ADDITIVE FOR A BITUMINOUS BINDER RESPECTIVELY A BITUMINOUS COMPOSITE MATERIAL

Abstract

An additive for a bituminous binder respectively a bituminous composite material, able to reduce bituminous binder respectively bituminous composite material viscosity when an alternating magnetic field is applied, in particular for healing pavement cracks and in-depth micro-cracks in asphalt, wherein the additive comprises an amount of magnetic iron oxide particles should be improved, in order to reach bituminous composite material respectively a bituminous binder which can be melted in a faster and simplified way, in particular usable for crack healing of asphalt structures on site. This is reached by forming the additive comprising at least a part of magnetic iron oxide nanoparticles with average sizes between 1 nm and 300 nm coated with a fatty acid.

Claims

1. Use of an additive, comprising at least a part of magnetic iron-, cobalt-, nickel- or rare earth-based oxide nanoparticles, with average sizes in length and/or width between 1 nm and 300 nm, which are coated with a surfactant as part of a bituminous binder respectively a bituminous composite material, able to reduce viscosity of a bituminous binder respectively bituminous composite material by applying an alternating magnetic field, for healing adhesive and cohesive pavement cracks and in-depth micro-cracks in asphalt.

2. Use according to claim 1, wherein the surfactant comprises fatty acid like oleic acid, carboxylates such as sodium citrate, polymers such as Polyvinyl alcohol, or inorganic materials such as silica.

3. Use according to claim 1, wherein the surfactant comprises poly(vinyl)butyral, Poly(vinyl)pirrolidone, sorbitan oleate, block copolymer, sodium dodecyl sulfate or alkylphenol ethoxylates.

4. Use according to claim 1, wherein an amount of Fe3O4 and/or -Fe2O3O (maghemite) is used for the magnetic iron oxide nanoparticles.

5. Use according to claim 1, wherein the average thickness of the surfactant coating is between 1 nm and 10 nm, preferably between 1 nm and 5 nm.

6. Method for production of an additive for a bituminous binder respectively a bituminous composite material, enable to reduce bituminous binder respectively bituminous composite material viscosity when an alternating magnetic field is applied, in particular for healing adhesive and cohesive pavement cracks and in-depth micro-cracks in asphalt, wherein the additive comprises an amount of magnetic oxide particles, comprising the steps of: mixing of magnetic iron-, cobalt-, nickel- or rare earth-based oxide nanoparticles with average sizes between 1 nm and 300 nm with an amount of a surfactant in a solvent sonication and heating up to at least 40 C., preferably 60 C. for at least 2 hours, preferably twenty-four hours, while an additive solution comprising coated oxide nanoparticles with a surfactant coating on the nanoparticle surface is formed, before a polar aprotic solvent, in particular acetone, enabling removal of excess surfactant without destroying the coating, is added, for separation of the excess surfactant from the coated magnetic nanoparticles, followed by a subsequent trapping of the coated magnetic nanoparticles with a magnetic field and at least partly removing solvent, excess surfactant and the polar aprotic solvent, before finally the coated magnetic nanoparticles are miscible in a bituminous binder.

7. Method for production of an additive according to claim 6, wherein the solvent will at least be partly removed from the additive mixture, in particular by evaporation.

8. Method for production of an additive according to claim 6, wherein the solvent is water, toluene, xylene or tetrachloroethylene.

9. Method for production of an additive according to claim 6, wherein the surfactant comprises fatty acid like oleic acid, carboxylates such as sodium citrate, polymers such as Polyvinyl alcohol, or inorganic materials such as silica.

10. Method for production of an additive according to claim 6, wherein the surfactant comprises poly(vinyl)butyral, Poly(vinyl)pirrolidone, sorbitan oleate, block copolymer, sodium dodecyl sulfate or alkylphenol ethoxylates.

