CA2684443A1 - Method of producing bituminous paving mixes using foamed asphalt - Google Patents
Method of producing bituminous paving mixes using foamed asphalt Download PDFInfo
- Publication number
- CA2684443A1 CA2684443A1 CA2684443A CA2684443A CA2684443A1 CA 2684443 A1 CA2684443 A1 CA 2684443A1 CA 2684443 A CA2684443 A CA 2684443A CA 2684443 A CA2684443 A CA 2684443A CA 2684443 A1 CA2684443 A1 CA 2684443A1
- Authority
- CA
- Canada
- Prior art keywords
- asphalt
- mixing
- bitumen
- aggregate
- mix
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C19/00—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving
- E01C19/02—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving for preparing the materials
- E01C19/10—Apparatus or plants for premixing or precoating aggregate or fillers with non-hydraulic binders, e.g. with bitumen, with resins, i.e. producing mixtures or coating aggregates otherwise than by penetrating or surface dressing; Apparatus for premixing non-hydraulic mixtures prior to placing or for reconditioning salvaged non-hydraulic compositions
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
- B01F25/50—Circulation mixers, e.g. wherein at least part of the mixture is discharged from and reintroduced into a receptacle
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
- B01F27/60—Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a horizontal or inclined axis
- B01F27/70—Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a horizontal or inclined axis with paddles, blades or arms
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
- C08J9/06—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a chemical blowing agent
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L95/00—Compositions of bituminous materials, e.g. asphalt, tar, pitch
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
- B01F23/50—Mixing liquids with solids
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2395/00—Bituminous materials, e.g. asphalt, tar or pitch
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A30/00—Adapting or protecting infrastructure or their operation
- Y02A30/30—Adapting or protecting infrastructure or their operation in transportation, e.g. on roads, waterways or railways
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Polymers & Plastics (AREA)
- Civil Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Health & Medical Sciences (AREA)
- Medicinal Chemistry (AREA)
- Architecture (AREA)
- General Chemical & Material Sciences (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Road Paving Structures (AREA)
Abstract
The invention describes a process for preparing asphalt-aggregate compositions used for paving. According to the invention, the asphalt is foamed using a dry foaming method prior to mixing with the aggregate in the mixing plant. The foamed asphalt has a lower viscosity than the non-foamed asphalt and this has a double benefit. First, it reduces the mixing time required to obtain good coverage of the aggregate particles.
According to another aspect of the invention, the process can be used to produce warm mix asphalt by using temperatures lower than those normally encountered in hot mix asphalt plants, without any detrimental effect to the properties of the obtained mix. This invention can be applied to any new or existing asphalt mixing plant.
According to another aspect of the invention, the process can be used to produce warm mix asphalt by using temperatures lower than those normally encountered in hot mix asphalt plants, without any detrimental effect to the properties of the obtained mix. This invention can be applied to any new or existing asphalt mixing plant.
Description
Background and description of prior art Asphalt pavements consist of a mixture of asphalt cement (or asphalt binder) and aggregate. The aggregate consists of coarse aggregate such as crushed stone, and fine aggregate such as sand and fillers. The asphalt binder is most commonly obtained as the heavy fraction of petroleum refining and makes for approximately 4 to 7% of the total weight of the mix. The binder can be further modified through the addition of additives in order to improve the performance of the pavement, for example the rutting resistance, moisture sensitivity or serviceable temperature range.
Until the recent years there were two prevalent methods of obtaining asphalt concrete, namely the hot mix process and the cold mix process. In the hot mix process the aggregate and the binder are heated at elevated temperature, and then mixed until uniform coating of the aggregate is obtained. The hot mix facilities can be batch plants or drum-mix plants, where the aggregate and the asphalt cement are continuously fed in the process, while hot mix is withdrawn at the same rate.
A common method of obtaining cold mix asphalt is to emulsify the asphalt binder prior to mixing with the cold aggregate. This does not require a significant energy intake, and hence it is less expensive and more environmentally friendly than hot mix asphalt. The major drawback is that the quality of the asphalt concrete produced in this process is significantly inferior to hot mix asphalt, resulting in short life cycles of the pavement.
The reasons for the poor performance are related to the presence of water in the mix.
Among other things, this causes incomplete coverage of the aggregate with binder and poor adhesion of the two components. The lack of adequate adhesion causes further deterioration of the pavement by what is known as stripping, ravelling or pitting.
