Transcript BAHAN PERKERASAN MODUL ASPAL

BAHAN PERKERASAN
MODUL ASPAL
JENIS ASPAL
Aspal / bitumen / asphalt cement (AC) / penetration
grade adalah bahan pengikat (binder) bahan
perkerasan yang mempunyai sifat utama warna hitam
(umumnya) dan sensitif terhadap suhu.
Jenis-jenis aspal:
•Aspal bumi (fosil) atau bitumen
•Tars
•Aspal natural (Natural bitumen): aspal buton
•Biobitumen (aspal dari tumbuhan)
BITUMEN MANUFACTURE
•Crude oil is refined by fractional distillation to
separate gas, gasoline, kerosine, gas oil and long
residue.
•The long residue is then redistilled under vacuum at
350-400 C to produce short residue.
•The short residue consist of many different grades of
bitumen
•In many case, the vacuum residues are processed by
air ratification (blowing) to produce harder penetration
grade bitumens
•The harder bitumens can then be blended with softer
bitumens to produce intermediate grades
PROPERTY REQUIREMENT FOR
PENETRATION GRADE BITUMEN
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Penetration at 25oC
Softening point oC min and max
Ductility
Loss on heating for 5hr at 163oC
- Loss by mass % (max)
- Drop in penetration % (max)
Solubility in trichloroethylene % by mass (min)
Permitivity at 25oC and 1592 Hz (min)
CHARACTERISATION OF BITUMENS
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The behaviour of bitumen is complex.
It is required a large number of tests to describe
the properties of bitumen over a wide range of
operating conditions (temperature, stress, strain
rate).
To simplify, the mechanical behaviour of bitumen
is described using emperical tests and equations.
The basic tests used are:
- Penetration test (low temperature range <60oC)
- Softening point test (low temperature range <60oC)
- Viscosity test (high temperature range >60oC)
PENETRATION TEST
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This is an empirical test
To be approximately equivalent to a
measurement of ‘stiffness’ at a loading time of
0.4 seconds.
The penetration is the consistency expressed
as the distance in tenths of a millimetre that a
standard needle, of 100g, will penetrate
vertically into a sample of bitumen at 25oC in 5
seconds.
PENETRATION TEST
Digital
Manual
PENETRATION TEST
Penetration in unit of 0.1mm
100g
100g
Aspal
(25oC)
Start
Aspal
(25oC)
After 5 seconds
SOFTENING POINT TEST
Ring and ball test
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Two steel balls are placed on two discs of bitumen
contained within metal rings. These are raised in
temperature at a constant rate (5oC/min) in a water
bath. The softening point is the temperature (oC) at
which the bitumen softens enough to allow the balls
enveloped in bitumen to fall a distance of 25mm and
hit a plate.
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The softening point is approximately the
temperature at which the penetration is 800, hence
the notation T800PEN is used to described the softening
point
VISCOSITY
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Viscosity of a fluid is a measure of its resistance
to tangential or shear stress. It arises from
interaction and cohesion of fluid molecules. All
real fluids possess viscosity, though to varying
degrees. The shear stress in a solid is
proportional to strain whereas the shear stress
in a fluid is proportional to the rate of shearing
strain. It follows that there can be no shear
stress in a fluid which is at rest (Webber, 1974).
VISCOSITY
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As an example, a fluid confined between two
plates which are situated a very short distance y
apart. The lower plate is stationary whilst the
upper plate is moving at velocity v. The layer
adjacent to the stationary plate is at rest whilst
the layer adjacent to the moving plate has a
velocity v. The rate of shearing strain or velocity
gradient is dv/dy.
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The (dynamic) viscosity, µ, is expressed in mN
s/m2 or centipoises (ML-1T-1) and given by
µ = Shearing stress/rate of shearing strain
VISCOSITY
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Absolute viscosity is measured by pulling the
bitumen through the viscometer with a vacuum.
Kinematic viscosity express the bitumen flow under
its own weight.
Viscosity at temperature >60oC is determined using
rotational viscometer (Brookfield viscometer).
Viscometer at low temperature (< 60oC) and wide
range of loading time can be measured using DSR.
KINEMATIC VISCOSITY
Viscosity is also expressed as kinematic viscosity,
v, in which density is considered in the form µ/ρ.
Kinematic viscosity is expressed in mm2/s
(L2T-1) or centistokes where it is independent of
force.
The kinematic viscosity of a liquid reduces with
increasing temperature.
The kinematic viscosity of water at 15oC is about
1.14 mm2/s. At room temperature the kinematic
viscosity of air is about 13 times that of water.
