hra 1 Material for Civil Engineering aggregates
Apr 01, 2015
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Material for Civil Engineering
aggregates
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Definition
Materials (for construction) Inert material which, when bound together into a
conglomerated mass by a matrix, form: -concrete, -mastic mortar, -plaster.
An aggregation of sand, gravel, crushed stone, slag or other material composition used in combination with a binding medium to form: -bituminous and Portland cement, -concrete, -macadam, -mastic, -mortar cement, -plaster, or alone as: -railroad ballast, -filter beds, and -various manufacturing processes such as fluxing
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Classification
Natural Aggregate
Manufactured Aggregate
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Natural Aggregates
Taken from natural deposits without change in their nature during production, with the exception of crushing, sizing, grading or washing
Includes: pumice, shells, iron ore, lime rock
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Manufactured Aggregates
Aggregates produced as a direct product, rather than as a by-product of a manufacturing process
Includes: Blast furnace slag Clay Shale; Light weight aggregates
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Synthetic – Artificial Aggregates
By-product of an industrial process
Product of process developed to manufactured aggregate with special properties
Reclaimed or waste construction materials
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Classification based on Size
FINE Aggregate passing 9.5mm (3/8”) sieve, passing sieve no 4 (4.75mm)
and predominantly retained on 75u (no 200) sieve Aggregate passing no 4 and retained on the no 200 (75um) sieve
COARSE
Aggregate predominantly retained on the no 4 sieve (for Portland Cement Concrete)
The no 8 or no 10 sieve (for bituminous concrete)
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Composition & Structures
Natural Aggregates
Consist of naturally occurring material of mineral composition
Derived from rocks with single mineral or several different mineral
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NATURAL AGGREGATES
METAMORPHIC ROCK
IGNEOUS ROCK
SEDIMENTARY ROCK
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Composition & Structures
IGNEOUS ROCK
COOL MELTING FORMED (ABOVE OR BELOW THE
EARTH’S SURFACE)
CONSISTS OF CRYSTAL OR MINERALS IN A
CRYSTALLINE (OR GLOSSY) MATRIX
SIZE IS A FUNCTION OF COOLING RATE
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Composition & Structures
SEDIMENTARY ROCK
FORMED BY THE CONSOLIDATION OF
DEPOSITS, - WEATHERING PRODUCTS AND
EROSION OF ROCKS (EARTH SURFACE)
LESS MECHANICAL COMPACTIONS
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Composition & Structures
METAMORPHIC ROCK
FORMED BY THE APPLICATION OF INTENSE HEAT
AND PRESSURE TO SEDIMENTARY ROCKS
LESS POROUS, STRONG MATRIX
(RECRYSTALLIZATION)
STRONGED AND LESS ANISOTROPIC COMPACTED
TO SEDIMENTARY ROCKS
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ROCKS TYPE Specific Gravity
POROSITY (% - vol)
IGNEOUS BasaltGranite
2.6 – 3.02.6 – 3.0
50 – 200100 – 250
SEDIMENTARY ShaleLimestoneSandstone
2.0 – 2.72.3 – 2.82.2 – 2.7
10 – 100 35 – 250 20 – 175
METAMORPHIC StateMarbleQuartzite
2.6 – 2.92.6 – 2.82.6 – 2.7
100 – 200100 – 250100 - 300
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Principles and Procedures
The use and process: QUALITY : high (estimate) COST : low (estimate)
The procedures: Excavation Transportation Washing Crushing Sizing
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procedures
Processing plant
Site
Transportation (truck, rail, conveyor belt)
Washing : before and/or after
Excavator: digging
Removal of organic material (silt; clay; leaves; mud)
Method: blasting; dragging; pumping
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Sizing and screening
1. Sizing: by crusher
2. Proper and desirable size
3. Crusher type:
size of designed aggregate
Sieve : vibratory screen
Set of sieves with designated diameter
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d
sieve
d
D
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Sieve analysis
h
D
X gram
(X- z) gram
Retained = coarser
X’ gram coarser
X” gram finer
X”‘ gram finer
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Grain distribution
10 1 0.1 0.01 0.0.01
0
20
60
80
100%
by w
eig
ht
finer
Diameter, log, mm
40
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End of session