Note: Descriptions are shown in the official language in which they were submitted.
~ 2190538
PROCESS FOR PROCESSING, STORING, BLENDING AND UTILIZATION OF
RECYCLABLE MODIFIED SHINGLE WASTE ASPHALT IN THE MANUFACTURING
OF HOT MIX
5 Ba.l~
Field of Invention
This invention relates generally to the recycling of plant waste originating in the Illallura~lul~ of
asphaltic roofing shingles. More precisely, the invention relates to processes and apparatus for
preparing this waste to form novel recyclable asphalt materials and for using them as ingredients in
10 asphalt paving compositions.
Prior Art
It is known in the art to use various recyclable materials (recycled asphalt, rubber, glass, fibrous
material etc.) in the manufacture of asphaltic paving ~iunl,uua;livl~ It is known that roofing shingle
waste products comprise materials that would be useful in making asphalt paving mixtures. It is also
15 known that adding dust to the surface of sticky materials may reduce the likelihood that such
materials will A~,h.,n~ when placed together. It is known to use shredders and hammer mills to
reduce materials to smaller chunks or particles. All of the elements of the apparatus rnmhin~ti~n.c
disclosed herein are known with the exception of the modified hammer mill.
It is known that the waste from the Illavura~ of asphaltic roofing shingles has both advantages
20 and diSddVa l~agci~ as a recycled material. Shingle waste is advantageous in that it imcludes resinous,
particulate and fibrous material (a,u~lu~hl~ ly 40% asphalt, 20% cellulose fiber and ~0~/O trap rock
granules) all of which is, in certain l~lu~)ullivlls, compatible with asphalt paving ~nnp~iti-m~ It is
also ~d~a~ eVU~ that such waste material is available in large quantities. Shingle waste is
di~adva ~lageuu~ in that the particulate material, i.e. trap rock, is very abrasive and destructive to
25 rendering tools and the resinous material tends to "gum up" rendering machinerv and to Ag~
previously reduced material (thereby reversing the rendering process). The gumming problem results
when the asphalt resin flows when it is heated, for example, by the frictional energy generated in the
rendering machines and coats the surfaces of the machinery. In summary, it is known that the waste
shingle material is useful in paving Cu~ u~iliulls, but the handling and reducing problems presented
30 by such material have impeded its large scale, commercial adoption.
. , _ . . . . . .. . . .
~ 21~0538
It is an object of the present invention to provide novel processes and apparatus for producing novel
recycled shingle waste products which are capable of being stored and transported and which are
useful in the IllallJrh. lulc of hot mix paving compositions. Other objects, features, and advantages of
the present invention will become apparent upon reading the following description in conjunction
5 with the drawings and claims.
SUMMARY OF THE INVENTION
In this description the following words have these meanings:
shingle waste - waste from roofing shingle m~nllf~tllring plants and the like including
shingles, parts thereof, materials used in the manufacture of shingles and foreign
materials;
modified shingle waste - the product resulting from the first stage of processing in
accordance with this invention wherein the shingle waste is reduced to a~lu~i ud~ly
minus 1/~ inches in particle size;
. recycled asphalt - asphalt paving material that has been removed from a road or the like
for recycling and pulverized or otherwise reduced in size for use in an asphalt plant;
~lullgle/a~llalt/sand mix - a mixture of pre~11 tl~rminr~ quantities of modified shingle
waste, recycled asphalt products and sand.
The present invention includes:
~ a process and novel apparatus for processing shingle waste to make a modified shingle
waste product that is useful as an ingredient in the Illa~lurh,Lul~; of hot mix paving
nf~nnro.~itif-nc
a continuation of the process in which the modified shingle waste product is mixed with
recycled asphalt and/or sand to make a shin~le/a~ àlL/~all.l mix also useful as an
ingredient in the u~ullurd~Lu~: of hot mix paving compositions;
2190~38
further novel apparatus and ~nfiml~ltir~n~ of the process in which prP~f~-min~d
quantities of modified shingle waste, recycled asphalt, sand, aggregate and liquid
asphalt are mixed to form an asphalt paving ~~u~ , and
~ a novel product, namely a ~ .gle/a~lullàlt/sand mix.
