Note: Descriptions are shown in the official language in which they were submitted.
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AN ASPHALT RECYCLING SYSTEM AND METHOD FOR PRODUCING A NEW
ASPHALT LAYER FROM THE ASPHALT TO BE RECYCLED
TECHNICAL FIELD
The present invention relates to asphalt recycling systems which provide the
asphalt
layer (RAP), which is desired to be recycled by being removed from the place
thereof,
to be converted into recycled asphalt concrete (RAC), and particularly relates
to
asphalt recycling systems with respect to the prior art part of Claim 1.
KNOWN STATE OF THE ART
As known, asphalt concrete obtained from the aggregate and bitumen mixture is
used
as different layers like corrosion layer, binder, straightening layer and base
layers on
road's upper structure. Each of these layers is produced by means of recipes
prepared
in laboratory with respect to the methods of international standards in order
to provide
different performance requirements. Different performances expected from each
layer
are provided by means of recipes prepared by different maximum particle
dimension,
different gradation and different bitumen proportions. These performance
requirements
are valid also for the layers to be realized using the recycled asphalt
concrete (RAC).
Asphalt concrete which is applied to roads should be removed after certain
usage.
Today, because of the environmental conditions, removed asphalt concrete
should be
recycled and used in the production of new asphalt concrete. Moreover,
recycling of
the removed asphalt concrete (hereafter it will be called RAP) and the usage
thereof in
the production of new asphalt concrete provides economic advantages. As the
proportion of removed asphalt used increases in the production of new asphalt
concrete, the economic advantage provided increases more.
Thus, in the related technical field, recycling can be realized by the usage
of removed
(RAP) asphalt concrete in the production of new asphalt concrete. In the
present art,
there is a plurality of technological recycling methods used for the recycling
of asphalt.
Whatever the recycling method, the recycling of the RAP and the proportion of
the RAP
in the new mixture depends on maximum granule dimension, gradation and the
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bitumen proportion included and the results of the measurement of the aging
and
fatigue characteristics of the bitumen included. The removed asphalt concrete
can be
added with the proportion that the new mixture can provide the desired
performance
characteristics.
The most frequent recycling method is the adding of the removed asphalt
concrete, in
cold form and in determined proportions to the new asphalt mixture realized in
the
asphalt plant mixer. This method is called cold recycling. With this method,
the
maximum recycling ratio which can be obtained is 20 %. In another frequent
recycling
method, RAP is brought to the process temperature in a heating mechanism which
operates in connection with a present asphalt plant and afterwards, the
asphalt plant is
added to the new mixture; this process is called hot recycling. With this
method, in the
beginning, the recycling ratio is greater than the recycling ratio of cold
recycling,
because of the disadvantages faced during the heating of the RAP in this
system and
during the advancing of RAP inside the system for feeding the RAP into the
asphalt
plant mixer, the recycling ratio decreases during usage.
One of the abovementioned disadvantages is that the bitumen inside the RAP is
heated and as a result, it fluidizes and it becomes adhesive, and as a result
of this,
RAP adheres and deep draws to the media (media like heating drum and conveyor
or
elevator) realizing heating and transfer. As the operation continues, RAP
which is deep
drawn and adhered to the wall of the media decreases the efficiency (flow
rate, heat,
etc.) of the mechanism. Moreover, during operation, since the RAP adheres to
the
inner walls and since the RAP narrows the media it adheres, the RAP should be
frequently cleaned, and therefore the mechanism should be stopped and cooled.
This
decreases the efficiency of the system. The second disadvantage is that since
the
asphalt plant is heated in a free manner before it is added to the new mixture
in the
mixer, and moreover during the transferring of this asphalt plant to the
mixture, the
homogeneity of the mixture is deteriorated and this homogeneity can not be
provided
again. Another disadvantage is that in the present hot recycling methods,
during
heating, the hot air obtained from a heat source (burner) and the RAP which
comprises
bitumen strike directly and instantly. This situation leads to the
deterioration of the
bitumen inside the RAP, which is already aged and fatigue.
