2,5,'2:-
THE POTENTIAL USE OF TAR SAND BITUMEN AS PAVING ASPHALT
J. Claine Petersen
Distinguished Scientist
Western Research Institute
larami e • Wyomi ng
. INTRODUCTION
The amount of asphalt used annually is about 30 million tons of
which about 24 million tons is used in paving.
Thus, the potential
exi sts for util i zati on of si gnifi cant amounts of tar sand bi tumen in
paving if the bitumen were commercially available and if the properties
of tar sand asphalts were suitable for paving use.
The commerci a 1
application of tar sand bitumen as a paving material has been limited to
the direct use of the tar sand as a surfacing material.
Tar sands from
the Asphalt Ridge,U~ah, deposit are quarried and blended with dry sand
to pave county roads, parking lots, and driveways.
Petroleum asphalt is
added to limestone tar sands from the Uvalde, Texas, deposit to prepare
a pa vi ng materi a 1.
Through the 1930' s, crushed tar sand from the Santa
Rosa, New Mexico, deposits were used to pave roads, streets, and airport
runways as far away as Seattle, Washington; and during the 1940's tar
sands from deposits in Utah, California, and Kentucky were quarried for
application as
quarri es,
paving
however,
materials.
The
tar
sands as obtained from
do not meet exi sti ng specifi cati ons as a hi ghway
construction material.
In thi s paper,
several
past studi es
(l-.!)
desi gned to evaluate
recovered tar sand bitumen as a pavi ng materi a 1 are revi ewed and the
Prepared for presentati on at the 1987 Summer Meeti ng of the Interstate
Oil Compact Commission, Coeur d'Alene, Idaho, June 22-24, 1987.
1
results of the studies compared.
Considerable data interpretation and
some additional data are supplied by the author.
The properties of tar
sand asphalts prepared from recovered bitumen are compared with those of
petroleum asphalts. The properties evaluated are those used for the
specification of paving asphalts together with additi.onal
properties
deemed important to the performance of asphalt in pavements.
MATERIALS EVALUATED
Tar sand asphalts prepared from different material sources and by
different recovery methods are discussed in this paper.
aspha lt
prepared
California
(Edna),
They are 1) an
from
sandstone
deposi ts
near
San
and
recovered
using
light
oil-assisted,
a
Lui s
Obi spo,
hot
(alkaline) water separation process U); 2) two asphalts prepared by a
similar
process
(Sunnyside)
and
from
Vernal
Asphalt
Ridge
(Asphalt
tar
Ridge),
sand
Utah
deposits
(~);
near
Price
3) two asphalts
prepared from bi tumen recovered duri ng the Larami e Energy Technology
Center's U.S. DOE in situ combustion project (TS-2C)
(il
conducted at
Utah's Northwest Asphalt Ridge deposit (Vernal); and 4) two asphalts
prepared from bi tumen recovered duri ng the Larami e Energy Technology
Center's U.S. DOE in situ steamflood recovery project (TS-IS)
conducted at the Utah Northwest Asphalt Ridge deposit.
(~),
also
The two asphalts
prepared from the in si tu combusti on bi tumen were prepared to grade by
the
author
evaluation.
and
supplied
to
the
subsequent
investigators
(~)
for
Several representative petroleum asphalts, identified in
the text, were used for property compari sons.
2
Experimental details
necessary for clarity are briefly provided as needed in the text.
For
additional detail the reader is referred to the original papers.
COMPARISON OF THE TAR SAND AND PETROLEUM ASPHALTS BASED ON
PROPERTIES OFTEN USED FOR SPECIFYING PAYING ASPHALTS
Before discussing the specific properties of the tar sand asphalts,
a few comments will be made regarding paving asphalt specifications.
These specifications, which have evolved over the years, deal with
easily measured asphalt properties that define the asphalt's suitability
for use in paving mixtures.
Consistency measurements (e.g., viscosity
or penetrati on) are probably the most important pri mary specifi cati on
considerations because they are important in determining the properties
of the pa vi ng mi xture duri ng preparati on and duri ng pavement construction
as well
as the properties of the
specification tests may not be functional
performance.
finished
pavement.
Some
with regard to pavement
Many important performance properties of paving asphalts
such as long-term durabil ity and factors related to pavement moi sture
damage are not adequately defined by standard specifications.
Thus,
additi ona 1 speci a 1 tests are often necessary; however, these speci a 1
tests have not been standardized for use in current paving technology.
Although each state or local unit may impose unique restrictions or
modifications regarding specifications, general specifications have been
adopted at the national level and can be found in readily available
publications (2..
~).
Specification-type data cited in the discussions
in this paper are those generally accepted by most transportation
agencies, although all agencies may not use the same types of data.
