Antioxidant and Anti-ravelling association for draining bituminous conglomerates

Abstract

The present patent application relates to an antioxidant and anti-ravelling association for draining bituminous conglomerates comprising or consisting of - diphenylmethane diisocyanate (MDI) in the form of isomers, oligomers, and / or polymers, - an organosilane of formula (I) below (formula I) wherein R1 is selected from: methyl, ethyl, methoxy, ethoxy, R2 is selected from: methyl or ethyl, R3 is selected from the group consisting of: -CH2-, -OCH2-, -CH2CH2-, -OCH2CH2-, - CH2CH2CH2-, -OCH2CH2CH2-, -NHCH2CH2-, -NHCH2CH2CH2-, R4 is selected from the group consisting of: NH2-, NH2CH2-, NH2CH2CH2-, SH-, characterized in that the weight ratio between diphenylmethane diisocyanate (MDI) and organosilane is comprised between 9:1 and 19:1.

Description

[0001] TITLE: "Antioxidant and anti-ravelling association for draining bituminous conglomerates'’'’

[0002] DESCRIPTION

[0003] FIELD OF THE INVENTION

[0004] The present invention falls within the field of technologies usable for draining and wear-resistant bituminous conglomerates, in particular in the identification of associations of antioxidant and anti-ravelling additives to be included in draining bituminous mixtures.

[0005] STATE OF THE ART

[0006] The road pavement is the upper part of the road structure, called the superstructure, and is formed by several layers consisting of stone aggregates, having suitable characteristics, bonded with bituminous binder. Each layer is determined by different materials and thicknesses, this is because the closer to the surface, the more the layer is in close contact with vehicles and, consequently, greater performance is required.

[0007] In general, a road pavement consists, starting from the top downwards, of:

[0008] - wearing course: it is the surface layer in contact with vehicles, for this reason it must be such as to guarantee a certain safety and driving comfort, in terms of grip and regularity of the road surface;

[0009] - binder: it is a connecting layer between the wearing course and the base, necessary to rectify the defects of the underlying surface;

[0010] - base: it is the core of the superstructure and performs a structural function, as it is necessary to distribute the loads induced by vehicles;

[0011] - foundation: with its position above the subgrade (lower part of the road structure), it allows the transmission of loads to the latter.

[0012] As the layer most exposed to road loads, the wearing course mat must be able to withstand the polishing actions induced by vehicles, also thanks to the use of precious materials (such as basalt or porphyry). The actions to which a wearing course is subjected can be divided into two main categories:

[0013] 1. traffic-induced actions;

[0014] 2. climate actions.

[0015] The wheels of the vehicles exert both vertical and tangential actions on the road surface; the former are produced by the weight force of the vehicles, the latter are tangential forces that are generated as a result of the adhesion between the tyre and the pavement.

[0016] A pavement is referred to as flexible when it consists of a structural package consisting of: a wearing course, a connection or binder and a base course, all consisting of bituminous concrete, in which the road package is then completed by a foundation course that transfers the loads to the subgrade.

[0017] In flexible pavement, the extent of the deformations and horizontal stresses induced by vertical actions, generally, increases proceeding from the upper to the lower layers of the pavement, which are therefore subjected to more severe tensile stresses, and is obviously dependent on the overall rigidity of the pavement and the subgrade; on the contrary, the deformations and vertical stresses induced by the same vertical actions decrease proceeding from the top downwards, so that the more superficial layers are subjected to more burdensome vertical compressive stresses; moreover, the tangential actions are mainly absorbed by the wearing course, within which tangential stresses are generated that are transmitted to the underlying course (binder) due to the adhesion generated between the two courses.

[0018] It follows that, in general, in the wearing course, an overall more severe state of tension is determined than that of the other courses of the pavement and, to guarantee the resistance of the course to this specific particularly severe state of tension, the wearing course must be made with a mixture characterized by high mechanical performance.

[0019] The latter, in the case of continuous gradation mixtures, known as "closed" mixtures, mainly depend on the characteristics of the aggregates that must have a petrographic nature and shape such as to guarantee high resistance to polishing, high internal friction angles of the lithic skeleton and, at the same time, good affinity with the binder, understood as the aggregate's ability to bind stably with the bitumen, without undergoing "stripping", that is, the detachment of the binder film from the granules.

[0020] In the case of gap-graded or open-graded mixtures, on the other hand, the mechanical performance depends mainly on the rheological properties of the binder, which must be able to provide the mixture with the necessary resistance to the state of tension generated in operation; for these mixtures, however, the aggregates must still have excellent mechanical characteristics in terms of resistance to polishing and crushing. The absence of the aforesaid requirements compromises the ability of the course to resist the state of tension that is generated therein and, with particular reference to the lack of affinity with the binder, the stripped aggregate of its bitumen film, in addition to not contributing to the mechanical resistance of the mixture, detaches from the rest of the mass, triggering a phenomenon of progressive localised deterioration (ravelling, with the formation of holes), with a consequent reduction in safety (loss of adhesion), driving comfort, and the ability to protect the underlying courses from water infiltration.

[0021] The climate actions to which a bituminous concrete pavement is subjected and, more markedly, the wearing course, are related to the thermal variations of the external environment and atmospheric agents in general, which alter the composition of the materials constituting the mixtures, in particular bitumen, and modify the mutual interactions thereof inducing degradation phenomena, firstly thermal cracking, the detachment of bitumen from aggregates and ageing phenomena due to solar radiation.

[0022] Given its visco-elastic nature, the close dependence of bitumen on temperature and the different response to the actions induced by it is known; in particular, at high operating temperatures, the accumulation of plastic deformations in the mixture generated by the thickening action due to the passage of vehicles, can cause rutting, that is, a depression of the pavement at the trajectory of the tyres. Moreover, in cases where the mixtures are particularly rich in bitumen, the passage of traffic can also cause the binder to bleed (flush) which manifests itself as the formation of conspicuous patches on the surface.

[0023] At low operating temperatures, on the other hand, and due to cyclical thermal oscillations, the breakage phenomenon commonly found is thermal cracking: bitumen is fragile and breaks due to thermal contractions caused by cold. Other types of cracks on the wearing layers are due to mechanisms of another nature, linked to fatigue phenomena, poor strength of the underlying courses or problems due to the action of water.

[0024] In flexible pavement, traffic stresses induce permanent deformations due to additional compaction and, in bituminous concrete courses, to tensile stresses.

[0025] Problems of the background art

[0026] The main task of a wearing course is to protect the courses below it from atmospheric agents and, with reference to safety and driving comfort, to guarantee a smooth rolling surface for vehicles. As mentioned so far, the package, understood as a resistant structure composed of several materials, under the effect of external actions, begins to yield, manifesting the degradation phenomena described above to a greater or lesser degree.

[0027] If then climatic variations in the environment in which the pavement is inserted come into play, the effects overlap. Therefore, a vicious circle begins in which water, and thus frost, triggers a series of problems at the structural and functional level; water acts first of all on the aggregates constituting the mixtures and, if then facilitated by the propagation of the degradation mechanisms, manages to penetrate into the underlying courses through the cracks that have formed, compromising the mechanical resistance characteristics of the latter and, consequently, of the entire superstructure.

