The present invention belongs to the sector of road building, and specifically the so-called "white" or unsurfaced roads, i.e. roads without road paving and in particular without asphalt covering.
More specifically, the invention belongs to the sector of unsurfaced roads mainly made from earthy materials.
Present status of the art
Different types of unsurfaced roads are known; in order for them not to be extremely muddy, they are covered with a rather stony material, in order to foster the rolling of wheels, thus preventing them from sinking into the soil.
Unsurfaced roads are often obtained by using materials directly taken from the crossed soil. Unsurfaced roads can be suitable for transit of vehicles or for pedestrian transit only and, possibly, transit small vehicles, depending on their characteristics.
Should a soil crossed by an unsurfaced road not provide any types of materials suitable for building, or should a road be requested with a harder surface, other materials, such as gravel and/or quarry rubble, are added to the material available in situ, quarry rubble being a calcareous material of various granulometries which is obtained from crushing rocks.
After being built, a good unsurfaced road should remain flat and draining for a time as long as possible, while preventing formation of puddles in the case of rain and also preventing water from running off, the latter being the main cause of surface disconnection for roads.
Also, an unsurfaced road should prevent formation of vegetation as much as possible.
Unsurfaced roads are common in rural areas in many countries, they are often narrow and little used, but they are also found in metropolitan areas of many developing countries, where they are also possibly used as important communication routes and have substantial widths.
The solutions according to the present status of the art feature a number of drawbacks, mainly related to the fact that often no rocking material is available locally, in which case it is necessary to select whether to build a dirt road very subject to being washed away, or to transport the necessary stony materials to the site, which results in often unaffordable costs.
Objects and summary of the invention
A first object of the present invention is thus to provide a machine and a method for building unsurfaced roads by using materials available in situ, even though of a mostly earthy type, without any supply of external materials additional to those available in the area to be treated.
A second object of the invention is to provide a machine and a method for building unsurfaced roads without altering the original level of the soil.
A further object of the invention is to build unsurfaced roads that do not alter the environmental temperatures and whose surface allows for a quick heat dispersion, even after a long exposure to solar radiation.
A not least object of the present invention is to build such unsurfaced roads as not to scatter their materials outside the treated surface, even in the case of heavy rains, as preferable for roads close to streams, watercourses, cultivated grounds, pastures, and the like.
A not less important object of the present invention is to realize unsurfaced roads that are also draining and whose color is the natural one of the soil that is crossed.
The scope of the present patent application aims at earthy surface stabilization and consolidation interventions, for a variety of uses and destinations, without any mild for supplying the present surfaces to be treated with any foreign soils, so as not to modify the original composition and color, with a goal of keeping the visual differences with respect to the pre- and post-treating surfaces down to minimum levels, while also minimizing planimetric-altimetric variations.
In other words, this invention consists of a machine and a method for quickly realizing unsurfaced roads or squares in one operating cycle, by properly treating the material of the soil to be crossed and adding an appropriate binder thereto. This machine performs an in situ mixing of the material being part of the surface area and of the directly treatable volumes, with a hydraulic binder and a non-toxic liquid aggregator, without any supply of other materials of different origins and natures.
According to the specified operating process, already existing beds, which are either made from soil, soil mixed with gravel or a natural rubble as for the most common rural white roads, are treated in situ. Generally, this operating process does not need any supply of an aggregate or soil from the outside, thus eliminating most of the pollution caused by the noxious gases emitted by the construction machinery and the on-track machines into the atmosphere.
A peculiarity of this treatment, which distinguishes it from any other similar treatments, is in that it uses a non-powdered, but rather liquid aggregator which, once high-pressure injected, is kneaded and mixed with the soil to be treated, together with hydraulic binders, thus preventing any risk of releasing such products into the environment.
Such peculiarity allows not only to make a better mixing in one step while the on-track machine passes through, but also to performs such treatment very safely even in areas where spaces are limited and do not allow external mixing operations. The component parts of the aggregator are not hazardous and are diluted in water up to reaching the correct percentages of use; the mixture thus obtained in a laboratory in the form of a concentrate is subsequently further diluted in a dedicated tank of the machine, in ideal proportions of approximately thirty liters per one thousand liters of water.
Other objects and advantages of the invention will be apparent to those skilled in the art upon reading the following text.
The above-described objects are achieved by a machine comprising a front spreader, a sprinkler and a rear milling machine driven by a self-propelled tractor.
