EP1987103A1

EP1987103A1 - Anti-ice and anti-snow composition for road pavings

Info

Publication number: EP1987103A1
Application number: EP06727334A
Authority: EP
Inventors: Edvinas Peleckas
Original assignee: Advanced Technologies (for) Road Applications(at)
Current assignee: Advanced Technologies (for) Road Applications(at)
Priority date: 2006-02-22
Filing date: 2006-02-22
Publication date: 2008-11-05
Also published as: WO2007096690A1

Abstract

The formulation, the preparation and the use of compositions for producing road pavings of the anti-ice type, namely such as not to allow, or such as to delay over time, the formation of ice adhering to the said paving, in the event of temperatures of the air less than zero or, likewise, so as to prevent the formation of ice resulting from 'freezing' rain or also prevent the adhesion of falling snow. The invention consists mainly of a composition essentially consisting of at least one organic salt of alkaline and/or alkaline earth metals having a molecular weight less than 200 Da, and at least one surfactant. The technology also performs other functions, such as eliminating the potential slipperiness caused by conventional ice-melting salts containing calcium chloride, in the event of excessive amounts applied, eliminating the aggressive action of the filtering liquids on vehicles and the reinforced cement road structures (such as bridges, viaducts, manholes, drainage channels and the like) and finally, reducing the potential pollution of water beds and the ground again as a result of the chlorides. The composition in question may be added to the usual mixture for forming road pavings or may be sprayed onto the road surface before or after snow falls/ice formation.

Description

Anti-ice and anti-snow composition for road pavings

The present invention relates to a technology for the preparation of bituminous conglomerate road pavings which are self de-icing, namely are such that they do not allow or such that they delay over time the formation of ice adhering to the said paving; this technology therefore makes it possible to eliminate or limit greatly the loss of safety due to the reduction in road-holding and braking properties on the road surface in winter conditions and prevent deterioration of the road structure and pollution of the water and land adjacent to the road bed. Principally the invention concerns a road paving composition, essentially consisting of at least one organic salt of alkaline and/or alkaline earth metals having a molecular weight less than 200 Da and at least one surfactant, achieving the abovementioned action by means of permanent incorporation inside various types of (closed or draining) pavings during different stages of their life (surfaces which are new, recycled or pre-existing on-site) or application onto the surface of the said paving. Prior art

One of the main problems of winter management of roads is the possible loss of adherence between tyres and the surface of the road paving, with the consequent risk of skidding, loss of control or reduction in the braking capacity of the vehicles when:

• a layer of ice is formed on said surfaces in the presence of high humidity levels of the air and temperatures falling below zero degrees;

• "freezing" rain is falling at a very low air temperature (resulting in the formation of "verglas");

• it is snowing with an intensity such as to allow the formation of compressed ice adhering to the abovementioned surfaces.

The current systems for preventing these dangerous conditions, the first two of which are most treacherous because often they are not readily obvious and are not uniform along the road, consist mainly in spreading, before the start of the abovementioned weather conditions, ice-dissolving salts which lower the freezing point of the atmospheric water (in the liquid or vapour phase), so that the formation of ice is prevented or so that the snow does not adhere to the paving. There already exist some devices or systems able to prevent this formation of ice. One of these consists in the insertion, in the paving, of electric heating resistances which are, however, costly and weaken the structure of the paving and also require the very costly use of power and electricity.

Another system is that of providing fixed installations in areas which are most exposed to these conditions so as to allow the automatic spraying of anti-ice liquid salts (generally calcium chloride in an aqueous solution) when required by the local weather conditions; these systems are also costly and localised and in any case give rise to problems of chloride pollution and attack.

A third system which has already been tested on roads in northern Europe with "closed" bituminous conglomerates (i.e. those with a percentage of empty spaces tending towards zero) consists in incorporating into the mixture for making bituminous conglomerates anti-ice chlorides which, however:

• are often released when the atmospheric temperature conditions are not such as to give rise to the dangers of ice formation and which therefore generate, owing to the nature of the salts incorporated, an uncontrolled increase in the slipperiness of the surfaces which become dangerous in the absence of ice;

• have an aggressive action on vehicles, road structures and the environment surrounding the road.