[0028] Many flexible pavements suffer from damage to the wearing course (or surface mat) due to the effects of water. The damage is the result of a lack of cohesion within the mixture, caused by the loss of bonding force between the asphalt and the cement concrete of the mixture, caused by the loss of bonding force between the bituminous binder and the aggregates. Because of these affinity problems with the bituminous binder, stripping of the aggregates or inert materials is observed. This is particularly true for particular types of aggregates, defined as hydrophilic, which "chemically" have a greater ability to bind with water rather than with bitumen, giving rise to stripping phenomena of the binder film that covers them. If this occurs, cohesion is lost, there is a decay of resistance to tangential actions, the detachment of the aggregate from the rest of the mass and the consequent ravelling. This phenomenon is linked to the ageing of bitumen and the high void content of draining or porous bituminous conglomerates and induces the adhesive fracture between the aggregates and the bitumen, and influences the durability thereof.

[0029] The more serious evolution of the degradation mechanism leads to the detachment of portions of concrete, the formation of holes and the subsequent accumulation of water in the holes, facilitating the risk of aquaplaning. The immediate consequences are safety-related risks due to loss of grip.

[0030] The poor aggregate-bitumen affinity combined with the passage of vehicles can also cause loss of grip due to the slipperiness of the road surface, as a result of the polishing of the aggregates. The phenomenon is attributable to the petrographic nature of the aggregates themselves, poorly resistant to the abrasive action produced by traffic, which causes wear of the surface roughness and consequent reduction in texture (micro-texture considers the quality of the aggregate composing the pavement; it is due to the roughness of the individual granular stone elements used in the surface layer of the road pavement. Differently, macro-texture considers the aggregate, but also the empty spaces of the pavement; it is the roughness due to the set of intergranular surface roughnesses of the pavement. An optimal texture is, therefore, essential for safety at high speeds and on wet surfaces; in fact, it allows the drainage of surface waters, optimising tyre-pavement contact).

[0031] Being particularly delicate, the porous mixture has several drawbacks that should not be underestimated. In particular, it is vulnerable because, being open, it is more exposed to atmospheric agents and therefore is subject, as mentioned above, to the risk of easily undergoing ravelling, thus leading to the disintegration of the road surface (it cannot be used in any area). Furthermore, due to the presence of interconnected pores, these tend to clog over time due to debris, leading to a loss of functionality of the draining action.

[0032] In addition to this, the use of milled materials and recycling aggregates is increasingly required with a view to greater eco-sustainability. In this sense, the aggregates used to make the gradation curve are usually virgin aggregates of first use, but it is possible to replace a fraction of the gradation with suitable recycled aggregates (RAP).

[0033] The percentage of use and the origin of the RAP depend on the layer of use; there are limits in the use of milled materials, as the aggregates are coated with a certain amount of bitumen, of which a small percentage is reactivated in the new mixture. Since reactivated bitumen is an oxidized (aged) binder, it is good that this percentage is limited, especially in the most important courses such as the surface mat.

[0034] The use of RAP, especially at relatively high percentages (for example, > 25% by weight of the total weight of the aggregates), weakens the performance of the pavement, as it contains a rigid and fragile oxidized bitumen; furthermore, the presence of RAP lumps can cause fragile points in the concrete with more frequent detachment and cracks in the asphalt. RAP stiffens the pavement, which will last less over time. In addition to this, RAP brings moisture therewith: this lowers the temperatures of the concrete, resulting in a worsening in the machinability and compaction of the pavement.

[0035] The need is therefore felt to identify additives to be used in a draining bituminous mixture which are able to reduce the phenomena of ravelling, leaching, as well as counteracting the ageing of the mixture itself, a property that would be desirable to preserve even when a high content of milled materials or RAP is used.

[0036] There is also a need to reduce the quantities of the aforesaid additives used with respect to the total weight of the bituminous mixture and / or aggregates with a view to reducing costs and waste.

[0037] SUMMARY OF THE INVENTION

[0038] A first object of the invention is an antioxidant and anti -ravelling association for draining bituminous conglomerates comprising or consisting of

[0039] - diphenylmethane diisocyanate (MDI) in the form of isomers, oligomers, and / or polymers,

[0040] - an organosilane of formula (I) below wherein

[0041] Ri is selected from: methyl, ethyl, methoxy, ethoxy, R.2 is selected from: methyl or ethyl,

[0042] R3 is selected from the group consisting of: -CH2-, -OCH2-, -CH2CH2-, -OCH2CH2-, - CH2CH2CH2-, -OCH2CH2CH2-, -NHCH2CH2-, -NHCH2CH2CH2-,

[0043] R4 is selected from the group consisting of: NH2-, NH2CH2-, NH2CH2CH2-, SH-, characterized in that the weight ratio between diphenylmethane diisocyanate (MDI) and organosilane is comprised between 9:1 and 19: 1.

[0044] A second object is the use of the aforesaid association for the preparation of draining bituminous conglomerates.

[0045] Advantages of the invention

[0046] The antioxidant and anti-ravelling association is an additive that is able to:

[0047] - decrease the detachment of portions of draining bituminous conglomerate, for example when subjected to friction action by vehicle tyres. The association of the invention induces a considerable reduction in the phenomenon of surface ravelling, not only in mixtures containing RAP, but also in comparison to the virgin mix design (see section 2.2.1 related to the Cantabro Loss Test and section 2.2.3 related to the scuffing resistance test),'

[0048] - guarantee a longer duration over time of the draining bituminous conglomerate, precisely by virtue of the antioxidant effect on bitumen, increasing the useful life (see section 2.2.4 related to the rheological analysis);

[0049] - give the bituminous mixture (or draining bituminous conglomerate) greater hydrophobicity;

[0050] - ensure better compatibility and cohesion properties, in other words a better adhesion of the bituminous binder to the stones of the aggregates is obtained. In addition to this, the association confers greater resistance to leaching by atmospheric agents, thus increasing the life of the pavement subjected to weather-precipitation (see section 2.2.2 related to the Water sensitivity test for the stripping phenomenon, which is the mechanism of damage due to water / humidity); The performance of the draining bituminous conglomerate is therefore guaranteed by virtue of the use of the association of the invention, which preserves the workability of the design mix at low temperatures and / or at lower temperatures than conventional ones during the production phase in the plant, during the mixing during the transport period and during the asphalt laying phase. The association of the invention allows the reduction of the creation temperature of the bituminous mixture by about 20°C with respect to standard concretes, without loss of workability in the laying phase. In addition to this, the association of the invention guarantees a reduction of energy and CO2 emissions in the environment.

