Method and equipment for producing storable cold mix asphalt

Abstract

The present invention relates to a method for producing storable cold mix asphalt comprising the steps of: a) obtaining reclaimed asphalt pavement (RAP) with an asphalt concentration of at least 4%; b) processing the RAP by milling and disaggregation, metal removal, classification by screening material smaller than 19 mm, and homogenising the RAP in stockpiles; c) introducing the RAP into production equipment consisting of an intermodal container comprising at least one conveyor belt with a hopper that opens onto same, the hopper further comprising infrared heating means; a mixing drum assembly with infrared heating means and additive injection means, keeping the temperature of the RAP on the conveyor belt assembly between 40 and 70°C; d) feeding RAP from the conveyor belt assembly into the mixing drum assembly for a residence time; and e) adding an additive comprising an amphiphilic surfactant derived from residual vegetable fatty acid ester to the mixture by means of the additive injection means and a metering pump. The temperature of the RAP in the output means of the mixing drum assembly is kept between 70 and 100°C by means of the infrared heating means, and the mixture in the mixing drum assembly has proportions of 95 to 99% RAP and 1 to 5% additive.

Description

[0001] Title: “Process and equipment for the production of storable cold asphalt mix”

[0002] DESCRIPTIVE MEMORANDUM

[0003] SCOPE

[0004] The present invention relates to the construction industry, in particular to road construction and pavement repair with reclaimed asphalt (RAP).

[0005] BACKGROUND

[0006] Recycled asphalt pavement (RAP) has become a valuable resource for the road construction industry due to its potential to reduce costs and lessen the environmental impact associated with producing new pavement. RAP consists of material recovered from pavements that have reached the end of their useful life, and its reuse in new asphalt mixtures offers a sustainable solution by reducing the need for virgin raw materials and minimizing the amount of waste generated. Furthermore, the implementation of RAP contributes to the conservation of natural resources, as it reduces the extraction of aggregates and utilizes residual asphalt in the recycled material.

[0007] The use of RAP in asphalt mixtures not only provides environmental benefits but also has a significant economic impact. Incorporating RAP into the production of new asphalt mixtures allows for a reduction in the use of virgin asphalt and aggregates, which in turn lowers paving costs.

[0008] Preliminary art

[0009] US Patent 10793720 describes a reclaimed asphalt composition and methods for manufacturing and using it. The patent describes a method for forming a paving composition using reclaimed asphalt pavement (RAP) and / or reclaimed asphalt shingles (RAS). The method comprises: a) providing a rejuvenated asphalt binder consisting essentially of bitumen, a block copolymer, and a bio-oil; b) providing virgin asphalt; c) heating the virgin asphalt to 160-200°C; d) providing RAP and / or RAS; and e) mixing the heated virgin asphalt, RAP / RAS, and the rejuvenated asphalt binder under conditions suitable for forming the paving composition.

[0010] The process described in document US10793720B2 involves the use of elevated temperatures, ranging from 160°C to 220°C, to mix RAP (Reclaimed Asphalt Pavement) with virgin asphalt and a rejuvenating binder composed of bio-oil and block copolymers. These high temperatures pose a significant flammability risk, as the RAP and virgin asphalt mixture may contain residual hydrocarbons and other volatile compounds that, when exposed to these temperatures, can release flammable gases. This could result in spontaneous ignition and the danger of explosions or burns during the mixing process. Furthermore, this hot mix requires the addition of virgin asphalt, making it more polluting. In addition, it requires specialized machinery and personnel for its application.

[0011] US patent 11186959 describes an asphalt and aggregate mixture and methods for preparing and using it that utilizes self-healing solid-phase cohesion and homogenization through liquid asphalt oligopolymerization technologies. It states that the mixtures are suitable for use in the installation of asphalt / concrete pavements, the repair of asphalt / concrete pavements, and the placement of overlays on existing asphalt / concrete pavements. It also states that the slurries may contain recycled asphalt / concrete pavement subject to treatment.

[0012] The process described in US11186959B2 focuses on the treatment of RAP, but it is not specifically designed to produce cold-mix asphalt that can be stored and used. In fact, the described process involves heating the RAP to temperatures that can reach up to 143°C (290°F). Cold mix asphalt is designed to be produced and applied at much lower temperatures, typically below 50°C, which facilitates storage and use without the need for additional heating. The fact that this process requires elevated temperatures is already a critical limitation for the production of a cold mix, as it compromises storage capacity and ease of application without reheating.

