U.S. patent application number 09/547126 was filed with the patent office on 2003-11-06 for composition for asphalt roofing materials.
Invention is credited to Curtis, Starr, Huege, Fred R..
Application Number | 20030207101 09/547126 |
Document ID | / |
Family ID | 29270908 |
Filed Date | 2003-11-06 |
United States Patent
Application |
20030207101 |
Kind Code |
A1 |
Huege, Fred R. ; et
al. |
November 6, 2003 |
Composition for asphalt roofing materials
Abstract
An asphalt roofing composition is provided in the form of a roll
or a shingle in which a hot mixture of an asphaltic base and filler
is applied to a substrate form, wherein the composition also
comprises an amount of Ca(OH).sub.2 (HL) in order to impart
strength and durability to the composition. The composition
contains HL between about 1-10%, and preferably between about 3-5%,
of the total composition by weight. The filler can be fly ash,
CaCO.sub.3, MgCO.sub.2.CaCO.sub.3, MgCO.sub.3, or other suitable
materials known in the art. In a typical embodiment of the
invention, the HL is added directly to the asphaltic base of the
composition either with the filler, or with filler added after
mixing the asphalt and HL.
Inventors: |
Huege, Fred R.;
(Colleyville, TX) ; Curtis, Starr; (Phoenix,
AZ) |
Correspondence
Address: |
CHARLES D. GUNTER, JR.
WHITAKER, CHALK, SWINDLE & SAWYER, LLP
3500 CITY CENTER TOWER II
301 COMMERCE STREET
FORT WORTH
TX
76102
US
|
Family ID: |
29270908 |
Appl. No.: |
09/547126 |
Filed: |
April 11, 2000 |
Current U.S.
Class: |
428/323 ;
428/489 |
Current CPC
Class: |
C08K 3/22 20130101; D06N
5/00 20130101; C08K 2003/2206 20130101; C08K 2003/2217 20130101;
Y10T 428/25 20150115; Y10T 428/31815 20150401; E04D 1/26 20130101;
C08K 3/22 20130101; C08L 95/00 20130101 |
Class at
Publication: |
428/323 ;
428/489 |
International
Class: |
D06N 005/00 |
Claims
What is claimed is:
1. An asphalt roofing composition in the form of a roll or a
shingle-like structure in which a hot mixture of an asphaltic base
and filler is applied to a substrate form, wherein the composition
also comprises an amount of an alkaline earth metal hydroxide in
order to impart strength and durability to the composition.
2. The composition of claim 1, wherein the alkaline earth metal
hydroxide is selected from a group consisting of Ca(OH).sub.2,
Mg(OH).sub.2, and Ca(OH).sub.2.Mg(OH).sub.2.
3. The composition of claim 1, wherein the alkaline earth metal
hydroxide is between about 1-10% by weight of asphalt.
4. The composition of claim 1, wherein the alkaline earth metal
hydroxide is between about 3-5% by weight of asphalt.
5. The composition of claim 1, wherein the filler is fly ash.
6. The composition of claim 1, wherein the filler is
CaCO.sub.3.
7. The composition of claim 1, wherein the filler is MgCO.sub.3 or
MgCO.sub.2.CaCO.sub.3.
8. The composition of claim 1, wherein the alkaline earth metal
hydroxide is first added directly to the asphaltic base of the
composition.
9. The composition of claim 1, wherein the alkaline earth metal
hydroxide is first added directly to the filler of the
composition.
10. The composition of claim 1, wherein the alkaline earth metal is
added first to the filler then to the asphaltic base of the
composition.
11. The composition of claim 1, wherein the composition is between
about 30% to 60% asphalt by weight.
12. An asphalt roofing composition in the form of a roll or a
shingle-like structure in which a hot mixture of an asphaltic base,
filler, and water is applied to a substrate form, wherein the
composition also comprises an amount of an alkaline earth metal
oxide in order to impart strength and durability to the
composition, the metal oxide reacting with water in the filler to
produce the corresponding metal hydroxide.
13. The composition of claim 12, wherein the alkaline earth metal
oxide is selected from a group consisting of CaO, MgO, and
CaO.MgO.
14. The composition of claim 12, wherein the alkaline earth metal
oxide is between about 1-10% by weight of asphalt.
15. The composition of claim 12, wherein the alkaline earth metal
oxide is between about 3-5% by weight of asphalt.
