Anti-icing additive composition for bituminous conglomerates

Abstract

An anti-icing composition suitable for incorporation in bituminous conglomerates for road paving, comprising an alkali metal chloride, an alkaline-earth metal carbonate, an alkali or alkaline-earth metal formate, a polysiloxane and optionally an alkaline-earth metal chloride, in which the polysiloxane is contained in an amount between 0.5 and 2.0% by weight of the total weight of the composition; it is also described a bituminous conglomerate adapted to provide an anti-icing road paving, comprising aggregates, bitumen, filler and from 2 to 6% by weight of such anti-icing composition of the weight of the aggregates.

Claims

1. An ani-icing composition suitable for incorporation in bituminous conglomerates for road paving, comprising an alkali metal chloride, an alkaline-earth metal carbonate, an alkali or alkaline-earth metal formate, a polysiloxane and optionally an alkaline-earth metal chloride, in which the polysiloxane is contained in an amount between 0.5 and 2.0% by weight of the total weight of the composition.

2. The anti-icing composition according to claim 1, comprising an alkali metal chloride and an alkaline-earth metal chloride, wherein said alkali metal chloride is sodium chloride and said alkaline earth metal chloride is calcium chloride.

3. The anti-icing composition according to claim 2, wherein said alkaline earth metal carbonate is calcium carbonate.

4. The anti-icing composition according to claim 3, wherein said formate is an alkali metal formate.

5. The anti-icing composition according to claim 4, consisting of the following components, indicated in percentages by weight of the total weight of the composition: TABLE-US-00013 sodium chloride 60-84 sodium formate 5-15 calcium chloride 5-15 calcium carbonate 2-8 polysiloxane 0.5-2.0.

6. The anti-icing composition according to claim 1, wherein said polysiloxane is a polydimethylsiloxane (dimethicone).

7. The anti-icing composition according to claim 6, wherein said polydimethylsiloxane has a viscosity of between 300 and 400 mm.sup.2/s.

8. The anti-icing composition according to claim 4, wherein metal formate is sodium formate.

9. The anti-icing composition according to claim 7, wherein said polydimethylsiloxane has a viscosity of between 325 and 375 mm.sup.2/s.

10. An anti-icing bituminous formulation comprising from 20 to 70% by weight of the anti-icing composition according to claim 1 and 30 to 80% by weight of bitumen.

11. The bituminous formulation according to claim 10, comprising from 30 to 60% by weight of said anti-icing composition and from 40 to 70% by weight of bitumen.

12. A bituminous conglomerate adapted to provide an anti-icing road paving, comprising aggregates, bitumen, filler and from 2 to 6% by weight of the weight of said aggregates, of said anti-icing composition according to claim 1.

13. A bituminous conglomerate adapted to provide an anti-icing road paving, comprising aggregates, bitumen, filler and from 3 to 5%, by weight of the weight of said aggregates, of said anti-icing composition according to claim 1.

14. A bituminous conglomerate adapted to provide an anti-icing road paving, comprising aggregates, filler and from 3 to 10%, by weight of the weight of said aggregates, of said anti-icing bituminous formulation according to claim 10.

15. A method for producing a bituminous conglomerate, comprising a step of adding, under stirring and at a temperature varying from 130 C. to 200 C., to a mixture of aggregates and filler, bitumen and an anti-icing composition according to claim 1.

16. A method for producing a bituminous conglomerate, comprising the step of adding, under stirring and at a temperature varying from 130 C. to 200 C., to a mixture of aggregates and filler, an anti-icing bituminous formulation according to claim 10.

17. A method for producing an anti-icing composition according to claim 1, which comprises the steps of mixing said alkali metal chloride, said alkali-earth metal carbonate, said alkali or alkaline-earth metal formate, and optionally said alkaline-earth metal chloride to obtain a mixture in the form of a homogeneous powder, and adding said polysiloxane dispersed in a finely divided form to said mixture in the form of a homogenous powder.

18. The method according to claim 17, wherein said step of adding the polysiloxane is performed by spraying the polysiloxane by means of a spray device onto said mixture in the form of a homogeneous powder which is kept under stirring in a mixer.

19. The method according to claim 18, wherein said mixer is a screw mixer.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 is a photograph of a slab made in laboratory with the bituminous conglomerate A of Example 6, containing the anti-icing composition according to Example 1.