3
The approach used by a 11 of the i nvesti gators to prepare candi date
tar sand asphalts was to first prepare a material, by distillation of
oi 1s if necessary, to meet consi stency specifi cati ons (penetrati on or
vi scos;ty). foll owed by the measurement of other properti es to determi ne
how these remai ni ng properti escompared wi th those of speci ncati on
petroleum asphalts.
Tar Sand Asphalts from Hot Water Process
In Table 1 the properties of the three tar sand asphalts recovered
by the hot water process (from tar sand deposits in Edna, California,
and Sunnysi de and Vernal,
Utah) are compared with the properti es of
three petroleum asphalts prepared from different crude oil sources.
The
consistency of all three petroleum asphalts was 80 penetration at 77°F
(2S·C); penetration values of the Edna, Sunnyside, and Vernal tar sand
asphalts
were
80,
84,
and
64,
respectively.
Both
viscosity
and
penetration measurements at temperatures other than 77°F (2S0C) for the
tar sand asphalts compare favorably with those of the petroleum asphalts
and fall within the normal range of variability expected for materials
from different sources.
Results of the ash determinations, spot tests, and loss on heating
measurements for the tar sand asphalts, however, were different than
correspondi ng results for the petrol eum asphalts and requi re further
di scussi on.
As seen in the table, the ash content of the tar sand
..
aspha 1ts was consi derab 1y hi gher than that of the petrol eum asphalts.
Also, ash determinations by direct ashing of the tar sand asphalts was
considerably higher than determinations by a filtration method using an
asphalt solution (ASTM D4-42).
The lower ash content obtained by
4
Tab 1e 1.
Compari son of PrQperti es of Tar Sand Asphalts Prepared from Hot
WUet-Separated Bitumen with Properties of Several Petroleum Asphalts
Edna,
Ca 1i fl
t1l
Asphalt yield, %
Ash, %
Spot test
Solubility in
carbontetrachloride, %
Specific gravity, 77°F (25°C)
Flash point, of (OC)
Penetration, dmm
77°F (25°C), 100g, 5 sec
60°F (15.5°C), 100g, 5 sec
34°F (1°C), 200g, 60 sec
Viscosity, poise
210°F (99°C)
275°F (135°C)
Ductility, 77°F (25°C), 5 cm/min
Softening point, of (OC)
Loss on heating, %
77°F (25°C) Pen of
loss on heating residue
1
2
3
'I
Data from (1)
Data from ("2)
ASTM 04-42Di rect ash
Tar sand asghalts
Sunnyside, Vernal,
Utah 2
Utah 2
L
Petroleum as~fia1ts
Kern Rtver, Oregon Basin, Tampi co,
Califl
Ca 1ifl
Mexico 1
100
100
94.5
0.5 3 , 2.0 4 0.8 3 , 2.14 0.5 3 , 1.8 4
Positive
Posi ti ve
Positi ve
53.0
03
Negative
43.6
03
Negative
72.2
03
Negati ve
99.6
1.087
505 (263)
100
1.012
550 (288)
100
1.028
570 (299)
100
1.038
510 (266)
80
26
14
24.4
2.71
116 (47)
0.45
66
100
1.020
460 (238)
84
32
23
62.6
7.39
100+
123 (51)
0.40
57
100
1.012
505 (263)
64
18
11
36.7
3.93
100+
121 (49)
0.11
54
80
22
10
18.3
1.93
100+
111 (44)
0
71
80
26
17
33.8
3.72
100+
116 (47)
0
70
80
34
26
72.6
7.31
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121 (49)
0.2
68
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fil trati on ref1 ects the fi neness of the mi nera 1 parti c1 es in the tar
sand asphalt.
Although most asphalt speci fi cati ons 1i mi t ash content,
sma 11 amounts of mi nera 1 matter in the asphalt may not necessaril y be
detrimental.
A certain amount of mineral fines are a normal part of a
pavement aggregate mixture.
Small amounts of ash in tar sand asphalts
coul d most 1i kel y be taken into account duri ng the desi gn of the
pavement mixtures.
The spot test measures the presence in asphalts of components that
are not soluble in petroleum naphtha.
functi ona 1 wi th
regard
to
pavement
The test in itself is nonperformance
and
was
i niti ally
deve loped to detect aspha lts that had been thermally cracked duri ng
manufacture.
Such asphalts often had poor component compatibility that
resulted in poor aging and flow characteristics.
The tar sand asphalts
probably gave a positive spot test because of the presence of the
mineral matter just described.
As will be seen later, evidence suggests
that tar sand asphalts may actually have better aging characteristics
than typical petroleum asphalts.
