Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02222072 1997-11-24
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A method of preparing and producing asphalt materials to
be laid out as a cold road construction or paving material.
The present invention relates to a method of cold produc-
tion of asphalt materials for a cold laying out as a roadbuilding or repair material.
It is well known that the traditional preparation of as-
phalt for laying out in smoking hot condition is highly en-
ergy consuming and expensive in investment costs of the pro-
duction equipment. It is undeniable that the associated heat-
ing conditions results of high quality, inasfar as the ap-
plied bituminous binder can be based on a bitumen having a
high viscosity at normal road temperatures, but, when heated,
adopts a substantially lower viscosity during the mi~;ng and
laying process, thus making the material shapeable and com-
pressible.
This 'hot' method, however, has noticeable limitations
and drawbacks, not only with respect to the high heat con-
sumption and the large investment costs, but also in that the
method should be seen as a totality in connection with a
given paving work. Since the material cannot be satisfacto-
rily laid out and compressed if the transportation distance
from the factory to the working site or the waiting time at
the laying site is so long that the material is cooled sub-
stantially, the method is sensitive to transportation dis-
tance as well as to irregularities in the laying rhythm.
Another drawback or limitation is that it is difficult or
highly undesirable to prepare minor amounts of material, e.g.
for small repair works.
Finally, it should be mentioned that the "hot" method
does not allow for a production of a high quality material to
be stored for later use with small repair works.
On this background it has been natural to speculate in a
cold preparation of the material, and as known by skilled
persons this is possible in bringing the bituminous binder toa cold stone material in a water emulsified and non-cohesive
condition; by the formulation of the emulsion or by addition
of different substances it is possible to determine when the
CONFIRt~llATION COPY
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emulsion should "break", i.e. render the bitumen particles
adhering to each other and to the stone material under preci-
pitation of the emulsion water. r
However, the method is very sensitive to variations in
5 the laying rhythm, i.e. there will be severe risks that an
already prepared material charge becomes unusable due to the
breaking of the emulsion taking place too early or too late.
An early breaking implies that the material conglutinates
prior to the laying out, whereby it may be difficult or im-
10 possible to lay the material in a satisfactory manner; by a
late breaking, by which the material will be shapeable during
the laying out, the laid out material, until the breaking oc-
curs, will be unstable in response to mechanical influence,
causing deformation of the material layer, and to rain water,
15 which will act to wash out the unbroken emulsion, whereby the
final binding will be inferior to the expected result. Al-
ready during the transportation of the material to the site,
traffic problems may be created owing to the fact that an
initial breaking of the emulsion results in the still unbro-
20 ken part of the emulsion being less viscid due to the water
precipitated from the broken part of the emulsion, flowing
from the vehicle transporting the material, this r~su~lting in
a surface mess of bitumen rich water which is very unpleasant
for car drivers.
On this background it has been endeavoured to adapt the
breaking such that a complete breaking has taken place at the
time the material leaves the mixer, but in these intermediate
solutions it has been necessary to use material fractions
with a content of a bitumen emulsion based on a low viscosity
bitumen, such that the final product will be bound by a bitu-
men that is less hard that achievable by the physically sim-
pler cooling of a high viscid bitumen binder.
With the present invention it has been recognised that
these circumstances may be changed fun~mentally such that an
effective breaking of the cold emulsion may occur in the lay-
ing phase, whether soon or long after the material was pre-
pared.
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In connection with the invention, the "material" is to be
understood as two or at least two material fractions, which
are prepared with latent breaking agents that will, each, be
activated by a mixing together with the other fraction, but
otherwise leaving the material fraction with the binder emul-
sion in a time non-determined, non-actuated condition. These
terms may be relative, inasfar as materials specifically
adapted for use within two months, could well be prepared
such that their emulsions could breake more o less after
three or eight months, should the material not be used as
planned.
According to the invention this may be easily realised in
preparing, for later mixing together, two separate material
fractions with binder emulsions of anionic and cationic type,
respectively. These binder emulsions may each be adapted to
be, over time, practically unlimited actuatable, also so as
to not break by the mixing together with the associated stone
fraction, and each of the two material fractions may thus be
produced to stock, when only they are kept strictly separate.
