Note: Descriptions are shown in the official language in which they were submitted.
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Background of the Invention
Roadways are part of any developed country's social infrastructure and make up
the majority of
means for transportation of people and goods. More than 80% of the world's
roads are paved with
asphalt concrete mixtures. Asphalt pavement's life cycle is shortened and
damaged by heavy traffic
loading and frequent travelling over a short period of time. In repairing
damaged asphalt pavements,
the pavement can have extended or shortened life, depending on the materials
used during the
production phase of asphalt concrete mixtures that are paved on the roadbed.
The extended life of
the pavement can save several billion dollars of government construction
budget each year in
repairing and maintaining roads. There are many ways to extend the life-cycle
of asphalt pavements.
One major method is to add chemical modifiers to asphalt concrete mixtures
during production in
the asphalt plant mixer. In this case, perfornlance of asphalt pavement
heavily depends on what kind
of chemical modifiers are used in production. This invention involves a highly
viscoelastic wann-
mix modifier that effectively improve perfonnance of asphalt pavements.
Summary of the Invention
The product in the patent is a particular chemical modifier (that is, a highly
viscoelastic warm mix
modifier) added to the mixer in the asphalt plant during production of the
asphalt concrete mixture
(asphalt mix) to enhance greatly pavement performance properties. Many
modifiers available in the
market are usually constituted by the polymers that have either strong
viscosity with weak elasticity,
or weak viscosity with strong elasticity. Polymers holding both properties
strong are hardly found.
Strong viscosity is needed to resist rutting of asphalt pavements during hot
summer, while high
elasticity is necessary in preventing pavement cracks during cold winter. The
modifier in this
invention is characterized to be the highly viscoelastic polymer that shows
both strong viscosity and
elasticity (called high viscoelasticity). This invention discloses how to make
the highly viscoelastic
modifier and suggests the composition. In addition, a warm mix additive is
added to the highly
viscoelastic modifier to reduce production temperature and air pollution.
These are called the highly
viscoelastic warm mix modifier in this invention. The major characteristic of
the warm mix additive
in this invention is to use combination of at least two warm mix additives
together to make far more
effective than using a single warm mix additive that is common industrial
practice. These are well
demonstrated in figures.
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Figure I illustrates comparison of temperature reduction effect between using
a single warm mix
additive (I, A, B & C) and combination of two warm mix additive (I+A, I+B, &
I+C) for each 1.2
and 2.4 grams dissolved in 98,8 and 97.6 grams of an asphalt binder. The
average 3.7 C (1.2-gram)
and 7.1 C (2.4-gram) reduction are shown for a single additive, while about
8.0 C ((0.6+0.6)-gram)
and 10.3 C ((1.2+1.2)-gram) reduction are displayed for combination of two
additives.
Figure 2 shows the same experiment done as Figure 1, except of using a warm
mix additive II
instead of I. Temperature reduction effect is compared between using a single
warm mix additive
(II, A, B & C) and combination of two warm mix additive (II+A, II+B, & II+C).
Here, too, the
average of 4.1 C (1.2-gram) and 6.4 C (2.4-gram) reduction are displayed for a
single additive,
while about 7.0 C ((0.6+0.6)-gram) and 8.2 C ((1.2+1.2)-gram) reduction are
demonstrated for
combination of two additives.
Figure 3 exhibits the elasticity of a Sasobit wax alone and a Sasobit wax plus
the elastic material
(R). Presence of the elastic material (R) shows better elastic effect.
Figure 4 demonstrates comparison of elasticity among an asphalt binder (A), A
plus R, and A plus R
plus a single warm mix additive (CM). Presence of CM makes even better
elasticity.
Figure 5 demonstrates comparison of elasticity among A, A plus R, and A plus R
plus a combined
warm-mix additive (CM+HCO). Combined two additives improves elastic effect
further better.
Figure 6 illustrates comparison of performance properties between highly
viscoelastic modifiers
(practice 1, 2, 3) and the general modifier (comparison 1, 2, 3).
Detailed Description of the Invention
[1] Roadways are social infrastructure and take charge of most transportation
of people and goods.
More than 80% of worldwide roads are paved with asphalt pavements, and most of
heavy traffic
loadings are absorbed into the asphalt pavement layer. Pavement life cycle is
shortened by heavy
traffic loading and impacts and bad construction practice. In repairing or
maintaining damaged
pavements, several billion dollars of national budgets are spent each year. If
the life cycle of asphalt
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pavements can be extended, tremendous construction budget can be saved.
Asphalt pavements are
constructed by paving asphalt concrete mixtures (produced from mixing an
asphalt binder,
aggregates and fillers at a high temperature) on the roadbed in the order of,
from bottom to top, a
base layer, an intermediate layer, and a surface layer with each paved layer
compacted by rollers to
finish construction. The important raw materials that determines pavement
quality are both asphalt
binders and aggregates under the assumption of construction well done.
However, aggregate size
and gradation cannot be a critical factor because these are usually a uniform
size, but asphalt binders
can affect greatly the pavement quality due to many modifications to be made.