A more recent approach to asphalt paving is the warm mix asphalt. In general terms, this process operates in a similar manner with the hot mix technology. One defining difference is that the components are heated to temperatures lower than those involved in hot mix plants. This temperature depends on the grade of the asphalt, but decreases of up to 50 C have been reported. Some of the advantages of the warm mix asphalt technologies are lower fuel consumption, less emissions of greenhouse gas and other pollutants, as well as shorter times before the road can be open to traffic.
There are several types of warm mix technologies available and considering the means used to obtain the reduction in temperature they can use either some kind of additive, or a process for foaming the asphalt, or a combination of both.
Asphaltan B is a mixture of compounds based on lignite (Montan) wax and other higher molecular weight hydrocarbons. Sasobit is a Fisher-Tropsh wax which is added in small amounts to the asphalt binder or directly to the mixing drum. The principle behind using waxes is the lubricating effect that they have when the temperature exceeds the melting temperature of the additive. Waxes however change the properties of the binder significantly, generally shifting up the service temperature range. This will carry with it a financial burden, since softer binders, which are needed to obtain a certain grade, are usually more expensive than harder binders. There is also concern that the presence of wax in the asphalt binder negatively affects the low temperature performance of the pavement due to crystallization. Other chemical additives are used to improve the workability and compaction of asphalt mixtures and they are available as emulsions or as stand-alone packages (EvothermTM family). As a general rule the use of additives significantly increases the unit cost of asphalt mix produced and may negatively affect the performance of the pavement.
US patent application 2008/0259714 describes a method and the apparatus to produce warm mix asphalt by foaming the asphalt binder prior to mixing it with the aggregate.
The foaming process reduces the viscosity of the binder, allowing mixing and compacting at reduced temperatures. The foaming of the asphalt is achieved by introducing from about 0.6 to about 2% water in the hot binder. This poses a concern from at least two perspectives. Firstly, water is introduced intentionally into the mix, and this carries with it the risks mentioned before, namely poor adhesion between the binder and the aggregate, and consequently it can be detrimental to the mix stability. Secondly, the water is vaporized and this is an energy intensive process, energy which is lost.
Other foaming processes make use of synthetic zeolites, such as Advera or Aspha-min . The zeolites contain approximately 20% water, which is released when the inorganic additive comes in contact with the heated binder. The released water vapours cause the foaming of the binder reducing the viscosity and thus improving workability.
The cost of the additive and the moisture introduced in the mix make this option less than satisfactory for producing warm mix asphalt.
Another technology using the foaming of the binder is known as LEA (Low Emission Asphalt). In brief, the hot coarse aggregate is mixed with the hot asphalt binder containing a chemical additive, the cold finer aggregate (sand) being subsequently added to the mix. The sand is wet, and the moisture present causes the foaming action of the binder. Significant energy savings are reported for this process, but again the moisture introduced in the mix points away from the generally accepted idea that moisture present in the mix is detrimental to mix properties and pavement performance.
Canadian patent 2238368 describes a process to prepare warm mix asphalt, in which a binder with a penetration of less than 200 dmm as measured by ASTM D5 at 25 C, most preferably below 10 dmm, is added to mixture of aggregate and another softer binder component of penetration higher than 200 dmm as measured by ASTM D5 at 25 C, most preferably higher than 800 dmm. This process can be operated at temperatures below 140 C. However, the use of two binder components would require additional storage facilities at the plant and some operational challenges. Also, most user agencies have specific requirements regarding the asphalt binders used on their projects.
Mixing two components would make it very difficult to predict the properties of the resulting asphalt mix. A variation of the above process is described in US patent 6846354, in which the hard bituminous binder is foamed by adding 2 to 7% water. Beyond suffering from the same shortcomings as the Canadian patent referenced herein, water is purposely introduced in the mix and this can adversely affect the properties of the mix.
A review of the available warm mix asphalt technologies reveals some important reasons for which they are less than ideal alternatives to hot mix asphalt. The cost of additives can be prohibitive, the properties of the asphalt binder are changed, or the moisture introduced in the asphalt mix raises concerns regarding the durability of the pavement. It would be desirable if a method would be developed that would allow the production of warm mix asphalt while at the same time circumventing the above mentioned shortcomings. One way would be to use a foaming agent other than water to produce foamed asphalt.