Loss on heating data were obtained from a test in which an asphalt
film was exposed to the atmosphere at 325°F (163°C) for a specified
period of time.
The test detects asphalts with volatile components that
might be lost both. during the hot mix operation and possibly during the
service life of the
pavement.
hardening of the asphalt.
during
the
test.
If
Volatile
loss
leads to undesirable
The asphalt also hardens from air oxidation
both
volatile
loss
and
oxidation
occur
simultaneously during the test, it is difficult to assess the relative
contribution of each factor to the total hardening of the asphalt.
Both
the Edna and Sunnyside tar sand asphalts showed relatively high volatile
6
loss
(Table
1)
compared with the
petroleum asphalts.
Thi sloss
undoubtedly contributed to the relatively high drop in 77°F (25°C)
penetration for the tar sand asphalts (80 to 66 and 84 to 57) during the
loss on heating test.
Support for thi s explanation can be found by
examination of the relatively lower drop in penetration (64 to 54) for
Volatile components found in the
the less volatile Vernal asphalt.
laboratory-prepared asphalts may not represent an inherent deficiency of
the
tar
sand
bitumen
but
may
reflect
the
presence
of
components
introduced by the the method of bitumen recovery and/or the inefficiency
of the laboratory distillation.
The previous investigators estimated
(2) that approximately two percent of the fuel oil diluent used in the
recovery process remained in the bitumen.
This may have contributed to
the volatility observed.
Tar Sand Asphalts from In Situ Steamflood
Data in Table 2 compare the properties of two tar sand asphalts
prepared from bi tumen obtained by in si tu steamf100d (.±.' 6) whi ch meet
the consi stency requi rements of AC-5 and AC-30 pa vi ng asphalts.
The
properties are compared with Table 1 and Table 2 ASTM specifications for
the corresponding grades of petroleum asphalts.
are more restrictive than those of Table 1.
Table 2 specifications
The data show that the tar
sand asphalts easily met both sets of speci fi cati ons.
The hi gh 77 of
(25°C) penetration value for the tar sand AC-5 asphalt suggests that it
has a low temperature suscepti bil i ty in the lower temperature range.
This property could be desirable
since it often relates to better
pavement resistance to low-temperature cracking.
The relatively high
ductility for the AC-30 tar sand asphalt also suggests the potential for
good low temperature flow properties.
7
Table 2.
Comparison of Properties of Tar Sand Asphalts Prepared from Utah
In Situ Steamflood-Bi-tumen-wlth SpeeHi-eationsfor Paving Asphalts l
AC-5 Asphalt
ASTM
Specifications
TS-IS
for AC-5
Bitumen
Yield from TS-IS Bitumen, %
Solubility in trichloroethylene, %
Flash point, C.O.C., of (OC)
AC-30 Asphalt
ASTM
Specifications
for AC-30
TS-1S
+600°F (+316°C)
residue
100
99.0 (min)
350 (177) (min)
99.7
450 (232)
93
99.0 (min)
450 (232) (min)
99.7
511 (266)
00
Penetration, 77°F (25°C), 100g, 5 sec
120 2 ,
140 3
Viscosity, poise
140°F (60°C)
275°F (135°C)
500±100
1.10 2 , 1.75 3 (min)
Thin-film oven test residue,
Viscosity, 140°F (60°C), poise
Ductility, 77°F (25°C), 5 cm/min
2500 (max)
100 2 ,3 (min)
(min)
223
515
1.70
2032
105+
50 (min)
3000±600
3.50 3 (min)
15000 (max)
40 3 (min)
63
2800
3.40
4290
105+
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2
3
Data from (4)
ASTM D-3381~ Table 1
ASTM D-3381, Table 2
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Tar Sand Asphalts from in Situ Combustion
In Table 3 the properties of two tar sand asphalts prepared from
bitumen obtained by in situ combusti on (l,..
properties
of a
petroleum asphalt
2.)
routinely
standard by the i nvesti gators (1.).
are compared wi th the
used
as
a laboratory
The two tar sand asphalts were
prepared to AC-IO grade, one by vacuum di sti 11 ati on and the other by
fl ash evaporati on.
fi ve percent.
Ash contents of these asphalts were hi gh at near
Thi s hi gh ash content is refl ected in the tri chl oro-
ethylene solubility data and possibly in the spot test results.
Note
that the laboratory standard petroleum asphalt also showed a positive
spot test. yet this asphalt typically performs well in the field.
As previously seen for the in situ steamflood tar sand asphalt.
both of the in situ combustion tar sand asphalts showed relatively high
77°F (25°C) penetration values of 196 and 208 compared with the minimum
of 70 and 60 shown in the ASTM Table 1 and Table 2 specifi cati ons.
respectively.
