RU2502760C2 - Method of producing asphalt mixture - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method is carried out by first feeding into a mixer (15) a dry aggregate which includes rock material essentially not containing filler. A foamed mixture of binding substances is then fed into the mixer (15) containing the dry aggregate. The mixture of binding substances is foamed when exiting the pre-foaming chamber (12) and then fed into the mixer (15). Said aggregate and foamed mixture of binding substances are then mixed. The mixture of binding substances includes a binding substance, an adhesion enhancing additive and a foaming agent, and the binding substance consists of bitumen. Further, the filler (6) is fed into the mixer (15), after which final mixing of the asphalt mixture is carried out. The method enables to obtain a hot asphalt mixture, having properties that are similar or better than those of the conventional hot asphalt mixture. Less smoke and foul smells are released when carrying out the method.

EFFECT: obtained asphalt mixture is easier to process, with respect to both production and application.

17 cl, 2 dwg

Description

Technical field

In General, the present invention relates to a method and mixer for producing an asphalt mixture intended for subsequent intermediate storage and subsequent laying in the form of a pavement or similar application. In particular, the present invention relates to a method and mixer for producing a so-called hot asphalt mix.

State of the art

In general, asphalt is a mixture of stone raw materials / aggregate and a binder, which is used to obtain the top layer of the pavement, the binder of the pavement and / or the main layer of the pavement, for example, in the construction of roads, airports, parking lots, etc. The traditional way of producing the so-called hot asphalt mix involves heating the aggregate to about 160 ° C, after which the entire aggregate is placed in a mixer, to which the heated binder is added in liquid form. After that, the asphalt mixture is mixed at a technological temperature of approximately 160 ° C until the final consistency and is sent for intermediate storage and subsequent laying. In general, traditionally, hot asphalt mix has improved characteristics compared to earlier attempts to obtain a warm asphalt mix (production temperature is approximately 70-120 ° C) and the so-called cold asphalt mix (production temperature is below 70 ° C); nevertheless, to obtain a hot asphalt mix, a large energy consumption is required and, in addition, a large amount of nitrogen oxides and carbon dioxide is released during its preparation and laying, which leads to dangerous consequences for the environment and to a deterioration of the working atmosphere for personnel laying asphalt.

Thus, for some time, efforts were aimed at reducing the temperature of obtaining hot asphalt mixture to a certain minimum without reducing the quality of the paved asphalt, and thus, efforts were also directed at obtaining a hot asphalt mixture having characteristics similar to those of traditional hot asphalt mix manufactured at approximately 160 ° C.

Patent publication EP 1398351 B1 describes a method for producing a warm and hot asphalt mixture, in which the entire aggregate is loaded into a mixer, a foaming agent, which is a polymerized fatty acid, is added to the heated bitumen, after which the resulting binder mixture is added to the aggregate in the form of a foam. US 2005/0018530 A1 describes a process for producing asphalt mixtures in the lower temperature range of a hot asphalt mixture, according to which aggregate is added to the asphalt mixture in two portions. In particular, the first portion of the Dried aggregate, essentially free of fine material, is loaded into the mixer, after which the mixture is heated and liquid bitumen is added; then a wet aggregate containing water, sand and fine material is loaded into the mixer, after which the bitumen is allowed to expand. However, asphalt mixtures obtained in accordance with the considered methods have their drawbacks. The most serious drawback is that the filler specified in EP publication and the fine material specified in US publication absorb a large amount of bitumen / bitumen mixture, since the filler is contained in the asphalt mixture during foaming / expansion of the bitumen / bitumen mixture. When laying such asphalt mixture on the road, a proportionally smaller amount of bitumen / bitumen mixture will bind to the aggregate stone, and a proportionally larger amount of bitumen / bitumen mixture will bind to fine material or aggregate. When using paved asphalt, the bitumen / bitumen mix associated with fine material or aggregate will be at increased risk of rapid removal from the asphalt. Thus, the above methods do not provide a hot asphalt mixture having characteristics similar to those of a traditional hot asphalt mixture, for example, with regard to durability, adhesive properties, etc.