[0051] Further, there is the possibility of reusing materials from milling pavements, allowing the achievement of a sustainable and circular system of the production of bituminous concretes, reducing the need for the supply of virgin materials. In other words, with the same performance, a decrease in the use of virgin materials and a decrease in the landfilling of waste resulting from the milling of existing pavements are achieved. Although using high milling contents (> 25% by weight on the total weight of the aggregates), the invention which is the subject matter of the invention improves the resistance of the binder against atmospheric agents and ultraviolet radiation (photooxidation phenomenon), ensuring an extension of the useful life of the pavement using the technology.

[0052] In the presence of RAP, the association of the invention is globally able to confine RAP lumps; stably connect the grains of the mixture; increase the resistance to oxidation generated by sunlight and climatic operating conditions.

[0053] DESCRIPTION OF THE FIGURES

[0054] Figure 1 with reference to the rheological analysis referred to in section 2.2.4, the graph shows the complex shear modulus curves for the formulations "PMB", "PMB+ EPOXYSILANE" and "PMB+ EPOXYSILANE+MDI" in the absence of ageing.

[0055] Figure 2 with reference to the rheological analysis referred to in section 2.2.4, the graph shows the complex shear modulus curves for the formulations "PMB", "PMB+ EPOXYSILANE" and "PMB+ EPOXYSILANE +MDI" after 7 days of exposure to artificial UV radiation (7-UV) corresponding to 5 years of real solar exposure. Figure 3 with reference to the rheological analysis referred to in section 2.2.4, the graph shows the complex shear modulus curves for the formulations "PMB", "PMB+ EPOXYSILANE" and "PMB+ EPOXYSILANE +MDI" after 14 days of exposure to artificial UV radiation (14-UV) corresponding to 10 years of real solar exposure.

[0056] Figure 4 with reference to the rheological analysis referred to in section 2.2.4, the graph shows the phase angle curves for the formulations "PMB", "PMB+ EPOXYSILANE" and "PMB+ EPOXYSILANE+MDI" in the absence of ageing.

[0057] Figure 5: with reference to the rheological analysis referred to in section 2.2.4, the graph shows the phase angle curves for the formulations "PMB", "PMB+ EPOXYSILANE" and "PMB+ EPOXYSILANE +MDI" after 7 days of exposure to artificial UV radiation (7-UV) corresponding to 5 years of real solar exposure.

[0058] Figure 6: with reference to the rheological analysis referred to in section 2.2.4, the graph shows the phase angle curves for the formulations "PMB", "PMB+ EPOXYSILANE" and "PMB+ EPOXYSILANE +MDI" after 14 days of exposure to artificial UV radiation (14-UV) corresponding to 10 years of real solar exposure.

[0059] DETAILED DESCRIPTION OF THE INVENTION

[0060] In the following, the invention and preferred embodiments thereof are described in more detail. It should be noted that, although the structure has been organised into paragraphs and sub-paragraphs, the information contained in each paragraph or subparagraph is not isolated, and is possibly combinable with that contained in other paragraphs or, more generally, with other information contained in the text of the patent application.

[0061] Antioxidant and anti-ravelling association

[0062] The antioxidant and anti-ravelling association for draining bituminous conglomerates (hereinafter also referred to as "combination") is an association that comprises or consists of: diphenylmethane diisocyanate (MDI) and the organosilane of formula I, described below.

[0063] Specifically, the association is an additive. Antioxidant means that the combination counteracts the photo-oxidative ageing of the draining bituminous conglomerate exposed to ultraviolet radiation in the emission field of the wavelength of UVA and UVB radiation.

[0064] Anti-ravelling means that the association counteracts the phenomenon of surface ravelling that affects the draining bituminous conglomerate.

[0065] Preferably, the association of the invention shows a hydrophobic character, with antileaching effect for draining bituminous conglomerates. In this sense, the combination is also called antioxidant, anti -ravelling and anti-leaching association.

[0066] Preferably, the association is a liquid additive, preferably it is of synthetic type.

[0067] Preferably, the association is heat resistant.

[0068] The antioxidant and anti-ravelling association for draining bituminous conglomerates comprises or consists of

[0069] - diphenylmethane diisocyanate (MDI) in the form of isomers, oligomers, and / or polymers,

[0070] - an organosilane of formula I below formula I wherein

[0071] Ri is selected from: methyl, ethyl, methoxy, ethoxy,

[0072] R2 is selected from: methyl or ethyl,

[0073] R3 is selected from the group consisting of: -CH2-, -OCH2-, -CH2CH2-, -OCH2CH2-, - CH2CH2CH2-, -OCH2CH2CH2-, -NHCH2CH2-, -NHCH2CH2CH2-,

[0074] R4 is selected from the group consisting of: NH2-, NH2CH2-, NH2CH2CH2-, SH-,

[0075] Diphenylmethane diisocyanate (MDI)

[0076] Preferably, the diphenylmethane diisocyanate (MDI) is also said methylene diphenyl diisocyanate. The diphenylmethane diisocyanate can be in the form of isomers (monomeric or mMDI), and / or oligomers, and / or polymers. In other words, the MDI can be selected from the group consisting of: MDI isomers, MDI oligomers, MDI polymers, and mixtures of the foregoing.

[0077] MDI oligomers means homo-oligomers of MDI, i.e. compounds consisting of the reaction between monomeric units of MDI, where the monomeric unit is therefore the "diphenylmethane diisocyanate", and where the monomeric unit is repeated a reduced number of times, preferably a number of times > 2 and < 10.

[0078] MDI polymers means homopolymers of MDI, i.e. compounds consisting of the reaction between monomeric units of MDI, where the monomeric unit is therefore the "diphenylmethane diisocyanate", where the monomeric unit is repeated a high number of times, preferably a number of times > 10, preferably > 100.

[0079] It should be noted that MDI polymers are more reactive and economical, but less stable to storage in the presence of the organosilane.

[0080] (Monomeric) isomers of MDI means the three isomers of MDI, i.e. 2,2’-MDI, 2,4’- MDI and 4,4’-MDI.

[0081] Preferably, the diphenylmethane diisocyanate is a mixture of 2,4’ -MDI and 4,4’ -MDI (monomeric) isomers.

[0082] Preferably, the diphenylmethane diisocyanate is a mixture of 2,4’ -MDI and 4,4’ -MDI, where the 2,4’ -MDI isomer and the 4,4’ -MDI isomer are comprised in a weight ratio between 1 :0.5 and 1 :2, preferably 1 : 1. Preferably, the 2,4’-MDI and 4,4’-MDI isomers are 50% by weight on the weight of the mixture, respectively.

[0083] In the state of the art, MDI is usually combined with polyols leading to a polyurethane reaction; moreover, when producing polyurethanes, the combination with an organosilane increases the wetting effect of the polyurethane. For the purposes of the invention, however, MDI is preferably in free or non-reactive form, in the sense that it does not react with other components present in the association or in the draining bituminous conglomerate. Organosilane

[0084] Preferably, Ri is equal to R2, preferably Ri and R2 are equal to R, where R is methyl or ethyl. In this embodiment, the organosilane is the compound of formula IA below:

[0085] R4-R3-Si-(OR)3formula IA

[0086] According to another alternative embodiment, Ri is different from R2, preferably Ri is methyl and R2is equal to methyl or ethyl. In this embodiment, the following compound of formula IB is obtained:

[0087] CH3

[0088] R4 R3Si (O R2)2 formula IB

[0089] Preferably, R3is selected from the group consisting of: -CH2CH2-, -OCH2-, - OCH2CH2-, -OCH2CH2CH2-, -CH2CH2CH2-, -NHCH2CH2CH2-.