[0013] Cold asphalt mixes are designed to be stable over extended storage periods, maintaining their workability and adhesion properties. However, the process described in US11186959B2, which involves self-regenerating cohesion and oligomerization of the asphalt through irradiation, can result in a mix that, while cohesive at high temperatures, may lose its adhesion and stability when cooled and stored. This poses a significant risk that the mix will harden or become brittle during storage, making cold application impossible without significant degradation of its mechanical properties.

[0014] Furthermore, this process also involves heating the RAP to high temperatures, which can release flammable gases and pose a significant risk of flammability and danger of explosions or burns during the mixing process.

[0015] Indeed, the hydrocarbons present in RAP (Recycled Asphalt Pavement) can begin to gasify at relatively low temperatures, depending on the composition of the asphalt and aggregates. Generally, the volatilization of lighter compounds can begin at temperatures around 120°C. However, as the temperature increases, especially above 150°C, the rate of hydrocarbon volatilization can increase significantly, releasing more volatile gases.

[0016] It is important to note that the risk of flammable gas emissions increases significantly when temperatures reach or exceed 200°C. At these temperatures, the lighter, more volatile components of asphalt and the hydrocarbon residues present in RAP can evaporate rapidly, creating a potentially hazardous environment if not handled with proper ventilation and temperature control. This is documented in industry safety standards and practices, such as the recommendations of the Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH) in the USA, which outline the risks associated with handling hot asphalt and RAP.

[0017] In addition to flammability risks, volatile gases released during the heating of RAP to high temperatures can have adverse effects on workers' health. Polycyclic aromatic hydrocarbons (PAHs) and other volatile organic compounds (VOCs) present in asphalt and RAP can be released into the air as vapors and aerosols. Exposure to these gases can cause a range of health problems, including respiratory irritation, headaches, dizziness, nausea, and in more severe cases, chronic respiratory diseases. Prolonged or repeated exposure to these compounds has been associated with an increased risk of developing cancer, cardiovascular disease, and damage to the central nervous system.For these reasons, safety regulations, such as those established by OSHA and NIOSH, also emphasize the importance of strict control measures, such as adequate ventilation and the use of personal protective equipment (PPE), to minimize exposure to these hazardous compounds during the processing of hot asphalt and RAP.

[0018] Thus, the use of RAP in high-temperature mixing processes presents significant safety and health risks. Since RAP comes from aged pavements, it may contain hydrocarbon residues and other volatile compounds that, when exposed to extreme heat during processing, can release flammable gases. These gases pose a serious hazard, as they can lead to flash fires, burns, and the risk of uncontrolled combustion during the process.

[0019] Technical problem addressed by the invention

[0020] A key technical problem addressed by the present invention is the significant safety risks, specifically the heating of RAP to elevated temperatures, which can release flammable volatile gases, including hydrocarbons, posing a serious hazard of ignition, explosions, and burns during the mixing process. These gases also have adverse health effects, such as respiratory irritation and an increased risk of chronic diseases and cancer in exposed workers. This safety issue underscores the need to develop RAP processing methods that minimize exposure to high temperatures, using techniques that reduce the risk of ignition and ensure a safe working environment.

[0021] In addition to safety concerns, prior art solutions are not easily adaptable for use in field conditions, limiting their usefulness in applications where a storable and usable cold mixture is required that can be used anytime, anywhere without additional preparation.

[0022] Thus, the need is observed to develop an asphalt mix production process that is safe, adaptable to field conditions, and suitable for continuous production, minimizing the risks associated with heating RAP and ensuring viability for cold applications without the drawbacks presented by the previous art.

[0023] Technical Solution of the present invention

[0024] An object of the present invention is a process for producing an asphalt mixture based on RAP and an additive based with safe equipment that keeps all flammable processes confined at prudent temperatures below 100 °C.

[0025] Another object of the present invention is equipment that allows the process of the present invention to be carried out.

[0026] Advantages of the present invention

[0027] The process and equipment for producing storable cold asphalt mix described in this invention represent a significant advancement in reducing the environmental impact of the road construction industry. By using Recycled Asphalt Pavement (RAP) as the primary raw material, the need to extract and process new materials is considerably reduced, thereby decreasing the consumption of natural resources and minimizing waste generation. This practice not only contributes to the sustainability of the sector but also aligns with the circular economy policies promoted by the State of Chile, which aim to maximize resource reuse and minimize waste.

[0028] Furthermore, the process of the present invention is highly energy-efficient, operating at significantly lower temperatures than those required by traditional asphalt mixture production methods. This approach not only decreases greenhouse gas emissions associated with material heating but also reduces the risk of releasing hazardous volatile compounds during production. In this way, the process aligns with the objectives set forth in the Circular Economy Roadmap for Construction, promoted by the Chilean Ministry of the Environment, which encourages more sustainable management of materials and waste in the industry.