Penetration values measured at 39.2°F (4°C) were also
relatively high.
indicating a softer asphalt at lower temperatures.
Softening points of the asphalts. on the other hand, were relatively
hi gh,
i ndi cati ng
greater
resi stance
to
flow
at
somewhat
hi gher
temperatures.
Viscosity data at 275°F (135°C) show that the viscosity temperature
suscepti bil i ty of the tar sand asphalts was re 1ati ve 1y hi gh at hi gh
temperatures.
This is evidenced by a relatively low viscosity (below
specifications) in this temperature region.
This temperature region is
used during mixing and pavement 1aydown.
Finally. the results of the thin film oven test show that both tar
sand asphalts lost weight on heating as a result of volatile loss. while
9
Table 3.
o
Comparison of Properties of Tar Sand Asphalts Prepared from In Situ COlllbustion
Process Bitumen with Properties of Laboratory Standard Petroleum Asphaltl
Ash, %
Spot test
Solubility, trichloroethylene, %
Flash point, of
(OC)
Specific Gravity, 77°F (25°C)
Penetration, dmm
77°F (25°C), 100g, 5 sec
60°F (I5.5°C), 100g, 5 sec
39.2°F (4°C), 100g, 5 sec
39.2°F (4°C), 200g, 60 sec
Viscosity, poise
77°F (25°C)
140°F (60°C)
275°F (135°C)
Ductility, 77°F (25°C), 5 em/min
Softening point, of (OC)
Thin film oven test
Loss on heating, %
Pen of residue, 77°F (25°C)
Due of residue, 77°F (25°C)
Vis of residue, 140°F (60°C)
2
3
4
Data from (3)
ASTM D-338C
Table 1
Table 2
TS-2C Vac
distilled tar
sand asphalt
TS-2C Flash
evaporated tar
sand asphalt
about 5
Positive
94
568 (298)
about 5
Positive
95
562 (294)
0.998
0.995
196
55
14
55
208
67
12
65
2.6x10 5
1070
1. 36
53
127 (53)
2.3x10 5
960
1. 29
60
121 (49)
1.5
88
62
3400
2.1
94
101
3800
ASTM
Speci fi cati ons 2
for AC-10
99.0 (mi n)
425 3 , 450 4 (min)
(219) (232)
Lab standard
petroleum
asphalt
Posi ti ve
99.9
697 (369)
1.02
70 3 , 60 4 (min)
118
4
26
1000±200
1.50 3 , 2.50 4 (min)
50 3 , 75 4 (min)
5000 (max)
5.8x105
1580
3.8
150+
107 (42)
Negative
68
150+
3050
the petroleum asphalt showed negligible loss.
As mentioned previously,
these volatiles may be present because of inefficient laboratory distillation during bitumen recovery.
The higher volatile loss for the two
asphalts is seen for the asphalt that was obtained by the relatively
inefficient flash evaporation procedure.
In spite of the relatively
high volatile losses during heating, the 140°F (60°C) viscosities of the
tar sand asphalt resi dues after heati ng (3400 and 3800 poi se) were sti 11
below the maximum allowed by the specifications.
Volatile losses of the
magnitude seen produce significant hardening of the asphalt and probably
account for the major portion of the hardening seen during the thin film
oven test, thus suggesting that the tar sand asphalts are inherently
resistant to oxidative hardening.
1ater in
more detail.
Oxidative hardening will be discussed
The ductil i ty values of the tar sand asphalt
resi dues from the thi n fil magi ng test were hi gher than the ductil i ty
\.,
_.,
values measured before thin
film aging.
These
results are
highly
unusua 1 and suggest desi rab 1e agi ng characteri sti cs for the tar sand
asphalts.
TEMPERATURE SUSCEPTIBILITY OF TAR SAND ASPHALTS
The suscepti bi 1ity of asphalt to physi ca 1 property change wi th
varying temperature is an important performance-related variable.
general,
a
high
susceptibility
to
a
change
in
consistency
In
with
temperature is undesirable because this can lead to unstable pavements
at high temperatures, which may deform or rut; and to highly brittle
pa vements at low temperature, whi ch may crack from therma 11y-i nduced
11
stress.
The temperature susceptibilities of the tar sand asphalts were
computed by a number of different methods
corresponding calculated data for several
(l) and compared with
petroleum asphalts.
The
results of these calculations are shown in Table 4.
The vi seosi ty temperature suscepti btl i ty through the temperature
range of 140 OF (60°C) and 275 OF (135°C) is shown by data in the fi rst
two line entries of Table 4.
temperature susceptibility.