Advantageously is the sprinkler preferably placed in an intermediate position between the spreader and the milling machine and comprises a tank, a pump, and high-pressure nozzles directed towards the soil.
According to an advantageous and practical embodiment, the spreader comprises an upper portion which contains a hydraulic binder and a lower portion which spreads the hydraulic binder all over the full width of the machine.
According to an advantageous and practical embodiment, the sprinkler comprises a tank which contains water with a liquid aggregator, also called chemical binder, added thereto, and a plurality of nozzles which high-pressure sprinkle the mixture of water and liquid aggregator on the soil; sprinkling takes place thanks to a pump and covers the whole width of the machine.
The milling machine raises and processes the soil and homogeneously mixes the hydraulic binder and the liquid aggregator therewith.
Typically is the milling machine comprised of a frame equipped with a rotary shaft, in which operating members, also called knives, are inserted. Usually a metal sheet or guard is present in the rear part of the machine to prevent clods of the soil turned over by the knives being thrown away.
The milling machine is used to cut up and process the soil by mixing it with the hydraulic binder and the liquid aggregator; usually, the milling machine is moved by the tractor and its rotary shaft is driven by the power take-off of the tractor.
After an appropriate time interval, often lasting approximately one hour, which is necessary to let the aqueous mixture with the liquid aggregator react with the hydraulic binder, the processing is completed by a road roller which passes on and compresses the soil previously treated by the machine according to the present patent application.
The hydraulic binder is selected as a function of the type of soil on which the unsurfaced road is to be realized; usually a Portland 325 cement is used, whereas a Portland 425 cement is used in the case of a particularly incoherent soil, containing much humus or featuring high humidity, in that the Portland 425 cement features a greater aggregation force, but it shall be used with caution because its use results in an increased risk that cracks form in the finished road.
It is also possible to use Pozzolana cement or lime or even a mixture thereof; a high degree of impermeability of the final product can be achieved by properly selecting the hydraulic binder.
The main types of soil that can be treated are basically the following.
Medium soil, like those of already existing white roads, with the presence of stones and inert materials in addition to soil; the analyses and tests made demonstrated that in this case that the wear resistance of a road substantially increases up to levels comparable to those of a road having an asphalt surface, while featuring a greater draining effectiveness.
Soils with a strong presence of stones and rubble; in this case wear resistance substantially increases, thus rendering a road extremely wear resistant.
Soils with a prevailing presence of lime and without stones or inert materials; in these cases, it might be necessary to add a small percentage of sand and inert materials to the hydraulic binder.
Note in this regard that, even though using a spreader is comfortable and functional, the machine according to the present patent application can also operates without it, provided bags of hydraulic binder are previously spread on the soil, along the layout of the road to be built.
According to a preferred embodiment, the liquid aggregator, which is dissolved in water before being sprinkled on the layout of the road to be built, consists of an aqueous solution of a mixture of powdered sodium silicate and sodium hydroxide.
The liquid aggregator might also be dissolved in salt water by properly correcting its acidity and decreasing its sodium content. This solution is of a special interest in building underground barriers for countering the erosion of see coasts; in this case, the milling width is reduced down to few tens of centimeters, whereas its depth increases up to beyond one meter or one meter and half.
In one particularly convenient and functional embodiment, the machine according to the present patent application is capable of sprinkling water, or a mixture of water and liquid aggregator, even in front of the spreader, both in order to decrease dust and to soften soil; this preliminary sprinkling reduces the risk that the hydraulic binder be transported outside the layout in the presence of wind.
In a particularly high performing solution, the machine is capable of sprinkling the mixture of water and liquid aggregator even inside the milling machine, in particular by directing jets inside the crushing area. In order to facilitate this function, the invention possibly comprises an auxiliary tank, usually placed above the milling machine.
According to a first embodiment, the liquid aggregator is comprised of an aqueous solution obtained by dissolving a mixture of powdered materials, composed of one third of sodium hydroxide and two thirds of sodium silicate, in water.
In order to get better performances, especially on soils featuring a high content of humus and high ionic impurities, it is advisable to adopt a mixture of powdered materials indicatively formed of 40% of powdered sodium silicate, 20% of sodium hydroxide, 10% of sodium tripolyphosphate, and 30% of potassium chloride; these percentages might undergo small variations in the order of 10%, preferably in the order of 5%.