[2] Asphalt binders showing comparatively less molecular weight inherently
possess considerably
inferior physical properties compared to polymers having a high molecular
weight. Thus, by using
polymer resins possessing excellent physical properties, the inferior
properties of asphalt binders can
be improved in order to extend life cycle of pavements. The polymer additive
to be used for this
purpose is called the modifier, and the asphalt binder containing the modifier
is called the modified
asphalt binder. However, note that according to kinds of modifiers used, there
exists many
differences in physical property improvements of asphalt binder. In producing
modified asphalt
concrete mixtures (modified ASCON) by adding modifiers or modified asphalt
binders, both high
heating (160-170 C, hot mix asphalt) or medium heating (120-140 C, warm mix
asphalt)
production methods exist. The latter method (the warm mix asphalt production
method) is favored in
the view of reduction of environmental pollution and saving of energy. In
addition, the production of
RAP (Reclaimed Asphalt Pavement)) recycled hot mix asphalt mixing with some
virgin materials is
a recently increasing trend to prevent land pollution and to save construction
cost. This invention
belongs to the technology area of the modified, RAP-recycled (or virgin) warm
mix asphalt
production including all technologies mentioned above.
Technical Field & Prior Art
[3] Generally, performance properties of asphalt pavements respond sensitively
on magnitude of
traffic loading and seasonal temperature variation such that both effects
often cause flitting and
fatigue cracking of asphalt pavements. That is, under heavy traffic loading,
asphalt pavements
experience various cracks at low temperatures (at less than -10 C) due to the
increase of stiffness
caused by material contraction. Meanwhile, rutting takes place due to shear
flow of materials caused
by weakened pavement viscosity at high temperatures (higher than 50 C).
Generally modern
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economic expansion makes number of automobiles, traffic volume and heavily
loaded trucks
increased such that pavement problems mentioned above become accelerated and
life cycle of
existing pavements is drastically shortened. Therefore, major roadways
commonly use modified
asphalt pavements instead of regular ones to prevent decrease of pavement life
cycle. A modifier
can be included as a key material element in constructing modified asphalt
pavements. The modifier
can be constituted from a single polymer (i.e., styrene-butadiene-styrene
(SBS), low density
polyethylene (LDPE), etc.), but is usually composed of both elastic materials
(to resist cracks in the
cold winter) and viscous materials (to minimize rutting in the hot summer).
[4] Let's review the previous technologies on polymer modifiers. In Korean
patent 2002-034496,
gilsonite was used as a viscosity thickening agent and styrenebutadiene-
styrene (SBS) was used as
an elasticity enforcing agent. In Korean patent 2003-004579, gilsonite was
used as a viscosity
thickening agent, crumb rubber was used as an elasticity enforcing agent, and
in Korean patent 10-
0669079, asphaltite powder and polyethylene (PE) powder was used as viscosity
thickening agents
and crumb rubber as an elasticity enforcing agent, respectively. Gilsonite (a
highly viscous liquid)
and asphaltite (solid powder) are naturally produced at the northeastern
corner of Utah, USA. Both
containing asphaltenes as a major element are characterized to be rigid and
strongly stiffened. These
materials have disadvantage of producing early pavement cracks due to strong
stiffness. Hence,
gilsonite as a viscosity thickening agent claimed in 2002-034496 and 2003-
004579 cannot be a
desirable agent in the view of pavement performance properties compared to
better different
viscosity thickening agents available. In Korean patent 10-2007-0669079, to
resolve the above
brittleness problem, Polyethylene (PE, a general purpose polymer) is also
included. If more PE are
added, brittleness is lessened, but lack of binder adhesion on aggregates
results, due to there being
no functional groups present in the PE molecule that promote adhesion.
[5] In Korean patent 10-2003-005537, epoxy resin and petroleum resin as
viscosity thickening
agents, and SBS and rubber as elasticity enforcing agents, and in Korean
patent 10-2003-0069911,
petroleum resin as a viscosity thickening agent, SBS and rubber as elasticity
enforcing agents,
respectively, are used as compositions. Here, too, because epoxy and petroleum
resin have
disadvantage of producing early pavement cracks due to strong brittleness, the
modifier including
those compounds cannot be a good agent. In addition, the epoxy resin is
economically expensive.
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[6] In Korean patent 10-2005-0076461, waste PE film as a viscosity thickening
agent is only used
without an elasticity enforcing agent. Even though waste PE film is
inexpensive, it is not a good
modifier as explained above, and cold winter can cause easy cracks on
pavements due to no
elasticity present.
[7] In Korean patent 10-2001-0037903, aromatic petroleum resin as a viscosity
thickening agent,
and SBS and rubber as elasticity enforcing agents, and additionally aromatic
processing oil and
antioxidant are added together as compositions. Even here, petroleum resin as
a viscosity thickening
agent is not desirable due to strong brittleness.
[8] In Korean patent 10-2006-0122508, high density polyethylene (HDPE) as a
viscosity thickening
agent, and crumb rubber as an elasticity-enforcing agent are used as
compositions. Because HDPE is
a partially crystalline polymer, crystallization formed at low temperatures
increases stiffness to
make early pavement cracks, and also no functional groups are present in the
HDPE molecule so it
has poor adhesion on aggregates. Above all, HDPE does not have good
compatibility with crumb
rubber used. All these suggest that the compositions mentioned above will
produce an inferior
modifier.
[9] In conclusion, among traditional compositions of modifiers, most polymer
resins used as a
viscosity thickening agent are general polymer resins with medium viscosity
(i.e., waste PE, HDPE,
low density polyethylene (LDPE), Ethylene vinyl acetate (EVA), etc.), not high
viscosity. If the
regular amount of those polymers is added in making modified asphalt binder,
the viscocity fails.
This brings relatively easy rutting. In the contrary, adding large amounts to
increase viscocity, is
cost prohibitive. Furthermore, polymers that can acquire high enough viscosity
at elevated
temperatures (i.e., gilsonte, asphaltite, petroleum resin, epoxy resin, etc.)
can be brittle at low
temperatures resulting to easy pavement cracks.
