METHOD AND COMPOSITION FOR ROUGHENING THE ROAD SURFACE

Abstract: Laying method of the type in which: on the roadbed (1) a binding liquid or pasty layer (2) is laid, substantially made up of binding resin that sticks to the surface of the road carpet and subsequently hardens; on said liquid or pasty layer (2), before the hardening, an aggregate material layer in granules (3) is evenly laid, in such a way that once the hardening of said resin (2) has occurred, said aggregate material in granules (3) is strongly bound to the road carpet; the aggregate material in granules that has not been adequately fixed to the roadbed is removed; where: said aggregate material in granules is artificially produced; its granules are polygon-shaped with sharp corners; the constitutent material is a mixture of forsterite, spinel, magnesium chromate and iron in which the presence of A1203 for a value comprised between 5 % and 15 % preferably about 10/11 % is provided. In this way an optimal coating is obtained.

Description: DESCRIPTION METHOD AND COMPOSITION FOR ROUGHENING THE ROAD SURFACE Technical Field This invention has for object a composition for the superficial roughening of road pavings, method and machine for the respective laying. Also the improved carpet obtained by such method, is integrate part of this invention . Background Art The new pavings in bituminous conglomerate have substantially a transversal friction coefficient (C.A.T.), measured on a wet surface, that on average is equal to 65. This friction coefficient is not sufficient to ensure adequate safety particularly at high speeds. All this is worsened by the rapid wear of the road carpet that becomes slippery in a short time, reducing such coefficient. As a consequence, in the road sections with curves having a reduced radius of curvature, turn-off, gradient sections, crossings, entry and exit from tunnels, viaducts, etc., it is advised to subject the road carpet to a particular coating process to increase the value of the paving roughness, or to increase the value of the transversal friction coefficient. The technologies presently used to satisfy this need generally consist in the laying, usually by jetting, on the paving, of a binder material layer and in its fast shotblasting with grit sizes comprised between 1 and 4 mm. After the removal of the exceeding grit, that is of that grit which is not bound by the binding material layer, the road paving may be normally run after about 2 - 5 hours. The binding material is generally made up of bitumen modified with elastomers, otherwise tar plasticised resins or also pure epoxy resins are used. Being required to the binding material an extreme and durable adhesion to the underlying conglomerate and to the covering grits, the more reliable binding materials, particularly used on highways where the are intense traffic flows, are made up of materials based on pure epoxy resins. Because the epoxy polymers are bicomponents, for the spreading must be used sophisticated technologies, which ensure an even and continuous spreading . The grits usually utilized for the most important laying are the bauxite subjected to calcination, that is to a process that eliminates its volatile substances . Drawbacks of the prior art These technologies in use for carrying out the surface roughening of road carpets present some problems. In particular, the use of a natural substance such as bauxite, as an aggregate in grit that has the drawback of a reduced evenness of the characteristics of the material, such as for example the hardness, the polyhedral shape of the granules, as well as the porosity. These parameters can vary because of the difference of escavation strata in the same quarry, the bauxite originated from different quarries, etc. Besides this there are difficulties in standardizing and in repeating the roughening, that is different results are found, even if using the same materials. Purpose of the present invention Purpose of the present invention is that of solving the above mentioned problems, allowing to obtain a surface roughening of road pavings having a high performance efficiency and a better life and stability of the chemical- physical and performance characteristics of the materials used. A further purpose is that of ensuring a possibility of repeating the global roughening characteristics when the modalities of laying and of the materials used are the same. A further purpose is that of supplying a perfect adhesion of the aggregate material to the binding material, in order to ensure a high duration of the roughening also in road pavings with very intense traffic. The above explained task, as well as the mentioned purposes and other ones, that eventually, will be better enhanced later, are achieved as claimed by means of the