US patent 2,876,126 discloses a process for mixing fine aggregate with asphalt by foaming the asphalt prior to mixing with the fine aggregate in order to obtain a flowable composition. The foaming action is obtained by incorporating a gas, a gassing agent or a solvent into the asphalt mass. Optionally, the process can be carried out at elevated pressures when solvent is used to create the foaming action. The invention requires the bitumen to have a proportion of 8 to 15% by weight of the total composition, fine aggregates (maximum size 7 mm) and it is used for making asphalt mastics.
US patent 4,256,734 discloses the use of foamed asphalt for road surfacing.
The foaming action can be obtained for example by injecting a gas or a liquid into the hot binder. The boiling point of the liquid must be lower than the temperature of the binder to ensure it evaporates. Optionally, when a liquid is used as foaming agent the pressure can be increased in order to keep the liquid from evaporating before leaving the mixing chamber. The invention deals exclusively with road surfacing, where the binder and the aggregate are not mixed prior to laying on the road.
Explanation of technical terms As used herein, the terms asphalt cement or asphalt binder or binder or asphalt or bitumen refer to a material that is used in conjunction with aggregate to produce asphalt concrete and they are used interchangeably.
As used herein, the terms aggregate or aggregate material refers to crushed stone and other particulate materials that are used in the construction of asphalt concrete such as sand, gravel, natural and synthetic fibres and others.
As used herein, the term asphalt concrete refers to bituminous paving mixes.
As used herein, the terms gas and gaseous component refer to a substance or mixture of substances that exist in gas phase under conditions of normal temperature and pressure.
As used herein, a gassing agent is a substance or a mixture of substances that release a gaseous component when added to the hot bitumen. The released gas is the result of either thermal decomposition of the gassing agent, or of a chemical reaction.
As used herein, a dry asphalt foaming method refers to a method of foaming the asphalt in which foaming is caused by a component that under conditions of normal temperature and pressure is not in liquid form. Notwithstanding the above, and although not recommended because of the reasons discussed above, water vapours could still be used in conjunction with the said non-liquid components without departing from the spirit and teachings of this invention.
Summary of the invention The present invention describes a process to produce asphalt-aggregate mixes used for paving applications. In one embodiment of this invention the asphalt binder is mixed with a gas or a mixture of gases at super atmospheric pressure. The asphalt and the gas component are introduced in a mixing chamber where they are allowed to stay in contact such that the gas will dissolve and/or disperse in the binder. The efficiency of the mixing process can be improved with the aid of one or more mechanical mixers or some other method available to the practitioner, such as, for example, recirculation of the mixture of asphalt cement and gases. The mixing chamber may consist of one independent enclosure or several enclosures. The chamber has one or more inlets for the liquid asphalt, one or more inlets for the gaseous component, and one or more outlets for the asphalt/gas mix.
Alternatively, the liquid asphalt and the gas component may be pre-mixed prior to entering the mixing chamber, such that they share some or all of the inlets.
The asphalt-gas mixing chamber can alternatively be replaced by in-line mixing such as directly into the line that transports the liquid asphalt to the aggregate-asphalt mixing compartment.
When the mixture of asphalt and gas exits the mixing chamber at pressures below those present in the mixing chamber, the gas expands and causes the foaming of the liquid binder. In this foamed state the asphalt binder may be further processed in the asphalt mixing plant.
In another embodiment of this invention, the bitumen is mixed with gassing agents in order to obtain foamed asphalt. Without limiting the scope of the invention, examples of possible gassing agents are inorganic carbonates, azo derivatives and the combination of isocyanates with a suitable co-reagent.
Brief description of the drawings Figure 1 shows a schematic comparison of asphalt mix production routes using the conventional hot mix process and the process involving dry foaming of the binder prior to mixing with aggregate.
Figure 2 shows an example of a method to foam the binder. This particular example uses air specified amounts (ratio) of air and binder which are mixed together with the air of mechanical mixers. The asphalt/air mix is inspected and should the desired properties not be met, some of the mix can be recirculated to obtain better dispersion or air in asphalt.
Until the recent years there were two prevalent methods of obtaining asphalt concrete, namely the hot mix process and the cold mix process. In the hot mix process the aggregate and the binder are heated at elevated temperature, and then mixed until uniform coating of the aggregate is obtained. The hot mix facilities can be batch plants or drum-mix plants, where the aggregate and the asphalt cement are continuously fed in the process, while hot mix is withdrawn at the same rate.