Greater numerical values indicate greater
In general, data for the tar sand asphalts
were similar to data for the petroleum asphalts, except for the two in
situ combustion asphalts (TS-2C vacuum residue and TS-2C flash residue)
which
showed
higher temperature
exists that the high mineral
susceptibilities.
The possibility
fines contents of these asphalts may
contribute to the increased viscosity temperature susceptibility of
these asphalts in the hi gh temperature range.
In the mi dtemperature
range, the viscosity temperature susceptibilities of the two tar sand in
si tu combusti on asphalts were si mil ar to that of the 1ab standard
asphalt, as seen by data in the third line entry of Table 4.
The
penetration ratio (fourth line, Table 4), calculated from penetration
determinations at 39.2°F (4°C) and 77°F (25°C). indicate that the two in
situ combustion asphalts may have lower temperature susceptibilities in
the low temperature range than the other tar sand asphalts and most of
the petroleum asphalts.
Lower numerical values for penetration index
and data in the remaining line entries in Table 4 indicate lower
temperature susceptibilities.
Data in the fifth line entry (penetration
index) show that the two in si tu combusti on asphalts ex hi bit reduced
temperature
susceptibilities
compared
with
all
other
asphalts
calculated from the penetration at 77°C (25°C) and the softening
12
as
Table 4.
Comparison of Temperature Susceptibilities of Tar Sa.nd Asphalts
with Temperature Susceptibilities of Petroleum Asphalts l
,
Parameter
Edna,
Calif
Sunnysi de,
Utah
Tar sand aSEhalts
Vernal,
Utah
VTS2,3 (140, 275·F)
( 60, 135·C)
VTS4,3 (210, 275·F)
( 99, 135·C)
3.68
3.57
3.00
w
Penetration
17.5
27.4
3.77
4.22
TS-2C
Flash
resid
Kern
Ri ver,
Calif
Petroleum aSEhalts
Oregon
Lab
Basi n,
Tampi co,
Mexico
standard
Calif
3.45
4.23
3.83
3.42
VTS5,3 (77, 140·F)
(25, 60·C)
ratio 6 ,7
TS-IS
(AC-5)
TS-2C
TS-IS
Vac
(AC-30) resi d
3.41
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3.22
3.61
3.50
3.52
17.2
28
31
12.5
21.2
32.5
22
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Penetration index 8 ,7
-0.92
0.28
-0.74
4.3
3.7
-1. 73
-0.92
-0.14
-1.4
Pen/vis number 9 ,7
-1.05
0.49
-1.27
-1.20
-1.20
-1.55
-0.58
-0.75
-0.10
1 Parameters calculated from data in (2) and (3); methods of calculation found in (3)
2 Viscosity temperature susceptibility-:- calculated from viscosities at 140 (60) and-275·F (135·C)
3 Greater numbers mean greater temperature susceptibility
4 Viscosity temperature susceptibility, calculated from viscosities at 210 (99) and 275·F (135·C)
5 Viscosity temperature susceptibility, calculated from viscosities at 77 (25) and 140·F (60·C)
6 Calculated from penetrations at 39.2 (4) and 77·F (25·C)
7 Lower numbers mean greater temperature susceptibility
8 Calculated from penetration at 77·F (25·C) and softening point, ·F
9 Calculated from penetration at 77·F (25·C) and viscosity at 275·F (135·C)
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point.
Calculated pen/vis numbers in the last line entry in the table,
obtained from penetration data at 77°F and viscosity data at 140°F
(60"C) - midrange temperature determinations - show that the temperature
susceptibilities of all asphalts were within the same general range.
In summary, the tar sand asphalts, except for the two in situ
combusti on
asphalts,
petY'ol eum asphalts.
showed
S1 mil ar
temperature
suscepti bi 1 i ties to
The two in si tu combusti on tar sand asphalts, on
the other hand, seemed to have greater temperature susceptibility in the
hi gher temperature range and lower temperature suscepti bil i ty in the
lower temperature range.'
COMPOSITION-RELATED PROPERTY COMPARISONS
Limited
composition
petro 1eum asphalts.
contents
of
several
data
are
available comparing tar
sand and
Table 5 summari zes vanadi urn, sulfur, and nitrogen
of
the
study
asphalts
together
with
data
on
component analyses as determi ned from sol ubil tty and chromatographi c
characteri sti cs.
The vanadi urn content of the two in situ combusti on
aspha lts was low at near 4 ppm.
Many petrol eum asphalts have hi gher
vanadium contents than this, sometimes exceeding 1000 ppm.
The sulfur
content of the Cal iforni a tar sand asphalt was 3.24 %, in the mi drange
region for petroleum asphalts, while the Utah tar sand asphalts showed
low sulfur contents of 0.50 and 0.38%.