It is then possible at any time to collect from the stock re-
spective portions of the two types, which, upon a mixing to-
gether that need not be very intensive, may be brought to
laying out whether in connection with larger construction or
renovation works or with more isolated repair works.
It is a known phenomenon that by a contact between re-
spective anionic and cationic bituminous binder emulsions
both emulsions will break, resulting in an actuated binder
with the similar viscosity as the basic bitumen used in the
emulsions, but this knowledge has not earlier been used with
practical advantages should the idea have arised, a conclu-
sion might have been that the reaction would be almost imme-
diate, rendering the mixed material non-shapeable, but in
practice no problems in this respect are observed. It may be
a precaution, however, to seek to slow down the actual break-
ing and hence the speed of coalescence in the laid out mate-
rial, e.g. in using invert emulsions (water in oil).
The advantages achievable by the very simple t~hni que
according to the invention are substantial. As a first sub-
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stantial advantage it is possible, in both types of material,
to use emulsions based on bitumen with a very high viscosity,
such that the resulting binder in the laid out product may be
fully as strong or hard as in hot laid materials; the known
cold laying techniques have had a weakness in just this re-
spect, as it has been required to make at least partial use
of emulsions based on relatively low viscid bitumen, which
has restricted the applicability of these methods.
As already indicated, the new technique will imply that
the asphalt plants are free to run a production to stock,
which can be done by an even production such that the produc-
tion capacity can be adjusted to an average consumption and
not to an acute maximum consumption during separate periods
of time, this implying a much more economic production.
In the same plants or in regional storing places for the
two types of materials, of course, mixing facilities should
be at disposal, operable with a capacity as required during
periods with high consumption of the material to be laid out,
but this equipment may be rather simple; it should be able to
effect a mixing, but the mixing need not be particularly in-
tensive or uniform, because in the laid out material a cer-
tain migration of the anionic and cationic emulsions will oc-
cur. Thus, it is not necessary to use real compulsive mixers,
as a sufficient mixing is achievable already by a current
merging of flows of the two types of materials. As mentioned,
a more homogenous mixing could even have the adverse effect
of accelerating the breaking of the emulsions to such an ex-
tent that a sufficient shapeability was jeopardised.
Something similar may apply to the production of the two
material types themselves. The asphalt plant should not nec-
essarily be equipped with a conventional compulsive mixing
equipment, since for both types of material it will be suffi-
cient to effect a spraying dosing of the emulsion e.g. on a
falling flow of the stone material; when the material is
thereafter stocked without any breaking of the emulsion, the
emulsion may then, gradually, distribute itself over the sur-
face portions of the stones that might be left uncoated by
the spraying, such that the stones may nevertheless be fully
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coated when the time comes to mix the two types of material.
This conditions a significant cost saving in processing
equipment and labour in the asphalt plants.
It should be noted, however, that the stone material will
normally include a fine fraction such as sand, and when the
m~t~rial is pr~essed as ~ere described the fine fraction
will tend to be preferentially coated. For this reason it may
be preferred to effect a conventional homogenous ~;~;ng of
the respective material types, unless the different fractions
are processed individually.
Also to be noted is that the emulsions are liable to un-
dergo some degree of breaking as a result of their contacting
the stone material. Such a partial breaking, which leaves the
material fully shapeable, has the advantage of ensuring that
the stones are durably coated with a cohesive and adhesive
layer of binder.
In periods with high consumption, the collection of the
material from the stock or the storing places can be supple-
mented by a delivery of the material directly from the pro-
cessing equipment of the asphalt plant, inasfar as both of
the material types may be equally usable after storing and
; ?~;~tely after being prepared.
By the traditional "hot" method, as mentioned, a very
good result is obtained, but it is to be noted that the asso-
ciated strong heating is not only highly energy consuming,
but also results in a ductility reducing hardening of the
binder. With the invention this will be totally avoided, and
it is an important result that a paving made in accordance
with the invention may be still stronger than a conventional
hot laid paving, and it may even be more resistant against
weakening by the influence of rain water, inasfar as the ap-
plied emulsions may contain active adhesion agents.