Another important disadvantage is related to the chemical additives used. As
known,
thanks to the different chemical additive substances, the RAP is improved
which was
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deteriorated because of aging and fatigue, thus, RAC with higher performance
with a
higher level of recycling can be obtained. In order to realize the desired
affect on the
RAP, these chemical additives, which are desired to be affective on RAP,
should be
used by taking into consideration whole of the mixture, in other words, said
chemical
additives should have bigger proportions in the mixture.
As a solution to the abovementioned problems, the applicant provided the
patent
application W02009058103. In this application, a system is disclosed which has
at
least 3 edges and which has a body with a transmission channel extending along
the
periphery. Accordingly, RAP is moved along the periphery of the body by means
of the
pallets inside said transmission channel and meanwhile, it is subject to heat
in order to
have the required process temperature. After the desired process temperature
is
obtained, RAP is stored in an accumulation reservoir where the temperature
thereof is
preserved and it is automatically transferred to the asphalt plant mixer where
new
asphalt concrete production is realized. Thus, recycling can be obtained with
the
bringing of the RAP to the process temperature by means of an efficient and
homogeneous heating and with the addition of the required additives.
However, using this novel and advantageous system, in order to produce RAC
from
RAP, the system has to function in connection with an asphalt plant. As a
result of the
researches realized by the applicant, with novel revisions, this system is
seen to be
possible to be used in RAC production by operation independent of an asphalt
plant.
BRIEF DESCRIPTION OF THE INVENTION
The present invention is a novel hot asphalt recycling system which eliminates
the
abovementioned disadvantages and which brings new advantages to the related
technical field.
An object of the subject matter invention is to increase heating efficiency of
the
systems providing hot RAP to an asphalt plant in order to be used in new
asphalt
concrete production, thus, the object is to provide the usage of maximum
proportion of
RAP in the new asphalt mixture.
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Another object of the subject matter invention is to produce RAC which will
form the
bitumen base, from the asphalt which is desired to be recycled (RAP) as
independently
of an asphalt plant.
In order to reach said objects, the present invention relates to a hot asphalt
recycling
system comprising a heat-insulated body with a closed volume; at least one RAP
material transmission channel within said frame, said channel being embodied
so as to
produce a geometrical shape with at least three edges; a transmission line
displacing
within said RAP material transmission channel and comprising a plurality of
transmission plates positioned thereon at certain intervals; an outer air
channel which
substantially encircles said transmission channel and wherein hot air is
circulated; an
accumulation reservoir which is formed inside the body and where the RAP at
certain
temperature is stored so as to preserve the temperature of the RAP; and a
discharge
unit which is used to discharge the hot RAP material within the accumulation
reservoir
to the desired media; in order to obtain RAC, which is to be used in the
production of
both of the asphalt layers (binder and bitumen base), from RAP material.
The system is characterized by comprising an inner air channel which is
positioned in
the inner volume of the body, connects an air inlet pipe which provides the
primary hot
air input to the body to the said outer air channel and at least a section of
which
extends at the vicinity of the transmission line; in order to lengthen the
path the hot air
takes inside the body and thus in order to transfer the heat, which is
provided by the
heat source and which circulates inside the body, to the RAP in an efficient
manner.
Another improvement of the system is that the system comprises a mixer wherein
the
RAP coming from the discharge mechanism, new bitumen at a predetermined amount
and optionally at least one chemical additive are mixed for a predetermined
period; in
order to produce RAC from the hot RAP, accumulated in the accumulation
reservoir, as
independently of an asphalt plant.
In a preferred embodiment of the present invention, at least some part of said
inner air
channel comprises parts extending together with the transmission channel so as
to
partly extend substantially parallel to the transmission channel.
In another preferred embodiment of the present invention, a horizontal part
passes
through said inner air channel's accumulation reservoir.
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In another preferred embodiment of the present invention, said inner air
channel
comprises a lower part extending at the bottom part of the body; an vertical
part
extending so as to contact the transmission channel inwardly along a part of
the
vertical edge of the body at the continuation of the lower part; a horizontal
part
extending substantially horizontally at the continuation of said vertical
part; and an
output part which extends at the continuation of the horizontal part so as to
connect the
inner air channel to the outer air channel.