A common method of obtaining cold mix asphalt is to emulsify the asphalt binder prior to mixing with the cold aggregate. This does not require a significant energy intake, and hence it is less expensive and more environmentally friendly than hot mix asphalt. The major drawback is that the quality of the asphalt concrete produced in this process is significantly inferior to hot mix asphalt, resulting in short life cycles of the pavement.
The reasons for the poor performance are related to the presence of water in the mix.
Among other things, this causes incomplete coverage of the aggregate with binder and poor adhesion of the two components. The lack of adequate adhesion causes further deterioration of the pavement by what is known as stripping, ravelling or pitting.
A more recent approach to asphalt paving is the warm mix asphalt. In general terms, this process operates in a similar manner with the hot mix technology. One defining difference is that the components are heated to temperatures lower than those involved in hot mix plants. This temperature depends on the grade of the asphalt, but decreases of up to 50 C have been reported. Some of the advantages of the warm mix asphalt technologies are lower fuel consumption, less emissions of greenhouse gas and other pollutants, as well as shorter times before the road can be open to traffic.
There are several types of warm mix technologies available and considering the means used to obtain the reduction in temperature they can use either some kind of additive, or a process for foaming the asphalt, or a combination of both.
Asphaltan B is a mixture of compounds based on lignite (Montan) wax and other higher molecular weight hydrocarbons. Sasobit is a Fisher-Tropsh wax which is added in small amounts to the asphalt binder or directly to the mixing drum. The principle behind using waxes is the lubricating effect that they have when the temperature exceeds the melting temperature of the additive. Waxes however change the properties of the binder significantly, generally shifting up the service temperature range. This will carry with it a financial burden, since softer binders, which are needed to obtain a certain grade, are usually more expensive than harder binders. There is also concern that the presence of wax in the asphalt binder negatively affects the low temperature performance of the pavement due to crystallization. Other chemical additives are used to improve the workability and compaction of asphalt mixtures and they are available as emulsions or as stand-alone packages (EvothermTM family). As a general rule the use of additives significantly increases the unit cost of asphalt mix produced and may negatively affect the performance of the pavement.
US patent application 2008/0259714 describes a method and the apparatus to produce warm mix asphalt by foaming the asphalt binder prior to mixing it with the aggregate.
The foaming process reduces the viscosity of the binder, allowing mixing and compacting at reduced temperatures. The foaming of the asphalt is achieved by introducing from about 0.6 to about 2% water in the hot binder. This poses a concern from at least two perspectives. Firstly, water is introduced intentionally into the mix, and this carries with it the risks mentioned before, namely poor adhesion between the binder and the aggregate, and consequently it can be detrimental to the mix stability. Secondly, the water is vaporized and this is an energy intensive process, energy which is lost.
Other foaming processes make use of synthetic zeolites, such as Advera or Aspha-min . The zeolites contain approximately 20% water, which is released when the inorganic additive comes in contact with the heated binder. The released water vapours cause the foaming of the binder reducing the viscosity and thus improving workability.
The cost of the additive and the moisture introduced in the mix make this option less than satisfactory for producing warm mix asphalt.
Another technology using the foaming of the binder is known as LEA (Low Emission Asphalt). In brief, the hot coarse aggregate is mixed with the hot asphalt binder containing a chemical additive, the cold finer aggregate (sand) being subsequently added to the mix. The sand is wet, and the moisture present causes the foaming action of the binder. Significant energy savings are reported for this process, but again the moisture introduced in the mix points away from the generally accepted idea that moisture present in the mix is detrimental to mix properties and pavement performance.
Canadian patent 2238368 describes a process to prepare warm mix asphalt, in which a binder with a penetration of less than 200 dmm as measured by ASTM D5 at 25 C, most preferably below 10 dmm, is added to mixture of aggregate and another softer binder component of penetration higher than 200 dmm as measured by ASTM D5 at 25 C, most preferably higher than 800 dmm. This process can be operated at temperatures below 140 C. However, the use of two binder components would require additional storage facilities at the plant and some operational challenges. Also, most user agencies have specific requirements regarding the asphalt binders used on their projects.
Mixing two components would make it very difficult to predict the properties of the resulting asphalt mix. A variation of the above process is described in US patent 6846354, in which the hard bituminous binder is foamed by adding 2 to 7% water. Beyond suffering from the same shortcomings as the Canadian patent referenced herein, water is purposely introduced in the mix and this can adversely affect the properties of the mix.
