Method for recycling asphalt

Abstract

The invention relates to a method for recycling reclaimed asphalt, in which method material of the reclaimed asphalt is separated at least into a first fraction and into a second fraction, wherein the first fraction has a smaller grain size than the second fraction. The second fraction is stored as recyclable reclaimed asphalt in order to be processed together with new material to form new asphalt. The material of the reclaimed asphalt is separated into the first fraction and the second fraction exclusively mechanically, and the recyclable reclaimed asphalt is provided for being processed to form the new asphalt without thermal or chemical treatment. This method allows for an optimized recycling of reclaimed asphalt having an increased PAH load.

Description

[0001] TITLE

[0002] ASPHALT RECYCLING PROCESS

[0003] TECHNICAL FIELD

[0004] The present invention relates to a process for recycling asphalt and a process for producing new asphalt using reclaimed asphalt.

[0005] STATE OF THE ART

[0006] Asphalt is a mixture of the binding agent bitumen and aggregates, along with any additives. It is used in road construction for pavements and in other areas, such as vehicle parking areas, runways, taxiways, and aircraft parking areas. Other applications include sealing in hydraulic engineering, particularly for dams, dams, and shipping canals, or for sealing landfills.

[0007] Road pavements typically consist of various asphalt layers, particularly surface, binder, and base courses, which differ in their composition. Asphalt layers for parking areas and other applications also differ in their composition. Therefore, asphalt recipes are developed for the production of the various asphalt types, which specify the mixing ratios of the individual components of each asphalt type.

[0008] The asphalt mix varies not only depending on the application, but also depending on the applicable regulations, which vary from country to country, and even from region to region. Special requests from the client, such as brightness, grip, or noise reduction, also alter the mix in terms of the type of mix, grain size, and binder. The asphalt recipes used to produce the asphalt vary accordingly. Depending on the supply, an asphalt producer's production can consist of more than one hundred asphalt recipes. The resulting asphalt product is subject to standards, target values, and tolerances.

[0009] Asphalt recipes for asphalt production are therefore complex and based on many years of experience. Plant control systems for asphalt production facilitate the selection and adherence to asphalt recipes, as well as recipe changes or adjustments during ongoing production.

[0010] During renovations and renewals, particularly in road construction, large quantities of old asphalt, also known as reclaimed asphalt, are generated. Reclaimed asphalt is created by milling or breaking up the asphalt pavement into slabs. It is processed into asphalt mix by subsequent crushing and screening. The reclaimed asphalt is later mixed with new asphalt mixes in an asphalt mixing plant. This can be done as a cold addition, with the reclaimed asphalt fed directly to the mixer via an intermediate silo and heated by the new mix. Alternatively, the reclaimed asphalt can be heated in a separate parallel drum and fed to the mixer as a hot addition.

[0011] Recycling reclaimed asphalt is essential from both an economic and ecological perspective. However, it is complex due to the requirements for asphalt properties and legal regulations. In particular, the processing of the bitumen is laborious. This means that only a small percentage of reclaimed asphalt is recycled.

[0012] Another problem is that reclaimed asphalt can contain varying levels of PAH contamination. From a technical perspective, reclaimed asphalt with normal PAH contamination is easier to recycle than reclaimed asphalt with medium or high PAH contamination. In Switzerland, for example, reclaimed asphalt with PAH contamination levels of 250 mg / kg or higher can only be recycled for new asphalt with great effort, if at all.

[0013] Some processes are already known in the state of the art that deal with the recycling of reclaimed asphalt.

[0014] GB 2 332 010 A discloses a recycling process for road material in which the road surface is crushed and the crushed material is sorted into fractions according to its size, the material of each fraction being recycled separately.

[0015] In FR 3 020 074 A, more than two material groups are formed that differ in their grain size. It is assumed that the fraction with the smallest grain size has the highest bitumen content.

[0016] EP 3 173 526 A1 also proposes crushing the reclaimed asphalt and storing it in material groups of different grain sizes. These fractions should allow for a more precise determination of the bitumen content of each fraction, allowing a mixture for new asphalt to be created.

[0017] WO 2020 / 071906 A1 proposes analyzing individual fractions of crushed reclaimed asphalt with different grain sizes and attaching them with RFID tags. The RFID tags provide information about the content of the fractions so that a new mix can be created.