In another preferred embodiment of the present invention, in order to provide
the hot air
exiting from the outer air channel to be transferred to the body inner volume
again, an
intermediate connection part is provided which connects the output of said
outer air
channel to a heating reservoir formed at the inner volume of the body.
In another preferred embodiment of the present invention, said heating
reservoir
comprises at least one first and one second directing wings extending on said
heating
reservoir body inner volume.
In another preferred embodiment of the present invention, the first directing
wing
comprises a flat part at least extending along a part of the diagonal edge of
the body so
as to have a certain distance in between.
In another preferred embodiment of the subject matter system, said second
directing
wing which extends beginning from a point substantially at a lower alignment
of the first
directing wing and which extends up to the vicinity of the lower alignment of
the
accumulation reservoir base.
In another preferred embodiment of the subject matter system, a bitumen
feeding unit
is provided which is controlled by the automatic control system and thanks to
this,
which transfers new additional bitumen to the mixer in desired times and in
desired
amounts.
In another preferred embodiment of the present invention, at least one
chemical
feeding unit is provided which is controlled by the automatic control system
and thanks
to this, which transfers chemical additive to the mixer in desired times and
in desired
amounts.
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In another preferred embodiment of the subject matter system, a directing unit
is
provided which directs the material exiting from said mixer to the RAC silo or
to an
asphalt plant.
In another preferred embodiment of the subject matter system, said directing
unit
comprises at least one silo output, at least one asphalt plant output and at
least one
flap which closes the silo output or asphalt plant output as responsive to the
commands
of the automatic control system.
In another preferred embodiment of the subject matter system, in order to
prevent the
RAP, which is heated and which becomes adhesive, from plastering to the inner
walls
of the transmission channel, said transmission plates have dimensions so as to
advance by contacting substantially to the inner wall of the transmission
channel.
In another preferred embodiment of the subject matter system, the subject
matter
system is operated independently from the asphalt plant and, the RAC, which is
to be
used in the production of bitumen base, is produced.
In another preferred embodiment of the subject matter system, in case of
cooperation
with asphalt plant; the RAC is produced which is to be used in the production
of
abrasion layer or binder.
The subject matter invention is a hot asphalt recycling method applied in
order to
obtain RAC by using RAP, where the RAP is to be used in the production of one
of the
asphalt layers by using RAP, characterized by comprising the steps of:
a) Providing a body with a closed volume which is thermally and substantially
insulated from the outer environment,
b) advancing the RAP inside a transmission channel extending in a direction so
as
to define at least three corners inside said body,
c) during said advancing process, circulating the hot air obtained from a hot
air
supply inside the inner volume of the body so as to provide heat transfer to a
certain part of the RAP inside the transmission channel,
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d) Circulating the hot air along the outer circumference of the body so as to
provide heat transfer to a certain part of the RAP inside the transmission
channel,
e) Circulating the hot air by directing the hot air inside the body so as to
provide
heat transfer to the RAP directly and indirectly,
f) Circulating the heated RAP inside the body so as to direct the RAP to the
accumulation reservoir, where the RAP is accumulated,
g) Transferring the hot RAP inside the accumulation reservoir to a mixer at a
predetermined arrangement,
h) Transferring new additional bitumen and optionally at least one chemical
additive to said mixer at a predetermined arrangement,
i) Mixing the hot RAP material, new additional bitumen and optionally
at least one
chemical additive for a predetermined duration inside the mixer and
discharging
this mixture to the desired outer environments.
In another preferred application of the subject matter method, in said step
(c), the hot
air is partly circulated at the vicinity of the transmission channel so as to
be
substantially parallel to the transmission channel.
In another preferred application of the subject matter method, in said step
(c), hot air is
passed through the accumulation reservoir.
In another preferred application of the subject matter method, in said step
(e), hot air is
circulated so as to advance along a certain part of the diagonal edge of the
body.
In another preferred application of the subject matter method, with respect to
the
operation options with or without asphalt plant, in said step (j), the
material exiting from
the mixer is directed to a silo or an asphalt plant.
In another preferred application of the subject matter method, in case of
operation
independent of the asphalt plant, the RAC material which will form the bitumen
base is
produced.