11. Bituminous composite material, comprising a bituminous binder in form of a thermoplastics material and amounts of a mineral filler and/or sand and/or stone aggregates, wherein the bituminous binder comprises at least a part of magnetic oxide nanoparticles with average sizes between 1 nm and 300 nm, which are coated with a surfactant, wherein the percentage by volume of the coated magnetic iron oxide nanoparticles in the bituminous binder lies between 0.1 vol. % and 5 vol. %.

12. Bituminous composite material according to claim 11, wherein the surfactant comprises fatty acid like oleic acid, carboxylates such as sodium citrate, polymers such as Polyvinyl alcohol, or inorganic materials such as silica.

13. Bituminous composite material according to claim 11, wherein the bituminous composite material comprises between 0.5 vol. % and 5 vol. % of magnetic coated oxide nanoparticles.

14. Bituminous composite material according to claim 11, wherein the average thickness of the surfactant coating is between 1 nm and 10 nm, preferably between 1 nm and 5 nm.

15. Method for production of a bituminous composite material according to claim 11, wherein, a bituminous binder is mixed with an additive, comprising at least a part of magnetic iron-, cobalt-, nickel- or rare earth-based oxide nanoparticles, with average sizes in length and/or width between 1 nm and 300 nm, which are coated with a surfactant, while the surfactant comprises fatty acid like oleic acid, carboxylates such as sodium citrate, polymers such as Polyvinyl alcohol, inorganic materials such as silica, poly(vinyl)butyral, poly(vinyl)pirrolidone, sorbitan oleate, block copolymer, sodium dodecyl sulfate or alkylphenol ethoxylates and additionally with portions of a mineral filler and/or sand and/or stone aggregates and/or other material components such as mineral aggregates.

16. Method for glueing together pre-fabricated bituminous elements to existing surfaces and/or healing pavement cracks and in-depth micro-cracks in asphalt in a bituminous composite material according to claim 11 comprising the steps of: applying an alternating magnetic field to the bituminous composite material for seconds up to two minutes, leading to temporary reduction of the bituminous binder viscosity, enabling flow of the bituminous composite material in the vicinity of the pavement crack and/or in the micro-crack in asphalt closing the crack and subsequent removal of the alternating magnetic field.

17. Method for healing pavement cracks and in-depth micro-cracks in asphalt according to claim 16, wherein an alternating magnetic field in the range between 0.1 to 1 MHz, preferably 285 kHz with an amplitude in the range between 10 to 100 mT is applied to a bituminous composite material containing magnetic coated nanoparticles for sufficient time until the bituminous binder filled in the crack.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] A preferred exemplary embodiment of the subject matter of the invention and results achievable with the subject matter of the invention are described below in conjunction with the attached drawings.

[0025] FIG. 1 shows a CryoSEM image of the coated magnetic nanoparticles distributed in bitumen, while

[0026] FIG. 2 shows a temperature kinetic curve (temperature vs. time) on bitumen comprising 1 vol. % of coated magnetic nanoparticles.

DESCRIPTION

[0027] For improving the applicability of a bituminous binder or bituminous composite materials, comprising amounts of a bituminous binder and components such as mineral filler, sand, stone aggregates and air voids in various concentrations, an additive could be found, which will be presented in the following. This additive can be part of the bituminous binder respectively of the bitumen or bituminous composite material, leading to much shorter application times, with much shorter melting times of the bituminous binder respectively the bituminous composite material.

[0028] The disclosed additive comprises an amount of coated magnetic nanoparticles, which can be embedded uniformly in a bituminous binder forming a bituminous composite material comprising the additive.

[0029] The bituminous binder usually comprises at least an amount of a thermoplastic bitumen-based material, including bitumen or polymer-modified bitumen (classical term to represent the modified bitumen), obtained from crude oil distillation with mixtures of organic hydrocarbons of high molecular weight. Persons skilled in the art know different bitumen-based materials, usable for bituminous binder.

[0030] Beside the bitumen-based material, the bituminous binder comprises an amount of an additive, comprising coated magnetic, especially ferromagnetic, ferrimagnetic or superparamagnetic, nanoparticles.

