The quality of the pavement is largely influenced by the method of laying the material. Asph alt concrete must always be carefully compacted. Otherwise, due to its insufficient density, the coating will be of poor quality, and the road will begin to collapse immediately after repair or construction. In this process, many nuances must be taken into account, in particular, the compaction coefficient of asph alt concrete should be taken into account.
Seal
Consolidate the road top layer already at the last stage of its laying. The effectiveness of this process will depend on the manufacturer of the product, the temperature at which the masonry is made, the proportion of bitumen, calculations, including the calculation of the asph alt concrete compaction factor, and many other factors.
Products with a high content of crushed sand are difficult to compact. But nevertheless, the procedure, even with their use, is very important. Thus, according to statistics, 50% of the destruction on the roads wascaused by the fact that the compaction of asph alt concrete was performed incorrectly, insufficiently.
Features
During the implementation of this process, the structure of the road surface is formed, which leads to its strength. The influence of competent compaction of asph alt concrete is manifested in the following processes:
- The solid particles of the material come together and it becomes stronger.
- The air is squeezed out and the coating becomes less porous, which in turn leads to an increase in water and frost resistance of roads.
- The number of bonds per unit volume is multiplied, which leads to durability and reliability of the coating.
- The temperature properties of AB improve, and the coating begins to respond less to heating or cooling.
Methods
There are several ways to carry out this manipulation. They are applied, taking into account the economic benefits of the entire event and the amount of work.
Rolling is the rolling of a drum or a pneumatic tire. The choice of equipment is made taking into account the rest of the units used, the features of the surface. As a result of the procedure, residual deformation appears in the layers.
In the process of increasing the density, it decreases. Ultimately, strong layers remain without deformation. During rolling, the compaction is very strong. It, when properly performed, does not even allow additional shrinkage of asph alt concrete after compaction when driving cars.
The best results are achieved when the temperature of the treatment products has been chosen to be optimal. Usually you need 60 degrees more than the softening point of the binders used. Most often, 105-120 ° C is enough. Carry out the procedure using special pavers designed specifically to work with this temperature.
Vibration is another way of rolling. When laying this type of surface, fluctuations are communicated, at which the best compaction is achieved. This requires special machines.
Determination of coefficient
To test the finished road surface, samples are cut or drilled in three places on a plot of 700 square meters. Samples are taken within 1-3 days if we are talking about a hot mixture, and 15-30 days if a cold mixture is used. The characteristics of the samples depend on the composition. In sandy asph alt concrete, the sample must have a size of at least 50 mm in diameter and a total mass of 1 kg. If it is a fine-grained material, then you need to use 70 mm and 2 kg. Coarse requires 100mm and 6kg.
From the samples for experiments, 3 samples of the shape of a parallelepiped are selected. The side length is 50-100 mm. To determine what compaction coefficient of asph alt concrete will be in this case, use the following algorithm:
- First of all, the samples are dried to constant weights, then cooled and hung in air.
- Then calculate the actual density.
- Next, calculate the average of 3 samples.
- Samples with cores are heated in thermal cabinets. The temperature for this procedure is determined separately for eachtype of mixture.
- Then the samples are crushed, distributing them into molds, compacted under a press with a pressure of 40 MPa, then the height is measured.
- Samples of hot mixes are compacted by vibration, and then additionally compacted under pressure.
Based on the obtained data, the density of the deformed samples is known. Calculate average standard values. Compaction factors are calculated by dividing the actual density by the standard. If it turns out that the value is insufficient, then it is considered that the calculation of the asph alt concrete compaction is incorrect: the surface is poorly compacted.
Meaning
There is no particular need to describe the significance of this indicator. Determining the compaction coefficient of asph alt concrete directly affects the subsequent characteristics of the surface. It is used both in the repair of coatings and in their construction.
At the moment, advanced technologies and formulas for calculating the compaction coefficient of asph alt concrete make it possible to most often complete the task of arranging the road successfully. The coating is even and quite dense. The average compaction coefficients of asph alt concrete, for example, for St. Petersburg over the past 5 years were 0.98-0.99. Compaction rejects rarely exceeded 3-5%.
List of requirements
The compaction coefficient of asph alt concrete according to GOST must meet a number of requirements. Among them are the following indicators:
- More than 0.98 for cold mixes.
- More than 0.98 - for hot mixes type B.
- More than 0.99 for hot mixestype A and B.
It is important and correct to use the road compaction flow chart.
Technological scheme
The main requirement in the compaction process is to perform the procedure at the highest possible surface temperature. When the temperature is raised to 100-140°C, the surface becomes less viscous. The roller applies tangential forces that exceed the shear resistance. This moment is the most successful for a competent increase in density.