With the invention it is a valuable result that the types
of material may occur as packed in sacks, whereby they can be
mixed to form very small total portions for execution of pro-
nounced small jobs, this so for not having been a realistic
possibility. Hereby the invention may provide for the option
CA 02222072 1997-11-24
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of the two types of material to be sold as sacked products in
various building markets and yet still be applicable for ad-
vanced laying out at a large scale.
It is known to make use of two material fractions that
are mixed together, but in the known art these stone frac-
tions have been coarse and fine, respectively, treated with
the same emulsion of a low viscid bitumen or with respective
emulsions of high and low viscid bitumen. With the invention,
a corresponding disting~ h; ng will not be excluded, but it
is clearly advantageous that it is possible to use the same
stone material for both types of material. This also implies
that the two material types are each "ready", both with re-
spect to their stone contents and their content of bitumen,
and consequently it will be a further possibility that e.g.
for small repair works it will be possible to use but a sing-
le sack of material, e.g. with a cationic emulsion, for the
breaking of which the user may purchase a complementary
breaking agent which is sprayed onto the material.
For obt;7;n;ng particularly good results it will be advan-
tageous to use precoated stones, i.e. stones prepared with a
coating of bitumen by a cold or hot process. Also various ad-
ditives may be used, e.g. some polymers or fibre material
that will stabilise the water against breaking of the emulsi-
on. The use of solvents may be entirely avoided.
With the method can be used almost m7~;m17~ high viscid
bitumen in both emulsions, e.g. with viscosities up to
200.000 mm2/sec. at 60~C.
A noticeable mixing of the emulsions or polymer modified
bituminous emulsions will occur ; mm~ tely by the bringing
together of the two material types as well as by the compres-
sion that is normally effected just after the laying out, and
in most cases the road will be ready to receive both traffic
and rain water as soon as the laying out and the 7-?ch~n;cal
aftertreatment is finished. The breaking and the binding oc-
cur from the very beginning all over the material, from bot-
tom to top, but the conditions can be controlled such that
the material remains shapeable during the laying out. It
should be mentioned that for just this reason it will be
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worth endeavouring that the preceding mixing operation should
not be particularly efficient, whereby the mixing will be
that much simpler to carry out.
The invention will be well suited for treatment and
utilisation of recycled asphalt, which will typically hold 4-
6% bituminous binder with good adhesion to the stones. The
material is re-worked by an addition of a few percent of ad-
ditional binder in emulsified form, whereafter the material
or the respective material types will be ready for a cold
laying out whenever required.
The two types of material should not necessarily be mixed
in the ratio 1:1, as in general terms they should only be
mixed in a ratio such that the associated and desired pH-ad-
justment for actuation of the emulsion breaking will be ob-
tained. If one emulsion is more acid than the other is basic,then it is relevant to use a relatively smaller amount of the
acid fraction.
In principle the invention is extended to the use of con-
tra-polar emulsions or agents which, breakingwise, will actu-
ate each other when being mixed together, but otherwise beingsubstantially non-breaking or at least non-breaking through a
desired period of time, ranging from few hours to several
years. This result is achievable by the use of the respective
anionic and cationic emulsions, but probably it can be
achieved also by means of other 'contra-polar systems' such
as different, but mutually miscible liquids or solids in liq-
uids or colloidal suspension or gells.
The invention may be used with a wide variety of modifi-
cations, e.g. as follows:
- the bituminous binders in the respective emulsions
are not of the same viscosity or rheology and may be hydro-
carbon binders or bitumens modified by polymers or additives,
or unmodified binders with or without additives such as sil-
ica furne or filler or fibres or carbon black or adhesion
agents;
- the bituminous emulsions are both cationic or both
anionic or non-ionic or combinations such that the two sepa-
rately coated material fractions when mixed together act as
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breaking agents for each other, either as PH modifiers or as
buffers or as destabilising chemical reaction initiators;
- the bituminous or hydrocarbon binders in the res-
pective emulsions react with each other after coalescence or
cross-link upon contact such that a higher cohesion or vis-
cosity results, with the benefit of enhanced properties of
the mixture of two material fractions.
