance decreases
Organic impurities
- delay setting time and reduce strength
Materials finer than 75 micro meter
- increase water absorption
- hard to mix concrete
Clay coating on surface
- reduced bond and strength
Soft particles
- stains and popouts
Alkali-reactive agg
- abnormal expansion and networks of cracks
coarse agg SG
2.68
Uniform graded
; steep curve
; agg has narrow size range
Gap grade
; has only small percentage of particles in the mid size range
continuous graded
; well graded
; minimum void content
; close to 0.45 density of fuller grade
ITZ
; Inter-facial Transition Zone
; Sort of micro channels btw cement and agg
; affected by poor compatibility, wall effect, agg cement reaction, bleeding