[0031] These magnetic oxide nanoparticles are not electrically conductive with an average size range of 1 nm to 300 nm in length and/or height. These used oxide nanoparticles provide larger thermal response as compared with the electrically-conductive materials known form prior art. The use of magnetic oxide nanoparticles is therefore more convenient for application like asphalt roads which include kilometres of asphalt as they are more suitable for heat generation and heat distribution.

[0032] In particular iron oxide nanoparticles are favored because of their higher magnetic response with respect to their size, their ease of synthesis and their low toxicity. Experiments showed best results using iron(III) oxide (Fe3O4) and iron(III) oxide, especially in gamma phase (-Fe2O3) known as maghemite. These iron oxide nanoparticles can be effectively applied to increase the durability of bituminous road structures. In this case, these particles would qualify as small mineral aggregates. Also, since they are oxides, corrosion can be avoided. Beside iron-based oxide nanoparticles, also cobalt-, nickel- or rare earth-based oxide nanoparticles can be used.

[0033] The homogeneity of the suspension of magnetic nanoparticles in the later bituminous binder respectively bitumen is ensured by modifying the surface of the nanoparticles to promote repulsion from each other.

[0034] Coating

[0035] The resulting additive comprises coated magnetic nanoparticles, in particular iron-based oxide nanoparticles, in the above mentioned average size range, coated with surfactant-like material, for example a fatty acid, in particular coated with oleic acid, wherein the coated magnetic nanoparticles are dispersed in a non-polar liquid respectively low polarity liquid.

[0036] Several classes of surfactant-like materials corresponding surfactants in the sense of this invention, comprising surface active molecules, can be used to coat the magnetic oxide nanoparticles surface. Some examples include carboxylates such as sodium citrate and oleic acid, polymers such as Polyvinyl alcohol, or inorganic materials such as silica.

[0037] Other possibilities of surface active molecules are poly(vinyl)butyral, Poly(vinyl)pirrolidone, sorbitan oleates (trade names e.g. Span 80, Span 85), block copolymers (e.g. Pluronic family), sodium dodecyl sulfate, alkylphenol ethoxylates and others. Here we propose to use oleic acid as an example of a typical surface active molecule leading to promising results, enabling a later high magnetic response from bituminous composite materials while simultaneously guaranteeing the mechanical stability of its bituminous binder.

[0038] The resulting thickness of the surfactant or surfactant-like coating lies between 1 nm and 10 nm, most preferred between 1 nm and 5 nm, basically the molecular chain size of the used molecules.

[0039] Method for Preparation of the Additive, Bituminous Binder and Bitumen Composite Material

[0040] The method for preparation of the additive respectively the bituminous binder respectively the bituminous composite material, comprising magnetic nanoparticles will be described in the following.

[0041] (1) Modification of the Magnetic Nanoparticles Surface

[0042] Magnetic nanoparticles, in form of magnetic iron oxide nanoparticles within the above mentioned average size range are immersed in any liquid solvent in which the nanoparticles can be dispersed in the presence of the surfactant-like surface active molecules. Here especially water is used, the coating could also be formed by mixing for example the nanoparticles with toluene or an equivalent non-polar solvent or low polarity solvent in the presence of Span 80 or Span 85.

[0043] Fatty acid, in particular oleic acid, will be added, acting as surfactant, before the solution is subjected to sonication and then heated up to 60 C. for 24 hours. The oleic acid partly forms a film on the iron oxide nanoparticles building a fixed coating. The surface of the magnetic nanoparticles is thereby modified.

[0044] Afterwards a polar, aprotic solvent, in particular acetone is added to the suspension to separate the excess oleic acid from the nanoparticles, without removing the coating of the iron oxide nanoparticles. The coated magnetic oxide particles are removed from the suspension by simple drying or by washing the coated particles with any solvent that enables removal of excess surfactant without destroying the coating, therefore other solvents than acetone could be used.

[0045] In the next step, the excess oleic acid respectively not coated amount of oleic acid, water and acetone are then nearly completely removed by trapping the nanoparticles using a magnet.