[0090] According to a preferred form, R3is selected from the group consisting of: -CH2CH2- , -OCH2-, -OCH2CH2-, -OCH2CH2CH2-.

[0091] Still preferably, R3is selected from the group consisting of: -OCH2CH2CH2-, - NHCH2CH2CH2-, -CH2CH2CH2-.

[0092] Preferably, R4is selected from the group consisting of: NH2-, NH2CH2CH2-, SH-,

[0093] Further preferably, R4is selected from

[0094] Preferably, the organosilane is a compound selected from the group consisting of the following compounds of Table 1 :

[0095] Table 1

[0096] Preferably the organosilane is the compound of formula IAI, i.e. the compound 3- glycidyl-oxypropyl-trimethoxy-silane. It should be noted that the compounds of Table 1 are known molecules; the relative synthetic method is also known.

[0097] MDI weight ratio: organosilane of formula (I) and percentage by weight of the association on the weight of the draining bituminous conglomerate

[0098] The weight ratio of diphenylmethane diisocyanate to organosilane is comprised between 9: 1 and 19: 1, preferably comprised between 10: 1 and 17: 1, preferably equal to 9: 1.

[0099] The association is comprised in the draining bituminous conglomerate in an amount comprised between 0.01% and 0.20% by weight, preferably between 0.01% and 0.15% by weight, preferably between 0.01% and 0.10% by weight, preferably between 0.01% and 0.09% by weight, preferably between 0.03% and 0.09% by weight, preferably between 0.03% and 0.07% by weight, preferably between 0.03% and 0.05% by weight, preferably between 0.03% and 0.04% by weight, preferably equal to 0.04% by weight, based on the total weight of the conglomerate.

[0100] In these quantitative ranges and weight ratios, the Applicant considers that the association of the diphenylmethane diisocyanate and the organosilane of formula (I) can guarantee good mechanical performance and the anti -ravelling, antioxidant and anti-leaching effects, even in the presence of high percentage RAP.

[0101] Draining bituminous conglomerate

[0102] Preferably, draining bituminous conglomerate, hereinafter also referred to as "porous bituminous mixture" or "conglomerate", means a bituminous mixture. Bituminous mixture means a mixture comprising or consisting of: aggregates, at least one bituminous binder, fibres, possibly additives.

[0103] For the purposes of the invention, the draining bituminous conglomerate is of the open- graded type. In this sense, the conglomerate is also defined as open or porous.

[0104] A mixture is called draining (alternatively "open", but also "porous", "porous asphalt concrete - PAC"), if it has a high percentage of voids, preferably the percentage of voids must be at least 15% (> 15% by weight). This percentage guarantees the right connection between the pores present in the mixture, so as to allow water to permeate, moving away from the surface. With an open-graded road surface, the water film does not have the proper conditions to form and, in addition, during the passage of vehicles, the wheels impart a certain pressure on the water present, conveying it along the voids. If the void rate falls in the 10-15% range, the interconnection between the pores is not ensured. This implies that, always with the passage of vehicles, the overpressures induced on the water present in the cavities could be such as to crumble the pavement (precisely because the water has no way to permeate). Generally speaking, a good drainage system consists of 20% voids (motorway specifications require a similar percentage).

[0105] Preferably, the draining bituminous conglomerate is wearing, in the sense that it is used for the wearing course of road pavements, i.e. the surface layer in contact with vehicles.

[0106] Preferably, the draining bituminous conglomerate comprises the antioxidant and antiravelling association of the invention described above, preferably in combination with at least one bituminous binder and aggregates.

[0107] The draining bituminous conglomerate preferably comprises or consists of

[0108] - aggregates or inert materials,

[0109] - at least one bituminous binder, preferably one or two bituminous binders,

[0110] - the antioxidant and anti -ravelling association of the invention,

[0111] - optionally other additives,

[0112] - fibres.

[0113] Aggregates

[0114] The aggregates or inert materials represent the solid structure of a bituminous mixture and are used, in different percentages, in various sizes.

[0115] For the purposes of the invention, the fraction of small or fine aggregates is limited so as to have a high percentage of voids. Preferably, the invention does not contain fine aggregates or, alternatively, comprises a fraction of fine aggregates < 0.5% by weight on the total weight of the concrete, preferably < 0.1% by weight of the total weight of the conglomerate. For the purposes of the invention, the aggregates are preferably inert materials characterized by a size > 2 mm, i.e. retained on the sieve with an opening of 2 mm, preferably > 2 and < 16 mm.

[0116] Fine aggregates, on the other hand, mean aggregates characterized by a size comprised between 2 mm and 0.063 mm, that is, retained on the sieve with an opening between 2 mm and 0.063 mm. These are useful for filling the voids between larger granules.

[0117] Filler, on the other hand, means the fraction of inert aggregates characterized by a size < 0.063 mm, i.e. passing through the sieve with an opening of 0.063 mm.

[0118] Preferably, the percentage amount of the fillers comprised in the draining bituminous conglomerate is comprised between 1.5% and 3.5% by weight, preferably between 2% and 3% by weight, preferably equal to 3% by weight, on the total weight of the concrete.

[0119] Preferably, the aggregates comprise both aggregates of stone material and fillers.

[0120] According to a first embodiment, the aggregates can be virgin or first-use aggregates.

[0121] Examples of virgin or first-use aggregates are raw materials of the calcareous or basaltic or porphyry type.

[0122] In accordance with a second embodiment, the aggregates or inert materials used can also comprise recycling aggregates (milled recycled asphalt or RAP). In other words, the bituminous concrete preferably contains milled recycled asphalt or RAP material.

[0123] Preferably, the milled recycled asphalt is comprised in the draining bituminous conglomerate at an amount > 25% by weight, preferably > 25% and < 35% by weight, preferably > 25% and < 33% by weight, preferably > 25% and < 30% by weight, on the total weight of the aggregates.

[0124] Preferably, the milled recycled asphalt is comprised in the draining bituminous conglomerate at an amount > 21% by weight, preferably > 21% and < 33% by weight, preferably > 21% and < 30% by weight, preferably > 23% and < 25% by weight, preferably > 23% and < 24% by weight, on the total weight of the conglomerate. Preferably, the aggregates or inert materials are selected from the group consisting of: sand; crushed stone; RAP; grit; filler, e.g. calcareous filler; and mixtures of the foregoing.

[0125] Still preferably, the aggregates or inert materials are selected from the group consisting of: sand 0-4; crushed stone 8 / 16; crushed stone 12 / 16; RAP 8 / 20; grit 6 / 10; limestone filler; and mixtures of the foregoing.