Objectives of the invention

The objectives of the present invention are to eliminate the above disadvantages and problems associated with known methods for producing asphalt mixtures, and provide an improved method. The main objective of the present invention is to provide an improved method for producing an asphalt mixture, discussed above, which includes obtaining an asphalt mixture in the lower temperature range of a hot asphalt mixture having characteristics similar or improved compared to the characteristics of a traditional hot asphalt mixture, for example, increased durability, adhesive properties, lack of cavities, rigidity / impact resistance, etc. paved asphalt.

Another objective of the present invention is to provide a method in which less smoke and unpleasant odors are released by reducing dust emissions.

Another objective of the present invention is to provide a method that is less harmful to the environment and can improve the working area for personnel by reducing energy consumption and reducing emissions of carbon dioxide and nitrogen oxides.

Another objective of the present invention is to provide a method for obtaining an asphalt mixture, easier to handle, both in relation to receipt, and in relation to laying.

According to the invention, at least the main problem is solved by applying the described method, which is characterized in that it includes the following operations: loading into the mixer the dried aggregate, including stone raw materials, essentially not containing filler; then loading the foamed binder mixture into a mixer that contains dried aggregate; the mixture of binders foams upon exiting the pre-foaming chamber and is loaded into the mixer; after which the indicated aggregate and the foamed binder mixture are mixed, and then the filler is loaded into the mixer; then perform the final mixing of the asphalt mixture.

Thus, the present invention is based on the fact that in the manufacture of asphalt from an asphalt mixture, it is important that the binder mixture binds to the aggregate stone in layers / coatings having a significant thickness, even before the filler has a high absorbency in the asphalt mixture.

Preferred embodiments of the present invention are further defined in the dependent claims.

Preferably, the binder mixture includes bitumen, a fatty acid adhesion improver, and a water blowing agent to provide a strong and long lasting foam, which results in an easy to process asphalt mixture that binds to the aggregate stone to form layers of significant thickness before adding filler.

Other advantages and features of the invention are discussed in other dependent claims, as well as in the description of preferred embodiments of the invention set forth below.

Brief Description of the Drawings

A more complete understanding of the above and other advantages and features of the present invention can be obtained after considering the other dependent claims, as well as the description of the preferred embodiments below, accompanied by the accompanying drawings.

Figure 1 schematically shows a side view of the mixer according to the invention, as well as some parts of the installation for mixing asphalt.

In FIG. 2, a schematic enlarged view of a top view of the mixer of FIG. 1 is shown.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

First, turn to Figure 1.

The asphalt mixture for the most part consists of aggregate 1, or stone raw materials, usually constituting at least 80% by weight, preferably about 90% by weight, of the total weight of the asphalt mixture.

The aggregate can additionally be divided into different fractions or size classes, partially into fractions, including filler, sand and stone, for example, 0-2, 0-4, 0-8, 0-11, 0-16 and 0-22, partially into fractions that essentially include only sand and Stone, for example, 4-8, 8-11, 11-16 and 16-22. The numbers indicated are the hole sizes, expressed in millimeters, the holes in the sieve through which the aggregate particles pass and through which the aggregate particles do not pass, respectively. The amount of aggregate of the corresponding fraction is mainly determined by the end use of a particular asphalt mix, i.e. place and use of ready paved asphalt. In a conventional asphalt mix, approximately half of the aggregate is fractions comprising a filler, for example, 0-4 and 0-8, and the remainder are fractions substantially free of filler, for example, 4-8, 8-11 and 11-16.