method of laying of the type in which: - a liquid or pasty binding layer is laid on the roadbed, substantially made up of binding resin that sticks to the surface of the road carpet and subsequently harden s ; on said liquid or pasty layer, before of the hardening, an aggregate material layer in granules is evenly laid, - in such a way that once the hardening of said resin has occurred, said aggregate material in granules is strongly bound to the road carpet; - the aggregate material in granules which has not adequately remained fixed to the roadbed is removed; characterised in that: • said aggregate material in granules is artificially produced; • it has polygon-shaped granules with sharp corners; • the constituent material includes substantially a matrix composed of a piroxen group and forsterite or olivine. Advantageously the mixture is a mixture of forsterite (olivine), spinel, magnesium chromate or magnesite and iron. Advantageously the spinel is a primary spinel. Advantages of the innovation In this way it is obtained a road carpet having the maximum effectiveness and performance both as coefficient of friction, and as life time of said friction coefficient, but even more in particular a maximum and absolute evenness of the friction coefficient on all the coated road surface without unevenness of the friction coefficient that otherwise would occur if the aggregate granulated material had not such qualitative stability. Advantageously said granules are mainly cube-shaped and have a rough surface. In this way the surface friction coefficient is absolutely kept constant in any area of the surface by improving the performance of the road carpet, being known that a more adherent surface section when it is adjacent to a less adherent surface section can deviate a braking vehicle. The roughness of the grains additionally improves the friction coefficient. Advantageously said binding resin is a bicomponent based on epoxy resins. The maximum prill adherence is thus obtained. As much advantageously said prill has the following composition: SiO 40%, A1203 11%, MgO 40%, CaO 2%, Cr203 4%, Fe 1% Further characteristics and advantages of the invention, will be better explained with the aid of the description of preferred form of embodiment, with the aid of the included drawings. Description Figure 1 shows schematically, in a partially section perspective view, a road paving section roughened by the method according to the invention. Figures 2,3,4,5,6 show the diagrams with section through the quaternary system Si02 - CaO - MgO - A1203, respectively with alumina quantities (A1203) of 5% (Fig.2); 10% (Fig.3); 15% (Fig.4) and 20% (Fig.5). The optimal solution, as claimed, being about the Alumina composition at 10% - Fig.3. Figure 6 shows the block scheme of the preferential system for the distribution of the binding resin obviously mounted on jetting vehicle of the roadbed. It is anyway normal that at first a suitable cleaning will be carried out as in the known laying art. For what concerns the material of the present invention, in order to obtain a porous material and in a dead heat highly resistant to crushing and abrasion, the influences of the single mineralogical components were studied. Tests and characteristics of the mineralogical components The tests of the mineralogical components gave the results shown in figures from 2 to 5. From tests and studies it was found that the Spinel formation in the melting product is fundamental. This is found in grains developed idiomorphically between the edges of the Piroxene. In the phase diagrams as in figures from 3 to 5 the Spinel appears just at about 15% A1203, where it is stable at 1550°C, then it still exists during the reaching of the liquefaction temperature of the basic product. In these idiomorphic grains this regards therefore a Primary spinel. In fact the Spinel crystals can have a different form of development and can look like dendrites. The dendrites grow for example in strongly sub-cooled metals while the branches of the dendrites grow in that direction in which the fastest crystallization is possible. By a crystallographic point also a further phase could be interesting. According to evaluations this phase could bring the crystal shape through a growth of the skeleton during which the growing surfaces are formed incomplete of edges and angles. This means that the crystallization and the material inflow are not in equilibrium and therefore energetically the positions of more favourable constructions are preferred. As such formations in the tests are always found inside a brown glass matrix this would mean similarly the cooling effects. Also a metasomatic transformation of the glass phase (with a renewal of the zeolite) with a long ageing could be expected. It results anyway