CA1249105A - Road asphalt compositions containing visbreaking residues - Google Patents

Abstract

Abstract:

A road asphalt composition having a penetration at 25°C in the range of 85 to 100 is made by blending to-gether: (a) a pitch having an initial boiling point of at least 520°C obtained as a residue in the visbreaking of crude oil, and (b) a distillation residue having a penetration at 25°C in the range of 150 to 500 obtained in the distillation of crude oil.

Description

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Road asphalt compositions containinq visbreaking residues Background of the Invention This invention relates to asphaltic compositions which are suitable for use as road paving materials.
Asphalt is a natural constituent of crude oils and is typically produced from the distillation residues of refining feedstocks. This product is of very signifi-cant industrial importance since it is widely used in the construction of roads, building materials and othe industrial applications. This asphalt has normally been obtained from conventional petroleum oils.
With the changing economics of the petroleum industry, there is a trend toward the conversion of heavy hydro-carbon oils, such as distillation residues, to light and intermediate naphthas of good quality for reforming feed~
stocks, fuel oil and gas oils.
Most petroleum refineries have visbreaker units and produce visbreaking pitches, i.e. residues of distillation boiling above 524C. It has been reported by Giavarini, Fuel, 63, lS15 (1984) that visbxeaking residuum by itself is not suitable for road asphalt production as this re-siduum is very temperature susceptible and is thermally unstable. Nevertheless, this visbreaking residuum would be an attractive component of a road asphalt composition if its deficencies could be overcome.

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Asphalt cement specifications for road paving purposes are given in Table 1 below.

Table 1 - Asphalt cement specifications for road purpose (16-GP-3M) Grade 85~100 _ 120-150 150-200 Requirements Min. Max. Min. Max. Min. MaxO ASTM
_ ___ _ Method Penetration 85 100 120 150 150 200 D5 (25C, 100~, 5s) Flash point 230 - 220 - 220 - D92 (CO C, C) Ductility 100 - 100 - 100 D113 (25C, 5 cm/min, cm) Thin film oven test 47 ~- 42 - 40 - D 1745 (Pen. of residue % of original Pen.) Solubility in Tri~
chloroethylene 99.0 - 99.0 - 99.0 - D 2042 (wt ~) Summary of the Invention I~ has been found in accordance wi~h the present inven-tion that visbreaking residues can be used as a component of road asphalt compositions when blended with suitable other materials.
Thus, the invention in its broadest aspect relates to a paving grade asphalt composition having a penetration at 25C in the range of 85 to 100 which comprises a blend of (a-) a petroleum pitch having an initial boiling point of at least 520C obt~ined as a residue in the visbreaking of crude oil, and (b) a distillation residue having a penetration at 25C in the range of 150 to 500 obtained in the distillation of crude oil.
The pitches that are used in the present inventLon are residues of visbreaking which usually boil above 520C and they typically come from the visbreaking of regular crude olls. While the pitches wh.ich can be used may be derived from visbreaking processes providing a wide range of conversions, they are usually derived frotn processes having a conversion in the range of about 20 to 35~.
The distillation residue is typically a natural or virgin hydrocarbQn product in that it has been subjected to distillation only. The distlllation residues should have a minimum penetration at 25C of 150 and typically have penetrations in the range of 150 to 500. The dis-tillation residue can obtained from a wide variety ~f natural or virgin sourees, including bitumen from tar sands, heavy oils and from eonventional crude oils. The bitumens and heavy oils normally contain a large propor-tion of materials which boil above 524C, and a parti-cularly suitable distillation residue is one derived from Athabasca bitumen.
The visbreaking residue and distillation residue can be blended in ~idely varying proportions, provided the resulting blend meets the specification of Table 1.
Normally the composition will contain from 20 to 85% by weight of visbreaking piteh, with a range of 25 to 55%
by weight being preferred.
Descri~on of the Preferred Embodiment _ Throughout this speeification, certain special terms of the art are used which are defined as follows:
A~E~ Charàeteristie (Ie) The Ie is defined as follows Ic = -~Saturates + Asphaltenes wt~
Arc~a~cs~ Resms Asphalt cements typically have Ic value in the range of 0.4 to 0.9.
: Craeking Temperature of Asphalt Cements An important factor in the eold Morth Ameriean cli-: .