Each fraction of aggregate 1 is stored in a special bin 2 for the source material, two of which are shown in the figures. At the beginning of the manufacture of a new batch of asphalt mix, a predetermined amount of aggregate 1 is loaded from the corresponding bin 2 for the source material onto a conveyor belt or similar device by which the aggregate is sent to the dryer 3. In the shown embodiment of the invention, the dryer 3 is a counter-current rotary dryer having a slight downward slope, which, while in operation, rotates. The aggregate 1 is loaded into the first upper end part of the dryer 3, and it spontaneously unloads from its second lower end part, due to the rotation of the countercurrent rotary dryer. In dryer 3, aggregate 1 is heated to a temperature of 100 to 130 ° C, preferably about 120 ° C, whereby aggregate 1 is dried.

In dryer 3, along with other influences, aggregate 1 is "scattered" in the form of a curtain of material through a heat stream generated by the heat source located in dryer 3. In the curtain of aggregate, moisture and flue gas are separated from aggregate 1, which leave dryer 3 through a chimney 4 located in the first upper end part of the dryer 3. A separator 5 including a filter (not shown) is located throughout the chimney 4. Filler 6 is collected in the separator 5, which is sent to the hopper 7 for the filler, and the moisture and flue gases are filtered and sent to the atmosphere through the chimney 8. In addition, the filler, essentially free of filler, is additionally heated until the above temperature is reached.

The heated aggregate, consisting of raw stone material substantially free of aggregate, is then transported via an elevator 9 or similar device to the aggregate hopper 10. The aggregate hopper 10 may have a design that allows the heated aggregate to be divided again into different fractions, i.e. place it in different sections of the aggregate hopper 10, as shown in FIG. 1, or the hopper may have a structure including only one section. The design of the aggregate hopper 10 allows the aggregate to be sieved through a series of sieves with a gradually decreasing hole diameter, so that particles of a certain size pass through one sieve, but do not pass through the next, and then they are sent to the section of the aggregate hopper 10, intended for particles of appropriate size or fraction. Thus, the smallest fraction is collected in the leftmost section of the aggregate hopper 10 shown in FIG. 1, and the largest fraction is collected in the leftmost section of the aggregate hopper 10 shown in FIG. 1. Filler 6 is typically represented by particles less than 0.063 millimeters in size; however, the method according to the invention allows the inclusion in the filler 6 and larger particles, for example, less than 0.08 mm. In addition, sand and stone represent that part of the aggregate, the particle sizes of which exceed the particle size of the filler and are usually less than 22 millimeters, and which is called stone above. It should be noted that for the implementation of the invention, it is particularly important that the filler 6 preferably includes dust that is separated from the filler 1 during heating / drying.

The second essential component of the asphalt mix is a mixture of binders that binds the aggregate in the finished asphalt. The amount of the binder mixture in the asphalt mixture, as well as the amount of aggregate 1, depends on the intended use of the finished asphalt and ranges from 3 to 10% by weight, preferably about 5-7% by weight. from the total mass of asphalt mix.

According to a preferred embodiment of the invention, the binder mixture comprises a binder, a bonding agent, and a blowing agent.

Obtaining a mixture of binders includes the following operations: transporting the binder through a pipe 11 in the chamber 12 pre-foaming. Then, the adhesion improver is added to the binder via a conduit 13 connected to the binder conduit 11, after which the mixture of the binder and the adhesion improver is charged into the pre-foaming chamber 12. Then, the blowing agent is directly loaded into the pre-foaming chamber 12 through a conduit 14, where a binder and adhesion improver are mixed. The binder is heated to a temperature of 130 to 200 ° C, preferably 180 ° C, and then mixed with the adhesion improver in the pipe 11. The adhesion improver and the blowing agent can preferably have the same temperature as the environment , which facilitates their processing.

The binder preferably contains bitumen, which, for example, can be extracted from crude oil or natural bitumen, or can be obtained by any other method known in the art, or can consist of a mixture of bitumen. Preferably, instead of emulsion binder and viscosity regulating binder, which are traditionally used to produce cold and warm asphalt, respectively, penetration bitumen is used.