5 Stated generally, the process for reducing shingle waste to modified shingle waste comprises:
1. shredding masses of shingle waste into large chunks of~ / minus 4 inches;
2. mixing the large chunks with small chunks OfalJ~Iu~hlla~ly minus I inch and with dust
aggregate of approximately minus 1/4 inches;
3. screening the large chunks, small chunks and dust aggregate on one or more screens to
separate particles Of a,ulJIu~hll~.t~.ly minus 1/4 inch in dimension from over-screen
material of larger dimension;
4. mixing the over-screen material with a sufficient quantity of dust aggregate of minus 1/4
inches to impede ~ggl(m~r~tion
5. passing the mixture of over-screen material and dust aggregate past a magnet to remove
metal;
6. adding water to the mixture of over-screen material and dust aggregate to control dust
and to assist in shredding;
7. shredding the mixture of over-screen material and the dust aggregate to reduce the large
chunks to small chunks of minus 1 inch;
8. returning the small chunks and dust aggregate to step 2 to be mixed with the large
chunks; and
9. continuing the above process steps to produce, in step 3, a desired quantity of screened
minus 1/4 inch particles, hereafter referred to as "modified shingle waste".
~ 2190538
The combination of apparatus for practicing this part of the process of this invention includes a
shredder to reduce the shingle waste to large chunks having a largest dimension of a~ Jl u~ wl~ly 4
inches, a first surge bin to mix the large chunks with small chunks and dust aggregate, a screening
plant having one or more screens to separate particles of a modified shingle waste that pass through
5 the screen(s) with a largest dimension of a~ hllal~ly 1/~ inches from over-screen material that
passes over the screen(s), a second surge bin to supply dust aggregate, an el~ a~l.ct and a
modified hammer mill in which hammers, pivotally mounted on a rotating flywheel within a drum,
are fitted with a pivotally mounted tool. Standard conveyor means may be used to transfer materials
from station to station for processing.
10 It is generally desirable to process the shingle waste at a location remote from an asphalt paving
production plant. In most cases shredding will occur at or near shingle waste storage sites near a
shingle " IA1111 rh~ g plant. These sites will generally have large quantities of shingle waste piled
in storage, randomly mixed and largely Aggl~lmPrAfP~ in masses. Following the first stage of the
rendering process described above, the shredded shingles may be stored in piles and shipped in mass
15 quantities with reduced Aggll~mPrAfion While the dusting during the rendering process reduces the
tendency to agglomerate and the modified shingle waste produced by this process is a useful product,
Agglr)mPrAfion may increase over time. Unless it is used soon after shredding, the modified shingle
waste may clump or stick together making stockpiling, transportation and use difficult. Thus, the
distaulce between the processing site and the asphalt plant that will use the material can be a limiting
20 factor for the use of tbe modif ed shingle waste. In the next stage of the process a novel product of
~h;.~gle/a~ dlt/sand mix is manufactured to address this problem.
This fulther stage of processing in the present invention comprises:
10. mixing a prpdplprminrd quantity of modified shingle waste with a ~Ic~ tr~ ",i", d amount
of pulveri~d recycled asphalt and sand to make a shingle/asphalt sand mix.
25 The pre~PI~rminPd quantities of modified shingle waste, recycled asphalt and sand are set by
reference to quantities of each material on hand and ready for recycling, the malce-up suitable for
easy introduction into an asphalt plant and tlle mixture .1, ..,,. Irl;~ c that will result in reduced
2190~38
~lgglnmPr~tinn and good flowability. Generally, the majority of this mixture by weight will be the
modified shingle waste.
The quantities of materials on hand for recycling may affect the ~nmpncitinn of the mixture. For
example, if there was no recycled asphalt available, the mixture may be made with only modified
S shingle waste and sand. In this case the l~lGd~l~~ ~ ~ I 81~ d quantity of recycled asphalt in the mix would
be CC/o. Good results can be obtained with sand without recycled asphalt, and this mixture is a
preferred Glllbod;lllGIl~ Recycled asphalt is added to the mixture to dispose of it, but flovvability is
believed to be obtained primarily from sand in the mix. The mixture can be useful without sand,
however, and with recycled asphalt. In that case the ~ r~ d quantity of sand would be 0%.
10 The factor of easy introduction into an asphalt plant may be explained as follows. An asphalt plant
may wish to introduce a certain percentage of recycled fiber in the resulting hot mix. Assuming that
the modifed shingle waste contains about 20% fiber, the mixture of modified shingle waste and
recycled asphalt and samd may be balanced so that the quantities of this mixture introduced in the
asphalt plant will introduce the correct amount of fiber into the hot mix.