mates is the cracking temperature of asphalt pavement.
Based on road tests over 5 years, a nomograph has been developed which allows the prediction of the road crack-ing temperature of asphalt pavements. This is described in Gaw, et al., "Road Performances After Five Years and Laboratory Predictions of Low Temperature Per~ormance"~
Proceedings Can. Tech. Asphalt Association, 45 (1974).
The cracking temperature is easily calculated by deter- ' mining the penetration of the asphalt cement at two dif-ferent temperatures.
Cohesivit~
In surface dressing, aggregates are deposited on a film of asphalt cement on the road. The resistance to the stripping of the aggregates due to traffic is related to a property which can be defined as the cohesivity. For an 85 - 100 penetration road asphalt cement, the measure-i ment of the cohesivity v. temperature allows the compari-son of different asphalt cements.
The cohesivity was determined by the ram pendulum method as described in Marvillet, et al., "Cohesion", Critere d'appreciation des hauts pour enduits '1Symposium Eurobitume, Cannes, France, 1981. The method consists of ~easuring the energy absorbed by the breakage of a cement film. A striped 1 cm cube representing an aggregate is glued with asphalt cement on a support. The cube over the support allows 1 mm thickness of asphalt cement. The tip of the ram pendulum hits the cube after travelling 180 around a shaft. On impact, the asphalt cement bonded to the support is broken on the median sideO A dial fixed to the shaft allows the measurement of the travel of the ram pendulum in degrees.
Temperature Suscepti_ility Thermal susceptibility of asphalt cements is an im-portant characteristic for predicting the behaviour of asphalt pavements. A low temperature susceptibility is most desirable.
The method used for determining temperature suscep-tibility was that developed by the "Laboratoire Central des Ponts et Chaussees" in France and shown as ~ethod RLB-1-1964 in the text "Bitwnes et bitumes fluxes", Dunod 1965. This method is based on the determination of the penetration a~ dif~erent temperatures. The penetration index (PI) is ca]culated from these data. The PI indi-cates the thermal susceptibi~ity of asphalt cements.
Certain preferred features of the present invention will be better understood from consideration of the experimental data in the following examples.
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Samples of a variety of blending materials and asphalt cements were obtained as follows:
1. Visbreaking distillation residue (+524C), about 30~ conversion and obtained from the Petro Canada refinery in Montreal

2. Visbreaking distillation residue ~+524C), about 30% conversion and obtained from a refinery in France

3. Asphalt cement 85-100 penetration obtained from the Petro Canada refinery in Montreal

4. Asphalt cement 85-100 penetration obtained from a refinery in France

5~ Interprovincial Pipeline Crude (IPL) distillation residue ~+427C)

6. Athabasca bitumen distillation residue (+371C) Blending Different blends were prepared using as one component of each blend the visbreaking residue samples described above and as the other component one of the distillation residue samples. These blends were prepared to meet the 85-100 penetration specification of Table 1. The actual s blends prepared were as follows:
1. Asphalt cement blend obtained from mixing 68 wt %
Sample 1 with 32 wt % Sample 5 2. Asphalt cement blend obtained from mixing 85 wt Sample 2 with 15 wt % Sample 5 3. Asphalt cement blend obtained from mixing 46 wt %
Sample 1 with 54 wt % Sample 6 The above blending materials, blends and asphalt cements had the chemical analyses and physical properties shown in Tables 2, 3 and 4 below.