[10] Recently, the warm mix asphalt (WMA) production instead of the hot mix
asphalt (HMA) has
received more attention in attempt to resolving the fuel consumption and the
air pollution problem in
HMA production, and many patents are issued about it. In Korean patent 10-2012-
0073529,
maleicpolyethylene wax and processing oil are used as a warm-mix additive, and
SBS or styrene-
butadiene-rubber (SBR) as a modifier are used. However, SBS or SBR is a weakly
viscous and
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elastic polymer. Thus it will cause pavement cracks, but has a greater
probability of allowing rutting
due to the weak viscosity.
[11] Korean patent 10-0823352 suggests a processing wax by Fisher- Tropsh
method (called a
sasobit wax) as a warm mix additive, amine or lime soda as an anti-stripping
agent, and ethylene-
vinyl acetate (EVA) copolymer and an inorganic powder as a modifier. However,
the EVA resin is
not considered as a proper modifier because it shows relatively weak viscosity
and is not elastic
either at low temperatures. The Sasobit wax as a warm mix additive also
increases brittleness at low
temperatures (cracks) and softening at high temperatures (rutting).
[12] The Korean patent 10-1166155 claims a warm mix additive by choosing at
least one among
processing oil, plasticizer, linseed oil, bean oil and rice oil, and, a
modifier by choosing
polyurethane (PU) polymerized by reacting with polyols (or polyamines) and
isocyanate under
catalysts (cobalt type, lead type, phosphorous type). However, it has failed
to provide any
polymerization details of the polyurethane resultant from the reaction so the
physical properties of
polymerized polyurethane are unknown, as is whether it is proper to be used as
a modifier or not.
[13] The Korean patent 10-1023425 uses at least one among processing oil,
petroleum resin and
sasobit wax as a warm mix additive, and SBS or waterdispersed acrylic emulsion
as a modifier.
However, total viscosity of modified asphalt viscosity is still so weak that
it is expected for the
modified binder likely to cause a flitting problem. In Korean patent 10-
1023425, use of at least one
among rosin, polyethylene (PE), Bunker-C oil and asphalt binder as a warm mix
additive, and a
mixture of EVA and at least one of SBS, styrene-isoprene-styrene (SIS), LDPE,
HDPE, PU chip,
ethylene-propylene-diem (EPDM) chip as a modifier are claimed to be used. In
the patent, good
crack resistance has been shown by using elastic materials like SBS, SIS, PU
chip, EPDM chip, but
possibility of the pavement rutting problem cannot be avoided due because EVA,
LDPE, or HDPE
are weakly viscous general purpose polymers. Even though HDPE has a relatively
high viscosity
leading to better rut resistance, it is a nonpolar (adhesion problem on
aggregates) and crystalline
(easily cracked at low temperatures due to contraction) polymer. If used as a
modifier, a small
amount of HDPE, which will fail to increase viscosity, should be used.
[14] According to the above patent literature survey, most of patents suggest
use of a single or at
least one as a warm mix additive and most of modifiers used are characterized
either to have good
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elastic property with low viscosity or highly brittle viscosity with low
elasticity. It is hardly found
for a modifier to have good elasticity and also highly tough viscosity as a
desirable modifier.
Technical Problems
[15] Most of polymers used for a viscosity thickening agent known as existing
modifiers are not
totally free from pavement rutting, because they are general purpose polymers
and do not possess
enough viscosity. Thus, there were attempts to increase viscosity by using a
rigid and stiff polymer
found among general purpose resins. However, increased stiffness can cause
early pavement cracks
during the cold winter period. It is natural that many modifiers include
elastic polymers to resist
cracks at low temperatures, but most of them contain weak or even no viscous
polymers as a
viscosity thickening agent. For these modifiers, pavement rutting takes place
easily due to weakened
viscosity during hot summer. Thus, the subject of this invention is to claim
what kinds of viscous
polymers should be used together with elastic polymers for rut resistance in
hot summer and crack
resistance in cold winter.
[16] Additional topic about the use of warm mix additive to provide wann mix
effect to modified
asphalt mixes is included in this invention. Here, instead of simply using a
single or at least one
warm mix additives, detailed information of what kinds of warm mix additives
used and what is the
best composition to be an effective additive becomes a major concern. In
addition, compositions of
asphalt concrete mixes and their manufacturing technologies by using newly
suggested modifiers
and warm mix additives are also disclosed in this invention.
[17] More RAP (Reclaimed Asphalt Pavement; construction waste) recycling is a
timely task to be
resolved because of reduction of land pollution and construction cost, and
saving of natural
resources. The present RAP recycled pavements experience early pavement
damages due to poor
performance problems (i.e., rutting, fatigue cracking, etc). As the result,
shortened pavement life is
another immediate task to be resolved.
1181 Methods of Problem Resolution
[19] This invention provides methodology to solve the technical limitations
mentioned above. That
is, under consideration of environmental and economic advantages, production
of warm mix asphalt
("WMA") (100-140 C) instead of hot mix asphalt ("HMA") (150-180' C) is
preferred. In order to
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improve limited pavement quality of general virgin (or recycled) WMA as well
as modified virgin
(or recycled) WMA, this invention is to provide new compositions and
manufacturing methods of
highly viscoelastic WMA modifiers that show excellent performance properties
even under severe
weather condition during hot summer and cold winter. Furthermore, it is to
provide technical
characteristics relating to compositions and manufacturing methods of modified
virgin (or recycled)
WMA by using new highly viscoelastic modifiers claimed here.