16. The composition of claim 12, wherein the filler is fly ash.
17. The composition of claim 12, wherein the filler is
CaCO.sub.3.
18. The composition of claim 12, wherein the filler is MgCO.sub.3
or MgCO.sub.2.CaCO.sub.3.
19. The composition of claim 12, wherein the alkaline earth metal
oxide is first added directly to the asphaltic base of the
composition.
20. The composition of claim 12, wherein the alkaline earth metal
oxide is added first to the filler with water, the oxide and water
thus reacting to form the corresponding hydroxide, the hydroxide
and filler then being added to the asphaltic base of the
composition.
21. The composition of claim 12, wherein the composition is between
about 30% to 60% asphalt by weight.
22. A method of forming an asphalt roofing composition in the form
of a roll or a shingle-like structure, the method comprising:
heating an amount of asphalt; providing a desired amount of an
alkaline earth metal hydroxide; providing a filler; combining the
asphalt, metal hydroxide, and filler to form the composition; and
placing the composition onto a substrate form and allowing the
second hot mixture to cool around the substrate form.
23. The method of claim 22, wherein the hot asphalt and the metal
hydroxide are first mixed to form a mixture, and the filler is then
added to form the composition.
24. The method of claim 22, wherein the metal hydroxide and filler
are first mixed to form a mixture, and the hot asphalt is then
added to form the composition.
25. The method of claim 22, wherein the alkaline earth metal
hydroxide is selected from a group consisting of
Ca(OH).sub.2.Mg(OH).sub.2, and Ca(OH).sub.2.Mg(OH).sub.2.
26. The method of claim 22, wherein the alkaline earth metal
hydroxide is between about 1-10% by weight of asphalt.
27. The method of claim 22, wherein the alkaline earth metal
hydroxide is between about 3-5% by weight of asphalt.
28. The method of claim 22, wherein the composition is between
about 30% to 60% asphalt by weight.
29. The method of claim 22, wherein the substrate form is a
fiberglass mat.
30. A method of forming an asphalt roofing composition in the form
of a roll or a shingle-like structure, the method comprising:
heating an amount of asphalt; providing a desired amount of an
alkaline earth metal oxide; providing a filler and water; combining
the asphalt, metal oxide, water and filler to form the composition;
and placing the composition onto a substrate form and allowing the
second hot mixture to cool around the substrate form.
31. The method of claim 30, wherein the metal hydroxide and filler
are first mixed with water to form a mixture, and the hot asphalt
then being added to form the composition.
32. The method of claim 30, wherein the alkaline earth metal oxide
is selected from a group consisting of CaO, MgO, and CaO.MgO.
33. The method of claim 30, wherein the alkaline earth metal oxide
is between about 1-10% by weight of asphalt.
34. The method of claim 30, wherein the alkaline earth metal oxide
is between about 3-5% by weight of asphalt.
35. The method of claim 30, wherein the composition is between
about 30% to 60% asphalt by weight.
36. The method of claim 30, wherein the substrate form is a
fiberglass mat.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to asphaltic or bituminous roofing
materials and methods, and more particularly to the manufacture of
such roofing materials to which hydrated lime
(Ca(OH).sub.2/abbreviated as "HL") is added to improve the
strength, durability and antioxidant qualities of the roofing
material. The roofing materials may be shingles, rolls, or other
materials to be placed on roofs.
[0003] 2. Description of the Prior Art
[0004] Asphalt roofing shingles are manufactured by taking a
continuous base sheet of organic felt or fibreglass (generally, a
web or form), saturating it in a base asphalt, covering it with a
coating asphalt, and then embedding granules on the top side of the
coated sheet. The granules protect the asphalt from breaking down
through oxidization by ultra violet rays. Fillers such as
CaCO.sub.3 and/or fly ash may also be used in the asphalt
composition. Finally, synthetic polymeric materials may also be
added to the asphalt. The finished sheet is cut into lanes and to a
desired length of shingles.
[0005] More specifically, in the manufacture of roofing shingles or
rolls, a heated asphaltic/filler blend is applied to a substrate
web or substrate form, such as a glass fiber mat or a felt. The mat
or felt is pre-shaped in the form that is desired for roofing
purposes. After the form or web is impregnated with the asphaltic
mix, a granular treatment may be applied to the hot asphalt surface
and rolled or pressed into place. The coated web composition is
then cooled so that it may be cut and bundled as shingles, or
formed into rolls.