[0018] These processes attempt to recycle as large quantities of reclaimed asphalt as possible. However, legal regulations, fluctuations in the type of reclaimed asphalt, aging of the bitumen, and an excessive proportion of fine minerals limit the use of bituminous reclaimed asphalt in newly produced asphalt. This means that bitumen either has to be isolated from the reclaimed asphalt using complex processes, or that only a small percentage of the smallest grain size material group, which contains the largest proportion of bitumen, can be directly reused. Typically, the material group with the smallest grain size contains the most bitumen. The reuse of this material group is often not possible with current technology, either due to regulations or other reasons. This is suboptimal from an ecological and economic perspective. This is because bitumen accounts for approximately one-third of the cost of asphalt pavement.Even a small increase in the percentage of directly recyclable bituminous material leads to a significant reduction in the production costs of new asphalt.

[0019] In this text, including the patent claims, the term "asphalt" also includes surfaces that contain PAH-containing or other binders (PAH = polycyclic aromatic hydrocarbons) instead of or in addition to bitumen. In particular, according to this text, the term also includes tar.

[0020] The term "bitumen" in this text, including the patent claims, is to be understood as "binder" unless otherwise stated in the text.

[0021] The term "reclaimed asphalt" includes material from the pavements, whereby in some embodiments, material from the sub-layers of the pavement is also included, such as material from the coffer layer, in particular RC gravel or RC A gravel.

[0022] The term "fraction" refers to a group or portion of aggregate, particularly the original reclaimed asphalt, that failed to pass the next smaller screen during screening and is stored together in a separate storage facility until further use. The grain size within this fraction generally ranges from the apertures of the last screen through which the material passed to the next smaller screen through which the material failed. Depending on the grain size range, the material is referred to as grit or sand.

[0023] The term "sieve curve," also called "grading line," refers to a grain size distribution curve determined by sieving the rock. This "sieve curve" allows the grain size distribution of the rock to be graphically recorded.

[0024] The term "asphalt recipe" refers to the mixing ratio of the individual components used to produce asphalt. The individual components are typically graded aggregates and binders, particularly bitumen. Instead of "asphalt recipe," the term "pavement recipe" is also used.

[0025] PRESENTATION OF THE INVENTION

[0026] It is an object of the invention to optimize the recycling of reclaimed asphalt, in particular for reclaimed asphalt with increased PAH contamination.

[0027] This object is achieved by a method having the features of claim 1 or 14.

[0028] In the inventive process for recycling reclaimed asphalt, reclaimed asphalt material is divided into at least a first fraction and a second fraction, with the first fraction having a smaller grain size than the second fraction. The second fraction is stored as recyclable reclaimed asphalt to be processed together with virgin material into new asphalt. The reclaimed asphalt material is separated exclusively mechanically into the first fraction and the second fraction, and the recyclable reclaimed asphalt is provided for further processing into new asphalt without thermal or chemical treatment.

[0029] Providing the reclaimed asphalt "without thermal or chemical treatment" may involve cleaning the reclaimed asphalt and / or the second fraction with water. For example, they may be washed to remove entrained fines. However, exclusively dry-mechanical treatment of the reclaimed asphalt is preferred, especially since the reclaimed asphalt typically already contains a liquid component. In some preferred variants of the process, the aforementioned provision also takes place "without washing."

[0030] Providing "without thermal or chemical influence" may also include heating the second fraction before being added to the new material, in order to feed it as a hot addition to a mixing tower of a paving plant. This heating does not affect the composition of the second fraction and therefore does not constitute thermal influence within the meaning of the invention claimed here. Alternatively, the second fraction can be added to the new material in a cold state.

[0031] The inventive method has the advantage that the fractionation of the reclaimed asphalt into at least two fractions leads to an enrichment of PAHs in the first fraction with a smaller grain size and a depletion of PAHs in the second fraction with a larger grain size. This is the case because PAHs are part of the binder, and the binder is present in a larger mass percentage in finer fractions.

[0032] This allows the second fraction to be recycled without the need for expensive and complex processes. The first fraction is preferably used as waste and is not reused to form new asphalt.

[0033] If the grain size range of the second fraction is relatively large, PAH-contaminated binder can be removed from the recycling process and mineral material can still be optimally reused.