When the mixture cools, the bitumen becomes harder. More efforts are needed to increase the density: for example, at a temperature of 70 ° C, the number of passes by the roller triples. The duration of action is affected by the friction of sand and stone, and the level of adhesion of bitumen to stone.
When aggregates with working bodies for compaction are used, then there are opportunities for compaction by the forces of technology. This leads to the creation of even coating layers. Types of pavers and pre-compaction efforts influence the choice of roller type. Usually additional compaction is carried out using light rollers of 5-6 tons or pneumatic tires.
The duration of the procedure is affected by the thickness of the layer, its appearance and weather conditions. When the temperature is below 10 °C, the procedure is carried out in a couple of minutes.
Act of Trial Compaction
Acts of trial compaction are classified as production and technical documentation during road works. They draw up acts after they conduct research to determine the value of the compaction coefficient of asph alt concrete.
The composition of acts includes a number of nuances. The list ends with the following items:
- Name and features of the object.
- Material specifications.
- The conditions under which it is compacted are the temperature of both the coating and the air.
- Number of passes made, rink speed.
- Laboratory test results - layer thickness, density, compaction coefficient of the asph alt concrete leveling layer.
Acts are signed by representatives of the laboratories that conducted the analyzes, representatives of manufacturers.
Laying
The finished road surface must comply with the requirements of GOST and TU. If, for example, the compaction coefficient of asph alt concrete does not comply with GOST, then the road is destroyed very quickly, and funds are again spent on its repair.
Laying the surface is carried out in the following steps:
- First of all, they study the features of the soil, the level of groundwater, the correctness of other geodetic works. Then choose the appropriate type of coverage. It is chosen both taking into account the characteristics of the site and the necessary requirements for the road.
- Next choose equipment. They calculate the deadlines for completing the task, determine the approximate date for the launch of the road.
- Staging work is underway.
Be sure to pay great attention to the selection of asph alt paving machines, the calculation of the required asph alt concrete compaction coefficient, and compliance with the requirements of GOST.
Required Items
At the same time, the construction of roads consists not only ofstyling procedures. After all, you must first demolish the upper layers of the soil, rid them of the roots of trees and grasses. Otherwise, the coating will be broken by them. Carefully carry out the device of the drainage system.
Then lay the foundation. Rarely it is made of monolithic concrete: the thing is that such a foundation costs much more than its competitors. Therefore, crushed stone is more often used. Lay it in layers: first, the bottom layer of large stones - up to 70 mm, which allows you to drain groundwater, then the middle one - up to 40 mm, which helps to evenly distribute the loads, and at the end the top one - up to 20 mm, it also distributes loads and contributes to shrinkage of asph alt concrete after compaction.
How to style
The process itself is produced by asph alt pavers. These are modules on caterpillars or with tractor moves, working bodies are attached to them - a tamper bar and a screed. The plate is vibrating and static.
Dump trucks load the mixture into the receiving hoppers of the machine, then it goes to the auger chamber and is distributed over the entire paving width. Machines are selected based on their power and performance. This is important because different types of construction require very different properties of aggregates. Usually, smooth coatings are obtained using tracked vehicles. But in the conditions of narrow city streets, wheeled vehicles are used more often. The wider the paving, the more economical the process.
To finally compact the coating, use devices that match the type of surface. It maybe light rollers up to 4 tons, medium - up to 6 tons, tandem rollers, vibrating plates and so on.
Staff
Performers play a big role. We need people who will correctly calculate the required coefficient of compaction of asph alt concrete, because otherwise the whole process will be done in vain. To create a durable surface you need:
- Asph alt pavers operator.
- Dump truck driver.
- Master road builders in the amount of 5-10 people.
All of them must strictly follow the technological instructions for laying AB.
Technological instruction
The creation of the road surface should take place in the warm season at a temperature of +10 degrees in autumn and +5 in spring.
According to the GOST standard, AB materials are divided into two varieties:
- For styling at air temperatures above +5 °C.
- For styling at -25 to +5°C.
The process is carried out according to approximately the same schemes. But the heating temperature of the mixture will be different. It will depend on the weather, type of asph alt concrete, surface thickness. Never lay asph alt when it rains.
Like the incorrect determination of the compaction coefficient of asph alt concrete, errors in delivering a mixture of a certain temperature can be fatal. They try to reduce delivery time to the minimum values.
Asph alt is loaded into pavers continuously. If there are pauses, then the remnants of the material are not removed from the hoppers so that the feeder does not cool down. They are being covered until supplies resume. By the end of the work, the mixture must be consumed to the end, and asph alt concrete should not remain anywhere.