[0006] The use of tar with HL to cover roofs is old in the art, as
disclosed in U.S. Pat. No. 61,787 (disclosing first coating wooden
shingles with HL, allowing it to dry, then coating the shingles
with the tar, followed by sand). Asphaltic or bituminous materials
as used in the roofing industry for pre-fabricated shingles or
asphalt rolls are well known in the art, with the examples being
described in U.S. Pat. No. 4,405,680 (disclosing a specific type of
asphalt with glass filaments and method of manufacture), and U.S.
Pat. No. 4,559,267 (disclosing a sealant bound to asphalt sheets).
Prior to application to the substrate or web form, the asphalt is
typically heated in an asphalt heater to a temperature of up to
500.degree. F. The heated asphalt is then blended with a filler
that may or may not be chemically inert, the filler also having
been preheated to a temperature necessary so as not to chill the
mix and to facilitate blending with the asphalt.
[0007] The choice filler has traditionally been based on
considerations of availability, compatibility and cost. An inert
filler material which has been preferred and used by many roofing
plants is powder limestone (CaCO.sub.3) or dolomite
(CaCO.sub.3.MgCO.sub.3), usually at a rate of about 40% to 70% by
weight of the mix. Other materials may also be blended with the
asphalt, such as block and anti-block polymers and thinners, as
well known in the art.
[0008] Powder limestone often has been a filler of choice as it is
widely available at a relatively low cost, and is compatible with
the asphalt mix. However, it is a poor conductor of heat when
compared to fly ash. It is relatively slow to heat, and therefore,
in the mix, tends to insulate the asphalt and retards the cooling
of the composite web or form. Further, CaCO.sub.3 is an active base
material, and it therefore tends to be acted upon by the weak acid
and the precipitation (acid rain) and is believed to contribute to
a shortened life of the roofing material. More importantly,
limestone fillers have been documented as the cause of algae growth
and discoloration in asphaltic shingled roofs. This is somewhat
undesirable since it decreases the life of the shingles, and also
lowers the aesthetic quality of the shingles. In this regard,
MgCO.sub.3 may be a better filler for asphalt.
[0009] In any case, it is desirable to have present in the asphalt
shingle a substance that can counter these and other detrimental
effects of filler agents or the asphalt itself. At the same time,
it is desirable to improve the durability of roofing material and
increase its tear strength. While HL has been recently disclosed in
use as a filler in asphalt for paving roads (U.S. Ser. No.
09/110,410, filed on Jul. 6, 1998), HL has not been used in asphalt
shingles or other roofing materials. Thus, the present invention
discloses a roofing composition that is an improvement on the prior
art that incorporates the advantages of HL.
SUMMARY OF THE INVENTION
[0010] One object of the present invention is to provide an
improved roofing composition of shingles or asphalt roll having a
low cost additive that imparts improved tear strength to the
shingles, and is cost effective to use.
[0011] Another object of the present invention is to provide an
asphalt shingle of improved strength that can be made with various
types of asphalt.
[0012] These and other objects are achieved in an asphalt roofing
composition in the form of a roll or a shingle-like structure in
which a hot mixture of an asphaltic base and filler is applied to a
substrate form, wherein the composition also comprises an amount of
hydrated lime (HL, such as any alkaline earth metal hydroxide) in
order to impart strength and durability to the composition. The
composition contains HL between about 1-10%, and preferably between
about 3-5%, of the asphalt by weight. The filler can be fly ash,
CaCO.sub.3, MgCO.sub.2.CaCO.sub.3, MgCO.sub.3, or other suitable
materials known in the art. In a typical embodiment of the
invention, the HL is added directly to the asphaltic base of the
composition either with the filler, or with filler added after
mixing the asphalt and HL, or mixing the asphalt with the filler
and then adding the HL.
[0013] Additional objects, features and advantages will be apparent
in the written description which follows.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a graph of a SHRP parameter as a measure of
permanent deformation potential for different asphalt binders with
the addition of 20% HL by weight of asphalt binder;
[0015] FIG. 2 is a graph of the change in viscosity of one HMA
composition as a function of reaction time and blending time;
[0016] FIG. 3 is a graph similar to FIG. 2, but showing the results
obtained with a second HMA composition;
[0017] FIG. 4 is a graph of fracture toughness for one HMA
composition with the addition of 20% by weight of HL;
[0018] FIG. 5 is a graph similar to FIG. 4, but with a second HMA
composition;
[0019] FIG. 6 is a graph of accumulated shear deformation for HMA
mixes using two different bituminous binders;
[0020] FIG. 7 is a graph of controlled-stain fatigue life comparing
HMA's with and without the addition of HL;
[0021] FIG. 8 is a top view of a typical asphalt shingle;
[0022] FIG. 9 is a top view of a roof having asphalt roll material
placed below a series of asphalt shingles; and
[0023] FIG. 10 is a graph of the tear strength of the shingles of
the invention when compared to traditional (control) shingles.