from the analysis that the crushed stone grains can be substantially formed by two ores, Piroxene and Olivine. The grain substantially consists of Olivine and Magnetite. These grains could be the first distillation products of the melted mass. In the Spinel tests grains with a considerable porosity are found. Such grains produce their effects greatly weakening the strength and in relation with the ratio of their presence the strength of all the grains mixture. The ores content of these samples has been determined with weight 4,2% of magnetite, crushed stone grains (magnetite+chromite) separable. It was said also as claimed that the optimal composition of said prill is the following: Si02 40%, A1203 11%, MgO 40%, CaO 2%, Cr203 4%, Fe 1%; As seen the formulation according to the ternary diagram of Fig. 3 is the one closer to the optimal characteristics. The grey fields on the inside indicate the intervals of the product solidification. The crystallographic analysis has confirmed the presence of Spinel crystals in a matrix composed of a Piroxene Group and Phosphate Rock. Because it probably was a primary Spinel. The crushes stone grains are substantially formed by two prevailing ores: Piroxene and Olivine, that represent the first distillation products of the melt mass with a considerable porosity. The technical characteristics resulted were the following: Density at 20°C g/cm 3 = 2,90 - 3,10 pH = 9,8 Friction resistance 60 Water absorption after 3 days = 0,03 Mainly cubic shape of the grains Affinity with the bitumen = optimal equal to limestone. Additional data The aggregate material is made up of a material, commercially known with the trade-mark MC-1, that is made up of a forsterite mixture (olivine), spinel, magnesium chromate (magnesite) and iron in the indicated and claimed parameters . Such aggregate material has a high porosity, in order to ensure a great contact surface with the binding material. Additionally, the same aggregate material has a high hardness, intended as crushing resistance and a non- smoothness, as well as a high abrasion resistance. Such material has, additionally, a high acoustic insulation, deriving from the granules intrinsic porosity and an even colour. In particular, because the aggregate material is artificially produced, it is found, in such material, a perfect stability of the mineralogical and chemical- physical characteristics that a natural grit could not ensure. The above mentioned aggregate material, that can be placed in the area of the piroxene group and of the forsterites structurally has a morphology and a texture that resembles natural rock of the basic magnetites type with, additionally, pores size and distribution that exclude a capillary water absorption. In all components the surface angularity and roughness stand out. When observed with the naked eye, the differences respect to a magmatic rock having a low tufaceous presence are limited, except for a slightly higher chromatic variation . The boiling test of such aggregate materials has not shown any tendency to disaggregation. At the microscope test the presence of free lime or magnesium (CaO or MgO) inclusions or of other components with tendency to the swelling was not noticed. The aforementioned aggregate materials have, consequently, a high volumetric stability. Tests and characteristics of the binding material The optimal binding material has been identified as a bicomponent epoxy resin "RTC" ("A:B" )=2: 1 with suitable formula of the hardener (B) for giving to the final product the characteristic of a liquid without solid charges (= without filler or quartz), low viscosity, average reactivity, high wettability: Specific weight Kg/dmc about. 1,12 Polymeric content on the total % 100 Stoichiometric ratio on the total (A:B)= 100: 50 Colourless Pot life at 23(+/-) 2°C = 14-18 minutes Hardening time in film at 23(+/-) 2°C, start minutes 100-110. Linear thermal expansion coefficient °C-1 = about. 10,5x10 " ^ Compression breaking unitary load Mpa >/= 60 Module E Mpa >/= 6,000 Bending breaking unitary load Mpa >/= 32 Cutting breaking unitary load Mpa >/= 30 Traction breaking unitary load Mpa >/= 25 Breaking elongation % >/= 15 Adhesion on els (tearing test adhesion) Mpa about. 3 Type of breakage 100% cohesion els. Laying process The laying process provides as said, to carry out the laying, on the road paving 1 to be roughened, of a binding material layer 2, that is made up of a bicomponent polymer and preferably of a bicomponent epoxy resin . Immediately after the laying of the binding material layer 2, it is carried out the laying, on such binding material layer, of an aggregate material layer 3, in granules, artificially produced for the construction of road carpets with better characteristics as said and claimed . Substantially the phases are the following: • preparation of the bottom, consisting in removing the surface signalization and in a cleaning from oils, naphtha, hydrocarbons and dust by means of the prior art; • laying of the binder by using a prearranged movable equipment according to the characteristics of Fig.6, by low pressure airless jetting means with fan 95°, in order to lay constantly about. 