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:red_flag:AGGREGATE (2) - Coggle Diagram
:red_flag:AGGREGATE (2)
Characteristic of aggregate
-Will not react chemically with cement
-Abrasion resistance
-Resistance to freezing and thawing
-Compressive strength
-Good particle shape
-Good surface texture
Properties of aggregate
1. Strength
-Normally strength of concrete doesn't exceed 80 N/mm2 (20 - 50 N/mm2)
-Strength of rock aggregate (70 - 350 N/mm2)
-Test
1) Aggregate crushing value (ACV)
2) Aggregate impact value (AIV)
3) Ten percent fines value (TFV)
2. Hardness
-Ability to withstand wear/ load/ applied pressure
-Hardness depend on the type of parent rock -Test
1) Abrasion test
-satisfactory aggregate abrasion value should have:
- not more 30% - used for wearing surface
- not more 50% - used for non wearing surface
4. Durability
-Ability to with stand external and internal damaging attack
-Test
*Soundness
-Aggregate with high modulus of elasticity:
*Produce higher modulus of elasticity of concrete
-Effect the magnitude of creep & shrinkage
-Compressibility reduce distress in concrete
-Aggregate of moderate/ low strength
5. Porosity
-Various sizes, small/ big - can be seen with eyes or microscope
-Will absorb water when dry and release when it wet, depend on sizes & volume of aggregate
-Porosity of aggregate contribute to overall porosity of concrete
6. Water absorption
-Weight of water absorbed by an oven dry aggregate in reaching the saturated & surface dry condition
-Determine by measure the increase in weight of oven dry sample immersed in water for 24 hour and weighed at saturated and surface dry condition
3. Toughness
-Resistance of aggregate to failure by impact -Test
1) Aggregate impact test
2) AIV must be :
- not exceed 30% : wearing surface
*not exceed 45% : non wearing surface
Particle shape of aggregate
-Influence the property of concrete, mobility of fresh concrete & bond between aggregate and mortar paste.
*Flaky
-material of which the thickness is small relative to other 2 dimensions
-E.g laminated rock
*Elongated
-The agg usually angular, is shaped and the length is considerable larger than the other 2 dimensions
*Flaky and Elongated
-Material having the length which is considerable larger than the width
-Width is considerable larger than the thickness
*Rounded
-Full water-worn/ completely shaped by attrition / abrasion
-E.g river or sea shore gravel
*Irregular
-Naturally/ partially shaped by attrition and having rounded edges
-E.g other gravel land/ dug flint
*Angular
-Processing well defined edges formed at the intersection/ roughly planes surface
-E.g crushed rocks of all types
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5.0 Bulk density
-Mass of aggregate in a given volume
-Between 1450-1750 kg/m3
-Factor effecting bulk density are :
Particle size
Size
Grading of aggregate
Moisture content
-Used for judging the quality of aggregate
-Higher bulk density indicates that they are fewer voids to be filled by sand and cement
-Extent of bulking depends on :
% moisture content in agg
Fineness of fine agg
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Testing of aggregate
a) Sieve analysis
b) Toughness, hardness and abrasion resistance
c) Soundness
d) Absorption
e) Specific gravity