DETAILED DESCRIPTION OF THE INVENTION
[0024] The following abbreviations are used throughout the
specification: SHRP is Strategic Highway Research Program; HL is
hydrated lime (Ca(OH).sub.2.Mg(OH).sub.2 or
Ca(OH).sub.2.Mg(OH).sub.2); HMA is hot mix asphalt; and IDT is
Indirect Tensile. Other abbreviations are defined as they are
used.
[0025] The present invention is directed to improvements in asphalt
roofing materials and similar bituminous compositions in which a
lime component, preferably HL, is added directly to the asphalt or
asphalt in one embodiment, or first to the filler and then to the
asphalt in another embodiment. In yet another embodiment, the HL is
added to the mixture of filler and asphalt. Hereinafter, the terms
"bitumen" and "asphalt" are used interchangeably. Further, the term
HL is used to refer in general to any alkaline earth metal
hydroxide such as Mg(OH).sub.2 and Ca(OH).sub.2, or mineral mixture
thereof (generally, Ca(OH).sub.2.Mg(OH).sub.2). In the disclosure
which follows, the term "quicklime" refers to alkaline earth metal
oxides such as CaO, while the use of HL refers to alkaline earth
metal hydroxides such as Ca(OH).sub.2.
[0026] In the production of HL, limestone or calcium carbonate is
first heated to remove carbon dioxide. The remaining CaO is a very
active chemical. To improve the handling characteristics of the
quicklime, a controlled amount of water is added to form HL. Adding
a HL component to the aggregate or filler (e.g., rock, sand, fly
ash, limestone) in asphaltic compositions is done in the present
invention with the intention of improving the bond between the
aggregate/filler, fiber glass matte or other substrate form, and
asphalt, especially in the presence of water which has a stronger
affinity for the aggregate than the asphalt does. This in turn
improves the tear strength of the shingle-like structure or roofing
material. Hydrated lime added to the aggregate is an effective
antistripping agent and has been considered to have ancillary
positive effects on the asphalt mixture.
[0027] The mechanism by which HL improves aggregate-asphalt
adhesion and moisture sensitivity when the HL is added directly to
aggregate is reasonably well understood although some arguments
still exist as to the mechanisms responsible. It is theorized that
the lime decreases the interfacial tension between the asphalt and
water, thus resulting in good adhesion. It is also thought that the
HL improves the stripping resistance by interacting with the
carboxylic acids in the asphalt. This interaction forms insoluble
products that are readily adsorbed onto the surface of the
aggregate or filler, or in the specific case of roofing materials,
the substrate form or web used to make the shingle-like structures
or rolls. Some studies indicate that strong adsorption of calcium
onto mineral aggregate surfaces may contribute to bonding of
asphalt cements with the aggregate or filler.
[0028] The following data demonstrates that HL added directly to
asphalt has a multi-functional effect. The effect which is achieved
is more than simply that of an antistrip additive. Hydrated lime
was added directly to five different asphalts (denoted AAB, AD,
AAF, AAG and AAM) which represent the range of asphalts that would
reasonably be encountered in the United States and throughout most
of the world, as discussed in Table 1. Each of the selected
asphalts represents a wide variety of asphalt chemical and physical
properties. The research in the asphalt study concentrated on using
testing techniques that are now being accepted by the industry as
part of the Strategic Highway Research Program's (SHRP) Superpave
protocol. However, some non-traditional tests were also performed.
The testing protocol is given below in Table 1. Although these data
apply to asphalt compositions for road use, they also equally apply
in general to the use of asphalt/HL compositions in any conditions
where there is exposure to weather and physical stresses. These
results, along with those discussed in FIG. 10 below, show that the
asphaltic shingle composition of the present invention has improved
characteristics relative to typical asphalt shingles, the HL having
unexpected benefits.
1TABLE 1 Tests performed upon various bituminous compositions.