[0126] Preferably, the aggregates are comprised in an amount comprised between 20% and 40% by weight, preferably between 25% and 35% by weight, preferably between 30% and 35% by weight, preferably equal to about 30% by weight, on the total weight of the conglomerate.

[0127] Preferably, the aggregates of stone material are comprised in an amount comprised between 92% and 99% by weight, preferably between 93% and 98% by weight, preferably between 95% and 98% by weight, preferably between 96% and 98% by weight, preferably equal to 97% by weight, on the total weight of the aggregates,' the remaining part of the aggregates is preferably instead constituted by the filler aggregates.

[0128] At least one bituminous binder

[0129] Bitumen is a binder produced in refineries and derives from the residues of the distillation of oil, with the characteristic of being a waterproof and thermoplastic material; it requires high temperatures to be processed.

[0130] Preferably, the at least one bituminous binder is selected from the group consisting of: unmodified or standard bitumen; modified bitumen; bitumen combined with RAP; and mixtures of the foregoing.

[0131] Preferably, the at least one bituminous binder is selected from the group consisting of: unmodified or standard bitumen; modified hard bitumen; modified bitumen or modifier-added bitumen; bitumen combined with RAP; and mixtures of the foregoing.

[0132] Unmodified or standard bitumen (also called "traditional") is that which has not undergone any chemical or performance modification treatment. Modified bitumen or modifier-added bitumen is bitumen that has been subjected to a chemical or performance modification treatment by adding polymers, such as Styrene Butadiene Styrene (SBS) polymer (modified bitumen, PmB). In this specific case, the modification is called wet and consists of creating a bituminous mixture with a binder whose rheology is modified with specific polymers (depending on the final product to be obtained), which means that at the time of production of the bitumen itself, it undergoes a specific modification process.

[0133] Hard modified bitumen involves the use of a 5 / 6% percentage of an elastomer, so as to have an elastic return of 75% and an extension of the range of use.

[0134] Bitumen combined with RAP means a mixture consisting of bitumen, preferably modified bitumen, and RAP, where the RAP is in an amount comprised between 15% and 40% by weight on the total weight of the mixture.

[0135] Preferably, the at least one bituminous binder is comprised in the concrete in an amount comprised between 2% and 9% by weight, preferably between 3% and 8% by weight, preferably between 4% and 7.5% by weight, preferably between 4.5% and 7.5% by weight, preferably between 4.5% and 6.5% by weight, preferably between 4.5% and 5.5% by weight, preferably equal to 4.7% by weight, on the total weight of the conglomerate.

[0136] Preferably, the at least one bituminous binder is comprised in an amount comprised between 3% and 9% by weight, preferably between 4% and 9% by weight, preferably between 5% and 8.5% by weight, preferably between 5% and 6.5% by weight, preferably between 6% and 8.5% by weight, preferably equal to 8% by weight, on the total weight of the aggregates.

[0137] Other additives

[0138] Preferably, the draining bituminous conglomerate also contains other mono-functional or poly-functional additives, in the sense that they can have a single function or more than one function, for example a plasticizing, wetting, adhesion-activating function.

[0139] Known additives that can preferably be included in the concrete are selected from the group consisting of plasticizers; wetting agents; adhesion activators; rheological modifiers; and combinations of the foregoing.

[0140] An example of an additive usable for the purposes of the invention is ACF-L5 on RAP, of a phosphoric nature, preferably consisting of phosphoric esters; this is a high performance regenerating liquid additive for bitumen for making warm and hot bituminous conglomerates made with both modified bitumen and standard bitumen and containing regenerants, plasticizers and adhesion activators.

[0141] Examples of phosphoric esters are preferably selected from the group consisting of: C8-C18 alkyl phosphate; tri-2-ethylhexyl phosphate (or tri-octyl phosphate); cresyldiphenyl phosphate; oleyl alcohol phosphate, ethoxylated; and combinations of the foregoing.

[0142] Preferably, the other additives (excluding the association of the invention) are comprised in the draining bituminous conglomerate in an amount comprised between 0.03% and 0.08% by weight, preferably between 0.03% and 0.07% by weight, preferably between 0.03% and 0.05% by weight, preferably between 0.04% and 0.05% by weight, preferably equal to 0.04% by weight, on the total weight of the conglomerate .

[0143] Preferably, the other additives are comprised in the draining bituminous conglomerate in an amount comprised between 0.05% and 0.3% by weight, preferably between 0.1% and 0.3% by weight, preferably between 0.15% and 0.25% by weight, preferably between 0.15% and 0.20% by weight, on the total weight of the aggregates.

[0144] Fibres

[0145] Preferably, the draining bituminous conglomerate also contains fibres, preferably cellulose-based fibres. The addition of organic binders to the cellulose fibre increases the plasticity of the bitumen, facilitating the laying of the asphalt, and decreasing the risk of deformation thereof under traffic.

[0146] The fibres are filaments that can be of different nature and have multiple functions, in particular: they retain excess bitumen, preventing it from draining, but also contribute to increasing the mechanical performance of the mixture, improving the stability and fatigue resistance thereof.

[0147] The fibres compensate for the discontinuity of the gradation curve typical of draining bituminous conglomerates, significantly reducing the separation between the bitumen and the inert material (aggregates). The fibres form a high thickness film surrounding the aggregate, allowing the formation of a stable lattice bond of the bituminous mass. An example of fibres usable for the purpose of the invention is MAPEFIBRE FPC plus, which are cellulose-based fibres.

[0148] Preferably, fibres are comprised in the draining bituminous conglomerate in an amount comprised between 0.2% and 0.7% by weight, preferably between 0.2% and 0.6% by weight, preferably between 0.3% and 0.6% by weight, preferably between 0.3% and 0.5% by weight, preferably between 0.3% and 0.4% by weight, preferably equal to 0.34% or 0.4% by weight on the total weight of the conglomerate.

[0149] Association of the invention

[0150] Preferably, the draining bituminous conglomerate comprises the association in an amount comprised between 0.01% and 0.20% by weight, preferably between 0.01% and 0.15% by weight, preferably between 0.01% and 0.10% by weight, preferably between 0.01% and 0.09% by weight, preferably between 0.03% and 0.09% by weight, preferably between 0.03% and 0.07% by weight, preferably between 0.03% and 0.05% by weight, preferably between 0.03% and 0.04% by weight, preferably equal to 0.04% by weight, based on the total weight of the conglomerate.

[0151] Preferably, the association is comprised in the draining bituminous conglomerate in combination with aggregates and at least one bituminous binder, and in which the association is in an amount comprised between 0.5% and 3% by weight, preferably between 0.5% and 2% by weight, preferably between 0.5% and 1.5% by weight, preferably between 1% and 1.5% by weight, preferably equal to 1.1% by weight, on the total weight of the aggregates.

[0152] Preferably, the organosilane of formula I is comprised in the draining bituminous conglomerate in an amount comprised between 0.05% and 0.2% by weight, preferably comprised between 0.1% and 0.2% by weight, preferably between 0.1% and 0.15% by weight, preferably equal to 0.1% by weight, on the total weight of the aggregates.