[0029] Finally, the equipment's ability to process and store cold asphalt mix facilitates its transport and application in diverse climatic conditions and geographic locations, including remote areas. This not only reduces the need for material transport, thus decreasing the carbon footprint, but also improves the efficiency of road maintenance operations. Taken together, these features reinforce the invention's commitment to the circular economy and environmental protection, contributing to a more responsible and sustainable construction industry, in line with Chile's environmental goals.

[0030] Advantageously, the process of the present invention eliminates the addition of virgin asphalt to the process mixture, thus also contributing to environmental protection and sustainability by recycling existing materials. This approach maximizes the use of recycled resources and minimizes the environmental impact associated with the extraction and processing of new materials.

[0031] Advantageously, the equipment of the present invention can also be easily transported by moving the shipping container directly to RAP processing plants or pavement repair sites where asphalt mix is ​​required or where processed RAP is available for recovery into storable, cold-applied asphalt mix, thus facilitating the availability of the process and pavement rehabilitation. This contributes to good practices and environmental protection. This functionality also allows for mix production in communities located far from production centers (asphalt and concrete plants). Furthermore, it reduces transportation costs and minimizes pollution.

[0032] The equipment of the present invention advantageously allows the risks of the RAP mixing and heating process to be contained within a firm and secure container, and thanks to its infrared heating means, it provides radiant energy of medium temperature that minimizes the risk of evaporation of flammable gases and reduces the risks of the process.

[0033] The equipment of the present invention also advantageously allows work to be carried out autonomously thanks to an electric generator that provides power to the equipment.

[0034] Another advantage of the process of the present invention is the production of a cold-storeable and usable asphalt mixture that is stable during long storage periods, maintaining its adhesive and mechanical properties without the need for preheating before application. This allows the mixture to be used directly on the job site, at any time and under any weather conditions, which is not possible with mixtures that require high temperatures for activation. The ease of storage and the versatility of application enable rapid repairs and road maintenance in a variety of environments.

[0035] Furthermore, the process can operate continuously thanks to its control mechanisms, which offers a significant advantage over technologies that are limited to intermittent operations.

[0036] BRIEF DESCRIPTION OF THE FIGURES

[0037] The following figures describe a preferred and exemplary embodiment of the present invention. It should be appreciated that the figures are provided for illustrative purposes only and that the invention is not limited by these illustrations. Well-known components, materials, or methods are not necessarily described in great detail to avoid obscuring the present description. Any specific structural and functional details described herein should not be construed as limiting, but merely as a basis for the claims and as a representative basis for teaching a person skilled in the art to employ the invention in various ways.

[0038] Figure 1 schematically presents equipment for the production of asphalt mixture according to the present invention.

[0039] DETAILED DESCRIPTION OF THE INVENTION

[0040] The present invention relates to a process for producing cold-applied, storable asphalt mix, which consists of the following steps: a) obtaining recycled asphalt pavement (RAP) with an asphalt concentration of at least 4%; b) processing said RAP by grinding and disintegration, metal removal, classification by sieving below 19 mm, and homogenization of the RAP in stockpiles; c) introducing said RAP into a production equipment consisting of a shipping or road transport container comprising at least one conveyor belt with a hopper that feeds into it, said hopper also comprising infrared electric heating means;an inclined mixing drum assembly with asphalt mix outlet means, aligned feeding means for the conveyor belt drop, with infrared heating means and additive injection means, a feeding and control assembly, with a controller such as a PLC programmable logic controller, for feeding and controlling at least the conveyor belt assembly, the infrared heating means of said hopper and of the mixing drum assembly and the additive injection means, and maintaining the temperature of the RAP in the conveyor belt assembly by means of said heating means between 40 and 70 °C; d) feeding the mixing drum assembly with RAP from the conveyor belt assembly, for a residence time to keep the RAP in the conveyor belt assembly moving to raise its temperature and remove moisture;(e) adding to the mixture an additive based on a compound of an amphiphilic surfactant based on residual vegetable fatty acid ester by means of said additive injection means and said dosing pump; wherein the temperature of the RAP in the outlet means of the mixing drum assembly is maintained by means of said infrared heating means between 70 and 100 °C; and the mixture in the mixing drum assembly has the proportions of 95 to 99% RAP and 1 to 5% additive.

[0041] According to the present invention, the asphalt mixture production process includes, after step e), an additional step of bagging the asphalt mixture for subsequent cold application.