Parameters Test Measured Purpose of Test Series I - Investigation
Creep Assess low of low temperature compliance temperature
performance versus time fracture properties IDT - Performed at
three of loading - (2 replicates for low temperatures for one
ultimate each mixture system - hour to provide low compliance, 18
samples) temperature creep rate of compliance on mixtures change in
subject to aging (loose compliance mix and compacted mix) according
to Superpave protocol IDT - Tensile strength at Stress and Assess
low three low temperatures on strain at temperature mixtures
subjected to failure fracture properties aging as described above
(18 samples) (AAMAS protocol) Series II - Investigation Creep
Assess intermediate of intermediate compliance temperature
temperature performance versus time fracture fatigue IDT - creep
and tensile of loading - properties strength at intermediate
ultimate (36 samples) temperature (20.degree. C). to compliance,
assess fracture rate of properties (AAMAS change in protocol)
compliance Series III - Retained Assess effect of HL Investigation
of moisture tensile on moisture resistance strength resistance (18
Perform AASHTO T-283 samples) SERIES IV - Investigation Creep
Assess effect of HL of high temperature compliance on high
temperature performance versus time rutting Compressive creep of
loading - (6 samples) performed at 60.degree. C. one ultimate hour
to assess permanent compliance, deformation potential rate of
(AAMAS protocol) change in compliance Repeated load (axial Ultimate
Assess loading) accumulated susceptibility of permanent deformation
strain, rate permanent testing of deformation and the at 60.degree.
C. accumulated effect of HL strain and (6 samples) slope of steady
state region Repeated shear permanent Same as above Same as above
deformation testing at (6 samples) 60.degree. C.
[0029] The following summary of the experimental work is divided
into three sections: high temperature rheology, low temperature
rheology and intermediate temperature rheology. At high
temperatures, asphalt becomes soft and susceptible to shoving and
rutting when used in roadways, and creeping or deformation when
used as roofing materials. The tests performed evaluated the
ability of the asphalt to withstand the stresses induced in high
temperature environments. At low temperatures, asphalt becomes hard
and susceptible to fracture. This is particularly true for asphalt
mixtures that have become embrittled due to aging. The tests
performed at low temperatures evaluate the ability of the asphalt
to withstand load-induced and environmentally induced stresses at
low temperatures. Load-induced fatigue cracking typically occurs at
low and intermediate temperatures. The test performed at
intermediate or average temperatures assess the ability of the
asphalt to withstand fatigue at average or nominal temperatures.
The tests were conducted by reacting the asphalts in mass with the
HL in closed containers in accordance with the previously
enunciated testing protocols.
[0030] Evaluation of the Effects of HL on High Temperature
Rheology. Hydrated lime added directly to the asphalt in selected
ranges from about 10% to about 20% by weight, based on the total
weight of asphalt binder produces several high temperature rheology
effects which can be summarized as follows:
[0031] Hydrated lime added to asphalts has a very positive filler
effect. This effect substantially improves high temperature
rheological parameters which relate to resistance to permanent
deformation. FIG. 1 shows how 20% HL by weight asphalt binder
dramatically changes the SHRP parameter G*/sin .delta. which is
related to permanent deformation potential. A high G*/sin .delta.
results in reduced permanent deformation potential. Somewhere
between 10% and 20% HL by weight asphalt binder is required to
provide the desired high temperature rheological changes. In the HL
containing shingles, only about 1 to 10% HL by total weight of
asphaltic/filler composition is required to effectuate an
improvement in tear strength and antioxidant properties.
[0032] The high temperature rheology of HL-filled asphalts is
dependent on the time and temperature of blending of HL with the
asphalt. The process is asphalt specific. This finding demonstrates
that the interaction between HL and asphalt is likely not simply
physical but a chemical interaction may also exist.
[0033] FIGS. 2 and 3 illustrate the effect of reaction time at
149.degree. C. on HL in asphalt AAD to reaction time of longer than
five minutes. However, asphalt AAM requires a reaction time of
about 40 minutes to achieve viscosity equilibrium. This indicates a
physio-chemical interaction unique to specific binders. Note that
the untreated asphalts are unaffected by reaction time. Since the
asphalts were reacted in mass in closed containers, oxidative aging
should not be a factor. However, the HL, when added to the asphalt
in roofing materials, will decrease oxidative aging and thus
improve the performance of the shingles or roll materials.
[0034] Evaluation of the Effects of HL on Low Temperature Rheology.