[0153] Preferably, organosilane of formula I is comprised in the draining bituminous conglomerate in an amount comprised between 0.001% and 0.007% by weight, preferably comprised between 0.001% and 0.005% by weight, preferably between 0.002% and 0.005% by weight, preferably between 0.002% and 0.004% by weight, preferably equal to 0.0036% by weight, on the total weight of the conglomerate. Preferably, the diphenylmethane diisocyanate (MDI) is comprised in the draining bituminous conglomerate in an amount comprised between 0.5% and 2% by weight, preferably comprised between 1% and 2% by weight, preferably between 1% and 1.5% by weight, preferably equal to 1% by weight, on the total weight of the aggregates.

[0154] Preferably, the diphenylmethane diisocyanate (MDI) is comprised in the draining bituminous conglomerate in an amount comprised between 0.01% and 0.07% by weight, preferably comprised between 0.01% and 0.05% by weight, preferably between 0.02% and 0.05% by weight, preferably between 0.02% and 0.04% by weight, preferably equal to 0.0364% by weight, on the total weight of the conglomerate.

[0155] Preferably, the draining bituminous conglomerate or the association does not contain compounds selected from the group consisting of: urethanes; polyurethanes; diols; polyols; and combinations of the foregoing.

[0156] Draining bituminous conglomerate preparation process

[0157] Preferably, the draining bituminous conglomerate preparation process comprises the following steps: a) prepare: the aggregates, the at least one bituminous binder, optionally the other additives, the association of the invention, and the fibres; b) heat the aggregates of stone material, preferably to a temperature between comprised between 120°C and 160°C, preferably between 140°C and 160°C; c) add the fibres to the hot aggregates, preferably before adding the at least one bituminous binder, and mix to obtain a primary mixture, ' d) separately combine the association of the invention with the at least one bituminous binder, preferably within a mixer or a tank, and mix to obtain a preparation,' e) optionally also add the other additives to the preparation and mix to obtain a preparation with other additives; f) insert the preparation (alternatively preferably the preparation with other additives) inside the primary mixture and mix to obtain a secondary mixture,' g) add the fillers to the secondary mixture and mix to obtain a final mixture corresponding to the draining bituminous conglomerate. Preferably, in a continuous plant, the association of the invention is introduced into the bituminous binder in-line, prior to introduction onto the hot aggregates.

[0158] Preferably, in a discontinuous plant, the association of the invention is introduced into the scale of the bituminous binder during the loading phase of the bitumen, before being introduced onto the hot aggregates.

[0159] Preferably, the draining bituminous conglomerate is of the WMA ("warm mix asphalt") type in the sense that it is obtained using reduced mixing temperatures with respect to the "hot" methodology (i.e. "Hot Mix Asphalt", or "HMA"), for which the temperatures are between 170°C and 190°C.

[0160] Mention is made of "warm" production technologies, which is that of the invention, when the aggregates together with the bitumen are heated to about 20-30°C less with respect to the hot technology. In this sense, the process temperatures are preferably comprised between 120°C and 160°C, preferably between 130°C and 160°C, preferably between 140°C and 160°C.

[0161] By virtue of the low operating temperatures at the plant, the ageing phenomenon of bitumen, associated with its oxidation and the loss of aromatic substances, is extremely low and it is understood how and why the mixtures produced at a warm temperature can be less sensitive to ageing phenomena during creation and laying.

[0162] Use of the association of the invention

[0163] Preferably, the association is used in draining bituminous conglomerates, preferably of draining wearing course bituminous conglomerates.

[0164] Preferably, the association of the invention is for use in the preparation of draining bituminous conglomerates.

[0165] Preferably, the association of the invention is for use in the preparation of draining bituminous conglomerates usable for the wearing course of a flexible road pavement.

[0166] EXAMPLES

[0167] Illustrative and non-limiting examples of the invention are given below.

[0168] It should be noted that: - "agg" means "aggregates";

[0169] - "g" means "grams";

[0170] - "epoxysilane" is the organosilane of formula IAI, i.e. the 3-glycidyl-oxypropyl- trimethoxy-silane compound referred to in Table 1; - "MDI" is a 50% mixture of 2,4'-MDI and 4,4'-MDI.

[0171] Example 1: Composition of the porous wearing course bituminous concrete comprising the association of the invention.

[0172] Table A

[0173] It should be noted that the association of the invention reported in example 1 consists of:

[0174] - 50% mixture of 2,4'-MDI and 4,4'-MDI, and - organosilane of formula IAI, i.e. the compound 3-glycidyl-oxypropyl-trimethoxy- silane, where the 50% mixture of 2,4'-MDI and 4,4'-MDI is 91% by weight on the total weight of the combination, while 3-glycidyl-oxypropyl-trimethoxy-silane is the remaining percentage part of the combination (9% by weight).

[0175] Considering the total 1.1% percentage value of the association of the invention as a function of the aggregate content (see the third column of Table A), the 1.0% consists of the aforesaid 50% mixture of 2,4'-MDI and 4,4'-MDI, while the remaining 0.1% consists of the organosilane of formula IAI.

[0176] Method of preparation:

[0177] In a continuous plant, the association of the invention is introduced into the bituminous binder in-line, before being introduced onto the hot aggregates; in a discontinuous plant, the association of the invention is instead introduced into the scale of the bituminous binder during the loading phase of the bitumen, before being introduced onto the hot aggregates.

[0178] Example 2: Performance tests in the presence of the association of the invention.

[0179] 2.1. Methodology: and ob jectives

[0180] The application of the association which is the subject of the invention specialized in confining the RAP lumps, stably connecting the grains of the mixture, and increasing the resistance to oxidation generated by sunlight and climatic operating conditions was studied.

[0181] Once the chemical compatibility and possible problems due to coalescence were verified, the mixtures with RAP content were created, then on tests were carried out on cylindrical specimens to verify the performance of the porous asphalt.

[0182] Specifically, destructive laboratory tests were carried out:

[0183] - Cantabro test (Cantabro Loss Test - see section 2.2.1);

[0184] - indirect tensile test (Indirect Tensile Stiffness Test - see section 2.2.2);

[0185] - scuff resistance test (see section 2.2.3).

[0186] The Cantabro and ITS tests are adapted to determine the particle loss of the specimens and the ultimate resistance to indirect tensile stiffness, respectively. The Cantabro test was used to evaluate and control the loss of material due to ravelling on the mixtures under dry or wet pavement conditions.

[0187] Following the production of the specimens for the Cantabro tests and ITS test by means of compaction with a rotary press (for ITS specimens) and compaction with the Marshall method (for Cantabro specimens), the dry and wet conditioning of the specimens was carried out for a certain period of time. Then, the two mechanical tests were carried out for each mixture, which are, precisely, the Cantabro test and the indirect tensile test.