Table 2 - Composition and pro~ es _ f the~ E~

Sample . 1 2 3 4 5 6 7 8 9 -Penetration 24 4285 85 too 24587 92 93 25C, 100 q, 5s soft Predicted - - -44 -37 - - -46 -46 -39 cracking temperature, i C
Cohesivity - - 40 43 - - 30 35 TM, C
CM, kg/cm2 - -8.7 7.7 - -7.3 6.8 Penetration - --0.5 -0.5 - -+105+0~4 ~0.1 Index (PI) -.. ..

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_ 9 The compound type distribution results of the samples are shown in Tables 5 and 6 below.

Table 5_ Compound-ty~e distribut_on of s~
_ __ (n-he~ e solubles, wt %~
aturates Mono-diaromatics Polyaromatics Resins . _ ~ ~
1 20.9 18.5 28.5 32.1 2 23.0 18.2 19.3 39.5 3 2(~.4 31.4 27.2 21.0 4 16.4 20.9 30.0 32.7 5 47.6 16.7 16.8 18.9 6 22.8 21.6 25.2 30.4

7 30.0 17.3 22.7 30.0

8 27.1 18.0 13.9 36.0 g 19.8 19.4 27.3 33.5 Table_6 - Compound-ty~e dist~ibution of samples S~ 5~-9~ romaticsResinsAsphaltenes Ic 114.1 31.8 21.7 32.4 *
217.5 28.5 30.0 24.0 *
317.7 51.0 18.3 13.0 0.44 413.0 40.2 25.9 20.9 0.51 545.3 31.9 18.0 ~.8 *
6l9.Q 39.0 25.4 16~6 *
722.6 30.1 22.6 24.7 0.89 8 21.3 28.9 28.2 21.6 0.75

9 _ _ 6 0 37.8 27.1 19 ol O ~ 54 * Ic is meaningful only for asphalt cement ,:

Gel permeation chromatography (GPC) was used ~or deter-mining the average molecular weight of the various samples herein. Tl-e results of these analyses are shown in Table 7 below.

Table 7 - Molecular weiqht distribution by gel _ permeation chromatography (GPC~

Average Molecular Wei~ht SampleOriginal Maltenes Asphaltenes 4 1970 10g0 4300 8 7~0 920 940 It will be seen from the above results that the pre-dicted cracking temperature oÇ asphalt pavements improved by increasing saturates and resins content.
The cohesivity tests indicated that the blends (Samples 7 and 8) are comparable to conventional asphalt cements ~Samples 3 and 4).
The temperature susceptibility tests indicated that conventional asphalt cements (Samples 3 and 4) are more temperature susceptible than the blends (Samples 7, 8 and 9). The best product in terms Qf low temperature susceptibility ~as the blend prepared in which the dis-tillation Lesidue was ohtained from Athabasca bitumen.

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Claims (7)

Claims:

1. A road asphalt composition having a penetration at 25°C in the range of 85 to 100 comprising a blend of:
(a) a pitch having an initial boiling point of at least 520°C obtained as a residue in the visbreaking of crude oil, and (b) a distillation residue having a penetration at 25°C in the range of 150 to 500 obtained in the distil-lation of crude oil.

2. A composition according to claim 1 wherein the distillation residue is obtained from the distillation of tar sand bitumen, heavy hydrocarbon oil, or conventional hydrocarbon oil.

3. A composition according to claim 2 wherein the distillation residue is obtained from the distillation of tar sand bitumen or heavy hydrocarbon oil containing a major proportion of material boiling above 524°C.

4. A composition according to claim 2 wherein the distillation residue is obtained from the distillation of tar sand bitumen.

5. A composition according to claim 2 wherein the visbreaking pitch is present in proportions ranging from about 20 to about 85% by weight of said blend.

6. A composition according to claim 5 wherein the visbreaking pitch is present in proportions ranging from about 25 to about 55% by weight of said blend.

7. A composition according to claim 5 wherein the visbreaking pitch is obtained from a process having a conversion in the range of about 20 to 35%.