In order to prepare the liquid aggregator, said mixture of powdered materials is dissolved in water; the weight of the water can vary in a range from a minimum value equal to approximately the weight of the quantity of the powdered mixture to be dissolved up to a weight approximately twice the weight of the powdered mixture, depending on the actual requirements.
Particularly advantageous dilution ratios are 1:1 or 1:1.2, but they could reach values up to 1:2.
The liquid aggregator is in turn dissolved in water in a percentage ranging from 2% to 6%, preferably from 3% to 5%, and usually 100 liters of a mixture of water and liquid aggregator are used to treat approximately one cubic meter of mixture of soil and hydraulic binder.
The percentages indicated above are those which offer best results in most cases, but slightly different percentages also offer good results.
Brief description of the drawings
Figure 1 shows a side view of the machine according to the present patent application, including a spreader (1), a spryer (2), a self-propelled tractor (4), and a rear milling machine (3), an auxiliary tank (32) and a cutting assembly (31) being visible on the latter.
The sprinkler (2) comprises a tank (21) and high-pressure nozzles (22).
Figure 2 shows a top view of the same machine, this view making it possible to highlight that the tractor, which tows the other elements of the machine, is a remotely controlled one, without a driver's cab.
Detailed description of an embodiment of the invention
In accordance with a particularly advantageous embodiment, the machine according to the present patent application comprises a self-propelled tractor (4) with a front spreader (1) for spreading a hydraulic binder, behind which there is a sprinkler (2) with a tank (21) and high-pressure nozzles (22); the tractor (4), often of a remotely controlled type, tows and drives a milling machine (3); in a particularly appreciated solution, the tractor is remotely controlled by an operator who remains on the ground, which makes it possible to safely use the machine even in areas that are difficult to access or feature big slopes.
Good results were obtained by means of high-pressure nozzles with an operating pressure between 4 MPa and 7 MPa, preferably between 5 MPa and 6,1 MPa.
According to a preferred embodiment, the hydraulic binder spreader (1) comprises a calibration system for adjusting the percentage of the aggregator, as a function of the geological characteristics of the soil in situ and of the carrying capacity and resistance to be achieved.
The milling machine comprises an auxiliary tank (32) placed above the cutting assembly (31), wherein the auxiliary tank in also capable of injecting the mixture of water and liquid aggregator and preferably directing it towards the crushing area of the cutting assembly (31) by way of high-pressure nozzles.
According to a particularly complete embodiment, the machine according to the present patent application comprises a priming pump for directly taking water in from canals or streams.
The liquid aggregator is an aqueous solution which comprises a mass percentage, of powdered sodium silicate ranging from 10% to 35%, as referred to the mass of the whole solution (%m/m) besides a percentage (%m/m) of powdered sodium hydroxide ranging from 5% to 20%.
In particular, when the mixture of powders comprises sodium silicate and sodium hydroxide only, their respective percentages range from 20% to 35% and from 10% to 20% for sodium silicate and sodium hydroxide respectively, depending on whether the mixture of powders is dissolved in a quantity of water equal to the weight of the mixture or in a quantity of water equal to twice the weight of the mixture. In general, a ratio of 1/3 of sodium hydroxide and 2/3 of sodium silicate is optimum for a mixture formed of two components only.
Whenever the mixture of powders also comprises sodium tripolyphosphate and potassium chloride, the indicative percentages (also in %m/m) are the following: sodium silicate: 40%, sodium hydroxide: 20%, sodium tripolyphosphate: 10%, potassium chloride: 30%.
The minimum concentration is obtained when the mixture of powders is dissolved in a quantity of water equal to twice its weight, in that case the weight percentages of the individual components are one third of those indicated above; should the mixture be dissolved in a quantity of water equal to its weight, the weight percentages of the individual components are half those indicated above.
For example, the percentage (%m/m) of powdered sodium silicate ranges from 10% to 25%, that of sodium hydroxide ranges from 5% to 12%, that of sodium tripolyphosphate ranges from 2% to 6%, and that of potassium chloride ranges from 7% to 18%.
The hydraulic binder dispenser shall include a calibration system in order to allow a different mix, if necessary to achieve special values of carrying capacity and resistance, as a function of the geological characteristics of the soil in situ.
A typical speed of forward movement of the machine is in the order of 5 meters per minute, the width of the layout is variable, in the order of a couple of meters or more, the milling depth is also variable and, for a road, it usually ranges from 10 to 40 centimeters, preferably from 15 to 30 centimeters.
