Transcript Pertemuan 4 - Sri Atmaja P. Rosyidi

Chapter 3
BASE COURSE
MINERAL AGGREGATE
Sri Atmaja P. Rosyidi
Definition
Aggregate is the term used to describe
rock used for road making and refers to
an assembly of discrete particles (i.e.
pieces of rock).
Introduction
1. Generally account for 30 percent of the cost of a
pavement structure
2. By weight: 92 to 96 percent of asphalt concrete to 65
to 85 percent of portland cement concrete
3. Aggregate (definition) : Combination of sand, gravel,
crushed stone or other material of mineral
composition with a binding medium (water,
bituminous, portland cement, lime, etc.) to form
materials such as asphalt concrete, portland cement
concrete, etc. Aggregates may be natural or
manufactured.
PARTICLE SHAPES
 Gravel: naturally rounded particles smooth texture
 Crushed stone: artificial crushing of
rock - generally with rough texture
The following definitions are from AASTHO M146
(Terms Relating to Subgrade, SoilAggregate, and Fill Materials):
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Soil-Aggregate (Dense-Graded Aggregate): Natural or
prepared mixtures consisting predominately of stone, gravel
or sand and containing silt-clay (minus 75 µm) material.
Binder (Soil Binder): Portion of soil passing a 425 µm sieve.
Stone: Crushed or naturally angular particles of rock which
will pass a 75 mm sieve and be retained on a 2.00 mm
sieve.
Gravel: Rounded particles of rock which will pass a 75 mm
sieve and be retained on a 2.00 mm sieve.
Sand: Granular material resulting from the disintegration,
grinding, or crushing of rock and which will pass the 2.00
mm sieve and be retained on the 75 µm sieve.
Silt-Clay: Fine soil particles which will pass the 75 µm sieve.
Silt Fraction: Material passing the 75 µm and larger than
0.002 mm.
Clay Fraction: Material smaller than 0.002 mm.
Additional definitions from AASHTO M147 (Materials for
Aggregate and Soil-Aggregate Subbase, Base and Surface
Courses):
 Coarse Aggregate: Aggregate retained on the 2.00
mm sieve and consisting of hard, durable particles or
fragments of stone, gravel or slag. A wear
requirement (AASHTO T96) is normally required.
 Fine Aggregate: Aggregate passing the 2.00 mm sieve
and consisting of natural or crushed sand, and fine
material particles passing the 75 µm. The fraction
passing the 75 µm sieve shall not be greater than
two-thirds of the fraction passing the 425 µm sieve.
The portion passing the 425 µm sieve shall have a LL
 25 and a PI  6. Fine aggregate shall be free from
vegetable matter and lumps or balls of clay.
Principal Aggregate Sources
 Igneous Rock
(exp. adamellite, andesite, basalt,
brecia, diorite, dolerite, granite, ect.)
Igneous rocks are largely cristalline and
formed during the cooling of molten rock.
They are usually composed of hard
materials and the interlocking fine-grained
crystal structure combines to product
strong, hard rock at least in the fresh state.
Principal Aggregate Sources
 Sedimentary Rocks
(exp. alluvial (water-based),
gravels, claystone, conglomerates, limestone, mudstone,
sand, sandstone, shale, siltstone)
Sedimentary rocks are formed from (i) water
deposition of granular soil, (ii) air deposition of fine
the granular soil, (iii) deposition of organic remains of
plants and animals, (iv) crystallisation of soluble
materials from solution. Sedimentary rocks are
usually mechanically weak and can be ripped and grid
roller. They are not widely used in rock making as
typically prone to abrasion and erosion and moisture
sensitive and of suspect durability.
Principal Aggregate Sources
 Metamorphosed Rock
(i.e. argilite, gneiss,
greenstone, hornfels, phyllite, quartz, slate, etc.)
These are rocks of igneous and
sedimentary rock that have been subjected
to heat and/or pressure of such magnitude
that new materials and textures are
formed. Although metamorphic rocks are
widespread, they are little used in rock
making because may often be closely
fractures or jointed.
Principal Aggregate Sources
 Organic Rock
(i.e. coral, limestone (sedimentary
rock), seashell)
Coral has been used successfully for road
making. Coral is composed of aragonite,
calcite, and dolomite. Coral is widely used
for pavement construction in the Pacific.
Seashell has also been used for road
making and some limestones are derived
from prehistoric coral beds.
Principal Aggregate Sources
 Artificial Rock
flyash, slag)
 Gravels
(i.e. bottom ash, flue dust,
(i.e. gravel, ironstone)
Gravels are naturally-occurring particulate
rocks that excellent fold making material.
However, relatively poor gravels are the only
road making materials available in some
areas and therefore find use despite such
problems as pro grading and shape and
tendency to lose strength when wet.
Remainder
Please for all of you that one of the
classes after mid term exam will be
arranged as a presentation class.
Student should provide a project
presentation regarding to the pavement
construction method and related
material testings. A submitted project is
written in a power point (ppt) with
maximum slides of 10.
Discussion Session
Please arrange some groups in 4 – 5
person for per group. Discuss about the
physical and mechanical characteristics
of aggregate that are need in order to
control the quality of aggregate.
You have 30 minutes left for discussion.