One of the classification parameters of bitumen or bitumen of various types or compounds of bitumen is the so-called penetration. As noted above, bitumens of various classes are used for different purposes and types of application in combination with various aggregate mixtures. The penetration number of bitumen for a particular type of bitumen is measured by inserting a needle into the test sample of bitumen with a certain pressure for a certain period of time at a certain temperature and measuring the penetration depth of the needle in tenths of a millimeter, dmm. Bitumen is usually used, the penetration number of which is from 50 to 430 dmm. Often used grade of bitumen has a penetration number of bitumen of 160-220 dmm.

The adhesion improver that is added to the binder mixture is at least 0.6% by weight. from the total mass of the mixture of binders and includes a fatty acid, for example, fatty acid of fir oil. Foaming agent added to the mixture of binders, is from 1 to 10 wt. -%, preferably 4-5% of the mass. from the total mass of the mixture of binders.

Now, in accordance with the description of the method for producing an asphalt mixture according to the invention, we turn to Figure 2.

The method according to the invention includes the following operations: loading into the mixer 15 aggregate, including stone raw materials and essentially not containing filler. The aggregate, for example, is composed of predetermined amounts of each fraction of aggregate, which are stored in the aggregate hopper 10 between processing operations, after which the aggregate is dry mixed to form a homogeneous aggregate mixture. According to one embodiment of the invention, dry mixing is performed for three seconds. Then, the foamed binder mixture is loaded into the mixer 15, where the aggregate and the foamed binder mixture are mixed, obtaining layers of a binder mixture having a significant thickness on each stone / particle aggregate. According to one embodiment of the invention, the loading of the foamed binder mixture and its mixing with the aggregate is carried out for four seconds. Then, filler 6 is loaded into the mixer, after which the final mixing of the asphalt mixture is performed to obtain a homogeneous asphalt mixture. According to one embodiment of the invention, the loading of the filler 6 is carried out within 2 seconds, the final wet mixing is performed within sixteen seconds. The above time intervals are examples of processing a batch of asphalt mix obtained in the mixer 15, designed for 2.5-5 tons of asphalt mix. The processing temperature in the mixer during the manufacture of the mixture is preferably from 100 to 120 ° C, more preferably approximately 110 ° C. It should be noted that this method leads to the production of a hot asphalt mix, and, in accordance with the currently accepted definitions, the temperatures used are at the boundary of the production of warm and hot asphalt mix.

Figure 1 shows that under the aggregate hopper 10 there is a weighing device 10a for the aggregate, which determines the number of respective fractions of the aggregate loaded into the mixer 15.

When the pre-foaming chamber 12 is present, the binder mixture is in a liquid state. When loading a mixture of binders into the mixer 15, it is sprayed under pressure through the nozzle 16 into the mixer 15, for example, under a pressure of 3-6 bar (3 · 10 ⁵ -6 · 10 ⁵ Pa). When the binder mixture reaches atmospheric pressure, at which the mixer for the asphalt mixture usually works, the binder mixture expands by about 20 times, respectively, creating a foam that settles over time, as the blowing agent evaporates. The binder mixture preferably remains, at least partially, foamed for most of the mixing time.

A foamed binder mixture has several advantages over liquid binder mixtures because it temporarily increases volume and decreases viscosity, which facilitates mixing of the binder mixture with the aggregate and provides a more uniform distribution of the aggregate. This allows an improved filler coating to be obtained with a mixture of binders with lower energy consumption. In particular, in accordance with the method according to the invention, the binder is converted into foam by adding a blowing agent. The blowing agent may be any material or mixture of materials that is capable of foaming a heated binder. The ability of the blowing agent to expand when heated above its boiling point is a very important property; the blowing agent preferably consists of water. The proportion of blowing agent in the mixture of binders decreases / it evaporates during the production and laying of asphalt, and after the completion of laying, a satisfactory pavement is obtained directly, which does not need additional curing. However, it should be noted that the finished asphalt can include and does include some blowing agent.