These systems consisting in the use of mixtures mainly composed of sodium and calcium chloride and sodium chloride, silicates and silanes have not lived up to expectations in terms of preventing or reducing the formation of ice and at the same time a reduction over time in the resistance to wear of the road surface and an increase in slipperiness has been noted. Description of the invention

The object of the present invention is to provide road surfaces, especially in the case of draining and noise-damping porous pavings, which in adverse weather conditions (as in winter) ensure conditions of maximum safety by preventing entirely the formation of ice due to atmospheric humidity or verglas and/or the snow from settling in the event of moderate snow falls and which, in the event of heavy or prolonged snow falls, make it possible to intervene with an ease and efficiency greater than in the case of normal closed pavings, using conventional salt spreaders and snow ploughs, while achieving a very marked reduction in the amount of aggressive salt used during the periods when ice alone is present and an increase in the probability of continuous management in safe conditions during snow falls, again with a reduction in the amount of salt used, even though less marked than in the case where ice alone is present.

This result is achieved with a particular composition which may be added to the bituminous conglomerate forming the road paving or may be applied onto the surface of the road paving itself without resulting in slipperiness in non-winter temperature and humidity conditions.

The road paving composition which forms the object of the present invention is essentially composed of at least one organic salt of alkaline and/or alkaline earth metals having a molecular weight less than 200 Da, preferably chosen from among sodium and/or calcium acetate and formate, and at least one surfactant. The preferred surfactant is a polyamine alkylamide, in particular a polyamine alkylamide with the formula:

where n is a prime number between 6 and 10, preferably 8, and m is a prime number between 1 and 6, preferably 4.

According to one aspect of the invention, the organic salt is present in an amount ranging between 90 and 99.8% and said surfactant is present in an amount ranging between 0.2 and 10%, relative to the total weight of the composition.

The composition may also contain:

• at least one alkylene glycol, preferably chosen from among ethylene and/or propylene glycol, in an amount ranging between 0 and 2%, relative to the total weight of the composition; • at least one siloxane in an amount ranging between 2 and 5%, relative to the total weight of the composition.

As mentioned above, the composition of the invention may be used as an additive which is incorporated in bituminous conglomerates, especially of the draining type (with an open bituminous composition) in adverse atmospheric conditions (as in winter), and, with a balanced release over the years, prevents or at least lowers, automatically, the formation of ice resulting from atmospheric humidity, or of verglas, or the settling of snow, in the case of snow falls which are not abundant, lowering the freezing point and allowing time for the routine intervention of salt- spreading machines and snow ploughs; said results being achieved without corrosive attack of the metals and the cement conglomerates forming the road. In the particular case of this type of application, the composition of the invention (called formulation A) preferably consists of:

• at least one organic salt, preferably sodium formate (45-99.5%, preferably 80-98%);

• at least one inorganic salt, preferably, calcium carbonate (0-50%, preferably 0-20%);

• siloxane (2-5%);

• surfactant (1-10%, preferably 1-5%);

• alkylene glycol (1-10%); where the inorganic salt is usually a carbonate of alkaline and/or alkaline earth metals, preferably calcium carbonate.

In order to exercise its anti-ice activity in an optimum manner, the composition in question is normally added to a bituminous preparation essentially consisting of 30 to 60% of the said composition, preferably 45 to 55%, and 40 to 70% of bitumen, preferably 45 to 55%, relative to the total weight of the preparation. This preparation may therefore be used for the composition of a bituminous conglomerate essentially consisting of the said preparation in combination with an inert, inorganic, granulated material, preferably chosen from silica and/or limestone; the preparation is preferably present in an amount ranging between 3 and 10% while the inert, inorganic, granulated material is preferably present in an amount ranging between 90 and 97%, relative to the total weight of the conglomerate.