In preferred ~mhn~1imrnfi the shingle/asphalt/sand mixture is in the range of about 50% - 80%
modified shingles and 50% - 20% recycled asphalt and sand. It is preferred to have a sufficient
quantity of sand to obtain good flowability of the mixture which may be determined empirically. It
is preferred that the sand be minus 1/477 and be a washed classified sand.
The resulting ~hill~;lc/~hdlt/sand mix can be stored and transported without the risk of significant
20 ~lnmPr~tinn The addition of this process step of blending the rnodified shingle waste with
.lr,lft..,.,;,.~d quantities of sand and recycled asphalt obtains a significant advantage. Now,
different blends of modified shingle waste, recycled asphalt and sand cam be made to produce various
shingle/asphalt/sand mixes at a location where the necessary reduction and mixing equipment can be
Pet~hlichP~ near an appropriate source of supply of raw materials. These various25 :,I.h.~lc/~hillt/sdnd mixes can be stored umtil required and then shipped to plants for the production
of different paving rnmpn~itinnc These plants may be at remote locations where it would be
impr~nti~:lhleor~".c."~.""~.,.ltoestablishthereductionandmixingequipment.
~ .. .. , .. . , .. ... .. . .. ..... . .. . . .. ...... ..... .. . . ... . . ~
~1 ~19~53~
The apparatus for combining the modified shingle waste with recycled asphait includes a first hopper
to contain a batch quantity of modified shingle waste and having a controllable discharge means to
regulate the discharge of modified shingle waste to a ~Irfl~lr"";,.Pd amount; a second hopper to
contain a batch quantity of recycled asphalt and having controllable discharge means to regulate the
S discharge of recycled asphalt to a 1" r~l f t~ 'd amount, a third hopper to contain a batch quantity of
sand and having controllable discharge means to regulate the discharge of sand to a plrfif t~ ,.,i.,Pd
amount and a conveyor belt including a belt weigh scaie to receive and convey the discharged
modified shingle waste, recycled asphalt and sand, i.e., the ~hi~ llàll/~fllld mix, to storage or
llal~lJulLaliull means. These hoppers and discharge control mfrhslnicmc, including computer
10 controls, conveyors and belt scales, are within the state of the art and will not be described in further
detail.
Both the modified shingle waste and the ~I.hl"lc/f ~LàlVsand mix may be introduced alone, or
together, into a hot mix ..,-".r~ ~..,i..g process to maice paving ~f)mpn~ition~ Three distinct
production apparatus are involved, namely a conventional batch plant operation, a conventional drum
15 mixer operation and a novel batch plant custom blend operation.
In a collv~lltiulldl batch plant operation, the process of this invention continues with a process for
, . .~. " . ri., 1-,, i . .,, asphalt paving composition comprising the steps of:
I l. introducing at least one of a ~ Plrl .,.i,.Pd amount of modified shingle waste and a
preflr tr rminf d amount of shingle/asphalVsand mix to form a recycle mixture;
12. shredding the recycle mixture to minus I inch;
13. combining the recycle mixture with prPfl- tf rminPfi quantities of heated virgin aggregate
to form a feed mixture;
14. introducing a controlled amount of liquid asphalt into the feed mixture to complement
the asphalt in the recycle mixture such that the total asphalt in the feed mixture reaches
a ~ k t~ , . , ;, .~d portion of the feed mixture; and
15. mixing the heated virgin aggregate, the recycle mix, and the liquid asphalt to form an
asphaltic hot mix paving f f~mpf~itif)n
~9Q~
It will be appreciated by those skilled in the art that an operator may choose to add other recycle
materials in addition to those specified in step 11. For example, the operator may also add recycled
asphalt pavement at this stage to the recycle mixture. Steps 11 and 12 may be practiced at ambient
It~ alulc thereby permitting the use of many materials that would not be useful if introduced
5 through the dryer.
A conventional drum mixer operation comprises a drum mixer into which liquid asphalt cement and
virgin aggregate supply are mixed and heated to form a paving composition. In the process of this
invention, modified shingle waste and/or a shingle/asphalt/sand mix is added to the drum mixer in
~lrJ~t~ l quantities to produce a desired paving composition. The paving composition thus
10 manufactured can be stored in asphalt storage silos or asphalt surge bins. Each silo or bin may store
a different type of paving composition which has been custom blended with particular quantities of
virgin aggregate, modified shingle waste, ~h~.gle/a~l.alt/sand mix and asphalt in the drum mixer.