The machine runs at a speed of 2.5-3m/min, the value is constant. Warm hot mixes are loaded when the tamper is on. In the case of working with cold materials, it is turned off. Be sure to cut the edges of the strips immediately after the completion of work to increase the density.
If there are unpaved narrow strips on the site, then asph alt concrete is laid manually. Not in all cases, the operation of machines is possible, if we are talking, for example, about narrow city streets, about bends. Alignment is carried out with metal rollers. Before starting work, the tools must be warmed up.
After laying the surface, compaction is carried out by means of rammers, rollers, vibration units and so on. If defects are found in some areas, they are lubricated with hot bitumen, and then, having been filled with asph alt concrete, they are compacted. During laying, the temperature of the mixture and the thickness of the layers are monitored.
Patching
Today, asph alt concrete is the main material used in road construction. All streets, bridges and airfields are laid out by him. But there are many types of it. For example, some of them are used in waterproofing roofs, tunnels, flooring and so on.
In winter, cold mixtures are used to seal holes in the roads. It is important to calculate the compaction coefficient of asph alt concrete, and in this case it is extremely accurate. They use the same formula for this. To calculate, divide the actual density of the samples by the standard. Properly adjusted value of asph alt concrete compaction after the paver allows asph alt to serve for a long time. If it is established that the density is insufficient, then the work is done again, otherwise the road will collapse quickly. Therefore, it is important to use the formula for the compaction coefficient of asph alt concrete correctly.
Technology
Patching is not the most difficult process. If the pothole is small, then close it with hand tools. The marking of the plots is carried out with maps, the contours are cut off with joint cutters, pneumatic or hydraulic jackhammers, perforators, and so on. If the hole is large, trail cutters are used.
Then the pit is cleared of construction waste and treated with liquid bitumen. This is also done by hand, and sometimes with the use of asph alt distributors. Asph alt concrete is delivered by dump trucks, but if the volumes are small and the defects are scattered, then there are risks that the mixture will harden early. Therefore, repairers with constant heating of the mixture are used.
Mixtures brought to the right temperatures are poured into the pit. They are applied manually or by pavers. If the pothole is shallow, then crushed stone is first laid in it. When determining the thickness of asph alt concrete paving, GOSTs of asph alt concrete compaction are taken into account, leaving a margin for it. Increase the density of the surface using manual mechanical or special rollers.
Expense
Amount of material,spent on road repair depends on the thickness of the layers and the area of the road sections. The thickness of the layers will depend on the type of road.
The values of both the AB volume and the compaction coefficient of asph alt concrete on sidewalks and parking lots will differ. For example, if you want to put asph alt on 10 square meters in a car park, you will need a layer of 4-5 cm of material, all because trucks are not expected to pass through here.
The calculation will be made as follows: 10 sq. m0.05 m2200 kg / cu. m, where the last value is the density of the material. That is, laying the coating on this site requires 1100 kg of the mixture.
In 1 cu. m - about 2250 kg. Therefore, in order to equip the site, you need 1100 kg / 2250 kg \u003d 0.49 cubic meters. m.
Equipment
The HAMM EU technique is often used to compact asph alt concrete and soil. The thing is that the equipment of this manufacturer is easy to operate. HAMM is often recommended in books on asph alt and soil compaction. This manufacturer has existed since 1911, so it managed to enter numerous collections of even old designs.
Quality control
Before paving work is started, always check the operating modes of the machines and set the required speed of the pavers. Working on the road surface, always determine the coefficient. compaction of asph alt concrete to clarify the composition of the group of rollers, their mode of operation. The required density is determined by examining samples that were taken after the pavement was laid by asph alt pavers. Samples are taken no earlier than 2 hours laterfrom the moment the car passed.
Important points
The surface is rolled down with a compacting machine always with 15 cm overlap of tracks. This value is the minimum for this indicator. The process must always be monitored so that each strip being rolled is processed by the machine the same number of times.
Rollers always return along the same lanes to already cooled surfaces and only maneuver there. This allows the road surface to be smoother. They begin to compact from the edges - edge bands. If they are absent from the edges, strips 30-40 cm wide are left uncompacted so as not to deform the uncompacted mixtures that have not cooled yet.
Further, such strips are compacted with rollers, which are specially equipped with devices for increasing the edge density or pneumatic wheel rollers. If the finisher moves in steps, the density is increased as the mix is laid, starting at the outer edges and moving towards the center. A strip 30-40 cm wide remains in the very center without compaction. It is started last, which allows you to achieve the connection of all laying strips.
Sealing of longitudinal seams is carried out in two ways. In the first, they begin to compact along the longitudinal seams, while the roller of the roller captures layers that have not yet been rolled by 10-20 cm. And the rest of the drum surface passes over rolled and cooled asph alt concrete pavements.