The nitrogen contents of the tar
sand asphalts generally were one percent or greater, which is usually
the upper limit for petroleum asphalts, whose typical
about 0.2 to about 0.6% nitrogen.
14
range is from
Table 5.
eom~ar.t~Q.l!.rr~~-eq-l)flIlT5tttnrr__ Related
Aspfialts
P-rQpertlesof Tar sand
with COrresponding Properties for Petroleum Asphalts l
Tar Sand asphalts
Property
Edna,
Calif
Sunnyside,
Utah
Vernal,
Utah
Vanadi um, ppm
Sulfur, %
3.24
0.50
0.38
Nitrogen, %
1. 23
0.96
1.2
Oil s, %
TS-2C
Vac resi d
TS-2C
Flash resid
3.7
4.2
Petroleum asphalts
Oregon
Tampi co,
Kern Ri vert Basi n,
Mexico
Calif
Calif
__ 2
__ 2
__ 2
1.23
4.81
6.12
__ 3
__ 3
__ 3
1.2
1.1
44
31.0
32.0
46.5
46.0
42.5
33
48.0
49.5
40.5
33.5
27.5
21.0
18.3
13.0
20.5
30.0
01
Resi ns,
%
Aspha1tenes, % 23
1
2
3
23
15
Data from (1-3) and records of author
Not determined. Typical range for most petroleum asphalts is from a few to over 1000 ppm
Not determined. Typical range for most petroleum asphalts is from 0.2 to 0.6%
Component analyses, as reflected in the oil, resin, and asphaltene
determinations that are reported in Table 5, are similar for both tar
sand and petroleum asphalts.
The significance of component analyses
wi th regard to asphalt performance has not been estab 1i shed.
Thi sis
not surpri si ng si nce the data report only wei ght percents offracti ons
and not information on the chemical composition of the fractions.
AGING CHARACTERISTICS OF TAR SAND ASPHALTS
Age-hardening of asphalts
in
pavement service, primarily from
reaction of the asphalt with atmospheric oxygen, is a major factor
contri buti ng to reduced durabi 1i ty, poor performance characteri sti cs,
and a shortened servi ce 1 i fe of asphalt pavements.
Data presented
earlier suggested that some tar sand asphalts might exhibit better-thanusual aging characteristics.
Data in Table 6 show the properties of the
two Utah in situ steamflood asphalts and four petroleum asphalts before
and after being subjected to the thin film accelerated aging test
(TFAAT).
The
TFAAT was
specifically designed
to
match,
in the
laboratory, the level of oxidative aging and the level of volatile loss
normally experienced by an asphalt in a typical pavement after 10-15
years of service.
In the test, a thin asphalt film (0.16 mm) is exposed
at 235°F (113°C) to air under conditions of restricted volatile loss for
a
period
evaluation.
of
72
hours,
followed
by
recovery
of the
asphalt
for
Because volatile loss is controlled, data obtained on
asphalts from this test should be more indicative of actual pavement
aging than data obtained from the thin film oven test in which volatile
16
Table 6.
Aging~Characteristics of Asphalts Aged Using the Thin Film
Accelerated Aging Test (TFAAT)l
I
1
Tar sand
TS-1S
(AC-S)
"
TS-1S
(AC-30)
AC-S
Petroleum
A
AC-20
as~ha1ts
As~halt
I
as~ha1ts
1
.. As~halt B
AC-20
AC""S
Viscosity,2 unaged
4.S9xl02
2.11xl0 3
6.81x10 2
2.53x10 3
5.14x10 2
2.S3x10 3
Vi scosity,2 aged
5.68x10 3
1. 74x10 4
9.02x104
1. 79x10 6
1.65x10 4
4.44x10 5
132
708
Agi ng
i ndex 3
Log viscosity increase
on agi ng 4
12.4
2.09
8.3
1.92
3.07
3.85
32
2.51
175
3.24
1
iI
I
I
It
I
~
Specialized laboratory aging test run at 23SoF (113°C) in which both the level of oxidation
and volatile loss are controlled to match 10-lS years of pavement aging
2 Complex dynamic shear viscosity, measured at 140°F (60°C) between 25 mm parallel plates
spaced 1.0 mm apart, sine wave loading at 50% strain, unaged and aged viscosity
readings at 15.9 and 0.126 radians/second, respectively
3 Viscosity after aging divided by viscosity before aging
4 Log viscosity after aging minus log viscosity before aging
1
J
7,
l
!
~
!I
i
1
q
I
i
~
,
I
\f
:!
I
I
I!
I,
!
!
j
loss is significantly greater than that which occurs during pavement
service.