[20] The modified virgin (or recycled) WMA by using the new highly
viscoelastic warm mix
modifier is constituted of 0.5-20 weight parts of a highly viscoelastic warm
mix modifier, 10-80
weight parts of an asphalt binder, 850-987.5 weight parts of aggregates, 2-50
weight parts of a filler,
small amount of an amine-type stripping agent and a little anti-oxidant. The
material with the above
composition is characterized to input into the mixer of asphalt plant at 80-
180oC and are mixed to
make modified virgin (or recycled) WMA (or HMA without a warm mix additive).
[21] The new highly viscoelastic warm mix modifier is the 100 weight percent
sum of the less than
100 weight percent highly viscoelastic modifier and the less than 100 weight
percent crack-resistant
warm-mix additive and a small amount of a reaction agent (i.e., benzoyl
peroxide, maleic anhydride,
acetaldehyde, platinum catalyst, etc.). Here, the highly viscoelastic modifier
indicates 100 weight
percent sum of the 10-90 weight percent combined viscous polymers and the 10-
90 weight percent
highly elastic polymers. Generally, asphalt binders or modified asphalt
binders have viscoelastic
properties, but most of them show either strong viscosity with low elasticity
or weak viscosity with
high elasticity. Almost all polymers fail to show both strong viscosity and
high elasticity at the same
time. To acquire strong property of both in a single modifier, it is necessary
to combine strongly
viscous polymers to highly elastic polymers in a proper way.
[22] In the above, strongly viscous polymers represent polymers possessing
very strong viscosity
compared to the general ones having medium viscosity. They are specified to be
polyethylene-tere-
phthalate (PET), polyester (or nylon), polypropylene (PP), coprene (copolymer
of PP and
polyethylene (PE)), and these polymers which have been coated with thin
aluminum film. However,
if a strongly viscous polymer by itself as a modifier is mixed together with
liquid asphalt binders at
a high temperature, drastic viscosity difference between the two liquids can
cause a dispersion
problem in the final binders made. Thus, general purpose polymers, having
medium viscosity, are
desirable to be mixed together with strongly viscous polymers to have
effective dispersion in asphalt
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binders even at high temperatures. Hence, this invention claims a combination
of viscous polymers
of at least one strongly viscous polymers and at least one general purpose
polymers as a viscous
polymer component. Here, the general purpose polymers represent low density
polyethylene
(LDPE), linear low density polyethylene (LLDPE), high density polyethylene
(HDPE), polyvinyl-
acetate (PVA), ethylene-vinyl-acetate copolymer (EVA), polybutene (PB), etc.
[23] Furthermore, combined viscous polymers include an adhesion sheet (or
film) joining together
on the boundary between one of the strongly viscous polymer sheets (or films)
to one of the general
polymer sheets (or films), and these adhesion sheets coated further with thin
aluminium film on one
side. These joined sheets produce the same effect of mixing the strongly
viscous polymers to the
general viscous polymers.
[24] The above viscous polymer sheets are widely used in the market as a
packaging material to
contain liquid medicine, cookies, liquid and solid food, liquid drink, etc.
[25] Mixing of the combined viscous polymers together with the highly elastic
polymers can
constitute the highly viscoelastic modifiers that are capable of showing both
strong viscosity and
high elasticity. Here, the highly elastic polymers are characterized to
include styrene-butadiene-
styrene (SBS), styrene-butadiene rubber (SBR), SBR latex, styrene-
isobutylenestyrene (SIS),
styrene-ethylene-butadiene-styrene (SEBS), scrape tire powder (or crumb
rubber), waste rubber
powder, natural rubber powder, ethylenepropylene-diem (EPDM) powder, liquid
natural rubber,
methyl methacrylate (MMA) resin, polyurethane (PU) powder, etc.
[26] In cold regions, the pavement elastic property becomes important to
prevent pavement
contraction that can cause crack generation. Meanwhile, in hot regions, the
pavement viscousity
property becomes important to prevent softening of pavements that can cause
rutting. Thus, to be
safe from harsh weather conditions, the ratio of adding combined viscous
polymers to highly elastic
polymers should be properly adjusted according to regional weather condition.
For this
consideration, the range of using ratio of the two different characters of
polymers should be flexibly
changed to be the sum of 100% by adding 10-90% combined viscous polymers to 10-
90% highly
elastic polymers.
[27] Production of the modified hot mix asphalt (HMA) by using highly
viscoelastic modifiers
generates problems like harmful gas evolution, fuel waste, and accelerated
oxidative aging of
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asphalt binders. However the modified warm mix asphalt (WMA) production can
substantially
reduce problems of the modified HMA production due to decreased temperatures.
For this purpose,
highly viscoelastic warm mix modifiers instead of highly viscoelastic hot mix
modifiers are
manufactured by adding crack-resistant warm mix additives to highly
viscoelastic modifiers. In the
above, the composition of highly viscoelastic warm mix modifiers is claimed to
be the 100 weight %
sum of the following material elements; they are less than 100 weight % of
highly viscoelastic
modifiers, less than 100 weight % of crack resistant warm mix additives and a
small amount of
reaction accelerators. Here, the 100 weight % implies to use only the
corresponding material alone
without any other. However, the 100 weight % sum means addition of highly
viscoelastic modifiers,
crack-resistant warm mix additives and a small reaction agent all together to
make the sum be 100%.
[28] Now, let us investigate compositional characteristics of crack-resistant
warm mix additives.
Generally, warm mix additives are agents that make asphalt mix production and
pavement
construction at reduced temperatures compared to the regular hot mix asphalt
by lowering viscosity
of asphalt binders. If patents of the warm mix additive are reviewed, most of
them are found to
claim either one or simply more than one additive without knowing the
different effect of using at
least two additives compared to one. However, this patent claims first time to
compose warm mix
additives as combination of at least two additives to be used together. Such a
claim is based on
scientific experiments obtained from broad research execution about
temperature reduction effect of
warm mix additives.