[0042] According to the present invention, said additive is an agent based on a compound consisting of an amphiphilic surfactant based on a residual vegetable fatty acid ester enriched with graphene (STRONGB), acid amides and tetraethylenepentamine surfactants; for example, the BIOROAD Lázaro additive from the company Unico green.

[0043] According to the present invention, the asphalt mixture production process can perform steps c) and ad) directly at a site where the asphalt mixture is required, such as at a pavement maintenance site.

[0044] According to the present invention, the asphalt mixture production process can be carried out directly in a RAR processing plant

[0045] According to the present invention, after the RAP is introduced into the production equipment, the advance of the conveyor belt, the infrared heating means of the hopper and the mixing drum assembly, and the dosing pump are controlled by the controller.

[0046] The following describes another object of the present invention with reference to Figure 1, an asphalt mixture production equipment (10) from RAP arranged on a surface (1), said production equipment (10), formed by a shipping or road transport container (100) with a structural frame (101) having an upper level (103) and a lower level (104); comprising: a conveyor belt assembly (110) with a conveyor belt (111), a weighbridge (112) at its exit end (114), a displacement motor (113), said conveyor belt assembly (110) arranged on said upper level (103) with reinforcements (102) to said structural frame (101);a hopper (120) in the top or roof (105) of the container (100) leading to the conveyor belt (111), said hopper (120) comprising infrared heating means (121) directed towards its internal cavity above the conveyor belt (111), a mixing drum assembly (130) comprising a mixing drum (131) with asphalt mix outlet means (134) such as an outlet hopper, and feeding means (132) aligned for the outlet (114) of the conveyor belt assembly (110) such as a gate in the cylindrical body of the drum, with infrared heating means (133) arranged to internally illuminate said mixing drum (131), said mixing drum assembly (130) is arranged at the lower level (104) with an angle of inclination of less than 30°;an additive injection assembly (140) with a dosing pump (141) connected to a tank (142) and an additive injection duct (143) distributing additive into the mixing drum (131); a feeding and control assembly (150) with a generator set (151), a distribution board (152) and programmable control means such as a PLC (153), for feeding and controlling at least the conveyor belt assembly (110), the infrared heating means (121, 133) of said hopper (120) and of the mixing drum assembly (130) and the dosing pump (141).

[0047] Preferably, the equipment of the present invention also comprises side rails (122) between the hopper and the conveyor belt to prevent spillage of RAP entering the equipment.

[0048] Preferably, the equipment of the present invention also comprises internal and external lights (154, 155) connected to the power and control assembly (150). Optionally, the equipment of the present invention also comprises thermal insulation in the container walls (100).

[0049] Preferably, the equipment of the present invention, said mixing drum assembly (130), comprises a motor (137) coupled to a reduction (136) that transmits its torque to the shaft of the mixing drum (131) by means of a chain and sprocket transmission (136).

[0050] Example of asphalt mixture produced according to the present invention.

[0051] An asphalt mixture, Mixture A, was produced with the equipment of the invention, with a RAP treated by grinding, disaggregated, homogenized, with the granulometry indicated in table 1, with a proportion of 98% RAP and 2% additive, amphiphilic surfactant based on residual vegetable fatty acid ester with Alpelchina less than 30%, enriched with graphene between 5% and 10%, acid amides and tetraethylenepentamine surfactants; marketed as BioRoad Lázaro™ by the company Único Green.

[0052] Table 1: Granulometry of aggregates in RAP obtained and processed

[0053] Table 2 below presents the mechanical characteristics of the resulting mixture, mixture A, compared with expected ranges of a hot-applied asphalt mixture and a cold-applied asphalt mixture, for its applicability in the industry.

[0054] Table 2: Mechanical properties of the asphalt mixture obtained.

[0055] mixture A: asphalt mixture obtained by the process of the present invention.

[0056] Table 3 below shows the results of mixture A, obtained in independent laboratories TERRA and LACEM according to specifications indicated in the methods, according to the Highway Manual Vol. 8 (2021).

[0057] Table 3: Comparison according to specifications - cold mix

[0058]

[0059] The following table presents a comparison of useful and advantageous characteristics of the mixture of the present invention Mixture A with an asphalt mixture for hot application and an asphalt mixture for cold application.

[0060] Table 4: Comparison of asphalt mixtures in applications and characteristics

[0061]

[0062] Although embodiments of the invention have been illustrated and described in detail in the drawings and description above, such illustration and description should be considered illustrative or exemplary and not restrictive; the invention is not limited to the examples specifically described. Persons skilled in the art understand and can realize other variations of the examples specifically described from a study of the drawings, description, and claims. In the specification and claims, the terms "comprising" and "including" are open-ended and do not exclude other elements or steps, and the indefinite article "a" does not exclude a plurality.