In another preferred application of the subject matter method, in case of
cooperation
with the asphalt plant, the RAC material which will form the abrasion or
binder layer is
produced.
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The structural and the characteristic features and all the advantages of the
subject
matter invention can be understood more precisely by means of the detailed
explanation which is written with references to these figures and therefore,
it had to be
evaluated with the detailed explanation and figures that are explained below.
BRIEF DESCRIPTION OF THE FIGURES
Figure 1 is a representative view of the system where the subject matter
asphalt
recycling system is applied.
Figure 2a is the solo perspective view of the subject matter asphalt recycling
system.
Figure 2b is the perspective view of the inner structure of the subject matter
asphalt
recycling system.
In Figure 3a, 3b, 3c and 3d, the views regarding the inner structure of the
subject
matter asphalt recycling system is given.
In Figure 4a and 4b, representative views regarding the operation of the
subject matter
asphalt recycling system with and without asphalt plant are given.
REFERENCE NUMBERS
10 Loading unit
11 Aggregate silo
12 Cold RAP silo
13 Band conveyor
14 Vertical elevator
20 Body
21 Transmission channel
211 Line end
22 Heating reservoir
221 First directing wing
222 Second directing wing
23 Transmission line
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231 Transmission plates
232 Chains
233 Chain gears
24 Outer air channel
241 Air inlet pipe
242 Vertical part
243 Diagonal part
244 Lower part
245 Upper part
246 Interconnection part
247 Air output pipe
248 Transmission pipe
25 Inner air channel
251 Lower part
252 Vertical part
253 Horizontal part
254 Output part
26 Accumulation reservoir
261 Hot RAP outlet
27 Discharge unit with loadcell
28 Feeding inlet
Bitumen feeding unit
Chemical feeding unit
Mixer
25 60 Directing unit
61 Silo outlet
62 Asphalt plant outlet
63 Flap
70 Hot air generator
30 71 Filter
80 RAC silo
90 Asphalt plant
91 Plant mixer
100 Hot RAP material
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THE DETAILED DESCRIPTION OF THE INVENTION
In this detailed explanation, the subject matter hot asphalt recycling system
is
explained with references to figures without forming any restrictive effect in
order to
make the subject more understandable.
With reference to Figure 1, hot air required for the subject matter hot
asphalt recycling
system (hereafter it will be called RS) is preferably provided by a hot air
generator (70)
which is preferably a burner. In this application of the subject matter
invention, air
which is provided by the hot air generator (70) and which is at 650 C
temperature is
decreased to 400-450 C by means of the air cooling system at the output of hot
air
generator (70). The hot air is given to RS from here by means of an air inlet
pipe (241).
Depending on the outer environment conditions, the temperature of the hot air
advancing along the air inlet pipe (241), which is directly in contact with
the outer
environment, decreases until it reaches the RS inlet, for instance, in a
preferred
application, the air entering the RS has a temperature between 390-440 C.
The cold RAP material which will be processed in RS and the additional
aggregate
which is to be mixed with cold RAP material are transferred to the RS by means
of a
loading unit (10). At said loading unit (10), there is at least one additional
aggregate silo
(11), at least one cold RAP silo (12), a band conveyor (13) which is
positioned under
said silos (11, 12), and an vertical elevator (14) which is positioned at the
end of the
band conveyor (13). Said silos (11, 12) have dosaged feeding units (not
illustrated in
the figure) which are controlled by the automatic control unit of the RS.
Thanks to this,
with respect to the cold RAP and additional aggregate proportions which are to
be used
in the mixture determined by the methods whose details are given below,
automatic
control unit adjusts the amount of material to be transferred to the band
conveyor (13).
For instance, if 70 % RAP material and 30 % aggregate are to be used in the
mixture,
the dosaged feeding units of the RAP silo (12) and the aggregate silo (11)
function with
respect to these proportions, and thanks to this, material is fed to the band
conveyor
(13) with desired proportions continuously. As a result, the material on the
band
conveyor (13) is elevated to the feeding inlet (28) on the upper edge of the
RS by
means of said vertical elevator (14) and the material is transferred to the
RS.