0,9 / 1,5 Kg per wA of binding product, according to the finishing degree of the bituminous conglomerate (open / closed); • saturation with grit having the claimed characteristics (laying of the grit on the binding product), whose granulometry of the monogranulated type is chosen in relation to the paving finishing degree, but also of the road section typology ; • suction of the exceeding grit, carried out after 5/6 hours from its laying, obviously depending on road carpet temperature and specifical characteristics of binding material and hardening component. The binding film thickness will be preferably from 0,5 to 1,5 mm. The laying temperature goes from 30 to 60° C. Machine for the preparation and cleaning of the roadbed This machine can be any of the cleaning machines for the roadbed preparation, which provide brushing means with eventual solvent and drying means, air-jet means not excluded both for drying eventual humidity and for removing any surface dust. Machine for the binder laying The machine for the laying includes a movable means made up of tanks for product heating, stirrers and computerised control of the recycled and sprayed product quantities +/ 5%. As the binding film thicknesses must be from 0,5 to 1,5 mm, the advancing speed will be calculated in proportion to the quantity of delivering. According to Figure 6 it is noticed that the machine includes two tanks of the bicomponent 4,5, both with a level meter 41,51 which convey respectively by heating means 42, 52 and pump 43, 53 operated by respective motors 431, 531, with temperature meter 44, 54 and flow-meters 45, 55 and nonreturn valves 46, 56 and recirculation electro-valves 47, 57, the two components "A, B" to a mixer 63, to which two solvents 6,7 are also simultaneously conveyed, by a common pump 61, and a nonreturn valve 62. The mixer 63 having mixed in exact proportions the components 4-A, 5-B and solvents 6-7, by jetting electro-valve 8 sends the heated mixture on the surface of the road carpet by the jetting apparatus 9. Machine for the grit application This also movable machine or train can be anyone of the prior art, both with scattered laying by a doser, and also with jet deliverer. Machine for removing the exceeding unbound grit This also movable machine or train can be anyone of the prior art, by brushes and suitable suction systems. Tests and analysis of the laying characteristics The affinity with the binders has been noticed by comparing it with that of a compact limestone, whose affinity is considered excellent on the basis of the theoretic and practical experiences. The test duration, normally fixed in 24 hours, has been increased up to 96 hours, allowing to check in the aggregates in object characteristics practically analogue to the limestone ones. The amount of faulty grains has been equal to about 10%, in the sizes > 4. From what previously described, it is clear that the invention fully reaches its purposes. In particular, it must be pointed out that the use of an artificially produced aggregate material, of the above mentioned type, allows to obtain a fully satisfactory transversal friction coefficient, as well as a high duration in time of such transversal friction coefficient and a constant roughening behaviour in the different zones that make it up. Advantageously the granular material is obtained by: - chromate melting (chromium ore); - substantial chromium elimination; - fast cooling in water for obtaining said crystallized granules

Claims: Claims 1. Laying method type in which: - on the roadbed (1) a liquid or pasty binding layer (2) is laid, substantially made up of binding resin that sticks to the road carpet surface and which subsequently hardens; - on said liquid or pasty layer (1), before the hardening, an aggregate layer in granules (3) is evenly laid, - in such a way that once said resin (2) has hardened, said aggregate material in granules (3) is strongly bound to the road carpet; - one removes the inert material in granules that is not adequately remained fixed to the roadbed; characterised in that: • said aggregate material in granules is artificially produced; • his granules are polygon-shaped with sharp corners; • the constituent material substantially includes a matrix consisting of a piroxene group and forsterite or olivine. 