The purpose of the adhesion improver is primarily to separate the blowing agent from the aggregate stone in order to obtain better adhesion / adhesion between the binder and the aggregate.

Thus, it was shown that the additive that improves adhesion also provides a longer period of time before the start of shrinkage of the foam formed by the mixture of binders. In addition, the adhesion improving additive has a lubricating effect on the asphalt mixture, both during its manufacture in the mixer 15 and during the laying of the asphalt mixture. Thus, thanks to the adhesion improver and the blowing agent, the asphalt mix acquires good technological characteristics, i.e. ease of tamping after installation, despite the fact that the installation temperature is less than 100 ° C, preferably from 80 to 100 ° C.

Filler 6, which is added to the asphalt mixture after adding a foamed mixture of binders, is preferably from 3 to 8% of the mass. from the total mass of asphalt mix. The filler 6, loaded into the mixer 15 during the manufacture of the mixture, at least partially consists of the same material as the filler, usually granite or a similar material, and may also include another material. For example, when using the so-called stone-rich aggregate, from which a small amount of filler can be separated during the heating operation, it may be necessary to add some limestone filler to the filler 6, which is loaded into the mixer 15. The limestone filler can traditionally be no more than 50% of the filler 6, loaded into the mixer 15. Other additives introduced into the filler 6, loaded into the mixer 15, may be a cellulosic filler, which ory is preferably not more than 1% by weight. from the total mass of asphalt mix.

The advantage of adding filler 6 after mixing the foamed mixture of binders and the filler, essentially not containing filler, is to obtain significant thicknesses of the layers / coatings of binder on each stone, after which filler 6 enters these layers and absorbs part of the binder mixture, not associated with a placeholder stone. This allows you to get a dense asphalt coating, inside of which rainwater does not penetrate, which breaks the asphalt or leaches the binder. A method of manufacturing an asphalt mixture according to the invention provides the production of compacted asphalt with a cavity content of approximately 3%.

Another advantage of the present invention is that, as shown, when adding recycled asphalt to the manufactured asphalt mixture, it is not necessary, unlike usual practice, to increase the processing temperature in the mixer 15.

In the mixer 15 according to the invention, there is at least one mixer shaft 17 on which the blades or vanes 18 are mounted. Preferably, the mixer 15 according to the invention includes two parallel interacting shaft 17 of the mixer, rotating independently and mounted in a holder 19 located in the mixer 15 which can rotate in opposite directions. In particular, the mixer shafts 17 rotate in such a way that the asphalt mix is mixed in from the outside inward and from top to bottom. Each mixer shaft 17 preferably includes eight blades 18 arranged in pairs, and the blades 18 of each pair are located diametrically opposite to each other on the mixer shaft 17. Each of the shafts 17 of the mixer is located at such a level in the holder 19, that most of the volume of the processed asphalt mixture is higher and not lower than the shaft 17 of the mixer. For this, the blades 18 have an active bearing surface 20, the axial length of which in the transverse direction to the shaft 17 of the mixer is 1.5-4 times its width. Each of the bearing surfaces 20 is preferably radially outward from the mixer shaft 17 and preferably has the same cross-sectional shape along its entire length. As shown in FIG. 2, a bearing surface having the indicated cross section preferably includes a flat portion that is substantially parallel to the mixer shaft 17 and a portion curved in the opposite direction of rotation R of the mixer shaft 17. Thus, the free outer edge of each blade 18 is curved in the form of a scapula. Unlike prior art mixers that simply “knead” the asphalt mixture, the mixer according to the invention “lifts and spins” the asphalt mixture.