The machine of the present invention can be used for tracking unsurfaced roads, in a practical embodiment the method comprises the following steps:
- a) spreading a hydraulic binder on the ground along the layout of the road;
- b) sprinkling the layout with an aqueous solution that contains a percentage of the liquid aggregator ranging from 2% to 6%;
- c) milling the ground of the layout to a depth ranging from 0.10 to 0.50 meters;
- d) making time elapse as necessary to make the liquid aggregator and the hydraulic binder become effective, then compressing the thus obtained layout by way of a road roller.
Advantageously said auxiliary tank (32) contains an aqueous solution of the liquid aggregator, which is high-pressure sprinkled in the crushing area of the cutting assembly (31) of said milling machine (3).
Preferably said hydraulic binder is Portland cement or Pozzolana cement or lime, or a mixture of these last two products.
The machine of the present invention can be used for building underground barriers to counter erosion of beaches, in a practical embodiment the method comprises the following steps:
- a) spreading a hydraulic binder on the ground along the layout of the underground barrier;
- b) sprinkling the layout with an aqueous solution containing a percentage of the liquid aggregator ranging from 2% to 6%;
- c) milling the ground of the layout to a depth ranging from 1.00 to 1.50 meters and a width ranging from 0.30 to 0.80 meters.
A machine for building unsurfaced roads comprising a self-propelled tractor (4) which tows and drives a milling machine (3), comprising a cutting assembly (31), characterized in that
- a sprinkler (2) installed in front of said milling machine (3) and comprising a tank (21), suitable for containing a mixture comprising water and a liquid aggregator, a pump and high-pressure nozzles (22), said high-pressure nozzles being directed towards the soil;
- a spreader (1), suitable for spreading at least one hydraulic binder, installed in a front position with respect to that of said milling machine (3);
wherein said self-propelled tractor (4) tows said sprinkler (2) and said spreader (1).
2. The machine according to claim 1 characterized in that said milling machine (3) comprises an auxiliary tank (32) suitable for containing a mixture comprising water and a liquid aggregator with high-pressure nozzles suitable for directing a jet inside the crushing area of said cutting assembly (31).
3. The machine according to claim 1 or 2 characterized in that said high-pressure nozzles (22) of said sprinkler (2) have an operating pressure between 5 MPa and 6,1 MPa.
4. A liquid aggregator for use with the machine according to any of the previous claims, characterized in that it comprises an aqueous solution of a mixture that comprises a percentage of powdered sodium silicate ranging from 10% to 35% and a percentage of sodium hydroxide ranging from 5% to 20%.
5. The liquid aggregator according to claim 4 characterized in that it comprises a percentage of powdered sodium hydroxide ranging from 10% to 25%, a percentage of sodium hydroxide ranging from 5% to 12%, a percentage of sodium tripolyphosphate ranging from 2% to 6%, and a percentage of potassium chloride ranging from 7% and 18%.
A method for tracking unsurfaced roads by using the machine according to claim 1 or 2 or 3, characterized in that
it comprises the following steps:
a) spreading a hydraulic binder on the ground along the layout of the road;
b) sprinkling the layout with an aqueous solution that contains a percentage of the liquid aggregator according to either claim 4 or 5 ranging from 2% to 6%;
c) milling the ground of the layout to a depth ranging from 0.10 to 0.50 meters;
d) making time elapse as necessary to make the liquid aggregator and the hydraulic binder become effective, then compressing the thus obtained layout by way of a road roller.
7. The method according to claim 6 with the use of the machine according to claim 2, characterized in that said auxiliary tank (32) contains an aqueous solution of the liquid aggregator according to either claim 4 or 5, which is high-pressure sprinkled in the crushing area of the cutting assembly (31) of said milling machine (3).
8. The method according to claim 6 or 7 characterized in that said hydraulic binder is Portland cement.
9. The method according to claim 6 or 7 characterized in that said hydraulic binder is Pozzolana cement, lime, or a mixture of these products.
A method for building underground barriers to counter erosion of beaches by using the machine according to either claim 1 or 2 or 3, characterized in that
it comprises the following steps:
a) spreading a hydraulic binder on the ground along the layout of the underground barrier;
b) sprinkling the layout with an aqueous solution containing a percentage of the liquid aggregator according to either claim 4 or 5 ranging from 2% to 6%;
c) milling the ground of the layout to a depth ranging from 1.00 to 1.50 meters and a width ranging from 0.30 to 0.80 meters.