[29] In Figure 1 below, a certain amount of a warm mix additive is uniformly
melted in an asphalt
binder at a medium temperature (1300 C) to make a test specimen. At a
specified temperature,
specimen viscosity is measured by using the Brookfield rotational viscometer.
By analyzing the
measured specimen viscosities compared to the asphalt binder viscosity,
temperature reduction of
each warm mix additive is evaluated and is shown in Figure 1.
[30] Temperature reduction of each warm mix additive I (1.2 gams and 2.4
grams), A (1.2 gams
and 2.4 grams), B (1.2 grams and 2.4 grams) & C (1.2 grains and 2.4 grams)
melted in asphalt
binders (98.8 grams and 97.6 grams) to make 100grams of warm-mix asphalt
binder specimens and
those reductions by using two combination warm mix additives of 1+A (0.6+0.6
grams and 1.2+1.2
grams), I+B( 0.6+0.6 grams and 1.2+1.2 grains), I+C (0.6+0.6 grams and 1.2+1.2
grams) melted in
the same asphalt binders (98.8 grams and 97.6 grams) to make 100 grams are
well demonstrated in
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Figure 1.
[31] As shown in Figure 1, the 1.2-gram and the 2.4-gram case for the single
warm mix additives (I,
A, B & C) show the average 3.7 C, and 7.1 C temperature reduction,
respectively, while the two
combination warm mix additive cases of (0.6+0.6)-gram and the (1.2+1.2)-gram
for I+A, I+B, &
I+C demonstrate the average 8.0 C (2.2-time increase), and 10.3 C (1.45- time
increase) temperature
reduction, respectively. This result confirms that combination of two
additives instead of single
additives, while using the identical aggregate amount, is further effective in
reducing production
temperature.
[32] By following the same experimental procedures in getting the data of
Figure 1, the temperature
reduction of different warm mix additives such as II, A, B, C and their two
combinations are
measured and exhibited in Figure 2. As shown in Figure 2, single additives
(II, A, B, C) used as 1.2-
gram to make 100 grams of an warm mix asphalt binder have shown the average of
4.1oC reduction
compared simply to 100 grams of an asphalt binder alone, and the average of
6.4' C reduction for
the case of 2.4-gram addition. Meanwhile, combination of two additives (II+A,
II+B, II+C) has
shown the average of 7 C temperature reduction for 1.2 (0.6+0.6) gram case
(about 1.7 times
increase compared to the single additive case) and the average of 8.2 C
reduction for 2.4 (1.2+1.2)
gram case (about 1.3 times increase compared to the single additive case).
Hence, Figure 2 obtains
the identical conclusion of Figure 1; that is, using combination of two warm
mix additives shows a
better temperature reduction effect than using single additives under the same
amount of additives
used. Thus, this invention claims that combination of at least two additives
must be used to get
better warm mix effect instead of using single additives.
[33] As claimed in the above, the warm mix additive of this invention is
characterized to include the
combination of at least two among all solid warm mix additives, the
combination of at least two
among all liquid warm mix additives, the combination of at least one in solid
additives and at least
one in liquid additives, and the rate of each combination is determined
arbitrary.
[34] In the above, the solid warm mix additive is characterized to include 12-
hydroxy stearic acid,
hydrogenated castor oil, Sasobit wax, petroleum resin, cumaron resin, pine
resin, ethylene-vinyl-
acetate (EVA) wax, polyethylene wax, polyamide wax, maleic-polyethylene wax
and all other solid
warm mix additives not mentioned here.
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[35] In the above, the liquid warm mix additive is characterized to include
liquid evotherm,
polyalkaneamer, ethylene-vinyl-acetate (EVA) emulsion, acryl emulsion, styrene-
butadiene-
rubber(SBR) emulsion, aromatic process oil, aliphatic process oil, mixed
processing oil of aromatic
and aliphatic oils, cutback asphalt, heavy oils, A, B & C bunker oil, asphalt
emulsion, industrial oils
(automobile engine oil, lubricant, compressor oil, ship engine oil), plant
oils (palm oil, coconut oil,
linseed oil, soybean oil, other bean oils, perilla oil, castor oil), animal
oils (cow oil, pig oil, fish oil),
various surface-active agents, various plasticizers, and all other liquid warm
mix additive not
mentioned here.
[36] Warm mix additives are widely used, but crack-resistant warm mix
additives may be unfamiliar
because they are introduced first time in this invention. Wax-type additives
that usually show a
melting point at 80-120 C are often used as a warm mix additive. These waxes
take a role of warm
mix additives by drastically decreasing their viscosities above their melting
points and by increasing
their hardness below their melting points. Hardening by waxes below the
melting point contributes
to overall material stiffening that has a positive effect of traffic loading
sport on pavements, but has
negative effect of local crack evolution that are eventually leading to large
pavement cracks. This is
mainly due to hardening effect of the wax-type warm mix additive. To avoid
this negative effect as
well as to enhance crack resistance, a small amount of elastic material can be
added to warm mix
additives. This additive is called a crack-resistant warm mix additive that
contributes to reducing
pavement cracks at low temperatures.
[37] The crack-resistant warm mix additive of this invention consists of 100
weight percent (wt. %)
sum of 20-100 wt. % of warm mix additive and less than 80 wt. % of the elastic
material. The
minimum of 20 wt. % warm mix additive indicates the least amount of the warm
mix additive to
produce warm mix effect, and the maximum 100 wt. % implies the case of the
whole warm mix
additive without any elastic material.