The batch plant custom blend operation is a novel cnmhin~tinn of apparatus similar to the
conventional batch-plant described above, but with the addition of hoppers containing modified
15 shingle waste amd shinglc/d~Jlldll/~alld mix and/or other recyclable materials for introduction at
ambient temperature. Each hopper has a controlled discharge means for dispensing a ~JlrJr~r~ .J
quantity onto a conveyor belt, which is then transported by the conveyor to a sbredder where it is
reduced and mixed, and discharged onto a conveyor for introduction into an aggregate hopper of the
batch-plant operation. The control of the mixture introduced into the plant is determined at the
20 hoppers and These modifications to the conventional batch plant permit it to nl~lurd~,lulc, in
sequence without shutdown, different types of paving compositions by altering the amount of
modified shingle waste and shingle/asphalt/sand mix in the composition of ingredients making up the
paving ... ,, . ,~
The custom blend batch plant operation has been designed to allow for the addition of any material,
25 at ambient temperature, to the mix. This plant design is used for materials which cannot be heated by
means of a rotary dryer. Instead, thcse materials are heated by mixing them with heated aggregate
which has passed through a dryer. The elevated temperature of the aggregate raises the tcl~ lalul~
of such materials so that the final mix temperaturc meets the required specifications for a hot mix
operation. The process permits an operator to vary l,,upo.~ s on a batch by batch basis in
.. .. .. ... . . . .. . .
=
~ 2190~38
sequential hot mixes to meet all spe~ifi~fions for normal paving compositions in regular operations
or for testing mix designs and materials.
The process may include, in addition to the materials described above, any flowable material which
is compatible with hot mix paving ~,UllllJO~ iUll~. Existing asphalt batch plants are designed to allow
5 only one specific recycled material or blend of recycled materials to be introduced by means of a
recycled material conveyor. The custom plant allows for more than one type of material, in any
proportion, or custom blend to be added on a batch to batch basis. The process is also easily adapted
to fully automatic computer control.
Iû Brief Description of the Drawings
In the figures illustrating a preferred embodiment of this invention:
Figure I is a schematic diagram of the process and apparatus for reduction of the shingle waste to
modified shingle waste,
Figure 2a is a schematic view of a conventional hammer mill;
15 Figure 2b is a schematic view of an improved hammer mill of this invention;
Figure 2c is a schematic perspective of a modified hammer mill of this invention;
Figure 3 is a schematic diagram of a process amd apparatus for blending modified shingle waste with
pulverized recycled asphalt and sand;
Figure 4 is a schematic diagram of an asphalt plant using the modified shingle waste of this
20 invention;
Figure 5 is a schematic diagram of a drum mixer asphalt plant using the modified shingle waste of
this invention and
Figure 6 is a schematic diagram of an asphalt plant adapted with dispensing apparatus to use
modified shingle waste and recycled asphalt in various mixes.
S 2190538
Description of the Preferred li' ' ~.-' '
Figure I shows a preferred Gllll)OdilllCllt of a process and apparatus to reduce shingle waste into a
modified shingle waste of this invention. Shingle waste I is fed into a Norkot MaxigrindTM shredder
2 that is sized to reduce the shingle waste to minus fouT inch chunks, i.e. "large chunks". The large
chunks discharge onto a conveyor 3 and are transported to a suTge bin 4. Within the surge bin 4, the
large chunks are mixed with returning small chunks (sized at minus one inch) and dust aggregate
(minus l/~ inch) from a hammer mill 10. The mixtuTe of material comprising large chunks, small
chunks and dust aggregate is discharged onto and transported by a conveyor 5 to a screening plant 6
for separation. In the screening plant 6, the material is first screened by a large mesh screen (not
shown separately) and the material passing through the large screen is then screened by a smaller
mesh screen (not shown separately) to allow minus one quarter inch particles to pass through the
lower screen. These minus one quarter inch particles are the modified shingle waste 15, which is a
novel product of this invention. It is advallLa~Guu~ to screen the minus one quarter inch material
before the hammer mill 10 because much of the highly abrasive trap rock in shingle waste is of this
size. Its early removal 5llh~t~nti~11y reduces the wear on the hammer mill 10.