Longitudinal seams are also compacted in this way: on the rink they pass through the already compacted layers only with the edges of the roller 10-20 cm. By carrying out such a maneuver, you can not collide with the movement of the vehicleon active lanes. Therefore, the passage is not difficult.
The sealing of the transverse seams is carried out in a perpendicular direction with respect to the laying of the AB mixture. In this case, the machine's roller hits hot, uncompacted road surfaces by 10-20 cm. It is more difficult to maneuver the roller in these conditions, since the area where it does this is limited. For this reason, it is more convenient to use small machines.
Consolidating the sections at the corners of the road, start from the concave sides and move further along a straight path. On already rolled sections of road surfaces, the roller is moved along tangents. The speed of the maneuvers of the machine must be the same. On these surfaces, rollers with compound rollers are more often used.
Difficulties in sealing
Over time, the load on highways and roads across the country only increases. For this reason, the requirements for their quality indicators are constantly growing. All this led to the invention of new methods and devices for increasing the density of surfaces. For example, vibrobeams of various types were collected. Well-known foreign manufacturers of road repair machines have developed screeds. Most often, vibrocompaction of road surfaces without rollers allows you to achieve better evenness. However, their use is not a guarantee that the specified degree of density will be achieved.
At the moment, many companies are investigating the use of vibrobeams in a variety of cases related to the repair and construction of roads. The Swiss have developed a new generation ice rink, whose workingthe organ vibrates both vertically and horizontally. It is constantly in contact with the surfaces of the compacted layers of the road.
A very important question is whether it is possible to continuously determine the degree of compaction of the pavement directly in the process of paving. This possibility already exists thanks to the invention of the radioisotope probe, which is placed under the frame of the rink. On the instrument panels located in the cab of the machine, the worker sees data on the extent to which the coating is compacted. If the color on the panel is yellow, then the density needs to be increased. If green, then the specified value of this main indicator has been received.
Reasons for marriage
Despite the strict regulation of the entire process, the availability of all necessary calculations, there are marriages in road repair. Their share is not very large, but it is. This usually happens if thin leveling layers of 2-3 cm are arranged. Sometimes marriages occur when laying a regular layer of 5-6 cm when sand mixtures are used. Sometimes this happens with thick bottom layers of 9-10 cm from coarse-grained mixtures.
It would seem that the cases are standard, and there can be no room for errors. What are the reasons for marriage?
Among the main prerequisites for its appearance are the tools themselves, which perform compaction operations. That is, the technical imperfections of technology, including vibratory rollers, lead to errors. Of course, this is taken into account when the human factor was excluded - the presence of violations, errors in calculations, omissions of the working group itself.
So, onat the household level, it would never occur to anyone to hammer nails using a sledgehammer, or start hammering railroad crutches using a homemade hammer. But road contractors actually get to do it on the roads. For example, they sometimes use the same roller that they have available to compact both thin layers of 2-3 cm, medium layers of 5-7 cm, and thick layers of asph alt concrete 10-12 cm. After analyzing and calculating, anyone will understand that in each of these cases it is necessary to change the speed of the technique.
If we also take into account the fact that the starting density of the hot mix after the paver has worked on it (with a compaction factor of 0.83-0.97), the granulometry composition, the viscosity of the bitumen, the strength and rigidity of the foundation, the technological stages of increasing the density, weather conditions, it immediately becomes clear why it is impossible to provide perfect work on the road surface with one or two rollers.
The contractor is not interested in purchasing a car for each individual case, because then they need a very large number.
Therefore, it is pointless to reproach manufacturers of equipment for road works that they do not take into account such features that pop up in practice and do not include in their products the ability to change the characteristics of machines. And even the principle of regulation itself, which is based on changing centrifugal forces by setting different values (usually there are about 2 of them), in rare cases gives reasonable steps and ranges of influence on the course of work. The machines are simply not capable of covering all the paving and compaction types and conditions listed.
The time has come to rethink and revise the very mechanism for implementing this procedure. Sometimes vibratory rollers of the same manufacturer, of the same weight, may have different compaction abilities. This proves that their practical purpose was not broadly conceived. It also often misleads the workers themselves, who do not have the criteria for selecting and using suitable types of machines.
Sometimes there is a feeling that failures happen because of too much “violence” on the road surface from the rink, and also because of its insufficient impact on the surface. All these factors lead to the fact that the process becomes quite unpredictable, and Russians constantly observe deplorable results on the roads of the country.
Conclusion
The way asph alt concrete is laid and compacted affects the road no less than the correct selection of mixtures for working on it. Violations of technology, incorrect calculation of the compaction coefficient should not be allowed, otherwise the roads will soon become unusable.