With reference to Figure 2a, the end part of the lower corner of the RS has a
cross
section like a cut vertical triangle and it comprises a body (20) with a heat
insulated
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closed volume. The heating process of the RAP material is realized in said
body (20).
Accordingly, the hot air which enters into the body (20) through the air inlet
pipe (241),
preferably through a lateral surface of the body (20) is transferred to the
cold RAP
which is circulated inside the system in an efficient and homogeneous manner,
and at
the end of the process, the hot air is transferred to a filter (71) by means
of an air
output pipe (247) and from there, the hot air is transferred to the
atmosphere. For
instance, in a preferred embodiment, the air temperature which is between 390-
440 C
at the inlet (241) decreases down to approximately 150-190 C at the air output
pipe
(247).
With reference to Figure 3a and 3b, the RS has a transmission channel (21)
which
extends along the inner periphery of the body (20) and which preferably has a
hollow
rectangular cross-section. Said transmission channel (21) is ended (211) with
the base
part becoming open at a point close to the middle of the upper edge of the
body (20),
thus, the carried RAP material is accumulated in an accumulation reservoir
(26) formed
inside the body (20). Said accumulation reservoir (26) preferably has a cross
section
like an inverse trapezoid which substantially extends downwardly from the
upper part of
the body (20).
In more details, with reference to Figure 3b and 3c, there is a transmission
line (23)
inside the transmission channel (21), which circulates the cold RAP entering
into the
RS and which meanwhile provides the RAP to be subjected to heat as detailed
below.
Said transmission line (23) has a plurality of transmission plates (231) which
are
positioned one after another so as to have a certain space in between and
which are
positioned inside the transmission channel (21) so as to be substantially
perpendicular
with respect to the extension direction of the transmission channel (21).
Thus, the RAP
material which is advanced by the transmission plates (231) is circulated
inside the
transmission channel (21).
Said transmission plates (231) have dimensions so as to substantially contact
with the
inner wall of the transmission channel (21). Thanks to this, during
circulation the
transmission plates (231) strip the inner wall of the transmission channel
(21)
continuously, thus they strip the deeply drawn RAP which becomes adhesive as a
result of the temperature, and they particularly strip the bitumen from the
wall, thus, the
accumulation of the bitumen on the wall is prevented and thereby the
inefficiency in
heat transfer is prevented. Thanks to this characteristic, the problem of
decrease in
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heating efficiency as a result of adhesive RAP is eliminated, which is one of
the biggest
handicaps in the previous systems. Said transmission plates (231) are
preferably
connected onto chains (232) and said chains (232) are connected to chain gears
(233)
where each one is positioned to one corner of the body (20). Thus, when the
chain
gears (233) are rotated by means of a drive mechanism with a reducer (not
illustrated
in the figure) and by means of an electric motor which is controlled by the
automatic
control unit of the RS, the transmission line (23) begins moving inside the
transmission
channel (21). On the other hand, in alternative embodiments, different drive
systems
can also be used.
Again with reference to Figure 3b and 3c, the asphalt which is poured from the
end of
the vertical elevator (14) to the feeding inlet (28), and the cold RAP which
is transferred
to the transmission line (23) preferably by means of an asphalt feeding screw
(not
illustrated in the figure) are moved along the transmission channel (21), at
the end of
the transmission channel (21), they are discharged to the accumulation
reservoir (26),
from there they are transferred to a discharge unit with loadcell (27) from
the hot RAP
output (261) of the accumulation reservoir (26). In more details, in times
determined by
the automatic control system, the valve (not illustrated in the figure) at the
hot RAP
outlet (261) is opened and thus the hot RAP is poured to the discharge unit
with
loadcell (27). When the amount of hot RAP poured to the discharge unit with
loadcell
(27) reaches a certain weight (for instance 1750 kg), it is poured to the
mixer (50). Said
weight amount is defined in the memory of the automatic control system by
being
predetermined with respect to the asphalt type desired to be produced and with
respect
to similar variables.