The findings with regard to low temperature rheology are summarized
as follows:
[0035] Hydrated lime increases the low temperature stiffness of
asphalts indicating that they are more susceptible to low
temperature fracture. However, HL added at rates of 12.5% by weight
of asphalt and below has a small effect on low temperature
stiffness and does not significantly affect the slope of the
stiffness versus time of loading curve determined using the low
temperature Bending Beam Rheometer test. SHRP research indicates
that the slope is more important. Thus, adding 1-10% HL to the
asphalt composition will also improve the properties of the roofing
materials.
[0036] To evaluate whether the stiffness increase at low
temperature due to HL addition is important, low temperature
fracture tests were performed. Hydrated lime substantially improves
low temperature fracture toughness. The improved fracture toughness
and minimal effect on the slope of the stiffness versus time of
loading curve indicates improved low temperature crack resistance
despite the increased stiffness.
[0037] FIGS. 4 and 5 illustrate the effect of HL in improving
fracture toughness.
[0038] The improved low temperature properties are due to a
synergistic effect of reduction in the effect of oxidative aging
(as all samples are aged to simulate pavement aging before testing)
and crack pinning, a phenomenon of energy dissipation due to
microcrack interception by the dispersion of HL particles in the
asphalt.
[0039] Evaluation of Effects of HL on Intermediate Temperature
Rheology. The filler effect of HL is obvious at all temperatures.
However, at low temperatures the stiffening effect was proven to be
more than compensated for by the improvement in fracture toughness.
No generally recognized accepted binder tests are available by
which to evaluate intermediate temperature fatigue susceptibility.
Therefore, the following mixture tests used: direct tensile fatigue
tests and microcrack healing tests. These tests provided favorable
results which are discussed in the mixture section.
[0040] HL in Asphalt--Effects on Mixture Properties. Hydrated lime
was added to two asphalts with very different chemical and physical
properties. These asphalts are designated AAD and AAM. Mixtures
with Watsonville granite aggregate and 5.05% asphalt by total
weight of the mixture were subject to two types of mixture tests:
repeated shear permanent deformation testing and direct tensile
fatigue testing. The repeated stress, permanent deformation testing
was performed to assess rutting potential in the mixtures tested.
The direct tensile fatigue testing was performed to assess the
effect of lime on the potential of the mixture to develop fatigue
cracking. These are two of the dominant distress mechanisms in hot
mix asphalt pavements and are responsible for the vast majority of
pavement damage and deterioration.
[0041] Results of Permanent Deformation Testing. The repeated shear
permanent deformation testing was performed at 40.degree. C. The
testing was performed using a testing protocol developed in the
SHRP research program to simulate the stress state that an asphalt
mixture is subjected to under a moving wheel load. During the
testing sequence the mixture is subjected to a constant ratio of
axial stress and repeated shearing stresses.
[0042] Tests were performed on HMA mixtures prepared with four
different asphalt binders with and without HL as follows: AAD, AAD
12.5% HL, AAM and AAM with 12.5% HL. Three identical samples were
prepared for each mixture and the mixtures were subjected to a
20,000 lbs. load application. The tests revealed that the addition
of HL reduced the level of permanent deformation on average about
300% (FIG. 6), based on values of ultimate permanent strain after
20,000 cycles. The data were considerably variable, however.
Although the above tests were performed on mixtures of asphalt and
granite aggregate, the same or similar results are expected with
glass filaments and/or fly ash, or the substrate forms used to make
the shingles or roofing rolls of the invention, as they have the
common property of being siliceous and/or carbonaceous.
[0043] Results of Direct Tensile Fatigue Testing. The purpose of
direct tensile fatigue testing was to assess the resistance of
asphalt mixtures to load-induced (controlled-strain) fatigue
testing at intermediate (or average annual) pavement and exterior
temperatures that shingles will be exposed to. Identical mixtures
of Watsonville granite and 5.0% asphalt (by total weight of the
mixture) were prepared with asphalt binders with and without HL as
follows: AAD, AAD with 12.0% HL, AAM and AAM with 12.5% HL.
Analysis of the results of controlled-strain fatigue testing
demonstrated two findings. First, at a given level of stiffness,
the addition of HL improved fatigue life. Second, the recovery of
dissipated energy (responsible for crack healing) after rest
periods is enhanced by the addition of HL for mixtures subject to
age hardening. For a given design stiffness and for a mixtures
subject to age hardening, the addition of HL appears to enhance the
resistance to fatigue cracking.
