Made on the basis of asphalt mix the road is considered one of the most profitable coatings. It is practical, inexpensive and generally allows you to provide the necessary characteristics for the operation. Of course, it is not without its drawbacks, but they, as a rule, manifest themselves in cases of non-compliance with the installation technology. On the other hand, a quality-made asphalt-concrete pavement provides a fairly high bearing capacity and elasticity. At the same time, there are different approaches to the creation of such roads and sites, the differences in which are caused by the mixture compositions and technologies of laying.
The composition of the asphalt mixture
The traditional technology of the device of asphalt provides for the presence in the main composition of mineral fillers and a binder component. The first group of materials includes sand and gravel. At the same time crushed stone can be replaced by gravel, and sand is used in whole or crushed form.
Also, depending on the requirements for the coating and its operating conditions, fine mineral powder can be used. The organic component for the binder of the basic composition is usually bitumen. The characteristics that the asphalt concrete pavement receives as a result are determined by the approach to the formation of the base mix. Differences in the methods of making a solution are due to the parameters of the components used. For example, gravel or crushed stone can be selected with a fraction of 10 to 40 mm. So bitumen can have different viscosity and density. These and other factors ultimately determine the characteristics of the coating.
Instructions for the delivery of mixtures to the object
First of all, the type, quantity and carrying capacity of the vehicles that will deliver are determined. This choice depends on the scope of work, the volume of the mixture and the rate of future installation. The transportation process includes several stages, including weighing, loading of the material, direct transportation and unloading at the receiving point. For maintenance of crushed-stone, cold and hot mixes use a dump truck with a clean body, which is covered with a protective awning or waterproof canopies. Molded mixtures, from which the asphalt concrete pavement is formed, are transported in so-called coders. These are cars with thermos-mixers, which ensure mixing and heating of the composition during transportation. As for the time of transportation, in the case of hot and mastic mixtures it depends on the characteristics of the mixture, and for cold solutions there are no restrictions on the duration of transportation.
The main event in the process of preparing for the finishing laying of the mixture is the device of the test coating. The length of this strip is not less than 200 m, and the width is taken in accordance with the parameters of the paver pass. Based on the results of the test installation, technologists determine the most appropriate recipe for the mixture, and if necessary, make adjustments to the method of its installation and compaction technology.
The test asphalt concrete pavement is checked for such characteristics as temperature, quality of compaction, condition of the base, etc. Special control technologies are used for this. In particular, non-destructive rapid methods and the collection of core samples, which are further investigated in laboratory conditions. On the basis of the conclusion obtained, technologists make recommendations for the manufacturer. If necessary, the composition of the mixture is adjusted for specific operating conditions of the coating.
Mixture distribution technique
Before the distribution of the finished mass, the paver slab is installed on the edge of the previously laid timber, the height of which will correspond to the thickness of the layer being arranged. In order to prevent the spreading of the mixture, sliding formwork is used – it must be moved behind the asphalt paver. If there is no such device, then even before the distribution begins in the longitudinal direction, it is necessary to fasten metal strips of about 20 m in length. The thickness of this barrier must not be less than the height of the coating being formed. By the way, the thickness of asphalt concrete pavements varies on average from 5 to 10 cm. As the masking and compaction proceeds, the metal bars are removed. As for the width, most often the distribution of the mixture is carried out with coverage of the entire roadway.
If, after the distribution of the base on the surface, defects are detected, they must be processed manually. It is practiced to use tampers, which allow to fix spotless seams, bumps and other defects. Usually, defects are formed in the areas of junction of the strips to the thrust elements – the same metal bars. Separately, gravel with gravel is also filled. These layers of asphalt concrete pavement are formed uniformly in bulk immediately after the distribution of the mixture. Next, the granular material is embedded into the base of the coating with a light roller.
The compaction process should go parallel to the operation of the autodrunner, which distributes the mixture. The tamping is performed continuously by a roller link. Smooth roller, pneumowheel and combined special equipment can also be used in the work. The force and load of compaction of cold and hot asphalt in structural layers are calculated by several factors. In particular, technologists take into account the characteristics of the density and temperature of the mass.
The asphalt concrete pavement is made of dense hot mix with a compaction factor of 0.99. Cold mixtures assume a load with a coefficient of 0.96. Cross-line mating of stacked lines arrange perpendicular to the road axis in one lane without leaving ledges. To fulfill this condition, the end of the previously arranged strip is trimmed with a special tool with a diamond disc.
Instructions for the repair of asphalt pavements
Before the direct execution of repair operations, the coating is inspected. To do this, the surface is cleaned with road brushes, after which geodetic tools are used to check the evenness of the coating. Depending on the nature of the detected defects, appropriate repair measures are applied. To further ensure the evenness of the layers using the slats, the place of the chipping is marked. The bar with the level impose on the overlap. The space under the bar, in which a decrease in thickness is noted, is considered as a line for future transverse trimming. Also repair of asphalt concrete pavement may include operations to build layers. Typically, such events are used for the device framing wells. For this special liners and reinforced concrete segments can be used.
Even before the start of the work, the target site should be fenced with appropriate traffic signs. People working at the site should be in working clothes, established by regulations. At night, the site should also be provided with lighting and signal lights. Separate safety measures are provided for solution handling processes. Thus, when unloading a carrier with a mixture, it is prohibited to find people between the car and the bunker with the material. During the laying and compaction of asphalt concrete pavement roads should be free of foreign objects and workers. After the completion of activities, all inventory, equipment and consumables should be removed from the floor and delivered to the appropriate storage sites.
Coating quality control
Quality assessment of the arranged coating is made using special tools. In particular, calibrated automated measuring instruments are used, as well as special equipment that allows you to derive a comprehensive output based on the data obtained. Among the most common characteristics, on the basis of which the “work” of asphalt concrete pavements is assessed, compliance with the design parameters in thickness and width, flatness of layers, slopes, temperature and quality of seams between the strips is noted.
Asphalt works are a set of technical measures. At the same time, the initial design calculations are of considerable importance from the point of view of forming a high-quality road surface. Even under the condition of good packing and sealing, the coating will not be able to perform its functions if an inappropriate mixture has been selected. Although the basic technology of asphalt concrete pavements provides for the use of a standard set of components to obtain a mortar for laying, their parameters may vary. Therefore, it is practiced to lay test mixes, which further give an idea of the most advantageous coating characteristics for a particular site. And in the future, responsibility for the quality of the road goes directly to the working team, which distributes and compacts the asphalt-concrete mass.