Brookfield viscometer
Rotational viscometer
DSR (Dynamic Shear Rheometer)
to measure viscosity of bitumen
THE BITUMEN TEST DATA CHART (BTDC)
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BTDC was developed by Heukelom.
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BTDC is a chart to express the relationship between
penetration and absolute viscosity (Poises).
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There are two equi-viscous lines on the chart, one occuring
at a penetration of 800 representing the softening point and
another at a penetration of 1.25 representing the Fraass
breaking point (an estimate temperature at which a thin film
of bitumen might crack).
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Generally bitumen produce data that plot as a straight line
on the chart.
TEMPERATURE SUSCEPTIBILITY (TS)
The consistency of bitumens varies with
temperature. This depends on the type
and grade of bitumen.
Temperature susceptibility (TS) is
expressed by Penetration Index (PI) that
developed by Pfeiffer & Van Doormaal.
TS of a bitumen can be seen on the BTDC
as a straight line with equation:
Log P= A*T + K
P= Penetration; A= slope of line
TEMPERATURE SUSCEPTIBILITY (TS)
Log (800) – log (P @ 25 C)
A=
TSP – 25 C
Log P
Because value A is too small and
this is inconvenient, so that PI was
developed to indicate the temp
susceptibility
Pen
20 (1 – 25A)
PI=
P=800
1 + 50 A
Higher PI means harder bitumen
25 C
TSP
Temperature
DETERMINING Penetration Index (PI)
Penetration at 25oC
(dmm)
Softening Point oC
PI
Softer
bitumen
The arrow indicates
the value increases
MECHANICAL PROPERTIES OF BITUMEN
STIFFNESS OF BITUMEN (Sb)
Sb = Stress/ strain
Sb can be measured using DSR
Condition
Response
Sb
High temperature
Viscous
Low
Long loading time
Viscous
Low
Low temperature
Elastic
High
Short loading time
Elastic
High
Empirical equation:
Loading time (sec)= 1/ Traffic speed (km/hr)
Condition
Loading time
Fast speed
0.01 – 0.10 sec
Parked vehicle
1min-10hours
EFFECT OF LOADING TIME & TEMPERATURE ON
BITUMEN STIFFNESS (Sb)
Sb
Elastic asymptote
Sb
Viscous
asymptote
T1 > T2 > T3
Loading time
Loading time
DETERMINING bitumen stiffness
1. Measure using DSR (Dynamic Shear Rheometer)
2. Predict using Van der Poel Nomograph
3. Calculate using equation
Using equation
Sb= 1.157 * 10-7 * t-0.368 * 2.718-PI (SP-T)5
Only applicable where:
Loading time (t)= between 0.01 and 0.1 seconds
Penetration Index (PI)= between -1.0 and +1.0
Temperature difference (SP-T)= between 20C and 60C
Sb in MPa; SP= softening point; T=temperature
DETERMINING Bitumen Stiffness (Sb)
Sb
Van der Poel Nomograph
PI
The arrow indicates the
value increases
Temperature difference oC
Above T800 pen
Below T800 pen
Loading time (t)
MODIFIED BITUMEN
Bitumen can be modified by adding an additive or modifier
in order to improve its mechanical properties, for examples:
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Obtaining stiffer asphalt mixture at high temperature to minimise
rutting
Obtaining softer asphalt mixture at low temperature to minimise
thermal cracking
Improving fatigue resistance
Improving bonding between aggregate and bitumen to reduce
stripping or moisture susceptibility
Improving abrasion resistance of mixture to reduce ravelling
Rejuvinating aged bitumen
Permitting thicker bitumen film to increase the mixture durability
Reducing flushing or bleeding
Improving resistance to ageing or oxidation
BITUMEN ADDITIVES OR MODIFIERS
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Filler: lime, Portland cement, fly ash
Rubber: natural latex, synthetic latex, reclaimed rubber
Plastic
Combination rubber and plastic
Fibre: rock wool, asbestos, cellulose
Hydrocarbon: recycling and rejuvinating oils, natural
asphalt (trinidad lake asphalt, buton asphalt)
Waste materials: recycled tyres
TES OTAK KIRI
BACA WARNANYA, BUKAN WORDNYA
KUNING
MERAH
HIJAU
HITAM
BIRU
ORANYE
COKLAT
JINGGA
ABU-ABU
tugas
TULIS TANGAN
BUAT PAPER TENTANG ASPAL (5
pages – kertas folio bergaris)
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