The material passing over the screens (hereafter Ihe "over-screen material 16") is transferred,
preferably by a conveyor belt (not shown), to a hammer mill 10. During this transfer to the hammer
milllO,theover-screenmateriall6receivesaprP~1~t~rrnin~dquantityofminusonequaTterinchdust
aggregate 17. Water is added before and in the harnmer mill 10 to control air borne dust and to
facilitate the shredding process in the hammer mill 10. This dust aggregate 17 is stored in a surge bin
7anddischargedonto,andtransportedby,aconveyor8ataul~,1rlrl.,,,,l~drate Itisthendischarged
from conveyor 8 onto the over-screen material 16. The rate of passage of the over-screen material 16
and the rate of the discharge of the dust aggregate 17 determme the proportions of the mixture. The
over-screen material 16 and dust aggregate 17 are then transferred past a magnet 9 to remove metal
and then discharged into a hammer mill 10 to reduce it to small chunks (minus one inch) and to mix
the small chunks with the dust aggregate 17. This harnmer mill product 18 of small chunks and dust
aggregate is then discharged onto a conveyor (not shown) and transported to the surge bin 4 to be
mixed with the large chunks as described above. The process continues to produce a desired quantity
of screened modified shingle waste 15.
219~38
A modified hammer mill 10 with improved hammers is disclosed for reducing the shingle waste.
The modifications may be explained in the context of a conventional hammer mill lOa which is
illustrated in Figure 2a. A conventional hammer mill lOa has an inlet chute 19, a plurality of
hammers 20 pivotally mounted on pins 21 about the face of a rotor 22 mounted on a rotor shaf 23
within an upper concave 24a and a lower concave 24b, the latter having a sizing screen 25 and a
plurality of cutting bars 26. Rotor shaft 23 is driven by a motor (not shown) to tum the rotor 22
causing the hammers 20 to swing around to smash and shred materials against the cutting bars 26.
The sizing screen 25 pemmits materials that have been reduced to a pr~(lPf~rmin~d size to pass
through and exit the hammer mill to a conveyor 27. The lower concave 24b is hinged to allow
oversized materials to pass to exit through the upper concave 24a onto the conveyor 27 without
damaging the mill 1 Oa.
Conventional hammer mills may be used to process shingle waste, but the extremely abrasive trap
rock in the shingles quickly erodes the hammers 20 and it is difficult, if not impr~cihl~, to maintain a
desired tolerance between the cutting bars 26 and the hammers 20 to control the size of the reduced
materials.
A modified hammer mill of this invention is illustrated in Figures 2b and 2c. It too has an inlet chute
119,apluralityofhammersl20pivotallymountedonpinsl21aboutthefaceofarotorl22moumted
on a rotor shaft 123 within an upper concave 124a and hinged lower concave 124b. The hammers
120 may be mounted altemately on either side of the plurality of rotors 122 to fully sweep the
interior of the mill. In the modified hammer mill, the hammers 120 are reshaped to attenuate (rather
than flaring out) from the mounting pin 121 to a cutting tool mount 128 having a cutting tool 129. In
preferred embodiments of this invention, tungsten carbide cutting teeth are used for the tools 129.
The hardened tools 129 wear slower and maintain tolerances longer than the original hammers 20.
Water jets (not shown) may be positioned to spray the tools 129 during processing to cool the tools
129, to reduce erosion of the tool surfaces and to reduce air borne dust in the mill. The hammer mill
10 has a screen plate 125 elevated over the lower concave 124a to replace the cutting bars 26 of the
original hammer mill. The shredding of materials happens between the tools 129 and the screen
plate 125. The screen plate 125 is aligned to and spaced from the turning circle of the ~ools 129 by a
prP~I~f~rmin.-d distance which is set by means of screen bolts 131 and lower concave adjustment
~ 219~S38
screw 133 to produce a desired si~ of shredded materials. Screen plate 125 is perforated with a
plurality of holes, preferably round and diamond shaped.