From the viscosity data in Table 6, the log viscosity increase
on agi ng and an agi ng index (vi seosi ty after agi ng di vi ded by vi scosi ty
before aging) were calculated and are reported in the table.
As seen in
the table, the vi scosity increase of the tar sand asphalts on agi ng was
significantly lower than
asphalts.
The
aging
the
index
viscosity
data
increase
al so
characteristics for the tar sand asphalts.
of the
suggest
petroleum
superior
aging
As will be seen in the next
section, tar sand asphalts recovered from laboratory-prepared pavement
mixtures also showed superior aging characteristics.
The reduced
hardening rate, together with favorable ductility in aged tar sand
asphalts, as mentioned previously, suggest that tar sand asphalts should
exhibit excellent durability in pavement service.
PROPERTIES OF ASPHALT-AGGREGATE MIXTURES PREPARED USING
TAR SAND ASPHALTS
Asphalt pavement mixtures were prepared in the laboratory (3) using
the two TS-2C in situ combusti on asphalts and the 1aboratory standard
petrol eum aspha 1t.
The 1aboratory mi xtures were prepared usi ng graded
gravel and limestone aggregates which met specifications for paving mixtures.
The wet and dry strengths of standard specimens fabricated from
these mi xtures are shown in Table 7.
Tensil e strengths of dry mixtures
prepared usi ng the petrol eum asphalt were hi gher than those prepared
from the tar sand asphalt; however, thi sis not unexpected because of
the higher initial viscosity of the petroleum asphalt (Table 3).
18
Values
Table 7.
Wet and Dry Strength Properties of Laboratory Pavement
Mixtures Prepared from Tar Sand Asphalts l
Tensile strength 2
Asphalt
Aggregate
Dry
After soak 3
Tensi 1e
strength
ratio'+
TS-2C
Vac' resid
Gravel
Li mestone
70
85
100
120
1.43
1.41
TS-2C
Flash resid
Gravel
Li mestone
70
85
73
110
1.04
1.29
Petro~eum
Gra ve 1
Li mestone
110
150
100
90
0.91
0.60
1ab standard
Data from (3)
Tensile spll'tting test, 68°F (20°C), 2 in./min displacement rate
After soaking vacuum-saturated specimen in water for seven days
at 68°F (20°C)
'+ Tensile strength after soak divided by dry tensile strength
1
2
3
for the mi xture prepared from the tar sand asphalt are acceptable.
particular
significance,
however,
are
the tensile
strengths of the
specimens after soaking in water for seven days at 68°F (20°C).
specimens
prepared
using
tar
sand
asphalts
Of
actually
increased
All
in
strength after exposure to water, while the specimens prepared using the
petroleum asphalt decreased in strength.
The relative differences in
strengths of the wet and dry samples are shown in the table as tensile
strength ratios.
Tensi 1e strength rati os for the tar sand asphalt
mixtures ranged from 1.04 to 1.43 compared with values of 0.91 and 0.60
for the petroleum asphalt mixtures.
Most petrol eum asphalt pavement mi xtures lose strength when wet.
In
fact,
poor pavement performance from the detri menta 1 effects of
moi sture is a major problem inmost parts of the country.
Further
confirmation of the ability of tar sand asphalts to produce asphalt-
19
aggregate mixtures with superior resistance to moisture damage is shown
by the test results in Table 8.
In the test
(~.
sma 11 bri quets are
prepared from asphalt-aggregate mi xtures in whi ch a uniform aggregate
size is used to allow water to easily penetrate the briquet and also to
maximize the effect of the asphalt-'aggregate adhesive bond properties on
briquet stabil ity.
These bri quets are submerged in water. suspended on
a stress pedestal. and subjected to freeze-thaw. warm water-soak cycling
until the briquets fail from cracking.
In the study from whi ch the
results in Table 8 were taken. a moisture-sensitive limestone aggregate
Note that the br; quets prepared us; ng the four petroleum
was u.sed.
asphalts failed in from one to seven freeze-thaw cycles.
However.
briquets prepared using the two tar sand asphalts failed after 10 and 14
repeated freeze-thaw cycles.
have
Results of this test using other materials
shown a fair correlation with results of moisture tests on
laboratory mixtures
Table 8.
(~)
and with field pavement results (11).
Susceptibility of Asphalt-Aggregate Briquets 1
to Moisture-Induced Damage 2
Asphalt 3
Type
Freeze-thaw
cycles to failure
B-2959
B-3036
8-3051
B-3602
Petroleum
Petroleum
Petroleum
Petrol eum
2
TS-2C Vac resi d
TS-2C Flash resid
Tar sand
Tar sand
14
10
1
2
3
1
2
7
Briquet prepared using a high calcium limestone
Data from (9)
All asphaltS; AC-10 grade
20
Asphalts used in the laboratory-prepared mixtures
(1)
described in
Table 7 were recovered from these mixtures by solvent extraction, and
physical properties were determined for the recovered asphalts.
are shown in Table 9.