Claims

CLAIMS 1 Process for obtaining cold asphalt mix in storage, CHARACTERIZED in that it comprises the steps of: a) obtaining recycled asphalt pavement (RAP) with an asphalt concentration of at least 4%; b) processing said RAP by grinding and disintegration, metal removal, classification by sieving under 19 mm, and homogenization of the RAP in stockpiles; c) introducing said RAP into a production equipment consisting of a container of maritime or road transport type comprising at least one conveyor belt with a hopper that empties into it, said hopper also comprising infrared heating means;an inclined mixing drum assembly with asphalt mix outlet means, aligned feeding means for the conveyor belt drop, with infrared heating means and additive injection means connected to a metering pump, a feeding and control assembly, with a programmable logic controller configured to feed and control at least the conveyor belt assembly, the infrared heating means of said hopper and of the mixing drum assembly and the additive injection means, and maintaining the temperature of the RAP in the conveyor belt assembly by said infrared heating means between 40 and 70 °C; d) feeding the mixing drum assembly with RAP from the conveyor belt assembly, for a residence time to keep the RAP in the conveyor belt assembly moving to raise its temperature and remove moisture;(e) adding to the mixture an additive based on a compound of an amphiphilic surfactant based on residual vegetable fatty acid ester by means of said additive injection means and said dosing pump; wherein the temperature of the RAP in the outlet means of the mixing drum assembly is maintained by means of said infrared heating means between; 70 and 100 °C; and the mixture in the mixing drum assembly has proportions of 95 to 99% RAP and 1 to 5% additive. 2.- A process according to claim 1, CHARACTERIZED in that it includes, after step e), an additional step of bagging the asphalt mixture for subsequent cold application. 3.- A process according to claim 1, CHARACTERIZED in that said additive is an agent based on a compound consisting of an amphiphilic surfactant based on residual vegetable fatty acid ester enriched with graphene, acid amides and tetraethylenepentamine surfactants. 4.- A process according to claim 1, CHARACTERIZED in that it is carried out directly in a RAP processing plant. 5.- A process according to claim 1, CHARACTERIZED in that steps c) and ad) are carried out directly at a site where the asphalt mixture is required to be used, such as, for example, at a pavement maintenance site. 6.- A process according to claim 1, CHARACTERIZED in that, after step c) of introducing said RAP into said production equipment, the advance of said conveyor belt, the infrared heating means of said hopper and of the mixing drum assembly and the dosing pump are controlled by said controller. 7.- An asphalt mix production unit (10) made from RAP, CHARACTERIZED in that it is formed by a shipping or road transport container (100) with a structural frame (101) having an upper level (103) and a lower level (104); comprising: a conveyor belt assembly (110) with a conveyor belt (111), a weighbridge (112) at its outlet end (114), a drive motor (113), said conveyor belt assembly (110) arranged at said upper level (103) with reinforcements (102) to said structural frame (101); a hopper (120) at the top or roof (105) of the container (100) leading into the conveyor belt (111), said hopper (120) comprising infrared heating means (121) directed into its internal cavity above the conveyor belt (111);a mixing drum assembly (130) comprising a mixing drum (131) with asphalt mix outlet means (134) and feed means (132) aligned for the outlet (114) of the conveyor belt assembly (110), with infrared heating means (133) arranged to internally illuminate said mixing drum (131), said mixing drum assembly (130) being arranged at the lower level (104) with an angle of inclination of less than 30°; an additive injection assembly (140) with a metering pump (141) connected to a tank (142) and an additive injection duct (143) distributing additive into the interior of the mixing drum (131);a feeding and control assembly (150) comprising a generator set (151), a distribution board (152) and programmable control means (153), for feeding and controlling at least the conveyor belt assembly (110), the infrared heating means (121, 133) of said hopper (120) and of the mixing drum assembly (130) and the dosing pump (141).; 8.- Equipment according to claim 7, CHARACTERIZED in that said mixing drum assembly (130) comprises a motor (137) coupled to a reduction (136) that transmits its torque to the shaft of the mixing drum (131) by means of a chain and sprocket transmission (136). 18 9.- Equipment according to claim 7, CHARACTERIZED in that it comprises internal and external lights (154, 155) connected to the power supply and control assembly (150). 10.- Equipment according to claim 7, CHARACTERIZED in that it comprises side rails (122) between the hopper and the conveyor belt to prevent spillage of RAP entering the equipment. 11.- Equipment according to claim 7, CHARACTERIZED in that it comprises thermal insulation in the walls of the container (100).

Images