A review of the available warm mix asphalt technologies reveals some important reasons for which they are less than ideal alternatives to hot mix asphalt. The cost of additives can be prohibitive, the properties of the asphalt binder are changed, or the moisture introduced in the asphalt mix raises concerns regarding the durability of the pavement. It would be desirable if a method would be developed that would allow the production of warm mix asphalt while at the same time circumventing the above mentioned shortcomings. One way would be to use a foaming agent other than water to produce foamed asphalt.
US patent 2,876,126 discloses a process for mixing fine aggregate with asphalt by foaming the asphalt prior to mixing with the fine aggregate in order to obtain a flowable composition. The foaming action is obtained by incorporating a gas, a gassing agent or a solvent into the asphalt mass. Optionally, the process can be carried out at elevated pressures when solvent is used to create the foaming action. The invention requires the bitumen to have a proportion of 8 to 15% by weight of the total composition, fine aggregates (maximum size 7 mm) and it is used for making asphalt mastics.
US patent 4,256,734 discloses the use of foamed asphalt for road surfacing.
The foaming action can be obtained for example by injecting a gas or a liquid into the hot binder. The boiling point of the liquid must be lower than the temperature of the binder to ensure it evaporates. Optionally, when a liquid is used as foaming agent the pressure can be increased in order to keep the liquid from evaporating before leaving the mixing chamber. The invention deals exclusively with road surfacing, where the binder and the aggregate are not mixed prior to laying on the road.
Explanation of technical terms As used herein, the terms asphalt cement or asphalt binder or binder or asphalt or bitumen refer to a material that is used in conjunction with aggregate to produce asphalt concrete and they are used interchangeably.
As used herein, the terms aggregate or aggregate material refers to crushed stone and other particulate materials that are used in the construction of asphalt concrete such as sand, gravel, natural and synthetic fibres and others.
As used herein, the term asphalt concrete refers to bituminous paving mixes.
As used herein, the terms gas and gaseous component refer to a substance or mixture of substances that exist in gas phase under conditions of normal temperature and pressure.
As used herein, a gassing agent is a substance or a mixture of substances that release a gaseous component when added to the hot bitumen. The released gas is the result of either thermal decomposition of the gassing agent, or of a chemical reaction.
As used herein, a dry asphalt foaming method refers to a method of foaming the asphalt in which foaming is caused by a component that under conditions of normal temperature and pressure is not in liquid form. Notwithstanding the above, and although not recommended because of the reasons discussed above, water vapours could still be used in conjunction with the said non-liquid components without departing from the spirit and teachings of this invention.
Summary of the invention The present invention describes a process to produce asphalt-aggregate mixes used for paving applications. In one embodiment of this invention the asphalt binder is mixed with a gas or a mixture of gases at super atmospheric pressure. The asphalt and the gas component are introduced in a mixing chamber where they are allowed to stay in contact such that the gas will dissolve and/or disperse in the binder. The efficiency of the mixing process can be improved with the aid of one or more mechanical mixers or some other method available to the practitioner, such as, for example, recirculation of the mixture of asphalt cement and gases. The mixing chamber may consist of one independent enclosure or several enclosures. The chamber has one or more inlets for the liquid asphalt, one or more inlets for the gaseous component, and one or more outlets for the asphalt/gas mix.
Alternatively, the liquid asphalt and the gas component may be pre-mixed prior to entering the mixing chamber, such that they share some or all of the inlets.
The asphalt-gas mixing chamber can alternatively be replaced by in-line mixing such as directly into the line that transports the liquid asphalt to the aggregate-asphalt mixing compartment.
When the mixture of asphalt and gas exits the mixing chamber at pressures below those present in the mixing chamber, the gas expands and causes the foaming of the liquid binder. In this foamed state the asphalt binder may be further processed in the asphalt mixing plant.
In another embodiment of this invention, the bitumen is mixed with gassing agents in order to obtain foamed asphalt. Without limiting the scope of the invention, examples of possible gassing agents are inorganic carbonates, azo derivatives and the combination of isocyanates with a suitable co-reagent.
Brief description of the drawings Figure 1 shows a schematic comparison of asphalt mix production routes using the conventional hot mix process and the process involving dry foaming of the binder prior to mixing with aggregate.