(2) FIG. 2 is a photograph of a slab made in laboratory with the comparison bituminous conglomerate B of Example 6, not containing the anti-icing composition according to the present invention.

DETAILED DESCRIPTION

(3) Hereinafter are some examples of anti-icing compositions according to the present invention, which have been prepared and tested with favorable results in relation to their effect of ice formation prevention.

Example 1

(4) TABLE-US-00002 Sodium chloride 70% Calcium chloride 13% Sodium formate 11% Calcium carbonate 5% Dimethicone with a viscosity 1% of 350 mm.sup.2/s at 25 C.

Example 2

(5) TABLE-US-00003 Sodium chloride 80% Sodium formate 12% Calcium carbonate 6% Dimethicone with a viscosity 2% of 300 mm.sup.2/s at 25 C.

Example 3

(6) TABLE-US-00004 Sodium chloride 60% Calcium chloride 15% Sodium formate 15% Calcium carbonate 8% Dimethicone with a viscosity 2% of 400 mm.sup.2/s at 25 C.

Example 4

(7) TABLE-US-00005 Sodium chloride 84% Calcium chloride 5% Sodium formate 5% Calcium carbonate 5.5% Dimethicone with a viscosity 0.5% of 350 mm.sup.2/s at 25 C.

(8) The compositions of Examples 1 to 4 were prepared by mixing the various salts listed, except calcium carbonate, in the form of coarse powders inside a screw mixer and uniformly spraying dimethicone over them by a spray gun, while they are kept under stirring. After the addition of dimethicone, the powdered calcium carbonate is added under stirring and stirring is continued until a homogeneous mixture is obtained.

Example 5 (Comparative)

(9) TABLE-US-00006 Sodium chloride 71% Calcium chloride 13% Sodium formate 11% Calcium carbonate 5%

(10) This composition is prepared by dosing the ingredients in the form of coarse powder in a screw mixer under stirring and stirring is continued until a homogeneous mixture is obtained.

Example 6

(11) Using the composition according to Example 1 three slabs of bituminous conglomerate containing such composition in the proportions indicated in the following Table 1 and having a diameter of 100 mm and a thickness of about 25 mm were prepared in the laboratory. Three slabs of bituminous conglomerate with the same composition but not containing the above composition were also prepared.

(12) TABLE-US-00007 TABLE 1 Bituminous Bituminous conglomerate A, conglomerater B, containing the without the composition of composition example 1 of example 1 Materials Parts by weight Parts by weight Inerts 6/12 20 20 Inerts 3/8 50 50 Sand 0-4 25 25 Filler (CaCO.sub.3) 5 5 Bitumen 50/70 5.5 5.5 Composition of 4 0 example 1 Total 109.5 105.5

(13) The bituminous conglomerate is prepared in the laboratory by bringing the aggregates (inerts, sand) and the filler to a temperature of 180 C. inside a 5 liter planetary mixer and adding to them, under stirring, the bitumen heated at 150 C. and, in the case of bituminous conglomerate A, also the composition of Example 1, both at room temperature, after which stirring is continued for 5 minutes.

(14) The bituminous conglomerate is then discharges from the planetary mixer, dosed in quantities of about 300 g inside a porcelain container and inserted into a rotary press (30 cycles) kept at a temperature of 150 C., applying a pressure of about 600 kPa to form respective slabs with a diameter of 100 mm, with a thickness of about 30 mm and a weight of about 100 g.

(15) The three slabs of conglomerate A and the three slabs of conglomerate B are then placed on respective non-metallic discs and introduced into a refrigerator at a temperature of 5 C. for at least 2 hours, so as to obtain the thermal normalization of the samples. Subsequently the slabs are sprayed onto their surface with water at a temperature of 4 C. (which simulates a situation of rain mixed with snow), 6 sprays (about 8-9 ml) and kept in the refrigerator at 5 C. for another 12 hours, afterwards a visual examination of the slabs is carried out to determine the possible presence of frost or ice on their surface.

(16) In case neither frost nor ice is formed, the slab is brought back to room temperature, the excess water is removed, the disc is cleaned, the slab is thrice immersed in water inside a becker and the procedure of normalization in refrigerator at 5 C., spraying with water at 4 C. and storage in refrigerator at 5 C. for 12 hours is repeated, eventually verifying the possible formation of ice or frost.