[0188] For each test, Cantabro and indirect tensile, 6 basic specimens were made for each mixture studied (MIXTURE ID: "MIX DESIGN VIRGIN CONCRETE WITH OPEN GRADATION", "VIRGIN + 25% RAP", "VIRGIN + 25% RAP + 0.1% EPOXYSILANE", "POROUS + 25% RAP + 0.1% EPOXYSILANE + 1.0% MDI"). Of these samples, for each test and for each mixture studied, half of the specimens were conditioned in a thermostatic bath at 40°C (wet conditioning, hence "PL wet", i.e. "Particle Loss wet") and the other half in a climatic chamber at 25°C (dry conditioning, hence "PL dry", i.e. "Particle Loss dry").

[0189] Furthermore, rheological characterization tests (Dynamic Shear Rheometer Test referred to in section 2.2.4) were carried out on the bituminous binders with the association of additives, that are the object of the invention.

[0190] For the purposes of the tests produced, the mixture ID "Open gradation virgin" has the following composition:

[0191] Table B

[0192] For the purposes of the test conducted, the mixture ID "VIRGIN + 25% RAP" corresponds to the mixture ID "Open gradation virgin" referred to in Table B added with 25% RAP by weight on the total weight of the aggregates.

[0193] For the purposes of the test conducted, the mixture ID "VIRGIN + 25% RAP + 0.1% EPOXYSILANE" corresponds to the mixture ID "Open gradation virgin" referred to in Table B added with 25% RAP by weight on the total weight of the aggregates and 0.1% of the organosilane of formula IAI by weight on the total weight of the aggregates.

[0194] For the purposes of the tests conducted, the mixture ID "POROUS + 25% RAP + 0.1% EPOXYSILANE + 1.0% MDI" is that of the invention, with reference to Example 1 of Table A.

[0195] 2.2. Mechanical characterization results

[0196] 2.2.1. Cantabro Loss Test - standard UNI EN 12697-17

[0197] The standard UNI EN 12697-17 refers to a test conducted on bituminous mixtures, in relation to the loss of particles from the porous asphalt specimen.

[0198] Bituminous concrete specimens were compacted by Marshall Compactor (impulsive type).

[0199] VMA (%) is the percentage index of the voids of the mixture of stone aggregates, an index that can be calculated in accordance with European standard EN 12697-8 for the determination of volumetric properties, so as to have feedback on the correct execution of compaction. The Particle Loss (PL) is determined by subtracting the weight of the same specimen from the weight of the initial specimen after testing it and dividing everything by the initial weight; therefore, by multiplying the result obtained by one hundred, the desired percentage is obtained. Awet-dry [%] is the percentage index calculated by difference between the average PL wet [%] and the average PL dry [%].

[0200] Table 2

[0201] It should be noted how, by inserting the 25% Virgin RAP ("VIRGIN + 25% RAP" mixture ID) with respect to the "VIRGIN CONCRETE DESIGN MIX WITH OPEN GRADATION" mixture ID, a considerable increase in AWet-dry [%] is observed, as a consequence of the fact that, as is known, RAP, especially at the relatively high percentages used, has a negative impact in terms of particle loss. The addition of the epoxy silane, although at low percentages, (Mixture ID: "VIRGIN + 25% RAP + 0.1% EPOXYSILANE") induces a clear improvement, reducing the loss of matter (from 12.8%, in the absence of epoxy silane, up to 4.4% with epoxy silane).

[0202] The best result is obtained with the "POROUS + 25% RAP + 0.1% EPOXYSILANE + 1.0% MDI" mixture ID of the invention, comparable to the "VIRGIN CONCRETE DESIGN MIX WITH OPEN GRADATION" mixture ID, despite the fact that there is 25% RAP.

[0203] 2.2.2. ITS - Standard UNI EN 12697-23 and Water Sensitivity - Standard UNI EN 12697-12

[0204] The indirect tensile stress test (or ITS) is the maximum tensile stress (calculated) applied to a cylindrical specimen loaded diametrically until breakage, at the test temperature and at the constant feed rate (equal to 50±2 mm / min).

[0205] In relation to bituminous mixtures, the standard UNI EN 12697-23 describes test methods for the determination of the indirect tensile strength of bituminous specimens.

[0206] The bituminous concrete specimens were compacted by rotary compactor - N3

[0130] , Usually, the compaction by means of a rotary press is used to study the volumetric characteristics, workability and denseness of the bituminous concrete analysed.

[0207] The ITS index [MPa], calculated for each specimen of Table 3, can be calculated according to equation (1) below wherein

[0208] P max = maximum load expressed in N; t = height of the specimen expressed in mm; d= diameter of the specimen expressed in mm.

[0209] In relation to bituminous mixtures, the standard UNI EN 12697-12 describes test methods for the determination of the water sensitivity of bituminous specimens. To evaluate the possible loss of performance suffered by the different mixtures due to the effect of water (water susceptibility), some specimens were conditioned for three days in water at 40°C before being tested by indirect tensile stress at a temperature of 25°C. The results obtained were compared with those obtained on similar samples conditioned in air at room temperature and tested at the same test temperature (25°C), obtaining the ITSR parameter or index.

[0210] The ITSR index [%] is calculated according to equation (2) below wherein ITSw or ITS wet = average indirect tensile strength of the wet specimens (three days in water after saturation);

[0211] Table 3

[0212] It should be noted that, with 25% VIRGIN RAP ("VIRGIN + 25% RAP" mixture ID) with respect to the "VIRGIN CONCRETE DESIGN MIX WITH OPEN GRADATION" mixture ID, a considerable reduction in ITSR [%] is observed, indicating that RAP, especially at relatively high percentages, contributes to greater rigidity, therefore to a decrease in mechanical performance, is observed. In fact, excessive stiffness leads to and triggers performance problems in the road pavement package.

[0213] The addition of epoxysilane (Mixture ID: "VIRGIN + 25% RAP + 0.1% EPOXYSILANE"), although at low percentages, induces a clear increase in the ISTR index (from 61%, in the absence of epoxysilane, up to 77% with epoxysilane).

[0214] The best result is obtained with the "POROUS + 25% RAP + 0.1% EPOXYSILANE + 1.0% MDI" mixture ID of the invention, comparable to the "VIRGIN CONCRETE DESIGN MIX WITH OPEN GRADATION" mixture ID, despite the fact that there is 25% RAP.

[0215] 2.2.3. Scuffing resistance test

[0216] The European Technical Specification CEN / TS 12697-50 is in relation to bituminous mixtures for the evaluation of resistance to scuffing.

[0217] This specification describes a test method for determining the resistance to rubbing of bituminous concrete mixtures used in surface courses and subjected to high shear stresses in road or airport pavements. These shear stresses occur in the contact area between the tyre and the pavement surface and may be caused by the curve of the vehicle. Due to these shear stresses, a loss of material occurs on the surface of these courses.

[0218] The test is normally carried out on asphalt courses with a high amount of air voids (e.g., porous asphalt), but may also be applied to other asphalt mixtures. Specimens produced in the laboratory or cut from the pavement are used. The test can be conducted to determine the scuffing resistance of the sound-absorbing surface courses, for which the regulatory damage criterion is ravelling. The test can also be carried out on other surface mixtures with a high resistance to permanent deformation. In the case where a mixture has a low resistance to permanent deformation, the formation of grooves may occur during the test. This can affect the test results.