Figure 2 shows an example of a method to foam the binder. This particular example uses air specified amounts (ratio) of air and binder which are mixed together with the air of mechanical mixers. The asphalt/air mix is inspected and should the desired properties not be met, some of the mix can be recirculated to obtain better dispersion or air in asphalt.
Claims (9)
1. A method of preparing bitumen-aggregate compositions comprising the steps of A. Foaming the bitumen using a dry method;
B. Mixing the asphalt/gas composition obtained in step (A) with aggregate in an asphalt mixing plant in order to produce asphalt paving mixtures.
B. Mixing the asphalt/gas composition obtained in step (A) with aggregate in an asphalt mixing plant in order to produce asphalt paving mixtures.
2. A method according to claim 1 where foaming of the bitumen is obtained by intimately mixing the bitumen with a gas or a mixture of gases.
3. A method according to claim 2, where the gas is air.
4. A method according to claim 2 where mixing takes place at super atmospheric pressures.
5. A method according to claim 1 where the mixing step (B) takes place at a pressure equal to or lower than the pressure used in claim 2.
6. A method according to claim 1 where the bitumen is a neat asphalt.
7. A method according to claim 1 where the bitumen is a modified asphalt.
8. A method according to claim 7 where the asphalt modifiers consist of additives known to be used for bitumen modification, including but not limited to surfactants, plastomers, elastomers, thermoplastic polymers, anti-stripping agents, asphalt extenders, chemical additives, fatty acids and their derivatives.
9. A method according to claim 1 where the gas promoting the foaming action is obtained in-situ by the addition of one or more gassing agents.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA2684443A CA2684443A1 (en) | 2009-10-30 | 2009-10-30 | Method of producing bituminous paving mixes using foamed asphalt |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA2684443A CA2684443A1 (en) | 2009-10-30 | 2009-10-30 | Method of producing bituminous paving mixes using foamed asphalt |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2684443A1 true CA2684443A1 (en) | 2011-04-30 |
Family
ID=43923115
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2684443A Abandoned CA2684443A1 (en) | 2009-10-30 | 2009-10-30 | Method of producing bituminous paving mixes using foamed asphalt |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2684443A1 (en) |
-
2009
- 2009-10-30 CA CA2684443A patent/CA2684443A1/en not_active Abandoned
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| DK1924650T3 (en) | BITUMINOUS COATING COMPOSITION AND PROCEDURE FOR BITUMINO COATING | |
| AU2001237823B2 (en) | Process and system for production of a warm foam mix asphalt composition | |
| EP2185649B1 (en) | Warm mix asphalt binder compositions containing lubricating additives | |
| US8454741B2 (en) | Bituminous paving composition and process for bituminous paving | |
| Croteau et al. | Warm mix asphalt paving technologies: a road builder's perspective | |
| EP2398859B1 (en) | Method for producing bituminous paving compositions | |
| CN109537404A (en) | A kind of cold in place recycling plate form rubber and cold-regenerated road surface construction method | |
| EP1767581B1 (en) | improved preparation of an asphalt mix, and use thereof | |
| Sanchez Alonso et al. | Sustainable asphalt mixes: use of additives and recycled materials | |
| CN108659552A (en) | A kind of environmental protection warm-mixed asphalt and preparation method thereof | |
| Chiu et al. | A study on properties of foamed-asphalt-treated mixes | |
| CA2684443A1 (en) | Method of producing bituminous paving mixes using foamed asphalt | |
| AU2011236730B2 (en) | High-performance coated material for pavement and a road surface | |
| Manolis et al. | Cold weather paving using warm mix asphalt technology | |
| US20230374311A1 (en) | A Bitumen Additive Comprising an Aqueous Wax Dispersion and Its Use to Obtain a Foamed Bitumen | |
| Arroyo-MartÃnez et al. | Warm Mix Asphalt | |
| Olard et al. | Laboratory performance-based assessment of half-warm mix asphalts with high recycling rate by means of the factorial experiment design approach | |
| Villegas et al. | Use of Foamed Asphalt and Foamed Bitumen for Recycled Asphalt Mixtures: A Review | |
| JPS6114255A (en) | Production of paving asphalt mixture containing rubber additive | |
| Hirato et al. | Development and Evaluation of a Warm Mix Asphalt Additive of Surfactant for Pre-mixing Asphalt | |
| Zhang et al. | Application of warm-mix modified asphalt mixture in highway maintenance project |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |
Effective date: 20131030 |