Figure 3 illustrates the process and apparatus for combining the modified shingle waste 15 with
recycled asphalt 30 and/or sand 31. In this process step the modified shingle waste 15 resulting from
S the above process is blended with recycled asphalt 30 and/or sand to make a shinglc/a~halL/~a..d mix
32. rPhe apparatus includes a means for L~ lhlg the modified shingle waste, for example a
loader lSa, to a first hopper 33 having a controllable discharge means 33a (computer controls permit
pr--grRmmRhle and remote control) to regulate the discharge of modified shingle waste to a
pr~ rmin~d flowrate; a means for Llal~ n Ling the pulverized asphalt, for example a loader 30a, to
10 a second hopper 34 to contain the recycled asphalt 30 and having similarly controllable discharge
means 34a to regulate the discharge of recycled asphalt 30 to a ~ l dl l d flowrate; a means for
O~ g the sand 31, for example a loader 31a, to a third hopper 35 to contain the sand 31 and
having similarly controllable discharge means 35a to regulate the discharge of the sand 31 to a
prc~ rmin~d flowrate and a conveyor belt 37 to receive and transport the discharged modified
15shingle waste 15 and recycled asphalt 30 and sand 31, having a belt scale 38 to weigh the resulting
mixture which, as noted above, will be referred to as the shingle/asphalt/sand mix 32.
The modified shingle waste 15 and the ~h ugle/a~ dlt/sand mix 32 may be introduced into hot mix
,r.. I-l,;l,g processes to make paving compositions in three distinct ways, in a conventional batch
plant operation illustrated in Figure 4, in a drum mixer operation illustrated in Figure S or in a batch
20 plant custom blend operation illustrated in Figure 6.
A conventional batch-plant operation 40 fo} 111~..111~;1. 1, ~. ;"g asphalt paving compositions is shown in
Figure 4. Ordinarily the lllallurd~,Lul~ comprises the steps of:
1. supplying to a dryer 41 ~lr~lrlrl I l l; l ll'~l quantities of virgin aggregate 42 from hoppers 43
discharged onto a conveyor 44 fitted with a belt scale 45;
252 heating the virgin aggregate 42 in the dryer 41 and discharging it onto a conveyor, such
as a bucket elevator 46;
21g~38
3. disllla~ lg the heated virgin aggregate 42 onto screens 47 for separation by particle
size into a plurality of plant temporary storage bins 49;
4. controlled discharge in pre(lptprrnin~d quantities from the plant temporary storage bins
49 into an aggregate hopper 50 and then into a pugmill 51; ar d
5. adding liquid asphalt cement 52 to such pugmill 51 in ~.l r~ d amounts regulated
by an asphalt weigh bucket 53.
In &is invention, the conventional batch plant 40 is adapted by the following process steps and
associated apparatus to use modified shingle waste 15 and/or ~I h.~le/d~lul.alt/sand mix 32:
1. mixing pre~tf~rrnin~l quantities of modified shingle waste 15 and pre~f.~tl rrnin.o.
quantities ~I inglc/a~,lldlt/sand mix 32 in a plant surge bin 54;
2. di~uLal~,illg the mixture 55 of modified shingle waste 15 and ~I hlglc/a~lulldlVsand mix
32 onto a conveyor 56 and transporting same to a shredder 57;
3. shredding the modified shingle waste 15 and shingle/asphalt/sand mix 32 to a size of
minus I inch;
4. ilall~lJullillg the shredded material 58 into the aggregate hopper 50 to be mixed with the
virgin aggregate supply 42 and ~ rh~rging the resultant mixture into the pugmill 51;
5. adding liquid asphalt 52 to the pugmill 51; and
6. mixing the liquid asphalt 52, shredded material 58 and virgin aggregate supply 42 for a
,UI~ f t 1111 i ~ d time in the pugmill 51 lo fomm an asphalt paving Culllpo~iliull~
20 Altematively, the shredded material 58 may be fed from the shredder 57 and discharged onto the
bucket elevator 46 onto virgin aggregate 42 being discharged from the dryer 41. This alternative
process, however, has the di~ad~allta~;~ that the asphalt resin in the shredded material 58 may tend to
clog the bucket elevator 46, and the plant elements above the pugmill 51. It becomes a problem
when the shredded material 58 is stored in an asphalt tower for a long period of time.
