The road made on the basis of asphalt concrete mix is considered one of the most profitable coatings. It is practical, inexpensive and generally provides the necessary characteristics for operation. Of course, it is not without its drawbacks, but they, as a rule, are manifested in cases of non-compliance with the laying technology. On the other hand, a well-constructed asphalt concrete coating provides a sufficiently 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 determined by the composition of the mixture and laying technologies.
The composition of the asphalt mix
The traditional technology of the device of asphalt provides for the presence in the basic composition of mineral fillers and a binder component. The first group of materials includes sand and gravel. In this case, 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, finely dispersed mineral powder may be used . The organic component for the ligament of the basic composition is usually bitumen. The characteristics that the asphalt concrete coating receives as a result are determined by the approach to the formation of the base mixture. The differences in the methods of manufacturing the 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 indicators. These and other factors ultimately determine the characteristics of the coating.
Instructions for the delivery of mixtures to the facility
First of all, the type, quantity and carrying capacity of the vehicles that will deliver will be determined. This choice depends on the size of the work, the volume of the mixture and the pace of future styling. The transportation process includes several stages, among which are weighing, loading of the material, direct transportation and unloading at the collection point. For servicing crushed stone, cold and hot mixtures, a dump truck with a clean body is used, which is covered with a protective awning or waterproof canopies. Cast mixtures, from which the asphalt concrete coating is formed, are transported in so-called coaches. These are cars with thermos-mixers that provide mixing and heating of the composition during transportation. As for the transportation time, 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.
Preparatory work
The main event in the process of preparing for the final laying of the mixture is the test coating device. The length of such a strip is not less than 200 m, and the width is taken in accordance with the parameters of the passage of the paver. Based on the results of the test stacking, technologists determine the most suitable mixture recipe, and also, if necessary, make adjustments to the methodology of its laying and compaction technology.
Trial asphalt concrete pavement is checked for such characteristics as temperature, compaction quality, base condition, etc. Special control technologies are used for this. In particular, non-destructive express methods and sampling, which are subsequently investigated in the laboratory. Based on the findings, the technologists make recommendations for the manufacturer. If necessary, the composition of the mixture is adjusted under the specific operating conditions of the coating.
Mix Distribution Technique
Before the distribution of the finished mass, the paver plate is installed on the edge of the previously laid timber, the height of which will correspond to the thickness of the layer being arranged. To prevent the spreading of the mixture, a sliding type of formwork is used - it must be moved behind the paver. If there is no such device, then before starting the distribution in the longitudinal direction, it is necessary to fix metal strips with a length of about 20 m. Moreover, the thickness of this barrier should be no less than the height of the formed coating. By the way, the thickness of asphalt concrete coatings on average varies from 5 to 10 cm. As the laying and compaction of the mass are completed, the metal bars are removed. As for the width, most often the distribution of the mixture is performed with the coverage of the entire roadway.
If defects are detected after the distribution of the substrate on the surface, they must be processed manually. The use of tammers is practiced, which allows precise correction of loose seams, tubercles and other flaws. Typically, defects are formed in the areas where the strips adjoin the stop elements - the same metal bars. Separate gravel is also covered with gravel. These layers of asphalt concrete pavement are uniformly formed in bulk immediately after the distribution of the mixture. Further, the granular material is recessed into the base of the coating with a light roller.
Compaction technology
The compaction process should go parallel to the operation of the asphalt distributor, which distributes the mixture. Tamping is performed continuously by the link of the rollers. Also in the work can be used smooth-rolled, pneumatic and combined special equipment. The force and load of compaction of cold and hot asphalt in the structural layers are calculated according to several indicators. In particular, technologists take into account density characteristics and mass temperature.
An asphalt concrete pavement is made of a dense hot mixture with a compaction coefficient of 0.99. Cold mixtures assume a load with a coefficient of 0.96. The transverse mates of the laid lines are arranged 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 disk.
Instructions for the repair of asphalt concrete pavements
Before performing repair operations directly, a coating inspection is performed. To do this, the surface is cleaned using road brushes, after which geodetic tools are used to check the evenness of the coating. Depending on the nature of the identified defects, appropriate repair measures are applied. To further ensure the evenness of the layers with the help of a rail, the stump is marked. A bar with a level is applied to the overlap. The place under the bar, in which a decrease in thickness is noted, is considered as a line of future transverse trimming. Also, repair of asphalt concrete pavement may include layer building operations. Typically, such measures are applied to the device covering the framing of wells. For this, special inserts and reinforced concrete segments can be used.
Safety instructions
Even before the start of work, the target area should be fenced with the use of appropriate road signs. People working on the site should be in overalls established by the regulations. At night, the site should also be provided with lighting and signal lights. Separate safety measures are provided for solution handling processes. So, when unloading the carrier with a mixture, it is forbidden for people to be between the car and the material bunker. During laying and compaction, the asphalt concrete pavement of roads should be free from foreign objects and workers. After the completion of the activities, all inventory, equipment and supplies should be removed from the cover and delivered to the appropriate storage location.
Coating quality control
Evaluation of the quality of the arranged coating is carried out using special tools. In particular, calibrated automated measuring instruments are used, as well as special equipment that allows us to derive a complex conclusion based on the data obtained. Among the most common characteristics, on the basis of which the “work” of asphalt concrete pavements is evaluated, compliance with design parameters by thickness and width, evenness of layers, slopes, temperature and quality of joints between the strips are noted.
Conclusion
Work on the installation of asphalt is a complex of technical measures. At the same time, the initial design calculations are of considerable importance from the point of view of the formation of high-quality pavement. Even with good laying and sealing, the coating will not be able to fulfill its functions if the wrong mixture has been selected. Although the basic technology of asphalt concrete coatings involves the use of a standard set of components to obtain a mortar for laying, their parameters may vary. Therefore, laying test mixtures is practiced, which later gives an idea of the most favorable coating characteristics for a particular site. And already in the future, responsibility for the quality of the road goes directly to the work team, which distributes and compacts the asphalt mass.