[38] Manufacturing of crack-resistant warm mix additives by adding elastic
materials is suggested
first time in this invention. Figure 3 exhibits viscoelastic property of a
Sasobit wax made by the
Fisher-Tropsh method and used widely as a warm mix additive in the world.
After a warm mix
asphalt specimen is made by resolving 2 wt. % Sasobit into an 98 wt. % asphalt
binder, this
specimen is used to measure its storage modulus, loss modulus and phase angle
(delta) in the
CA 02902935 2015-08-17
temperature range of 40 to 80oC by using the dynamic shear rheometer (DSR).
These three
properties are applied to compute its dynamic shear modulus and three
viscoelastic properties (i.e.,
sine (delta), cosine (delta) and tangent (delta)) at measured temperatures.
Here, sine (delta) is used
to represent the viscoelastic property of the warm mix asphalt specimen
because either of three
properties represents the same viscoelasticity of a given specimen. The value
of sine (delta) has
usually 0.3-1.0 according to content of elasticity contained. The sine (delta)
=1 represents a
completely viscous property, and the lesser sine (delta) from one implies the
more elastic property
contained with correspondingly decreased viscous property. Note that all
viscoelastic fluids show
tendency of sine (delta) to approach to one when temperature rises to the high
enough, while the
elastic property of viscoelastic fluids increases when temperature decreases,
that is, sine (delta) < I.
[39] In Figure 3, the sine (delta) of the warm mix asphalt including the 3 wt.
% sasobit wax is
compared with the one additionally added with the 3 wt. % of the elastic
material (R). The latter
demonstrates the smaller sine (delta) (that is, more elastic property)
throughout all temperatures
studied compared to the former. At the lowest temperature (40 C), the
difference of sine (delta) is
enlarged and at the highest (80 C), both approach to one showing almost no
difference. When
cracks of asphalt pavements are considered to take place relatively easily at
low temperature due to
material contraction, the fact that sine (delta) of the warm mix additive
deceases (or elasticity
increases) with low temperature indicates an elevation of pavement crack
resistance. In Figure 3
where the lowest temperature is 40 C, sine (delta) difference between the
former and the latter
becomes even larger when temperature decreases less than 40 C. This reminds
that the crack
resistant warm mix additive containing the elastic material will increase
crack resistance of asphalt
pavements at low temperatures and can prevent local pavement cracks.
[40] In Figure 4, measured sine (delta) values of an asphalt binder (I), an
asphalt binder including 3
wt. % R (an elastic material) (II), an asphalt binder containing 3 wt. % R and
0.8 wt. % CM (a warm
mix additive) (III), and finally an asphalt binder containing 3 wt. % R and 2
wt. % CM (IV) are
displayed with respect to a temperature change of 40-80 C. As same as Figure
3, the difference of
sine (delta) for each case is clearly manifested with decrease of temperature,
but becomes none at
the high temperature of 80 C (all approaching to sine (delta)=1, a totally
viscous fluid). II shows a
further better elastic property than I, but III with presence of 0.8% CM (warm
mix additive)
demonstrates even better crack resistance than II with no CM. It is noted that
III and IV show no
difference between the two. This means that a small amount of CM is enough.
CA 02902935 2015-08-17
[41] In Figure 5, measured sin(delta) values of an asphalt binder (I), an
asphalt binder including 3
wt% R (an elastic material) (II), and an asphalt binder containing 3 wt. % R
and 0.8 wt. % combined
warm mix additive (0.6 wt. % CM plus 0.2 wt. % HCO) (III) are displayed with
respect to a
temperature range of 40-80 C. Sin (delta) values in Figure 5 demonstrate the
similar trends shown
in Figure 3 and 4, but using 0.8 wt. % combined warm mix additive (0.6 wt. %
CM plus 0.2 wt%
HCO) results to better elastic effect (less sin(delta)) instead of using 0.8
wt. % single warm mix
additive (CM).
[42] Crack-resistant warm mix additives studied above can draw the following
conclusions; first,
combined warm mix additive turns out to be better warm mix effect compared to
the single one;
second, if an elastic material is added to a warm mix additive, the crack-
resistant effect at low
temperatures can be improved considerably; and, third, even for crack
resistance effect, combined
warm mix additives are better than using single ones.
[43] The elastic materials added in making the crack-resistant warm mix
additives of this invention
are identical to the highly elastic polymers mentioned previously, but the
only difference between
the two is to use relatively small amount in the crack-resistant additive.
These highly elastic
polymers are characterized to include at least one among SBS (styrenebutadiene-
styrene), SBR
(styrene-butadiene-rubber), SBR latex, SIS (styreneisoprene- styrene), SEBS
(styrene-ethylene-
butadiene-styrene), crum rubber (powdered waste tire), waste rubber powder,
natural rubber powder,
liquid natural rubber, EPDM (ethylene-propylene-diem) powder, MMA (methylmet-
acrylate) resin,
PU (polyurethane) powder and other highly elastic materials.
[44] This brings us to the investigative stage of the manufacturing method of
highly viscoelastic
warm-mix modifiers. Shapes of highly viscoelastic warm-mix modifiers can be
pellet, film, thin
plate, sheet, bottle, wire-coating, short fiber, waste scrap, powder, or
mixtures of these shapes. Their
material state is new, regenerated, waste, or mixtures of these. Wastes are
favored over others for
prevention of environmental pollution, waste recycling, and economic
advantage. There are three
manufacturing methods that are introduced below and one of them can be
selected for
manufacturing.