[0034] In some variants of the process, only this second fraction is recycled and, if necessary, mixed with virgin material. In other variants of this process, one or more fractions from another fractionation process are added to this second fraction. In the other fractionation process, reclaimed asphalt with a low PAH load was preferably fractionated. For example, with the process described in the patent application filed on the same day by the same applicant. In this other patent application, several fractions are formed and combined in a new quantity or weight ratio.

[0035] Depending on the process variant, either exactly two fractions are formed or more than two. In the latter case, only the fraction with the smallest grain size is not used in this form for the new asphalt.

[0036] In a first variant of the process, the second fraction is fed to a paving plant without further division or separation and mixed with virgin material to produce new asphalt. This can be done in a conventional manner by following existing asphalt recipes. Preferably, however, an optimizer is present that uses software with one or more optimization methods to maximize the recycled content in the new asphalt. The optimizer achieves this by adapting the respective asphalt recipe accordingly within the limits of the standards, specifications, and guidelines.

[0037] In another variant of the process, the second fraction is divided into further fractions with different grain sizes before storage or delivery, or before being added to new material. This division into more than two fractions enables the reclaimed asphalt material to be reformulated. This means that the fractions with different grain sizes can be combined into different groups. This enables the asphalt recipes to be optimized with a view to maximizing the recycling content. In addition, or alternatively, this allows the highest possible recycling rate of the reclaimed asphalt to be achieved. A corresponding optimizer and various optimization methods are described in detail in the patent application filed by the same applicant on the same day. The content of this application is incorporated into this text by reference.If the delivered reclaimed asphalt has a moderate PAH content, it is sufficient to perform the process only once to obtain the second fraction in the form of recyclable reclaimed asphalt. In this case, the reduction is sufficiently high.

[0038] However, reclaimed asphalt with high PAH contamination preferably undergoes the process twice or more, whereby the PAH contamination in the second fraction gradually decreases until it corresponds to a recyclable reclaimed asphalt.

[0039] Therefore, the reclaimed asphalt material is preferably divided once, twice, or several times into at least two fractions, depending on its PAH content (PAH = polycyclic aromatic hydrocarbons). The final fractionation produces the second fraction as recyclable reclaimed asphalt for further processing into new asphalt. During each pass through the fractionation process, the first fraction, i.e., the fraction with the smallest grain size, is removed from the process as waste and not used to form new asphalt.

[0040] Material that is passed through the fractionation process twice or more can be passed through the same process multiple times, particularly through the same crusher types and screen sizes. In particular, they can be passed through the same crusher and screens in a single circuit. In other variations of the process, different crushers and / or different screen sizes are used for the second or subsequent pass, and / or different types of fractionation processes are employed.

[0041] The definition of low, medium, and high PAH contamination varies by country or region. In Switzerland, it is common practice to describe a PAH content of less than 250 mg per kg of reclaimed asphalt as low or normal. Such material may be recycled. Material with a PAH contamination of more than 250 mg is generally considered to have increased contamination and may not be processed into new asphalt, or only in very small quantities. Material with a PAH contamination of more than 1,000 mg / kg may not be reused. The limit values ​​vary significantly by region and country.

[0042] For example, with a sieve size of 4 mm (the smallest particle size fraction), it has been shown that for a contamination level of 250 mg / kg to approximately 650 mg / kg, the process only needs to be run once to reduce the PAH contamination in the second fraction to less than 250 mg / kg. For a PAH contamination level of approximately 650 mg / kg to approximately 1000 mg / kg, it is sufficient to run the process twice.

[0043] The second fraction preferably has a predefined grain size x / y mm (mm = millimeters). Especially when the process is run through twice or more times, the grain size of the second fraction preferably does not change. In some variants of the process, however, the grain size of the second fraction is changed, for example, by using a different sieve size.

[0044] The material from the first fraction is highly contaminated with PAHs and therefore constitutes a waste stream. It is not used in this form for further processing into new asphalt. It is either properly disposed of or reused in other applications.

[0045] Preferably, the reclaimed asphalt material is divided into at least two fractions by crushing and screening. In some variants, additional mechanical means are used. However, the mechanical means are preferably limited to crushing, preferably using a rotor centrifugal crusher, and screening. Washing and air separation are also possible.

[0046] Preferably, at least one centrifugal rotor crusher is used. In one embodiment, the material is preferably screened first before using the centrifugal rotor crusher and then screened again. In other embodiments, the centrifugal rotor crusher is used before screening.