[0044] FIG. 7 illustrates typical fatigue results where cycles to
failure (Nf) are compared for untreated and HL treated mixtures at
various mixture stiffness.
[0045] An invention has been shown with several advantages. HL is
an effective multi-functional additive which is effective in
improving the high temperature performance of hot mix asphalt.
[0046] Uniaxial tensile controlled strain fatigue tests, performed
on mixtures with and without the addition of HL added directly to
the binder, demonstrate that the lime addition improves the fatigue
life of the mixture (resistance to cracking) when mixtures are
compared at a common level of stiffness.
[0047] Shingles, shingle-like structures which come in various
forms, or asphalt rolls used for roofing typically are made from
glass impregnated mats or substrate forms, the asphalt and fillers,
etc. being bound and formed around the mat or form. The shingles
can be as shown in FIG. 8, wherein asphalt shingle 10 having an
adhesive strip 12 is shown. A number of shingles 10 are placed upon
a roof 16 as in FIG. 9, wherein sheet material from a roll of
asphalt material 14 is first placed on the roof underneath the
layered shingles 10. The roll comprises a rolled sheet of asphaltic
material, usually formed around a substrate web or form, the layer
of material placed directly in contact with the wood roofing
material prior to addition of the shingles as in FIG. 8. Further,
various polymers can be added to the asphalt along with the HL of
the invention, such as disclosed in U.S. Pat. No. 4,405,680.
[0048] Typical fillers for the composition include limestone and/or
dolomite dust and glass fibers of various sizes and lengths, sand,
rock (of various mineral composition), and other substantially
siliceous materials in ground and/or powdered form. The asphalt
utilized in the asphalt composition of the present invention is
typical of the industry. An asphalt of this type typically has a
softening point of between, for example, 190.degree. F. and
240.degree. F. and a penetration at 77.degree. F. between, for
example, 14 dmm and 25 dmm (dmm is tenths of a millimeter). In
saturating the substrate form, the asphalt is maintained in a
molten state, preferably at a temperature any where between
350.degree. F. and 450.degree. F. At this temperature and without
any fillers or additives, the molten asphalt has a viscosity and
Saybolt furol seconds of 100 and 300.
[0049] The physical properties of the asphalt, as recited herein,
are for exemplary purposes only. Any asphalt which functions in the
manner to be described herein may be utilized, and in fact, may be
readily provided by those skilled in the art. In this regard, the
saturating or coating temperature of the molten asphalt, or the
operating temperature as it is commonly called, will depend in part
on the particular asphalt used and in part on other ingredients in
the overall composition. In any event, the temperature of the
asphalt should be sufficiently high to readily saturate or coat the
substrate form with the asphalt composition, yet it should not be
maintained at a temperature higher than necessary. This is, of
course, because a large amount of energy is required to maintain
the composition in its molten state.
[0050] The asphalt composition of the present invention preferably
includes between about 30% and 50% asphalt by weight of the total
composition. When less than approximately 30% is provided, the
asphalt does not satisfactorily fulfill its intended purpose, that
is, it does not satisfactorily provide the ultimately produced
shingle or roll with adequate physical characteristics. In
addition, it tends to be too viscous at the preferred saturating
temperatures and thus increases creep. On the other hand, providing
the composition with more than 50% asphalt is not necessary and,
taking into account costs considerations, is not preferable. In
this regard, to extend the asphalt, a suitable conventional filler,
such as for example, limestone and other mineral filler is added
thereto.
[0051] The mineral filler is dispersed throughout the asphalt by
conventional means. For example, mechanical agitation, when the
asphalt is in its molten state, preferably at this saturating
temperature. Between approximately 45% and 55% mineral filler, by
way of the total composition, is preferably utilized. The exact
percentage of mineral filler provided will be dictated by the
amount of asphalt and the amount of glass in the form of glass
fiber bundles which are utilized in the composition, especially
when these are the only ingredients comprising the composition. Of
course, the filler must not be of a type or an amount which will
prevent saturation of the base sheet at any reasonable saturating
temperature.
[0052] There are several principle methods of mixing the
composition of the invention. The first is to add the HL to the
molten asphalt. The second is to add the HL to the filler first,
mixing or agitating it thoroughly first, with or without excess
water, then adding the molten asphalt. A third method is to first
mix the asphalt and filler, then add the HL to the mixture. In
either case, the HL is added to between 1% and 10% of the added
asphalt. Preferably, the HL is added to an amount between 3% and 5%
of the weight of the asphalt. Hydrated lime is added as a powder.