CA 02902935 2015-08-17
[45] First, the compositional elements of the highly viscoelastic warm-mix
modifier described above
are put into a Banbury mixer (or kneader), and then are heated, melted and
well mixed to make a
uniform melt. This melt goes through an extruder to make several melt strands
that are cooled and
cut into solid pellets. These pellets are further made into fine particles or
powders by crushers or
pulverizers to be final products. This method is used in manufacturing the
most uniform highly
viscoelastic warm-mix modifiers.
[46] Second, the compositional elements of the highly viscoelastic warm-mix
modifier described
above are put directly into the extruder without going through a Banbury mixer
(or kneader). The
next procedures after the extrusion are exactly same as the first. The second
method is better than
the first in the view of less equipment purchase or reduced production
process.
[47] Third, after each compositional element of the highly viscoelastic warm
mix modifier is made
into fine particles or powders separately at an ambient temperature by using
crushers or pulverizers,
each element is physically mixed. This is the simplest and cheapest method of
manufacturing, but it
has a weak point of being locally non-uniform in each element of the
composition. This non-
uniformity does not make any problem to be used as the highly viscoelastic
warm-mix modifier in
the view of the overall material property.
[48] This invention is characterized to constitute the composition of the
virgin or the regenerated
highly viscoelastic warm mix asphalt concrete mixture by combining 0.5-20
weight parts of a highly
viscoelastic warm-mix modifier, 10-100 weight parts of an asphalt binder, 850-
987.5 weight parts of
aggregates, 2-50 parts of a filler, and, if necessary, a small amount of anti-
stripping agent and anti-
oxidant. The virgin or the regenerated highly viscoelastic warm mix asphalt
concrete mixture is
characteristically produced by heating this composition at 80-180 C and
mixing them in the mixer
of an asphalt concrete production plant.
[49] In the above asphalt concrete mix composition, the using range of the
highly viscoelastic warm-
mix modifier is 0.5-20 weight parts. Here, the 0.5 weight part is the minimum
amount for
manifestation of modifier's effect and being at least the 20 weight part makes
production very
difficult due to extremely high viscosity. Thus the usage is limited in the
range of 0.5-20 weight
parts.
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[50] In the above composition, the using range of an asphalt binder is 10- 100
weight parts. Here,
the 10 weight part is the minimum amount of asphalt binders to produce the
pavement base-layer
material by using 100% reclaimed asphalt pavement (RAP) aggregates, and the
maximum 100
weight parts implies asphalt binders required to produce the asphalt mastic.
But most of highly
viscoelastic warm-mix modified asphalt concrete mixtures use asphalt binders
in the range of 10-
100 weight parts.
[51] In the composition above, aggregates mean all virgin or all RAP or mixed
aggregates of virgin
and RAP. Especially, when RAP recycling is demanded a lot in the paving
industry for
environmental and economic aspect, necessity of RAP-recycled asphalt pavements
by using the
RAP aggregate is ever increasing. To describe usage of both virgin and RAP
aggregates together,
the aggregate is composed of 100% by adding the less than 100% virgin
aggregates to the less than
100% RAP. The 100% virgin aggregate indicates the one for the 100% virgin
highly viscoelastic
warm-mix modified asphalt concrete mixtures, the 100% RAP aggregate does the
one for the 100%
RAP-recycled highly viscoelastic warm-mix modified asphalt concrete mixtures,
and the sum of
100% by adding the virgin aggregate % to the RAP aggregate % does the one for
the partially RAP-
recycled highly viscoelastic warm-mix modified asphalt concrete mixtures. The
aggregate
distribution becomes from the maximum size of 53mm to the minimum of 0.001mm.
This size
distribution is characterized to consider usage of the 19-53mm size for most
of the base and the
intermediate layer, and usage of the less than 19mm size for most of the
surface, the wearing and the
mastic layer. For an example, the surface layer aggregate distribution for the
less than 19mm can
include all grades like dense, rut-resistant, mastic, low noise porous, bridge
surface, SMA (surface
matrix aggregate), airport taxilayer superpave, gap and an arbitrary grade by
a designer. In the
composition above, the 850-987.5 aggregate weight part represents solely the
aggregate part only
out of total 1000 weight parts by excluding all other constituents.
[52] Under hot summer temperatures, viscosity of the general and the modified
asphalt binder
coated on aggregates near pavement surfaces becomes softened, and binders
slowly flow downward
into vacant spaces by relaxation. The more the viscosity of binders is
weakened the faster the rate of
vacancy filling is accomplished with fast relaxation speed. As the result,
aggregate separation or
segregation from the pavement surface can easily take place due to thinner
coating thickness of
aggregates on the surface. To prevent the binder relaxation phenomenon by
increasing viscosity,
CA 02902935 2015-08-17
filler is added to asphalt binders. When the proper amount of filler is added
to a binder, it
strengthens asphalt pavements to promote stifthess and crack resistance that
reduce rutting and
fatigue cracking. Filler is an especially key material for porous asphalt
pavements because it
contributes to maintain the original air void not to be collapsed.
[53] In the above composition, a filler is characterized to include aggregate
powder, limestone
powder, furnace slag powder, cellulose fiber, glass fiber, polymer fiber
(i.e., polyethylene (PE) fiber,
polypropylene(PP) fiber, nylon fiber, etc.), carbon black, fly ash, glass
fiber, clay powder, calcium
carbonate powder, caustic soda, lime soda, cement, steel-making powder and
other fillers. Effect of
these fillers can be ignored less than 2 weight parts, and, above 50 weight
parts, asphalt binder
viscosity is increased too much such that production and construction are very
difficult to do. Also,
stiffness of an asphalt mixture itself increases too much to cause
acceleration of pavement cracks by
adding excessive fillers. That is why filler use is limited to within 2-50
weight parts.