[0219] The results show that the addition of the association of the invention leads to a substantial improvement in the phenomenon of surface ravelling, not only in mixtures containing RAP, but above all in comparison with the virgin design mix.

[0220] 2.2.4. Rheological analysis - Dynamic Shear Rheometer

[0221] The selection of the additives comprised in the association of the invention for bitumen occurred by rheological analysis carried out before and after the photo -oxi dative ageing procedure.

[0222] The procedure developed is aimed at reproducing the photo-oxidative ageing of bituminous binders exposed to ultraviolet radiation in the wavelength emission field of UVA and UVB radiation.

[0223] The following formulations were tested:

[0224] - the formulation "PMB+EPOXYSILANE+MDI", corresponding to the composition of Table A (Example 1);

[0225] - the formulation "PMB", corresponding to the composition of Table B;

[0226] - the formulation "PMB+ EPOXYSILANE", corresponding to the composition of Table B in which 0.1% of EPOXYSILANE has been added by weight on the total weight of the aggregates.

[0227] The ultraviolet radiation was obtained by using a mercury gas Photo Electronics H5007 / PE UV Lamp.

[0228] The ageing has the objective of simulating the exposure to solar radiation of the bitumen film covering the aggregates during the useful life of a road pavement in bituminous conglomerate.

[0229] The protocol developed reproduces accelerated ageing caused by the photo-oxidative phenomenon.

[0230] Through correlations to calculation models, the artificial radiation produced by the lamp was estimated, measured with the appropriate instrumentation composed of Luxmetro HD2102.2 Datalogger and the probes LP 471 UVA (with irradiation measurement in the UVA 315 nm - 400 nm spectral field and peak at 360 nm), LP 471 UVB (with irradiation measurement in the UVB 280 nm - 315 nm spectral field and peak at 305 nm) and LP 471 UVC (with irradiation measurement in the UVC 220 nm

[0231] - 280 nm spectral field and peak at 260 nm), which allowed to derive the respective ageing stages:

[0232] - 7 days of exposure to artificial UV radiation (7-UV) = 5 years of actual sun exposure;

[0233] - 14 days of exposure to artificial UV radiation (14-UV) = 10 years of actual sun exposure;

[0234] - 30 days of exposure to artificial UV radiation = 20 years of actual sun exposure.

[0235] The formulations adopted to obtain the equivalent radiation emitted by the UV lamp adopted in the laboratory and the actual solar radiation are the protocols proposed by the standard UNI 8477, the ENEA-SOLTERM correlation of the ENEA Actinometric Network and the Iqbal correlation.

[0236] Studies reported in the literature have shown how the ageing produced by solar radiation in the UV emission range acts with particular relevance on the most superficial course of flexible pavements in bituminous concrete, since its aggressiveness is maximized on the thin film of bitumen that covers the aggregates on the surface. This ageing was reproduced, as it was considered among the most aggressive and most disabling for the resilience of a bituminous conglomerate pavement in the long term, and was the method of selection and evaluation of the most performing blends.

[0237] The rheological analysis was carried out with the Dynamic Shear Rheometer Anton Paar MCR 702 instrumentation, the test proj ect was carried out in an oscillatory regime in the linear visco-elastic field through the execution of Frequency and Temperature Sweep. The characterization was performed at temperatures of 4, 10, 16, 22, 28, 34, 40, 46, 52, 58, 64, 72, 80, 86 °C (the change of the configuration of the tools / plate- plate of the rheometer was performed for the reference T of 34 °C).

[0238] The graphs in Figures 1-6 indicate the rheological parameters studied for the behaviour of bituminous mixtures from which the evolution of mechanical performance during the photo-oxidative ageing phenomenon is derived. From the graphs in question, it is possible to see the preservation of the visco-elastic characteristics of the bituminous mixture added with EPOXYSILANE, even after oxidation; it should also be noted that these visco-elastic characteristics are better when the association of the invention is present with respect to those of the bitumen without additive or added with only EPOXYSILANE.

[0239] Therefore, the graphs shown in Figures 1-6 demonstrate how, as the ageing state proceeds, the bituminous mixture containing the association of the invention referred to in Example 1 shows a better response to the photo-oxidation phenomenon with respect to the "PBM" and "PMB + EPOXYSILANE" formulations.

Claims

CLAIMS1. Antioxidant and anti-ravelling association for draining bituminous conglomerates comprising or consisting of- diphenylmethane diisocyanate (MDI) in the form of isomers, oligomers, and / or polymers,- an organosilane of formula (I) belowwhereinRi is selected from: methyl, ethyl, methoxy, ethoxy,R2 is selected from: methyl or ethyl,R3 is selected from the group consisting of: -CH2-, -OCH2-, -CH2CH2-, -OCH2CH2-, - CH2CH2CH2-, -OCH2CH2CH2-, -NHCH2CH2-, -NHCH2CH2CH2-,R4 is selected from the group consisting of: NH2-, NH2CH2-, NH2CH2CH2-, SH-,characterized in that the weight ratio between diphenylmethane diisocyanate (MDI) and organosilane is comprised between 9:1 and 19: 1.

2. Association according to claim 1, wherein the diphenylmethane diisocyanate is a mixture of isomers.

3. Association according to claim 1 or 2, wherein the diphenylmethane diisocyanate is a mixture of the 2,4’ -MDI and 4,4’ -MDI isomers.

4. Association according to any one of claims 1 to 3, wherein Ri and R2 are equal to each other and equal to R, wherein R is methyl or ethyl, whereby the organosilane of formula (IA)R4-R3-Si-(OR)3formula (IA) or wherein Ri is other than R2, preferably Ri is methyl and R2 is equal to methyl or ethyl, whereby the organosilane of formula (IB)CH3R4 R3Si (O R3)2 formula (IB)5. Association according to any one of claims 1 to 4, wherein R3 is selected from the group consisting of: -CH2CH2-, -OCH2-, -OCH2CH2-, -OCH2CH2CH2-.

6. Association according to any one of claims 1 to 5, wherein R4 is7. Draining bituminous conglomerate comprising the association according to any one of claims 1 to 6 in combination with aggregates and at least one bituminous binder, wherein the association is in an amount comprised between 0.5% and 3% by weight on the total weight of the aggregates.

8. Draining bituminous conglomerate according to claim 7, wherein the bituminous conglomerate also contains aggregates and milled recycled asphalt or RAP.

9. Draining bituminous conglomerate according to claim 8, wherein the milled recycled asphalt is comprised in the draining bituminous conglomerate in an amount > 25% by weight with respect to the total weight of the aggregates.

10. Draining bituminous conglomerate according to any one of claims 7 to 9, wherein the association is comprised in an amount comprised between 0.01% and 0.20% by weight on the total weight of the conglomerate.

11. Use of the association according to any one of claims 1 to 6, for the preparation of draining bituminous conglomerates, preferably draining wearing course bituminous conglomerates.

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