Alternatively, the composition of the present invention may be used in the form of a concentrated aqueous solution of a preparation which can be sprayed onto the road surface, both beforehand, if snow falls or ice formation on the asphalt are expected, and after the formation of ice or snow on the road, in order to dissolve them. In this case, the formulation (called formulation B) preferably consists of:

• water (50-75%, preferably 70-75%)

• at least one organic salt, preferably sodium formate (25-50%, preferably 25-30%)

• siloxane (0-5%)

• surfactant (0-10%)

• alkylene glycol (0-10%, preferably 0-5%) ACTION OF FORMULATION A

In the particular case of the formulation A, the anti-ice and/o anti-snow action may be explained as follows: the poly amine alkylamide is an adhesion activator which binds the fatty chain to the bitumen and the polar amine head to the surface of the acidic admixtures (e.g. siliceous RSiOH) in accordance with the following reaction:

Once formed, this complex reacts with the formate in accordance with the following equilibrium reaction:

RSiONa

The formate bonded electrostatically to the polyamine alkylamide hydrates in the presence of water to give the corresponding diol:

The above is applicable not only to admixtures of an acid nature (RSiOH), but also alkaline admixtures as can be seen from the following reactions:

and in the presence of the formate:

Na₂CO₃

This latter complex, containing the abovementioned diol, interferes, although remaining partly attached to the bitumen, with the perfectly geometrical formation of the ice crystals, since it produces hydrogen bonds and greater entropy with the water molecules. The potassium methylsiliconate is important in the formulation since it regulates the migration of the free ions from the inside of the bituminous conglomerate towards the outside of the road layer, forming a semi-hydrophobic film together with the bitumen. The CaCO₃ attenuates the hygroscopicity of the formate and improves its dispersion in the bitumen. The alkylene glycols help achieve the cryoscopic lowering of the water in contact with the asphalt, optimizing the effects of the formate. ACTION OF THE FORMULATION B

In the particular case of the formulation B, the preparation present in solution form dissolves the ice and/or snow owing to the interactions described above in case A, with the difference that this time binding of the fatty chain of the surfactant to the bitumen occurs only on the superficial part of the asphalt. It is not necessary, moreover, to add carbonates, since the preparation is present in an aqueous solution. Description of the production process

The preparation of the compositions according to the present invention may be performed using the methods known in the art such as, for example, those which are indicated below.

Formulation A:

- mixing the solid components;

- adding the liquid components;

- pseudo-sintering;

- packaging of the finished product.

The solid components are fed, by means of a suitable conveyor, into a specially designed mixer connected to a suitable dust recirculating capture and elimination system.

After a predetermined mixing time the liquid components are added in succession and mixing is continued to allow adsorption thereof on the powders and/or solid crystals previously mixed.

The preparation is discharged into a screw extractor which feeds an annular press where, under particular temperature and pressure conditions, a kind of sintering of the components is performed.

In fact materials with a high melting point, such as grains of powders coated with additives, treated in this system, owing to the local fusion which combines the individual grains of powder, are converted so that the product is intimately bonded and in each small grain (<10 micron) there is always the same percentage composition.

Formulation B:

Dilution in water with a high concentration of formulation A devoid of the calcium carbonate as described above and dilution thereof prior to use in the concentrate storage tanks along the roads where it will be used by means of spraying, in order to avoid the uneconomical transportation of the complete brine

(30% concentration).

Industrial application: The preparation of the self de-icing conglomerate, i.e. supplemented according to the present invention with formulation "A", envisages adding the preparation to the bitumen heated to melting point (about 140-160⁰C) in concentrations which vary from 3 to 6%.

In addition to the bitumen and the aforementioned additives, the bituminous composition of the present invention also includes an inert granulated material

(such as sand or the like), in accordance with the usual road construction technology performed in normal production plants.

The road pavings made with the composition in question prevent or at least delay over time the formation of ice adhering to the said paving, in the event of temperatures below zero, or prevent the formation of ice resulting from "freezing rain", or also prevent the "adhesion" of falling snow down to temperatures of 4 -

5°C below zero.

At the same time the potential slipperiness which is characteristic of de-icing salts based on excess calcium chlorides and the aggressive character of the filtering . liquids resulting therefrom are eliminated.