nn-~o
V~ O
The .,ùllv~llLiuual drum mixer ûperation 60 illustrated in Figure S includes a drum mixer 61 which is
fed with virgin aggregate 62 frûm feed hûppers 63 by means ûf a cûnveyor belt 64 equipped with a
belt scale 65 and with liquid asphalt 66. In this invention, the drum mixer 61 may also receive
pre~Pt~rminPd quantities ûf shingle/asphalt/sand mix 32 supplied from a hopper 66 which discharges
the shingle/asphalt/sand mix 32 ontû a conveyor 67 equipped with a belt scale 68. It is then
discharged into a shredder 69 to be shredded to minus I inch particles which are discharged onto a
conveyor 70 to feed them into the mixer 61. The product of the mixer 61 is discharged onto a drag
slat cûnveyor 71, fed into a shuttle conveyor 72 which discharges the product into one or more of the
storage silos 73 for lûading onto trucks (not shûwn).
In the custûm plant 80 shown in Figure 6, modified shingle ~vaste 15 and shingle/asphalt/sand mix 32
and other ~ ;r~l1 materials 100 are stored in and discharged from respective feeder hoppers 81,
82 and 83. The discharge is controlled by weigh scales 81 a, 82a amd 83a at the discharge end of each
hopper. When the last material has been weighed to the desired amounts, all the weighed materials
are fed by conveyor 8~ hllPcll~ly onto conveyor 85 which discharges into a shredder mixer 86.
The shredder 86 reduces the material to minus 1 inch and discharges it onto conveyor 87. Conveyor
87 operates at two different speeds, a slow speed to allow loading of all of the material from the
feeders bins 81-83 before it is required in the plant, and a fast speed to deliver the material quickly to
the plant on demand after the conveyor 87 is fully loaded. Thus there is no delay in the batch plant
operation although different mixes may be put in each batch. The conveyor 87 discharges into the
pugmill 91 by means of the aggregate hopper 90, or directly through a chute 88. If the sequence of
the batch plant is delayed then the plant cr~mp11tPri7Pd controls will stop the conveyor 87 and hold the
material until it is required to complete the batch cycle.
In other words, the process of reducmg shingle waste may be continued from the ~ lura~,Lul~ ûf
modified shingle waste and shingle/asphalt/samd mix to make a variety of paving compositions in a
custom blend plant by the additiûnal process steps of:
a) lla~l~rcll;llg quantities of modified shingle waste 15 to one or more first storage bins
81 and quantities of shin~lcla~uLàl~ d mix 32 to one or more second storage bins82;
~ 219~38
b) di~hal~i..g, from said one or more fi}st storage bins 81, a predetermined amount of
modified shingle waste 15 and rli~rh:~rging from said one or more second storage bins
82, a prP~tPrminP~f amount of shingle/asphalt/sand mix 32 onto a first conveyor belt
84;
c) I,,,,.~rr" ",g, with the conveyor belt 84, pre~PfPrminPd amounts of modified shingle
waste 15 and shingle/asphalt sand mix 32 to a shredder mixer 86;
d) reducing said pre~JPfPrminPd amounts of modified shingle waste 15 and
~I ingle/a~l,l.dlt/sand mix 32 to form a shredded recycle mixture 89 of approximately
minus I inch;
e) diD~,Ldu~ g the shredded recycle mixture 89 onto a second conveyor 87 operating at a
~urCc;~ ly slow speed to allow loading of all of the recycle mixture 89;
f) after di~,hal~illg all of the recycle mixture 89 onto the second conveyor 87, increasmg
the speed of the second conveyor 87 to deliver the recycle mixture 89 to an aggregate
hopper 90 of a batch plant;
g) mixing the recycle mixture 89 with pre~lPtPrminPd quantities of heated virgin
aggregate 92 to form a feed mixture;
h) introducing a controlled amount of liquid asphalt 94 into the feed mixture to
~,. " "~ 1 the asphalt in the recycle mixture 89 such that the total asphalt in the feed
mixture constitutes a prPdPtPrminp~l proportion of the feed mixture;
i) mixing the heated virgin aggregate 92, the recycle mix 89, and the liquid asphalt 94 to
form an asphalt hot mix paving composition; and
j) repeating the process with other prPrl~tPrminPd quantities of modified shingle waste
and ~hillgl~;/a~ àlt; heated virgin aggregate and liquid asphalt.
The description of the preferred embodiments is intended to be illustrative and explanatory of the
25 features of this invention. The full scope of the invention may be understood by reading the whole of
the ~pPrifir.~tifm both disclosure and claims, which follow hereafter.
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