[54] To construct the highly viscoelastic warm-mix modified asphalt pavement,
the corresponding
asphalt concrete mixture (the highly viscoelastic warm-mix ASCON) claimed
above must be
produced. Two methods of production exist and either one can be chosen.
[55] First, after the 0.5-20 weight-part highly viscoelastic warm-mix modifier
in the form of fine
powder (or particle) and the 10-100 weight part asphalt binder, both, are
entered into the liquid
mixing tank, then make processing of heating and mixing and passing through
the colloid-mill allow
manufacturing of the highly viscoelastic warm-mix asphalt binder in the form
of the uniform liquid.
This liquid binder is transported to the asphalt mixing plant and is stored in
the modified asphalt
storage tank. This liquid binder is pumped and sprayed into aggregates and
fillers already entered in
the mixer of the asphalt plant. When all are mixed together at the warm-mix
temperature, the highly
viscoelastic warm-mix modified asphalt concrete mixture can be produced. This
production method
is called the pre-mix type.
[56] Second, vinyl-film bags containing a specified amount of the highly
viscoelastic warm-mix
modifier in the form of fine powder (or particle) are transported to the
asphalt plant, and the
designed number of bags is dropped into the mixer of the plant already
containing specified amount
of aggregates and fillers. They are mixed under the warm-mix temperature by
spraying the general
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asphalt binders to produce the highly viscoelastic warm-mix modified asphalt
concrete mixture. This
production method is called the plant-mix type.
[57] The pre-mix production method is to mix asphalt binders and highly
viscoelastic warm-mix
modifiers in advance to manufacture the uniform highly viscoelastic warm-mix
liquid asphalt
binders. These are brought to the asphalt plant to spray on aggregates and
fillers for production of
the corresponding modified warm mix asphalt. Meanwhile, the plant-mix method
is to insert asphalt
binders, specified amount of highly viscoelastic warm-mix modifiers,
aggregates and fillers
separately in the mixer of the asphalt plant and mix them well at the warm-mix
temperature to
produce the corresponding modified warm mix asphalt (WMA). Because both
methods are to
produce the same modified warm mix asphalt (WMA), either method can be used.
[58] The highly viscoelastic warm mix modifier constituted by the above
composition can be
applied to construct diverse asphalt pavements; in examples, the low-noisy
modified warm-mix
porous asphalt pavement using the low-noisy porous aggregates; the surface and
the base layer of
the modified warm-mix general asphalt pavements using the dense-graded or the
superpave
aggregates; the modified warm-mix RAP-recycled asphalt pavement using mixed
aggregates of
RAP and virgin or only RAP aggregates; the modified warm-mix bridge surface
pavement using the
bridge surface aggregates; the modified warm-mix SMA asphalt pavement using
the SMA
aggregates; the modified warm-mix airport-taxiway asphalt pavement using the
airport-taxiway
aggregates. The very modifier takes a key role in improving functionality,
performance, life-cycle of
each pavement mentioned above.
[59] Effects of the Invention & Intended Use
[60] Use of the highly viscoelastic warm-mix modifier manufactured by mixing
the highly elastic
polymers, the viscous ones and the crack-resistant warm-mix agents in the
appropriate rate can make
production of all kinds of modified asphalt concrete mixtures at a warm mix
temperature that allow
to construct the durable modified asphalt pavements. Production and
construction of these
pavements in this invention have advantages of air pollution reduction, saving
of fuel consumption,
lowering of material oxidative aging, shortening of traffic opening time as
the result of warm-mix
effect, and also improvement of pavement performance properties and extension
of pavement life
cycle as the result of increased viscoelasticity of asphalt binders.
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[61] Asphalt pavements mentioned above are indicated to be the surface, the
intermediate, the base
layers of modified asphalt pavements to be paved on the general traffic, the
low-noisy porous, the
RAP-recycled, the cold and the hot regional, the bridge surface and the SMA
roadways, classified as
pavement functionality, and major highways, urban and suburban traffic roads,
industrial heavy
traffic roads, local highways, airport taxiways classified as pavement usage.
The environment-
friendly modified warm-mix asphalt pavement will also provide reduction of
pavement maintenance
cost due to the pavement life-cycle extension.
[62] Examples for Best Practices of the Invention
[63] Compositions of highly viscoelastic warm-mix modifiers for the practice
(1, 2, 3) and the
comparison (1, 2, 3) are listed in Figure 6. Each modifier shown in Figure 6
is well mixed with a
given amount of an asphalt binder at 1800C for 2 hours to produce a
homogeneous modified asphalt
binder. Penetration tests are performed at 25 C for these modified asphalt
binders and the measured
results are displayed in Figure 6. For physical property measurement of the
highly viscoelastic
warm-mix modified asphalt concrete mixtures, 955kg of 19mm dense-graded
aggregates (30 wt%
RAP + 70 wt% virgin aggregate), 35kg of an asphalt binder (AC-20), 4kg of a
filler (limestone
powder), and 6kg of each modifier in the practice and those in the comparison
are uniformly mixed
at 140oC in the Marshall mixer. Each modified mixture-specimen is made by
inserting each
concrete mixture into the Marshall mold and compacting both sides in the mold
applying 75
Marshall strokes. After each specimen is cured for one day at the room
temperature, it is released
from the mold. Marshall stability tests are performed for each specimen by
following the testing
specification and the results are included in Figure 6.
[64] Figure 6 shows that the penetration value of viscoelastic warm-mix
modified asphalt binders
and the Marshall Stability of its asphalt concrete mixture in the practice (of
this invention) are
turned out to be further better, compared to those values of a general asphalt
binder or other
modified asphalt concrete mixtures in the comparison.