2. Method according to previous claim, characterised in that said constituent material is a forsterite olivine, spinel, magnesium chromate or magnesite and iron mixture in which the presence of A1203 for a value substantially included between 5% and 20% preferably around 10/11% is provided. 3. Method according to claim 1 and/or 2, characterised in that said material in granules has the following composition: Si02 40%, A1203 11%, MgO 40%, CaO 2%, Cr203 4%, Fe 1% with an oscillation ratio of the % of more or less the 30% for each of the respective components. 4. Method according to previous claims, characterised in that said granular material has a rough surface and has predominantly a cubiform shape. 5. Method according to previous claims, characterised in that said binding material is a bicomponent polymer. 6. Method according to previous claims, characterised in that said binding material is made up of a bicomponent epoxy resin that is laid with a laying temperature that goes substantially from 30 to 60° C. and with a binding film thickness substantially between 0,5 to 1,5 mm. 7. Machine for the distribution of the binding material for carrying out the treatment method of the road surface according to any of the previous claims, characterised in that it when is on a movable means includes two tanks of the bicomponent (4,5), both with level meter (41,51) that convey respectively by heating means (42, 52) and pump (43, 53) operated by respective motors (431, 531), with temperature measurer (44, 54) and flow-meters (45, 55) and non return valves (46, 56) and recirculation electro-valves (47, 57), the two components "A, B" to a mixer (63), to which two solvents are also simultaneously conveyed (6,7), by a common pump (61), and nonreturn valve (62); and in which said mixer (63) having mixed the components (4-A, 5-B) and the solvents (6-7) in exact proportions, by a jetting electro-valve (8) sends the heated mixture on the surface of the road carpet by the jetting apparatus (9). 8. Material in granules to be laid as non-skid material by means of a binder (2) on the road surface, according to the method of any of the previous claims, characterised in that: • said aggregate material in granules is artificially produced; • its granules are polygon shaped with sharp corners; • the constituent material includes spinel in a matrix composed of a piroxene group and forsterite. 9. Material in granules to be laid as non-skid material by means of a binder (2) on the road surface, according to previous claim, characterised in that it is a mixture of fosterite, spinel, magnesium chromate and iron in which the presence of A1203 for a value included between 5% and 20% preferably about 10/11% is provided. 10. Material in granules to be laid as non-skid material by means of a binder (2) on the road surface, according to previous claim, characterised in that it has the following composition: Si02 40%, A1203 11%, MgO 40%, CaO 2%, Cr203 4%, Fe 1% with an oscillation ratio of the % of more or less 30% for each of the respective components. 11. Material in granules to be laid as non-skid material by means of a binder (2) on the road surface, according to any one of the claims 8,10, characterised in that the respective granules are mainly cubiform. 12. Material in granules to be laid as non-skid material by means of a binder (2) on the road surface, according to any of the claims from 8, to 11 , characterised in that the respective granules have a rough surface. 13. Material in granules to be laid as non-skid material by means of a binder (2) on the road surface, according to any one of the claims from 8, to 11, characterised in that: • it is a product derived from the melting of a chromium ore, in particular chromite, • the chromium is substantially extracted from the melted mass; • the melted mass is rapidly solidified by casting in water for obtaining a loose crystallized material in granules. 14. Carpet for the surface coating of the road pavings obtained with the method and materials as in previous claims, characterised in that the same is made up of a binding material and of an aggregate material layer, in granules, made up of an artificially produced aggregate material mixture, made up of forsterite and/or of spinel and/or of magnesium chromate and/or of iron, in which, the obtained surface is full of polygon-shaped granules with the respective sharp corners directed towards the top, being the base bound to the road carpet by a binding material 15. Carpet for road pavings, according to previous claim, characterised in that the same is made up of a binding material layer made up of a bicomponent polymer based on an epoxy resin.

Inventors: SPINOGLIO SILVIO, SPINOGLIO, SILVIO
Applicants: ITALGRIP S R L, SPINOGLIO SILVIO, ITALGRIP S.R.L., SPINOGLIO, SILVIO
Application year: 1997
Main classification: E01C7
IPC codes: C04B41, E01C7, E01C19