[0047] Preferably, the first fraction has a grain size of 0 / x mm and the second fraction has a grain size of x / y mm. Where x <y. In einer bevorzugten Variante ist x annähernd 4 mm und y annähernd 22 mm. Es lassen sich auch andere Zahlenkombinationen verwenden bzw. anstelle von 4 mm bzw. 22 mm lässt sich in dieser Kombination auch ein anderer Wert verwenden, beispielsweise 18 mm statt 22 mm bzw. 5 mm statt 4 mm.

[0048] Preferably, the delivered reclaimed asphalt is already sufficiently crushed. It preferably has a grain size of 0 / w mm before use in the process, where w is preferably approximately 80 mm. Preferably, the second fraction has a smaller grain size, so y is preferably <w. Der Ausbauasphalt mit der Körnung 0 / w lässt sich direkt im Verfahren in die zwei Fraktionen 0 / x mm und x / y mm aufteilen. Vorzugsweise wird er jedoch bereits vorgängig aufgeteilt, um in einem ersten Schritt bereits einen Teil der PAK Belastung zu vermindern. Hierzu wird er in die Fraktionen 0 / v mm und v / w mm aufgeteilt, wobei lediglich die Fraktion v / w mm in die erste Fraktion und in die zweite Fraktion aufgeteilt wird. Die Fraktion 0 / v mm bildet vorzugsweise einen Austrag und wird nicht zur Weiterverarbeitung zu neuem Asphalt verwendet. Vorzugsweise weist die Fraktion 0 / v mm annähernd oder genau dieselbe Körnung auf wie die erste Fraktion, d.h. vorzugsweise ist sie 0 / 4 mm.The division is preferably done by sieving.

[0049] Depending on the grain size of the reclaimed asphalt initially used, a portion of the reclaimed asphalt remains after the process as oversize or an additional fraction with a grain size larger than the second fraction. This portion of the reclaimed asphalt is preferably re-divided to deliver material to the first and second fractions. This portion of the reclaimed asphalt is preferably passed through the same process and the same processing system again. This re-dividing process can be repeated two or more times to divide as much material as possible into the first and second fractions.

[0050] The invention also encompasses a method for producing new asphalt using reclaimed asphalt that at least partially contains material from the second fraction according to the above method, to be processed together with new material to form new asphalt. Using software and an optimization method, an asphalt recipe for producing the new asphalt is created. The software-based mathematical optimization method is programmed to have at least one optimization objective that can be achieved in the best possible way. The method has at least the following optimization objective: the best possible maximization of a recycled content in the new asphalt, wherein the recycled content is formed at least partially by material from the second fraction. The optimization method takes into account a declared target for the new asphalt in achieving the best possible maximization. A suitable optimization method for this purpose is described in EP 23 152 256.6 of January 18, 2023, and in the POT application entitled "Process for Recycling Asphalt," filed by the applicant on the same date as the present application. The contents of these two applications are incorporated herein by reference.

[0051] When there are several optimization criteria or objectives, "best possible" is preferably understood as a Pareto optimum, which is determined using a weighted sum method.

[0052] The declared target is preferably a set of asphalt properties that will no longer be recalculated or another specification, such as a legal regulation, a standard, a guideline, and / or a customer specification. The asphalt recipe for an asphalt is defined based on the declared target.

[0053] The recycled content preferably includes at least some reclaimed asphalt that has been fractionated, with the resulting fractions being composed in a new ratio. The grading curves of the individual fractions are taken into account when developing the asphalt recipe. It can also include gravel from the cobblestone layer, for example.

[0054] A computer program product according to the invention includes the above-mentioned software.

[0055] Further embodiments and variants of the method are specified in the dependent claims.

[0056] BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Preferred embodiments of the invention are described below with reference to the drawing, which serves only for explanation and is not to be interpreted as limiting.

[0058] Figure 1 shows a schematic representation of the inventive processing of reclaimed asphalt in a processing plant.

[0059] DESCRIPTION OF PREFERRED EMBODIMENTS

[0060] Figure 1 shows a schematic representation of part of an asphalt processing plant. The representation is highly simplified. Plant areas not shown are known to those skilled in the art and are therefore not shown here for better readability of the figure. Reclaimed asphalt is delivered to the processing plant in blocks or as milled material. If not processed elsewhere, the reclaimed asphalt is crushed in at least one crusher to a fraction of 0 / w mm. Crushers are known in the art. They crush the blocks or milled material so that it can be fed to a screening plant.