In order for the abovementioned RS to be used in the production of at least
bitumen
base and moreover in the production of other asphalt layers without depending
on an
asphalt plant (90), the hot air provided by the hot air generator (70) should
be
transferred to the RAP, which is carried in the transmission channel (21), by
indirect
heating in the most efficient manner so as not to give damage to the
structural
properties of the bitumen. With respect to this, with reference to Figure 2b
and Figure
3a, the circulation of the hot air inside the RS body (20) so as to be in
correlation with
RAP is provided by means of particularly designed outer and inner air channels
(24,
25).
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Accordingly, the air inlet pipe (241) is connected to an inner air channel
(25) which is
embodied on the inner volume of the body (20). Said inner air channel (25)
comprises
a lower part (251) which is positioned at the lower part of the body (20) and
which has
a U like cross section; an vertical part (252) which extends so as to contact
with the
transmission channel (21) inwardly along a part of the vertical edge of the
body (20) at
the continuation of the lower part (251); and a horizontal part (253) which
essentially
extends horizontally so as to pass through the accumulation reservoir (26) at
the
continuation of said vertical part (252); and an output part (254) which
extends at the
continuation of the horizontal part (253) in order to connect the inner air
channel (25) to
the outer air channel (24). Thanks to the special design of said inner air
channel (25),
the distance the hot air advances inside the body (20) is maximized and during
this
circulation, maximum heat transfer is provided to the transmission channel
(21) and
thus to the RAP.
The air exiting from the inner air channel (25) is transferred to the outer
air channel (24)
by means of a transmission pipe (248). Said outer air channel (24) extends
along the
outer periphery of the body (20) so as to contact with the transmission
channel (21)
outwardly at each point thereof. In more details, said outer air channel (24)
essentially
comprises an upper part (245) which extends along the upper edge of the body
(20) by
beginning from the region where the accumulation reservoir (26) begins; a
diagonal
part (243) which extends along the hypotenuse edge of the body (20) at the
continuation of the upper part (245); a lower part (244) which extends along
the short
edge of the body (20); and an vertical part (242) which extends along the
vertical edge
of the body (20). With reference to Figure 2b and 3d, at the continuation of
the upper
part (245), there is an interconnection part (246) which extends parallel to
the ground
on the exterior of the lateral surface of the body (20) and which opens to a
heating
reservoir formed at the inner volume of the body (20) from the other end
thereof. Thus,
the hot air exiting from the outer air channel (24) is again transferred to
the heating
reservoir (22) in the opposite side.
Said heating reservoir (22) is defined by the first and second directing wings
(221,
222). The first directing wing (221) extends so as to begin from the end of
the
transmission line (23) and so that there is a certain distance in between
along the
diagonal edge of the body (20). The second directing wing (222) extends to the
lower
alignment of the base of the accumulation reservoir (26) by beginning from a
point on
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the diagonal edge of the body (20) and it extends at a substantially lower
alignment of
the first directing wing (221).
In more details, the first directing wing (221) has a curved part extending in
a convex
illustrated with arrows in Figure 3a and 3d, where hot air enters the body
(20) through
the air inlet pipe (241), it advances inside the body (20) along the inner air
channel
(25), afterwards it advances along the outer air channel (24), afterwards it
is directed
towards the heating reservoir (22) into the body (20), it moves inside the
heating
As a result, thanks to the particular design of the inner air channel (25) and
thanks to
the particular design of the outer air channel (24), much more efficient heat
transfer can
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In order to provide this, in the subject matter invention, in addition to the
abovementioned improvements, there is a mixer (50) at the lower alignment of
the
discharge unit with loadcell (27). In order to obtain the bitumen base, in
addition to the
hot RAP (100) exiting from the RS, additional new bitumen and when required, a
plurality of chemical substances (for instance, abrasion-preventive chemical
substances) which will improve the characteristics of the material should be
added to
the mixture. Therefore, a bitumen feeding unit (30) and a chemical feeding
unit (40)
transfer additional bitumen and chemical additives respectively in
predetermined
periods to said mixer (50). Thus in the mixer (50), hot RAP, new bitumen and
optionally
a mixture comprising the chemical additive are mixed for the desired duration.
Both the
bitumen feeding unit (30) and the chemical feeding unit (40) preferably
comprise one
each proportional pump (not illustrated in the figure) which is controlled by
an
automatic control system. Accordingly, prior to the process, the amount of
bitumen
and/or chemical substance to be added to the mixture is determined in the
memory of
the automatic control system and accordingly, the proportional pumps (not
illustrated in
the figure) are controlled.