[0046] (2)

[0047] In the next step the coated magnetic nanoparticles are dispersed in a low polarity solvent miscible with bituminous binder.

[0048] The resulting additive mixture comprises magnetic nanoparticles coated with the fatty acid, in particular coated with oleic acid and suspended in the low polarity solvent. In this form the additive can be mixed with a bituminous binder forming a part of the bituminous composite material. For instance, toluene, xylene or tetrachloroethylene can be added as low polarity solvent to the coated magnetic nanoparticles or the coated magnetic nanoparticles can be mixed with toluene, xylene or tetrachloroethylene. Here toluene was preferred.

[0049] (3)

[0050] Afterwards the liquid will at least partly be removed from the additive mixture obtained in (2) after mixing with toluene, for instance by evaporation. For example, if toluene is used as the miscible, it can be evaporated completely by heating the mixture at 160 C.

[0051] Adding Additive to Bituminous Binder

[0052] The additive respectively the at least partly evaporated additive mixture can be mixed with bituminous binder. As known the bituminous binder comprising the additive can be mixed with mineral filler and/or sand and/or stone aggregates and/or other material components such as mineral aggregates as necessary for the intended application, forming the bituminous composite material.

[0053] An example of a working bituminous composite material comprised:

[0054] Filler: 7.5 wt % weight per cent

[0055] Sand: 35 wt %

[0056] Mineral aggregates: 51 wt %

[0057] Bituminous binder: 6.5 wt % comprising 1 vol % of coated magnetic nanoparticles

[0058] As the bituminous composite material remains a thermoplastic, one can re-heat the bituminous composite material with bituminous binder comprising magnetic coated nanoparticles. It can also be used to allow glueing to interfaces. The magnetic coated nanoparticles remain suspended homogeneously in the binder respectively in the bituminous composite material.

[0059] As can be seen in the SEM-image FIG. 1 of a bituminous composite material surface, a uniform dispersion of loosely clusters of coated magnetic nanoparticles can be achieved. The clusters exhibit an average diameter of three to four micrometer and average distance between fifteen to twenty micrometers. By embedding the magnetic coated nanoparticles in the bituminous composite material allows an external alternating magnetic field to heat up uniformly the bitumen in a few seconds time as will be described in the following.

[0060] Thermal Activation

[0061] The invention also includes a method to thermally activate the embedded magnetic coated nanoparticles in the bituminous composite material by applying an alternating magnetic field. The temporary reduction of the bituminous binder viscosity thus achieved facilitates healing of micro-cracks in pavements by re-activating the adhesion between the binder and material components like grids or mineral aggregates.

[0062] Activation Method/Modifying Viscosity

[0063] The method to activate the magnetic coated nanoparticles for decreasing the viscosity of the bituminous binder in a bituminous composite material will be disclosed in the following.

[0064] In case a crack or a debonding between the bituminous binder and a mineral aggregate in an oldfashioned bituminous composite material (without the bituminous binder, we present here) should be filled or glued, bituminous composite material comprising the additive with magnetic coated nanoparticles has to be applied to or in a pavement crack and/or in a micro-crack in the oldfashioned asphalt. The micro-cracks we are addressing are ranged from few micrometer to few centimetre in length or width.

[0065] In the case of an adhesive or cohesive crack in a bituminous composite material (e.g. a pavement) comprising already the nanoparticles the activation can be applied directly as written in the following step (I).

[0066] (I) Application of an alternating magnetic field.

[0067] An alternating magnetic field is applied such that heat is generated from the magnetic coated nanoparticles within the bituminous composite material leading to an increase in the temperature of the bituminous composite material. For instance, an alternating magnetic field with a frequency of in the range of 0.1 to 1 MHz, preferably 0.3 kHz with an amplitude in the range of 10 to 100 30 mT applied to a bituminous composite material containing magnetic coated nanoparticles can generate enough heat in a few seconds to make the bitumen flow. The temperature obtained in the structure can be monitored using Infrared imaging techniques. The temperature has to be maintained long enough above a temperature where bitumen is able to flow (typically between 30 C. and 200 C. depending on the bituminous binder type) and below a temperature which could damage the bitumen.