Essentially the compositions according to the present invention differ from the known art as regards the following aspects:

- they are absolutely devoid of chlorides which, in addition to being a possible cause of slipperiness of the road surface, may have an aggressive action in respect of both the steel reinforcement and the bodywork of the vehicles as well as the environment surrounding the road;

- they are perfectly dispersed in the bitumen film so as to exercise their anti-ice action both on the exterior of the road surface (which makes contact with the tyres) and within the small channels inside the final structure of the draining/noise-damping conglomerates characterized by large internal areas lined with the film of supplemented bitumen, in contact with the water or moisture;

- they undergo gradual release from the exterior of the road surface, so that there is a migration from the inside of the paving (where they are in contact with the aggregates of the conglomerates) towards the outside (in contact with the air), renewing and ensuring the constant effectiveness of the inhibiting action; they do not alter the structure of the conglomerates contained inside them, in the sense that the adhesion of the bituminous film to the aggregates is not reduced, the self-repairing capacity of the road surface (in the sense of

"absorbing" any cracks caused by the traffic) is not impaired and their visco- elastic deformability is not increased.

Claims

B2006/00061810Claims

1. Road paving composition essentially consisting of at least one organic salt of alkaline and/or alkaline earth metals having a molecular weight less than 200 Da and at least one surfactant.

2. Composition according to Claim 1, characterized in that said organic salt is chosen from sodium and/or calcium acetate and formate.

3. Composition according to Claim 1, characterized in that said surfactant is a polyamine alkylamide.

4. Composition according to Claim 3, characterized in that said polyamine alkylamide has the formula:

where n is a prime number between 6 and 10 and m is a prime number between 1 and 6.

5. Composition according to Claim 4, characterized in that n is 8 and/or m is 4.

6. Composition according to any one of the preceding claims, characterized in that said organic salt is present in an amount ranging between 90 and 99.8% and said surfactant is present in an amount ranging between 0.2 and 10%, relative to the total weight of the composition.

7. Composition according to Claims 1-6, characterized in that it contains at least one alkylene glycol in an amount ranging between 0 and 2%, relative to the total weight of the composition.

8. Composition according to Claim 7, characterized in that said alkylene glycol is ethylene and/or propylene glycol.

9. Composition according to Claims 1-8, characterized in that it contains at least one siloxane in an amount ranging between 2 and 5%, relative to the total weight of the composition.

10. Composition according to Claims 1-9, characterized in that it contains from 45 to 99.5% of organic salt, from 0 to 50% of inorganic salt, from 1 to 10% of surfactant, from 2 to 5% of siloxane and from 1 to 10% of alkylene glycol, relative to the total weight of the composition.

11. Composition according to Claim 10, characterized in that it contains from 80 to 98% of organic salt, from 0 to 20% of inorganic salt, from 1 to 5% of surfactant, from 2 to 5% of siloxane and from 1 to 10% of alkylene glycol, relative to the total weight of the composition.

12. Composition according to Claim 10, characterized in that said inorganic salt is a carbonate of alkaline and/or alkaline earth metals, preferably calcium carbonate.

13. Bituminous preparation essentially consisting of 30 to 60% of a composition according to Claims 1-12 and 70% of bitumen, relative to the total weight of the preparation.

14. Preparation according to Claim 13, essentially consisting of 45 to 55% of a composition according to Claims 1-12 and 45 to 55% of bitumen, relative to the total weight of the preparation.

15. Bituminous conglomerate essentially consisting of a preparation according to Claims 13-14 and an inert, inorganic, granulated material.

16. Conglomerate according to Claim 15, characterized in that said inert, inorganic, granulated material is chosen from silica and/or limestone.

17. Conglomerate according to Claim 15, characterized in that said preparation is present in an amount ranging between 3 and 10% and said inert, inorganic, granulated material is present in an amount ranging between 90 and 97%, relative to the total weight of the conglomerate.

18. Use of a composition, a preparation and/or a conglomerate according to any one of the preceding claims, for preparing anti-ice road pavings.

19. Composition according to Claims 1-9, characterized in that it contains 25 to 50% of organic salt, 50 to 75% of water, 0 to 10% of surfactant, 0 to 5% of siloxane and 0 to 10% of alkylene glycol, relative to the total weight of the composition.

20. Composition according to Claim 19, characterized in that it contains 25 to 30% of organic salt, 70 to 75% of water, 0 to 5% of surfactant, 0 to 5% of siloxane and 0 to 10% of alkylene glycol, relative to the total weight of the composition.

21. Method for preventing the formation of ice and/or the adhesion of snow on the road paving and/or eliminating the ice which has formed thereon, this method comprising the application of a composition according to Claims 19- 20, optionally diluted with water, onto the surface of said road paving and/or the ice which has formed thereon.