On the other hand, the subject matter invention can be used together with an
asphalt
plant (90) when particularly binder or abrasion layer is desired to be
produced, thanks
to this, said asphalt layers can be produced by the asphalt plant (90) using
the
maximum possible proportion of RAP. Accordingly, at the output of said mixer
(50),
there is a directing unit (60). The directing unit (60) has at least one RAC
silo outlet
(61) and at least one asphalt plant outlet (62), and a flap (63) whose
movement is
controlled by the automatic control system closes one of these outlets (61,
62)
according to the condition. In other words, when bitumen base is desired to be
produced by operation independent of the asphalt plant, since only RS will be
used, the
asphalt plant outlet (62) is closed and the material exiting the mixer (50) is
directly
transferred to the silos (80) directly through the silo pipes. When binder or
abrasion
layer is desired to be produced by operating RS together with the asphalt
plant, this
time, the material exiting the mixer (50) is subject to additional processes,
and this
material is transferred to the asphalt plant's mixer (91) through the plant
pipe.
The RAC which is to be used in asphalt layers is desired to have certain
characteristics. These specifications are determined in national or
international norms
and these specifications also apply to the asphalt concrete (RAC) which is to
be
produced from RAP by means of RS.
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In order to produce RAC without using RAP in the asphalt plant, a plurality of
laboratory
studies should be realized beforehand, and accordingly, first of all, the
properties of
aggregate and bitumen which are the raw materials used in production should be
determined and accordingly, a mixture recipe should be prepared which will
meet the
performance properties of the asphalt layer in optimum level which is desired
to be
produced under certain process conditions. Different methods are used in
recipe
preparation; the most frequent method is the Marshall method.
Accordingly, by means of the recipe prepared in the laboratory, the gradation
of the
aggregate, which has certain physical, chemical and geometric properties and
which is
to be used as the raw material is determined which will provide the optimum
performance characteristics (stability, practical-volume specific weight, void
ratio, void
filled with asphalt, VFA and flow criteria) expected from the asphalt concrete
mixture
and the bitumen proportion which will be added to the mixture is determined.
In order to produce RAC using RAP, laboratory study should be realized using
the
same method. Here, the only difference is that, when the abovementioned recipe
is
being prepared, the characteristics of the RAP to be used in the mixture are
taken into
account. The most important factor during the preparation of recipe for RAC is
that the
characteristics like penetration and smoothing point of the bitumen which RAP
comprises are deteriorated because of the effects like fatigue and aging. The
deteriorations in these characteristics are predetermined and these
characteristics are
improved by a plurality of chemical additives and they become optimum.
Naturally, in
RAC production, removed asphalt concrete is used with appropriate
characteristics.
The characteristics of the RAP material determine the usage ratio in RAC
production.
When the characteristics of RAP are better, the usage ratio of RAP material in
the new
mixture is higher. As a result of the studies realized in laboratory,
different recycling
proportions are obtained with different operating conditions. By taking these
values into
account, the subject matter asphalt recycling system is operated by being
adapted to
all of the different operating conditions.
In addition to the abovementioned details, in order to obtain a mixture
appropriate to
the criteria for producing one of the asphalt layers in the mixer (50), the
automatic
control system used in the subject matter invention essentially comprises cold
RAP
material which is to be heated inside the body (20); additional aggregate
amount to be
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added to cold RAP; hot RAP (100) which is to be transferred to the mixer (50);
additional new bitumen to be transferred to the mixer (50); and optionally the
values
regarding the chemical additive amount in the memory thereof; and with respect
to said
values, the subject matter invention controls the cold RAP silo (12),
additional
aggregate silo (11), band conveyor (13), discharge unit with loadcell (27),
bitumen
feeding unit (30) and optionally the chemical feeding unit (40) respectively.
Said control
system moreover controls the advancing speed of the transmission line (23),
the
temperature of the air used in the system, flow rate, the operation process of
the mixer,
and the timings and sequences of the processes mentioned in this paragraph.
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