Possible modifications of the invention

The invention is not limited to the embodiments described above and shown in the images, which are for illustrative purposes only. The present patent application includes all modifications and variations of the preferred embodiments described herein, and thus, the present invention is limited by the appended claims and their equivalents. Thus, the Equipment may be subjected to any modification if it is included in the scope of the present invention.

For example, in addition to the additives specified in the description, the binder mixture may include other additives, for example, waxes, allowing to obtain a more rigid asphalt mixture.

It should also be noted that all information regarding terminology, for example, lower, upper, etc., refers to equipment whose orientation coincides with the orientation shown in the figures for clarity. Thus, the above terms indicate only the relative orientation of the devices in the shown embodiments, which can be changed if the equipment according to the invention has a different design.

It should also be noted that, even if it is not indicated that the elements of a specific embodiment can be used in combination with the elements of another embodiment, such a combination can nevertheless be implemented, if possible.

Claims (17)

1. A method of producing an asphalt mixture in a mixer (15), characterized in that the method includes the following operations:
- loaded into the mixer (15) dry aggregate, including stone raw materials, essentially not containing filler,
- then the foamed binder mixture is loaded into the mixer (15), which contains dry aggregate, while the binder mixture foams upon exiting the pre-foaming chamber (12) and it is loaded into the mixer (15), after which the indicated filler and the foamed binder mixture substances are mixed, and the mixture of binders includes a binder, an additive that improves adhesion, and a blowing agent, and the binder consists of bitumen, and
- then the filler (6) is loaded into the mixer (15), after which the final mixing of the asphalt mixture is performed. 2. The method according to claim 1, characterized in that the processing temperature in the mixer (15) is from 100 ° C to 120 ° C. 3. The method according to claim 1, characterized in that the aggregate, during the operation prior to loading the aggregate into the mixer, is heated to a temperature of 100 ° C to 130 ° C at which the aggregate is dried. 4. The method according to claim 3, characterized in that at least a portion of the filler (6) is separated from the filler during drying. 5. The method according to claim 1, characterized in that the asphalt mixture comprises at least 80 wt.% Aggregate in terms of the total weight of the asphalt mixture. 6. The method according to claim 1, characterized in that the asphalt mixture comprises from 3 to 10 wt.% A mixture of binders, calculated on the total weight of the asphalt mixture. 7. The method according to claim 1, characterized in that obtaining a mixture of binders includes the following operations:
- initially transport the binder through the pipeline (11) in the chamber (12) pre-foaming,
- then the adhesion improving additive is loaded into the pipeline (11), after which the mixture of bitumen and the adhesion improving additive is loaded into the pre-foaming chamber (12), and
- then the blowing agent is loaded into the pre-foaming chamber (12). 8. The method according to claim 7, characterized in that before transporting the binder through the pipeline (11) into the pre-foaming chamber, the temperature of the binder is from 130 ° C to 200 ° C. 9. The method according to claim 7, characterized in that the binder mixture comprises at least 0.6 wt.% Adhesion improver, calculated on the total weight of the binder mixture. 10. The method according to claim 7, characterized in that the adhesion improver comprises a fatty acid, for example a fir oil fatty acid. 11. The method according to claim 7, characterized in that the binder mixture comprises from 1 to 10 wt.% Blowing agent, calculated on the total weight of the binder mixture. 12. The method according to claim 7, characterized in that the blowing agent consists of water. 13. The method according to claim 1, characterized in that the asphalt mixture comprises from 3 to 8 wt.% Filler in terms of the total weight of the asphalt mixture. 14. The method according to claim 1, characterized in that the filler includes particles whose size is less than 0.063 mm 15. The method according to claim 1, characterized in that at least a portion of the filler contains the same material as the filler. 16. The method according to claim 1, characterized in that the filler includes not more than 50 wt.% Limestone filler in terms of the total weight of the filler. 17. The method according to claim 1, characterized in that the filler comprises not more than 1 wt.% Cellulose fiber, calculated on the total weight of the asphalt mixture.

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