[0068] (II) Removal of the alternating field.

[0069] After the high temperature is maintained long enough to enable bituminous binder to either adhere to a surface or to fill a crack, the alternating magnetic field is then removed.

[0070] As an example, practical heating measurements can be carried out using an alternating magnetic field developing 285 kHz for a magnetic field of 30 mT. Samples are inserted in a copper coil (50 mm, 3 turns) and then heated for twenty seconds. Sample surface temperature is recorded using infrared camera measuring the emitted IR radiation. The temperature increase over time is displayed in FIG. 2.

[0071] Industrial Application of Healing Cracks

[0072] With regards to the feasibility of using alternating magnetic field at the road scale, a setup designed for removing asphalt pavements is available on the market, WO200711102. This technique enables the heating of a steel plate on a bridge to delaminate the bituminous layer. Similar setups can be adapted for the heating of magnetic additives embedded in bituminous composite materials.

[0073] Typically in our case, we aim at healing cracks and debonding present in the topmost layer of the different road layers, which means not more than seven centimeters in thickness. As a result, the influence of the field attenuation should be limited.

[0074] In addition to pavement healing applications, the on-demand temperature induced reduction of bituminous binder viscosity in bituminous composite materials allows triggering multiple effects. For example, it can promote adhesion of the bituminous composite material to different surfaces, like attaching bituminous joint sealings to structural elements (e.g. made out of concrete) or glueing waterproofing membranes to the substrate.

[0075] Waterproofing membranes are used to act as a barrier between a building structure and water. Applying one or various layers of membranes prevents water from infiltrating. Typically, the bitumen-based membrane contains polymer modified bitumen and is sealed to the substrate by melting the bitumen using flame or hot air. Depending on the method, temperatures can reach 400 C. or even 800 C., leading to possible damages in the bitumen microstructure. However, by progressively heating the bitumen membrane using the combination of magnetic nanoparticles and an alternating magnetic field as described in this application, the membrane can reach a specific temperature without the associated negative effects of overheating.

[0076] Coated magnetic nanoparticles could also be used as a trigger for breaking bitumen emulsions. Bitumen emulsions are a dispersion of small droplets of bitumen in water dispersed by using an emulsifying agent. They are generally used for maintenance and do not require high temperature. The separation of water from bitumen in the emulsion is termed as breaking. After this step, the bitumen part becomes adhesive and water-resistant. To control the breaking, iron oxide coated nanoparticles can be incorporated into the bitumen droplets. By heating the nanoparticles with the aid of an alternating magnetic field, the breaking would be instantaneously activated throughout the entire material. In direct contrast to bigger additives, the nanoparticles do not affect the emulsion viscosity due to their smaller sizes as well as concentration. Moreover, they can also be used as a stabilizer, similar to the principle of a pickering emulsion. Indeed, as they can be electrically charged they would interact with the bitumen droplets at the interface between water and bitumen.

[0077] Such coated magnetic nanoparticles can also be used to control the expansion of foamed bitumen. Foamed bitumen consists of a mixture of air, water and bitumen. It is produced in an expansion chamber where a small quantity of water is injected into hot bitumen. The bitumen expands to 5-15 times its original volume and forms a foam. This foam is particularly beneficial in wetting and coating the surface of mineral aggregates with a small quantity of bitumen. The expansion time of the foam is an important parameter to be controlled. By adding magnetic coated nanoparticles, the expansion time can be regulated by activating/deactivating the nanoparticles with an alternating magnetic field. Once the coated magnetic nanoparticles start generating heat, the bubbles will start disappearing. Again, contrary to other additives, gravity has a negligible effect on the nanoparticles and therefore they can be located at the interface between the bubbles. They can also be used as a stabilizing agent during foaming and thereby stop the expansion by locally heating their surroundings.