(17) FIGS. 1 and 2 show respective photos of a slab of the bituminous conglomerate A and of a slab of the bituminous conglomerate B. In particular, FIG. 2 shows a slab of bituminous conglomerate B at the end of only one cycle of normalization, water spraying and storage at 5 C. for 12 hours, while FIG. 1 shows a slab of conglomerate A at the end of 5 cycles as above with the interposition of immersions in water as described above between each cycle. It is quite obvious that there is no ice in slab A while a layer of ice is clearly visible on the surface of slab B, formed at the end of the first step of the procedure described above.

(18) This shows that the presence of the anti-icing composition according to example 1 of the present invention inside the bituminous conglomerate A has completely prevented the formation of ice, wherein conglomerate B, in every single way equal to the conglomerate A except for the absence of the composition according to Example 1, did not show any anti-ice effect.

Example 7

(19) The absorption of moisture from the atmosphere by the composition according to Example 1 was verified and compared with the composition according to example 5, which is free of dimethicone.

(20) The verification was conducted by depositing a carefully measured quantity of each one of the above-mentioned compositions on four respective Petri glass plates and leaving these plates exposed to the atmospheric air at a temperature of about 20 C. for the periods indicated in the following Table 2. At the end of each period the quantity of humidity absorbed was determined (humidity content %) by means of a thermobalance at 120 C. for 20 minutes.

(21) TABLE-US-00008 TABLE 2 Example 1 (humidity Example 5 (humidity Time content %) content %) 1 day 1.02 2.3 30 days 1.7 4.6 60 days 2.0 9.5 90 days 1.8 9.3

(22) From the results presented in Table 2 it clearly emerges that the presence of a polysiloxane in the composition according to the present invention gives it a high degree of protection against atmospheric humidity, which results in the above-noted advantage of avoiding any packing phenomenon and any reduction of its flowability properties.

Example 8

(23) It has been verified whether the addition of the composition according to the present invention to a bituminous conglomerate would cause some alteration of the physical-mechanical properties of a wear layer made with such a conglomerate.

(24) For this purpose, specimens of bituminous conglomerate were made according to a SMA curve as shown in Table 3 below.

(25) TABLE-US-00009 TABLE 3 Bituminous Bituminous conglomerate SMA1, conglomerate SMA2, containing the without the composition of composition Example 1 of Example 1 Materials Parts by weight Parts by weight Inerts 6/12 10 10 Inerts 3/6 60 60 Sand 0-4 20 20 Filler (CaCO.sub.3) 10 10 Plastomers and 0.6 0.6 microfibers Bitumen 50/70 6.5 6.5 Composition of example 4 0 1 Total 111.1 107.1

(26) The specimens were prepared by depositing about 1.2 kg of bituminous conglomerate in a cylindrical container kept at 150 C. for at least 2 hours and pressing it in a rotary press to form a respective cylindrical specimen, with a diameter of 100 mm and a height of about 65 mm. For each specimen, the physical-mechanical determinations set out in Table 4 were performed:

(27) TABLE-US-00010 TABLE 4 Conglomerate Conglomerate Technical SMA1 SMA2 specifications Residual voids 12.5 10.5 9-13 (%) at 10 cycles Residual voids 4.6 3.8 2-5 (%) at 120 cycles Residual voids 3.5 1.1 1 (%) at 200 cycles GMM.sup.1 at 200 2449 2384 cycles (Maximal Specific Gravity) (kg/m.sup.3) GMB.sup.2 at 200 2365 2358 cycles (Bulk Specific Gravity) (kg/m.sup.3) ITS.sup.3 at 200 cycles 1.30 1.33 1.0-1.80 25 C. (N/mm.sup.2) CTI.sup.4 at 200 cycles 112 123 85 25 C. (N/mm.sup.2) .sup.1GMM is the theoretical maximum specific gravity (at zero air voids) of the bituminous conglomerate, measured according to AASHTO T 209 standard. 2GMB is the density of the conglomerate with the voids (bulk specific gravity), measured according to AASHTO T 166 standard. .sup.3ITS indicates the tensile strength evaluated according to UNI EN 12697-23 standard at a temperature of 25 C. .sup.4CTI indicates the indirect tensile strength coefficient evaluated according to UNI EN 12697-23 standard at a temperature of 25 C.

(28) The percentage of residual voids at 10 cycles simulates the compacting of the bituminous conglomerate after the paver has been applied; the 120-cycle residual voids percentage simulates the compacting of the bituminous conglomerate after rolling (i.e. after the paved road has been opened to traffic) and the percentage of voids at 200 cycles simulates the compacting of the bituminous conglomerate towards the end of the service life of the asphalt pavement (10-15 years).