[0061] The reclaimed asphalt is prepared to a grain size of 0 / w mm, where w is preferably approximately 80 mm. This material is fed into a feed hopper 1 via the feeder 10.

[0062] The feed hopper 1 is followed by a diverter, which in Figure 1 leads via an inlet 11 to a first screening system. The screening system comprises at least one screen, as it separates the feed material into two fractions with grain sizes of 0 / v mm and v / w mm. In this example, the grain sizes are 0 / 4 mm and 4 / 22 mm. Alternatively, more screens can be present. In particular, more than two fractions can be formed.

[0063] The fraction with the smaller grain size is conveyed via a discharge 12 to a depot 3 for discharge. Material from this depot 3 is properly disposed of or recycled, but is no longer used in this form for the production of new asphalt.

[0064] The fraction with the larger grain size is fed via line 13 to a crusher, preferably a rotor centrifugal crusher 4. From there, the crushed material is transported via line 14 to a second screening plant 5. This screening plant has at least two screens and separates the material into a first fraction with a grain size of 0 / x mm and a second fraction with a grain size of x / y mm. The oversize grain, i.e. the material that has not passed through the screens, forms another fraction with a grain size of y / w mm. In this example, the fractions are 0 / 4 mm, 4 / 22 mm, and 22 / 80 mm. Alternatively, more fractions can be formed.

[0065] The first fraction is fed to depot 3 via discharge 15. The second fraction is fed via forwarding line 16, via a diverter, and via forwarding line 17 to a storage facility 60 for recyclable reclaimed asphalt. This is the case when the starting material has a maximum average PAH load of up to X mg / kg. X is preferably approximately 650 mg / kg. This material is discharged for reuse via forwarding line 19 as needed. It usually ends up on a conveyor 8 that leads to a paving plant. If the starting material has a higher PAH load, the diverter is adjusted, as shown in Figure 1. It leads via forwarding line 18 to an intermediate storage facility 61. This material, which still has an excessive PAH load, is returned via return line 20 to the rotor centrifugal crusher 4 or to the second screening plant directly via forwarding line 13.In a preferred variant, as shown in Figure 1, this material is returned to the feed hopper 1.

[0066] However, when this material, which is still too heavily contaminated with PAHs, passes through again, the first screening plant 2 is preferably bypassed by a switch that can be set to a bypass 21. In Figure 1, however, the switch is directed to the first screening plant 2.

[0067] Material with a contamination of up to 1000 mg / kg PAH is usually only returned to the cycle once, i.e. it only goes through the process twice. During the second run, the switch is made in the forwarding line 16 to the storage facility 60. However, it is possible to run through the process more than twice. The storage facility 60 can be a single storage facility or comprise several storage facilities. Depending on the variant of the process, material that has run through the process more than once is stored in a separate storage facility 60, i.e. separate from material that has only run through the process fewer times. In other variants, material that has run through the process and is reused to form new asphalt is stored together, regardless of the number of runs.

[0068] The oversize material from the second screening plant 5 is fed via a transfer line 22 to an oversize material storage facility 7. From there, it also returns to the recycling system via the return line 20. The same applies to the material from the intermediate storage facility 61.

[0069] Alternatively, the oversize grain can be routed via a switch in the forwarding line 22 to the forwarding line 16 and thus deposited in the intermediate storage 61. In Figure 1, however, this switch is positioned toward the storage area 7 for the oversize grain.

[0070] The PAH-reduced material located in Warehouse 60 can be added to the new material in its existing form. Using a computer-implemented, software-based optimizer with a mathematical optimization method, optimized new asphalt recipes can be created that best accommodate customer specifications, comply with regulatory and legal requirements, and still maximize the recycled content of reclaimed asphalt in the new asphalt. Such optimization methods are described in detail in the applicant's patent application filed on the same day.

[0071] The recycled content of the new asphalt and the overall recycling rate of the reclaimed asphalt can be further maximized if the second fraction is divided into further fractions with different grain sizes before being added to the new material and these fractions are combined in new proportions.

[0072] The composition for maximizing the recycling share and utilization rate can also be calculated using the optimizer, as explained in detail in the aforementioned parallel patent application. The process according to the invention allows for optimized reuse of reclaimed asphalt with increased PAH contamination.

