COMPOSITION OF ASPHALT ADDITIVE AND METHOD OF OBTAINING IT

Abstract

The present invention relates to an asphalt additive for improving the characteristics of virgin asphalt cements and recycled binders by increasing elastic recovery, adhesion, tensile strength, and thermal susceptibility, and for use in RAP (Reclaimed Asphalt Pavement) for cold patching. The additive of the invention can be used in wearing courses, micro-surfacing, rehabilitation layers, new structures, patching, and crack-resistant layers. The additive composition of the invention is based on polybutenes, an adhesion promoter, rubber powder, and hydraulic oil.

Description

Composition of additive for asphalt TECHNICAL FIELD The present invention relates to an asphalt additive for improving the characteristics of virgin asphalt cements and recovered binders by increasing elastic recovery, adhesion, tensile strength and thermal susceptibility, and adding RAP for cold patching. The additive of the invention can be used in wearing courses, micro-pavements, rehabilitation layers, new structures, patching, and anti-crack layers. BACKGROUND The road transport system plays an important role in the growth and development of countries. Most national routes are constructed with flexible pavements. Additives improve the chemical affinity between the asphalt and the aggregate, as well as the performance of the asphalt mixture, increasing its resistance to the action of water. Asphalt modification is a technique for the effective use of asphalt in paving, which consists of adding polymers to conventional asphalts in order to improve their mechanical characteristics. The use of polymer-modified asphalts in road construction is a common practice internationally. Technological advances in polymer development now allow for the production of highly polymer-modified asphalt, giving the mixture excellent resistance to permanent deformations such as rutting. Furthermore, the reuse of asphaltic materials removed from pavements (RAP) has gained greater acceptance in recent decades. This material load and the demand for natural resources could be reduced by increasing the content of removed materials in the freshly produced asphalt product. Reclaimed Asphalt Pavement (RAP) is the material recovered from the asphalt layer of a pavement removed during reconstruction or rehabilitation. RAP consists of material recovered from flexible pavement that has reached the end of its service life; however, its characteristics allow it to be reused in new or rehabilitated structures. Incorporating this material into asphalt mixtures reduces the need for new material, generating cost savings and contributing to the conservation of natural resources. The implementation of RAP as a component of asphalt mixes is geared towards sustainability, serving as a measure to mitigate the environmental impact of reusing a waste material with high mechanical potential and reducing the extraction of aggregate sources. Furthermore, from an economic standpoint, replacing a percentage of the asphalt mix material with RAP represents savings in the amount of asphalt binder and virgin aggregates required for mix production, thus impacting the cost of the final product. From an economic point of view, the benefits are the reduction of paving costs, savings in raw material extraction (asphalt and aggregates), and a decrease in production times. The amount of reclaimed asphalt reused in asphalt manufacturing will increase even further in the coming years, likely reaching 50% by 2035 in Europe. The situation in other regions of the world is similar, forming a global trend and making asphalt one of the most important materials for recycling worldwide. Rejuvenation during most of the 20th century generally referred to the process of resurfacing an existing paved surface. A more durable solution is the reuse of materials such as reclaimed or recycled asphalt pavement (RAP). Road construction and roadwork companies often sometimes dismiss the use of RAP or are reluctant to use a higher content of RAP or RAS (recycled asphalt shingles) because they contain an asphalt binder that has aged considerably and is much stiffer than virgin binder. Consequently, there has been concern that incorporating a higher RAP content could result in asphalt mixtures with high stiffness and, therefore, could be susceptible to failures such as cracking or moisture damage. The increased stiffness can be mitigated to some extent by using a softer binder, but if incomplete mixing occurs between the soft binder and the much stiffer RAP binders, the resulting mixture may still be susceptible to cracking and moisture damage. However, asphalt in paving shows deterioration over time, resulting in higher viscosities at high temperatures and increased brittleness, and therefore a greater tendency to crack, particularly at lower temperatures. These aging effects are attributed to the asphalt's binder phase. To reuse reclaimed asphalt without compromising its performance, its property profile must closely approximate that of virgin asphalt. This so-called rejuvenation of aged asphalt in reclaimed asphalt is achieved with chemicals, known as rejuvenating agents, which are added appropriately during the asphalt manufacturing process. The main concerns expressed by asphalt manufacturers regarding this aspect are a perceived lack of overall performance and, especially, uncertainties regarding its long-term performance. Document US 2010 / 0034586 describes a rejuvenating agent suitable for rejuvenating asphalt (containing RAP), wherein said rejuvenating agent comprises one or more plant-derived oils. WO 2010 / 107134 describes an asphalt modifier (i.e., a bitumen modifier) ​​prepared by mixing a conjugated vinylaromatic-diene hydrocarbon block copolymer, an adherent resin, and a process oil. Document US20230220206A1 refers to a binding composition comprising a bituminous binder and at least one rejuvenating agent, wherein the rejuvenating agent comprises at least one asphaltene dispersant, selected from the group consisting of alkoxylates, N,N-dialkylamides of aliphatic carboxylic acids, N-alkyl lactams and poly(alkylamines). Document US20230278925A1 describes compositions and methods for improving or enhancing asphalt paving or repaving on road surfaces comprising the addition of the composition to the asphalt, where the composition comprises an oil-in-water emulsion carrier matrix, and a curing agent selected from the group consisting of ascorbic acid, benzoic acid, phthalic acid, cinnamic acid, citric acid, 2-pyridinecarboxylic acid, salicylic acid, and stearic acid. Document WO2017158206A1 shows a polymeric additive for the preparation of cold asphalt mixtures based on asphalt pavement milling material (RAP) with the addition of water comprising adhesion improvers, between 9% and 15% by volume, lubricants between 10% and 27% by volume, polymers between 30% and 47% by volume, emulsifiers between 4% and 10% by volume, and diluents between 30% and 47% by volume. Patent EP3107958 (B1) relates to an asphalt binder additive composition comprising: (a) a carrier matrix; and (b) an agent selected from the group consisting of a hardening agent and a masked hardening agent, wherein the hardening agent is selected from ascorbic acid, benzoic acid, phthalic acid, cinnamic acid, citric acid, 2-pyridine carboxylic acid and salicylic acid; the masked hardening agent is selected from methyl salicylate, ethyl salicylate, isopropyl salicylate and hexyl salicylate; and the carrier matrix is ​​an oil selected from rapeseed oil, coconut oil, linseed oil, safflower oil, soybean oil, tall oil, tung oil, silicone oils and mixtures thereof. The commonly used modifiers are polymeric: elastomers (such as Styrene-Butadiene-Styrene, SBS) and thermoplastics or plastomers (Styrene Vinyl Acetate, EVA; Ethylene Methyl Acrylate, EMA), which provide notable improvements to the physical and chemical properties of the binders, strengthening their cohesion and adhesion to the aggregates. Prior art additives improve the chemical properties of commercially available asphalts as well as recycled materials such as RAP. However, a challenge with these additives is producing a homogeneous mixture of consistent quality that can be easily dosed and ensures consistent quality in the finished additive. Therefore, the objective of the present invention was to develop an additive composition for both virgin asphalt and RAP that allows a homogeneous mixture, easy placement, better modular response to thermal changes, improved coverage of the aggregates, longer service life, environmentally friendly, and improvements in the characteristics of both traditional asphalt cements and RAP. SUMMARY OF THE INVENTION An object of the present invention is to provide an additive composition for traditional plant asphalt, to additivate RAP for cold patching and for resurfacing and micro-surfacing. Another object of the present invention is to provide a method for obtaining the additive composition for asphalt. The additive composition of the invention is based on polybutenes, an adhesion enhancer, rubber powder, and hydraulic oil. According to the present invention, traditional or conventional asphalt refers to CA 10, CA 20, and CA 30. CA 10 is used in the construction of asphalt pavements and has a viscosity at 60 °C minimum of 800 poises and maximum of 1600 poise according to IRAM 6837 standards. CA 20 is used in the construction of asphalt bases and pavements, it has a viscosity at 60 °C minimum of 1600 poise and maximum of 2400 poise according to IRAM 6837 standards. CA 30 is used in the construction of asphalt bases and pavements. Suitable for hot areas or areas with heavy traffic, it has a minimum viscosity at 60°C of 2400 poise and a maximum of 3600 poise according to IRAM 6837 standards. The RAP used is the aged and traffic-damaged material which is extracted directly from the on-site work or from a nearby work site, which is then selected and classified. The adhesion enhancer is a liquid product with the following characteristics: total amine index (mg KOH / g) 90.0 - 110.0 and moisture (% in step) 1.0 max. Rubber powder is rubber powder recovered from used tires. The type of stone aggregates that can be used in the mixture have sizes between 3-9 mm for micro-pavement thicknesses of 20-30 mm and for greater thicknesses up to 60 mm, aggregates of 6-12 mm and 6-20 mm are used. DETAILED DESCRIPTION All asphaltic materials used in road construction change their properties over time because they are affected by factors such as UV rays, heat, traffic loads, liquid spills, among others, factors that directly age the asphalt. Therefore, the durability of asphalt is defined as its ability to maintain the binding and cohesive properties of the mixture, and these depend on the physicochemical properties of the asphalt, which in turn regulate its rheological behavior and the properties of the