The asphalt/HL and/or filler/HL mixtures are typically agitated to
achieve an uniform distribution of the lime. This can be done with
a pug mill, however, in some cases vigorous mixing is not
necessary.
[0053] In one embodiment, the HL is added directly to the filler
first as a dry powder, both ground and mixed to form a homogeneous
mixture. The HL can be added prior to or after grinding the filler
material. In yet another embodiment, CaO (or CaO.MgO) is added to
wet or damp rock, thus being hydrated in a reaction between the CaO
and H.sub.2O to form Ca(OH).sub.2 (or Ca(OH).sub.2.Mg(OH).sub.2).
The reaction mixture is then ground to the desired particle size.
In yet another embodiment, CaO (or CaO.MgO) or HL slurry is added
to the rock prior to grinding to the desired particle size.
[0054] The HL can also be mixed with the asphalt as the asphalt is
heated to make the mixing easier. The temperature is dependent upon
the type of asphalt, as discussed above, and its viscosity.
[0055] As stated above, in accordance with the present invention, a
small percentage of glass in the form of glass fiber bundles is
added to the asphalt filler mixture. These glass fiber bundles are
dispersed throughout this mixture and could be dispersed throughout
the asphalt prior to the addition of the filler but in any case,
are added while the asphalt is in its molten state, preferably at
its saturating temperature. In this regard, the glass may be
dispersed in the asphalt by, for example, mechanical agitation.
[0056] As stated previously, the asphalt-filler mixture, when
maintained at the saturating temperature between 350.degree. F. and
450.degree. F., will have a sufficiently low viscosity so as to
permit easy saturation of the base sheet. While the addition of the
glass fiber bundles to this mixture will increase the viscosity
slightly, the amount and type of bundle selected must be such that
the overall composition at the saturating temperature has a
sufficiently viscosity level to permit easy saturation of the base
sheet.
[0057] The exact type of glass fiber mat which could be used may
vary and could also be readily determined by those skilled in the
art in view of the teaching of the present invention. However,
those which have been found to be acceptable are between
approximately 1/8 and 1/2 in length, including between 100 and 800
per bundle and having a filament diameter of, for example, 13 to 18
micrometers. The binder utilized in holder the micro filaments
together must be, of course, one of which will continue to hold the
bundles together, to at least to a substantial degree, and the
saturating temperature of the asphalt, even though the asphalt is
mildly agitated to disperse the glass bundles. It must also be one
which by melting, dissolving or any other way, allows the fiber
bundles to defilamentize to a large extent at substantially higher
asphalt temperatures, for example, at temperatures in excess of
700.degree. F. Limestone (CaCO.sub.3), sand, fly ash, and other
siliceous materials are typical binders used each alone or in some
combination.
[0058] In one embodiment of the present invention, the shingles are
manufactured by first providing a fiberglass mat of a preformed
shape and size. Hot asphalt having the filler and HL is then
applied to the top of the mat to the desired thickness. The asphalt
is then allowed to dry. Next, the uncoated side of the mat is
exposed, and hot asphalt is then applied to the uncoated surface to
the desired thickness. This is then allowed to dry. In a finished
product, sand or other decorative material may be added to the
surface prior to drying to adhere the sand or other material the
surface of the shingle.
[0059] The shingles of the present invention have the unexpected
advantage of having a greater tear strength than traditional
asphalt shingles not using HL. The data in FIG. 10 highlight this
aspect of the present invention, wherein control samples (filled
circles) of shingles that do not have HL were compared with the HL
containing shingles (closed squares) of the present invention.
Shingles of various thickness (in fractions of an inch) were
compared and the tear strength of each compared to one another. The
data for the HL shingles use a composition of 3% HL by weight of
asphalt. The line 101 is a best-fit line through the data for the
HL shingles of the invention, while the line 103 is the best-fit
line through the data for the control.
[0060] The increased tear strength of the HL shingles of the
present invention is an advantage over prior shingles. The shingles
of the present invention are more durable than prior shingles, and
at a minimal added cost as HL is a low cost additive. The low cost
is an advantage when compared to other asphalt shingles using
polymeric materials as additives to improve strength.
[0061] While the invention has been shown in only one of its forms,
it is not thus limited but is susceptible to various changes and
modifications without departing from the spirit thereof.
* * * * *