- the stone material may consist of pre-coated fines
an uncoated coarse particles or pre-coated coarse particles
and uncoated fines or blend of both or totally pre-coated ma-
terial by methods including the use of bituminous and hydro-
carbon emulsions, foamed bituminous or hydrocarbon of any po-
larity, hot coating or any combination of these;
- the prepared material fractions may consist of more
than two separate fractions and can be composed of fines or
coarse fractions in any ratio such that when homogeneously
mixed together the desired aggregate grating curve is formed;
- the emulsion system may include a two component
epoxy resin bitumen blend or polyurethane system as two sepa-
rate emulsion systems made to break each other.
- the bitumen in the emulsions may be of any
viscosity, as suitable for respective applications; there is
no upper limit, so viscosities of e.g. 200,000 og 500,000
mm2/sec. at 60~C may be applicable.
Examples:
Exam~le 1:
Material for short term storage or to be laid the day it
is produced.
)
Aaqreqate:
40% 8/12 mm R0nnegranit
20% 5/8 mm R0nnegranit
40~ 0/6 mm Sand
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Emulsions:
A: 70% anionic emulsion based on B180 produced in
accordance with ASTM class SS.
B: 70% cationic emulsion based on B180 produced in
accordance with ASTM class CSS.
From the aggregate two mixtures are made with an identi-
cal emulsion content of 7.4%, one based on type A emulsion
and the other on type B emulsion and brought to separate
storage bins.
Preparatory to loading onto trucks for transportation to
the site for the laying out the two mixtures are brought to-
gether simultaneously in the ration 1:1 on a loading conveyor
and consequently obtain a slight mixing falling onto the
trucks.
When laid the following compaction by rollers will cause
the two emulsions to break each other and when fully com-
pacted all the emulsion has broken whereafter the material
obtains its final strength.
ExamPle 2:
Agqregate:
The same as in example 1, but now precoated with 1.5%
25 B80.
Emulsions:
A: 70~ anionic emulsion based on B80 produced in
accordance with ASTM class MS.
B: 70~ cationic emulsion based on B80 produced in
accordance with ASTM class CMS.
Due to the precoating the emulsion content in the two
mixtures is reduced to 5.3%.
Storage, ~ g, laying and compaction as in example 1.
Materials that can be stored for a longer period of time.
Exam~le 3:
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Aqareqate:
The same as in example 2.
Emulsions:
A: 70% anionic emulsion based on B180 produced in
accordance with ASTM class SS.
B: 70% cationic emulsion based on B180 produced in
accordance with ASTM class CSS.
From the aggregate two mixtures are made with an identi-
cal emulsion content of 5.3% and stored in two separate
stockpiles. During storage the stockpiles should be covered
to protect the material containing unbroken emulsion from
rain. Prior to laying the two materials are brought together
in a similar manner as in example 1.
Exam~le 4:
Aqqreqate:
70% 6/16 mm recycled asphalt
30% 0/6 mm recycled asphalt
Emulsions:
A: 50% anionic emulsion based on B180 produced in
accordance with ASTM class SS.
B: 50% cationic emulsion based on B180 produced in
accordance with ASTM class CSS.
From the recycled asphalt two mixtures are made with an
identical emulsion content of 4.4% and stored in two separate
stockpiles.
The material is hereafter treated as in example 3.
Sacked materials for reinstatement purposes.
Exam~le 5:
Aqqreqate:
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70% 5/8 mm R~nnegranit
30% 0/6 mm Sand
The aggregate is precoated with 1.5~ B80.
Emulsions:
A: 70% anionic emulsion based on B180 produced in
accordance with ASTM class SS.
B: 70% cationic emulsion based on B180 produced in
accordance with ASTM class CSS.
From the aggregate two mixtures are made with an identi-
cal emulsion content of 5.7%.
The mixtures can be sacked in strong plastic sacks markedwith an A for the anionic mixture and a C for the cationic
mixture.
When a reinstatement job, e.g. repairing a pot-hole is to
be carried out material from sack A is mixed using a shovel
with an equal proportion of material from sack C and com-
pacted into the pot-hole resulting in a durable permanent re-
pair.
3S