mixture. A first aspect of the present invention relates to an additive composition for conventional asphalt and for RAP (Reclaimed Asphalt Pavement). More precisely, the invention relates to an additive composition based on polybutenes. In one respect, the polybutene-based additive composition comprises: a) 22.5% by weight of a first polybutene of molecular weight Mn 1200-1375 (g / mol), viscosity at 100 °C of 595-665 (mm2 / s) ASTM D445 standard, relative density at 15 / 15 (°C) 0.887 - 0.905 ASTM D1298 standard, flash point 170 PM (°C) ASTM D93 standard, b) 27.5% by weight of a second polybutene with molecular weight Mn 900-980 (g / mol), viscosity at 100 °C of 210-250 (mm² / s) according to ASTM D445, relative density at 15 / 15 (°C) 0.880-0.890 according to ASTM D1298, boiling point inflammation 165 PM (°C) ASTM D93 standard, c) 10% by weight of an adhesion promoter additive for asphalt mixtures, density (25°C) 0.858 g / cm3, total amine index 90.0-110.0 mgKOH / g, d) 2% by weight of PROBIMUL-CR®-62 rapid cut cationic emulsion (Asphalt residue, %>62, Residue on #20 mesh, %<0.1, Coating and water resistance >80 IRAM 6691 standard, Particle charge: positive IRAM 6690 standard. e) 28% by weight of a hydraulic oil 68 (Kinematic Viscosity at 40° C 68 cSt method ASTM D445, Viscosity Index 82 method ASTM D2270), f) 10% rubber powder, The additive of the invention is used to prepare asphalt mixtures with aggregates from domestic quarries. For micro-surfacing thicknesses of 20-30 mm, an aggregate size between 3-9 mm is used, and for greater thicknesses up to 60 mm, aggregates between 6-12 mm and 6-20 mm are used. The additive also allows for the construction of pavement layers of varying thicknesses, generally from 17-60 mm. Particle size distribution is important for achieving a homogeneous product by improving the coverage of the aggregates, thus facilitating their placement. The additive of the invention provides a better modular response to thermal changes, with excellent performance at low temperatures and without the stiffening of traditional mixtures, thereby improving the service life of the asphalt. High traffic stresses (vehicle weight) and deformations caused by climatic factors, associated with increasingly higher temperatures and prolonged exposure, make rutting a characteristic defect of asphalt. The polybutene-based additive of the present invention allows for the production of a modified asphalt that provides the mixture with excellent resistance to permanent deformation (rutting). The characteristics of this additive achieve very good performance against two of the most common and most relevant phenomena in the useful life of an asphalt layer: fatigue cracking and permanent deformation or rutting. Among other advantages, the suitability as a retarding layer for reflex cracking due to the proportion and continuity of the polymeric phase present, as well as the good workability of the mixture, even for asphalt bases in which low penetration asphalts are used, are also highlighted. The modification of asphalts with the incorporation of the additive of the invention allows the placement of asphalt mixtures at a lower temperature, achieving a reduction in greenhouse gases, lower consumption of fossil fuels and being environmentally friendly while maintaining their fundamental properties. The incorporation of rubber powder, derived from the recycling of end-of-life tires, into the additive composition improves the increase in friction. tire / pavement and the reduction of rolling noise or noise (noise pollution). Preparing and applying asphalt mixtures at lower temperatures allows for smooth transport over greater distances without being affected by climate changes. Another aspect of the invention is to provide a cold patching tool comprising the use of RAP to which the additive of the invention is incorporated. In another additional aspect, the additive of the invention provides the application in asphalt micro-surfacing by mixing the warm additive with selected RAP to improve existing pavements or pave secondary roads. The approach of recycling flexible pavements is a valuable contribution from a technical, economic and environmental point of view. The environmental benefits resulting from the implementation of asphalt mixtures with RAP include: - Reuse of material that has reached the end of its useful life. - Reduction in the volume of waste. - Decreased supply of virgin material. - Reduction in the extraction processes of limited raw materials. The benefits mentioned can be quantified by measuring the carbon footprint. This corresponds to a measure of carbon dioxide emissions into the atmosphere, caused directly or indirectly by a given activity. From an economic point of view, the following benefits are associated: - Reduction of paving costs. - Savings in import and extraction of raw materials (asphalt and aggregates). - Reduction in intervention times. Reduction in imports of products associated with the work. - Reduction in the percentages of asphalt additive required in the mixture. RAP consists of a material that has undergone a progressive aging and hardening process during its service life as a result of various mechanisms. The increased use of RAP also implies a significant reduction in transport costs, as is the case in our country with its extensive geography, where RAP is extracted at the construction site where the pavement surface is milled or at a nearby construction site. This