(29) As it can be noted from the data set out in Table 3, the wear layer made with the SMA1 conglomerate, containing the anti-icing composition according to Example 1, showed GMM and GMB values fully comparable to those of the SMA2 conglomerate, free of such anti-icing composition, and excellent values of tensile strength and indirect tensile strength coefficient.

(30) This means that the addition of the anti-icing composition according to the present invention to a bituminous conglomerate for road paving provides excellent protection against ice formation on the surface without significantly altering the physical-mechanical properties of the road pavement obtained with it.

Example 9

(31) A comparison test was performed between a composition according to the present invention and the composition according to Example 5, free of dimethicone and corresponding to the known product Winterpay.

(32) For this purpose, specimens of bituminous conglomerate were made according to a SMA curve as shown in Table 5 below.

(33) TABLE-US-00011 TABLE 5 Bituminous Bituminous conglomerate SMA1, conglomerate SMA5, containing the containing the composition of composition of Example 1 Example 5 Materials Parts by weight Parts by weight Inerts 6/12 10 10 Inerts 3/6 60 60 Sand 0-4 20 20 Filler (CaCO.sub.3) 10 10 Plastomers and 0.6 0.6 microfibers Bitumen 50/70 6.5 6.5 Composition of example 4 0 1 Composition of example 0 4 5 Total 111.1 111.1

(34) The specimens were prepared by depositing about 1.2 kg of bituminous conglomerate in a cylindric container kept at 150 C. for at least 2 hours and by pressing it in a rotary press to form a respective specimen of cylindrical form, with a diameter of 100 mm and a height of about 65 mm. For each sample, the physical-mechanical determinations set out in Table 6 were performed:

(35) TABLE-US-00012 TABLE 6 Conglomerate Conglomerate Technical SMA1 SMA5 specifications Residual voids 12.3 12.4 9-13 (%) at 10 cycles Residual voids 4.5 2.0 2-5 (%) at 120 cycles Residual voids 3.1 1.0 1 (%) at 200 cycles GMM.sup.1 at 200 2399 2420 cycles (Maximal Specific Gravity) (kg/m.sup.3) GMB.sup.2 at 200 2301 2424 cycles (Bulk Specific Gravity) (kg/m.sup.3) ITS.sup.3 at 200 1.28 1.60 1.0-1.80 cycles 25 C. (N/mm.sup.2) CTI.sup.4 at 200 108 134 85 cycles 25 C. (N/mm.sup.2) .sup.1GMM is the theoretical maximum specific gravity (at zero air voids) of the bituminous conglomerate, measured according to AASHTO T 209 standard. .sup.2GMB is the density of the conglomerate with the voids (bulk specific gravity), measured according to AASHTO T 166 standard. .sup.3ITS indicates the tensile strength evaluated according to UNI EN 12697-23 standard at a temperature of 25 C. .sup.4CTI indicates the indirect tensile strength coefficient evaluated according to UNI EN 12697-23 standard at a temperature of 25 C.

(36) As it can be noted from the data set out in Table 6, the wear layer made with the SMA1 conglomerate, containing the anti-icing composition according to Example 1, showed GMM and GMB values fully comparable to those of the SMA5 conglomerate containing the anti-icing composition according to Example 5, and excellent values of tensile strength and indirect tensile strength coefficient.

(37) This means that the presence of polysiloxane within the anti-icing composition according to the present invention has allowed to solve the above mentioned technical problem of overcoming the disadvantages associated with the product Winterpav (risk of inhalation of the very fine powder particles contained therein and packing phenomena due to hygroscopicity), ensuring the same anti-icing effect and without jeopardizing in any way the physical-mechanical properties of the road pavement made with a bituminous conglomerate containing such composition.

Example 10

(38) The behavior during storage of a batch of a product with a composition according to Example 1 was verified by keeping in a store at room temperature 1500 kg of this product closed in two polyethylene big bags (FIBCs) placed one over the other and the two of them over four bags made of low melting LDPE, each of which in turn contained 25 kg of the same composition. Two months later, the two big bags were inspected to check the status of the product and no packing phenomenon was detected and it was possible to empty the contents of these bags by gravity in only about 30 seconds, without any appreciable generation of fine dust. No packing phenomenon was found in the four low melting bags either.