Results
Of particular significance are the aging indexes
calcu.lated from the viscosities at 140·F (60·C) before and after the
aging.
The
conditioning.
aging
occurred
during
specimen
preparation
and
The tar sand asphalts showed lower aging indexes than the
petroleum asphalt.
Although the level of aging is relatively low for
these asphalts compared to the 1eve 1 of agi ng of the asphalts from the
TFAAT
described
earlier,
the
results
do
again
characteri sti cs for the tar sand asphalts.
suggest
good
aging
The softening point and
penetration data shown in Table 9 are less useful in evaluating the
changes on agi ng because non-Newtoni an flow beha vi or domi nates these
measurements; however, nothing about these data suggests abnormal aging
characteristics for the tar sand asphalts.
SUMMARY AND CONCLUSIONS
The
properties of several
tar
sand asphalts
prepared in
past
studies by several different investigators were compared with each other
and with the properties of petroleum asphalts.
These results were
revi ewed and di scussed wi th regard to the potential use of tar sand
bitumen in pavement applications.
The data show that tar sand bitumens
ha ve good potenti a 1 for use in
hi ghway pa vements that meet today IS
performance requirements.
No deficiencies in the tar sand asphalts were
found that would be expected to seriously affect performance.
21
On the
'\
9
Table 9.
Comparison of Properties of Asphalts Recovered from laboratory
Pavement Mixtures with Properties of Initial Asphaltsl
TS-2C Vac
distilled tar sand asphalt
Recovered from
Initial Gravel
Limestone
Penetration. 77°F(25°C). dmm
N
N
196
101
2.6x10 5 7.0x105
103
TS-2C Flash
evaporated tar sand asphalt
Recovered from
Initial Gravel
Limestone
208
91
120
Lab
standard petroleum asphalt
Recovered from
Initial Gravel limestone
118
55
53
2.3x10 5 1. Ox10 6 4.0x10 5
5.8x105
Viscosity. 140°F(60°C). poise 1.07x10 3 1.70x10 3 1.92x10 3
9.6x10 2
1.78x10 3 1.36x10 3
1.58x10 3 4.63x10 3 4.32x10 3
Softening point. °F(OC)
121 (44)
149(65)
Viscosity. 77°F(25°C). poise
Viscosity aging index 2 at
140°F (60°C)
1
2
127(53)
4.0x10 5
138(59)
150(66)
1. 59
1. 79
1.85
Data from (3)
Vi scosi ty oT recovered asphalt divi ded by vi seosi ty of i ni ti a 1 aspha 1t
141(61)
1.42
107(42)
3.9x10 6 3.8x10 6
129(54) 128(53)
2.93
2.73
other hand,
the data indicate that some tar sand asphalts may have
superior aging characteristics, being relatively resistant to oxidative
age
hardening
compared
with
typical
petroleum
asphalts.
Asphalt-
aggr'egate mixtures prepared usi ng two tar sand asphalts also showed
acceptab le strength p.roperti es and excell ent resi stance to moi stureinduced damage.
ACKNOWLEDGMENT
The author expresses thanks to the United States Department of
Energy
for
fundi ng the
preparati on
of thi s paper under Cooperati ve
Agreement Number DE-FC21-83FE60177.
REFERENCES
1.
Shea, G. P., and R. V. Higgens. "Laboratory Study of the Hot-Water
Process for Separating Hydrocarbons from Surface Deposits of
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October 1948, Report of Investigations 4246.
2.
Wenger, W. J., R. L. Hubbard, and M. L. Whisman. "Separation and
Utilization Studies of Bitumens from Bituminous Sandstones of
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Part II.
Analytical Data on Asphalt
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Mines, May 1952, Report of Investigations 4871.
3.
Button, J. W., J. A. Epps, and B. M. Gallaway.
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4.
Thomas, K. P., P. M. Harnsberger, and F. D. Guffey. "An Evaluation
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Center.
23
5.
Johnson, L. A., Jr., L. J. Fahy, L. J. Romanowski, Jr., R. V.
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6.
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7.
Annual Book of ASTM$tandards, Section 4, Construction, Volume 403,
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8.
Standard Specifications for Transportation i~aterials and Methods of
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9.
Plancher, H., G. Miyake, R. C Venable, and J. C. Petersen.
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10.
Petersen, J. C., H. Plancher, E. K. Ensley, R. L. Venable, and G.
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11.
Kennedy, T. W., F. L. Roberts, and K. IA. Lee.
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24