practice of recycling disposable products forms the so-called "circular" economy, where, considering the parameters of the management, monitoring and control of pavements, continuous feedback is obtained, developing sustainable pavements. The extreme climatic conditions of certain geographical areas, the increases in the load demands to which the pavements are exposed and the need to reduce road accidents make the use of additives such as the one of the invention in mixtures with conventional asphalts very appropriate in RAP, obtaining a new modified asphalt mixture to be placed. The RAP is processed until the required gradation is obtained, selecting and classifying it to subsequently carry out the mixing process with the additive of the invention to obtain micro-surfacing or overlays to improve existing pavements or pave secondary roads. The additive of the invention performs a specific function with RAP (Reclaimed Asphalt Pavement), providing clear improvements to its physical and chemical properties. Its components act on the periphery of the aggregate coated with aged asphalt, strengthening cohesion and adhesion to the aggregate, reducing viscosity, and improving ductility, thermal susceptibility, elasticity, and resistance to aging, thus acting as a rejuvenating agent. In this way, the RAP is recovered for use in both patching and asphalt micro-surfacing. Examples Example 1 Additive preparation The mixing takes place in a jacketed mixer through which heat exchange fluid circulates. The agitation is of the anchor type, powered by a geared motor. Polybutene is loaded a) and as it softens, polybutene b) is added, always maintaining agitation in order to improve the exchange with the hot walls of the equipment jacket. Once the temperature reaches 60°C, the ammoniacal adhesion promoter is added. When the temperature again reaches 60°C, the hydraulic oil with a kinematic viscosity of 68 cSt and the cationic emulsion are slowly incorporated. The powdered rubber is then added gradually to prevent lumps from forming and to ensure it doesn't become completely wetted. After all the additive components have been incorporated, the temperature is increased to 80°C to improve rubber wetting and ensure a more uniform fusion of all components. The mixture is then kept for 1 or 2 hours and a sample is taken for laboratory testing. Once the laboratory test is approved, the additive mixture is cooled to 50°C and packaged in sheet metal drums with a movable lid and strapping. Example 2 Tests with asphalts CA 20, CA 10 and CA 30 and the additive of the invention. The following table shows the tests on an asphalt mixture CA 20, construction of asphalt bases and pavements. Essays No Additive With Additive Density Marshall 2,396 2,391 % Empty 3.7 3.8 Stability Kg 1367.0 1297.0 Remaining Stability % 98.3 92.6 % Rutting 6.0 5.0 Marshall density: in Kg / cm3 Stability in Kg: according to standard VN -E 9-86. “Stability and Creep Test by the Marshall Method”. Rutting: according to UNE-EN-12697-22 standard, Procedure B, deformation in mm. % residual watts: air voids in an asphalt mixture, specified for each type. Rice Method This table shows that the additive does not alter the properties of the binder at the required temperatures for the Marshall and Rutting tests at 60°C. The results shown below are those for asphalt without additive and with 5% additive. Essays CA30 CA30 +Additive CA10 CA10 +Additive Penetration 55 55 86 75 Softening Point 54 52 48 47 Viscosity at 60°C 2900 3070 1700 1650 Viscosity at 135°C 520 575 397 450 With the additive, it is observed that the rutting parameters improve and it complies with the specifications of the National Directorate of Roads DNV 2017 for T1 type traffic. Penetration: in mm Softening point: in °C Example 3 RAP trials Reclaimed asphalt pavement (RAP) mixtures were used and the additive of the invention was incorporated as a binder rejuvenating agent. The results obtained without any curing process of the mixture are shown in the following tables: Three different percentages of the additive were incorporated into the RAP, mixed and compacted at room temperature (25°C) and medium temperature (80°C). Mixing and molding temperature at 25°C % of additive to RAP Marshall Density % of empty Stability KN RTI at 25 °C 2 2,201 7.9 N / A 1.1 3 2,194 8.2 N / A 1.0 4 2,177 7.7 N / A 0.9 % of voids: air-filled voids in an asphalt mixture, specified for each type Stability in Kilo Newton (KN), resistance per cm3 of the stability test RTI: indirect tensile strength, kPa (kilopascal) N / A: Not applicable Mixing and molding temperature at 80°C % of additive to RAP Marshall Density % of empty Stability KN RTI at 25 °C 2 2,305 5.2 3.0 1.6 3 2,312 4.2 3.1 1.5 4 2,315 2.5 3.2 1.3 The RAP was classified into two granulometric fractions and the percentage of asphalt in both fractions was taken into account to determine the amount of additive to use, according to the following graph: Ezequiel Bettatis - 23259657989 Digitally signed by PORTALTRAMITES - INPI Date: 2023.12.18 16:09:25 -03:00 Reason: Digitally Signed by the INPI Location: Buenos Aires, Argentina

Claims

1. An asphalt additive composition characterized in that it comprises: a) 22.5% by weight of a first polybutene, b) 27.5% by weight of a second polybutene, c) 10% by weight of an adhesion promoter additive, d) 2% by weight of a cationic high-shear emulsion, e) 28% by weight of a hydraulic oil, f) 10% by weight of rubber powder. Nine claims follow.