[0073] LIST OF REFERENCE SYMBOLS

[0074] Feeder of broken fraction with first screening plant of larger grain size

[0075] Depot for discharge 15 removal of the first fraction

[0076] Rotor centrifugal crusher 16 Transfer of the second second screening plant fraction storage for recyclable 17 Transfer to storage for

[0077] Reclaimed asphalt recyclable reclaimed asphalt

[0078] Cache 18 Forwarding in

[0079] Storage for oversize grain intermediate storage

[0080] Conveyor to the covering plant 19 Forwarding to

[0081] Supply of reclaimed asphalt reuse

[0082] Feed to the first screening plant 20 Return to the process

[0083] Discharge of the fraction with 21 bypassing the first smaller grain size screening plant

[0084] Forwarding of the fraction with 22 Forwarding of the oversize grain with larger grain size 23 Bypassing the storage for

[0085] Forwarding of oversize grain

Claims

PATENT CLAIMS 1. A process for recycling reclaimed asphalt, wherein material of the reclaimed asphalt is divided into at least a first fraction and a second fraction, wherein the first fraction has a smaller grain size than the second fraction, wherein the second fraction is stored as recyclable reclaimed asphalt to be processed together with new material to form new asphalt, characterized in that the material of the reclaimed asphalt is divided exclusively mechanically into the first fraction and the second fraction and that the recyclable reclaimed asphalt is provided for further processing into new asphalt without thermal or chemical influences.

2. Method according to claim 1, wherein the material of the reclaimed asphalt is divided once, twice or several times into at least two fractions depending on its PAH load (PAH = polycyclic aromatic hydrocarbons) until the second fraction is provided as recyclable reclaimed asphalt for further processing into new asphalt during the last fractionation.

3. A process according to any one of claims 1 or 2, wherein the first fraction forms a discharge and is not used to form new asphalt.

4. The method according to any one of claims 1 to 3, wherein the second fraction has a predefined grain size x / y mm.

5. Method according to one of claims 1 to 4, wherein the material of the reclaimed asphalt is divided into the at least two fractions by crushing and screening, preferably exclusively crushing and screening.

6. A method according to any one of claims 1 to 5, wherein a rotor centrifugal crusher is used and wherein the rotor centrifugal crusher is preferably used before screening.

7. The method according to any one of claims 1 to 6, wherein the first fraction has a grain size of 0 / x mm and the second fraction has a grain size of x / y mm, where x <y where x is preferably approximately 4 mm and y is preferably approximately 22 mm.

8. Method according to one of claims 1 to 7, wherein reclaimed asphalt with a grain size of 0 / w mm is used, where w is preferably approximately 80 mm.

9. Method according to claims 7 and 8, wherein y <w ist.

10. Method according to one of claims 8 or 9, wherein the reclaimed asphalt with the grain size 0 / w is divided into the fractions 0 / v mm and v / w mm, wherein the fraction v / w is subsequently divided into the first fraction and the second fraction.

11. A process according to claims 9 or 10, wherein the fraction 0 / v has approximately or exactly the same grain size as the first fraction.

12. The method according to any one of claims 1 to 11, wherein a portion of the reclaimed asphalt which, after division into the first fraction and the second fraction, has a grain size which is larger than the grain size of the second fraction, is divided again to supply material to the first fraction and to the second fraction, preferably being passed through the process again.

13. The method of claim 12, wherein said process is repeated two or more times.

14. A method for producing new asphalt using reclaimed asphalt which at least partially contains material from the second fraction according to one of claims 1 to 13, in order to be processed together with new material to form new asphalt, characterized in that a software-based optimization method is used to determine how much material of the second fraction is processed together with new material to form new asphalt, wherein the optimization method creates an optimized asphalt recipe for producing new asphalt, that the optimization method is programmed in such a way that it has at least one optimization objective which can be achieved in the best possible way when carrying out the method, and that the optimization method has at least the following optimization objective: best possible maximization of a recycled content in the new asphalt, wherein the The recycled content is at least partly formed by material from the second fraction, and the optimization process takes into account a declared target of the new asphalt when maximizing it to the best possible extent.

15. The method according to claim 14, wherein the recycled portion comprises at least partially reclaimed asphalt which is fractionated, the resulting fractions being composed in a new ratio to one another and their sieving curves being taken into account in the preparation of the asphalt recipe.

16. A computer program product comprising software according to any one of claims 14 or 15.

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