Asphalt is a natural or artificial multicomponent material based on surface (formed when reaching the surface of the earth) or petroleum (obtained as a result of oil refining and subsequent processing of tar remaining in the sediment) bitumen containing mineral fillers - gravel, crushed stone of various rocks, sand.

In fact, applying the term “asphalt” to road asphalt concrete mixtures is incorrect. The content of asphalt as a mixture of bitumen in the total mass is several times less and depends on the type of material.

Start of using asphalt for road construction

The first mention of the use of natural asphalt for laying roads dates back toXVIcentury and South America. The production of artificial cast asphalt mixtures appeared in the United States only at the end ofXIXcentury, bitumen-mineral compositions came to the streets of Europe a little earlier - in 1830-40. paved sidewalks and roadways in cities in France, Austria, Great Britain and Russia began to be replaced by asphalt surfaces.

The first trial and larger-scale asphalt paving experiment was carried out in St. Petersburg, but only by 1980. the new road material spread to other major cities. At the same time, our own plant was not built in Russia right away - for three decades, the then progressive product was purchased abroad.

America was again the pioneer in mechanized laying. It was here that a tarmacrator, from which hot bitumen poured, was first used to build a road.

Composition of natural and artificial asphalt

Natural asphalt is extracted from rare deposits - Peach Lake in Trinidad, the Dead Sea in Israel, Alberta in Canada, the Orinoco Belt in Venezuela, US states, Iran, and Cuba. The composition includes a mixture of bitumen up to 70%, inorganic inclusions and organic compounds.

Artificial asphalt concrete mixtures consist of two main components. The role of the binding component is viscous, low-viscosity or liquid petroleum, modified bitumen and PBB (polymer-bitumen binders). Crushed stone/gravel of different fractions from 5-10 mm to 20-40 mm, sand and mineral powder are used as fillers to improve strength, toughness and fill voids.

Asphalt concrete is a monolithic road surface obtained by laying and compacting an asphalt concrete mixture.

Asphalt production technology

The main steps in the production of any asphalt concrete mixture are preparation of components, mixing and storage in a bunker. Manufacturing is carried out on stationary and mobile (located near the site road construction) factories.

General technological steps:

• Preparation of mixture components. Mineral fillers are crushed and separated into fractions using a screen, dried, heated, dosed and fed into the mixer.
• Preparation of bitumen. The heated bitumen is fed to the bitumen melting plant, kept with constant stirring, adding a surfactant and raising the temperature until the moisture evaporates, and is sent to working boilers and to the mixer dosage.
• Mixing components. Prepared crushed stone/gravel and sand are fed into a forced-action asphalt mixer for “dry” mixing with the addition of mineral powder and subsequent addition of heated bitumen and mixing until a homogeneous mixture.
• Overload ready mixture. The hot asphalt mixture is sent to a storage bin or loaded into dump trucks for transportation to the construction site. The cold mixture is cooled and transported to a warehouse for storage.

Heating of crushed stone and bitumen during the production of hot mixtures is carried out to a temperature of 165…175 0 C and 140…155 0 C, when producing cold mixtures - up to 65...75 0 C and 110…120 0 C accordingly.

Classification of asphalt concrete mixtures is carried out according to residual porosity, type mineral materials, their fraction and percentage, bitumen binder and installation temperature.

Certain types of asphalt concrete mixtures

In addition to traditional and widely used asphalt concrete mixtures, there are more advanced road materials that differ from the former in composition and laying conditions.

These include:

• Crushed stone-mastic mixtures ShchMA with stabilizing additives.
• Cast asphalt concrete mixtures with an increased content of bitumen and mineral powder.
• Polymer-asphalt-ethony mixtures with the addition of polymers (elastomers).
• Colored hot and cold mixtures with coloring pigments.
• Glass-asphalt-ton mixtures with the inclusion of broken glass.
• Rubber-asphalt concrete and rubber drainage mixtures with rubber crumbs and polymer additives.
• Sulfur asphalt concrete mixtures with the presence of technical sulfur.

Each type of material has a specific area of ​​application, determined by the characteristics and operational properties of the resulting coating.

For people of the twenty-first century, asphalt is as commonplace as the cars it powers. perfect coverage for roads, but this was not always the case. More recently, in the nineteenth century, city streets were paved with cobblestones, but the rapid development of the automobile industry and the invention of the engine internal combustion forced improvements in pavement technology. Efficient and simple road production was required. Few people know, but asphalt was known in ancient times. In Babylon it was called "tar", and the ancient Romans knew it as "bitumen". But then it was used as a material for insulation from water in shipbuilding and the construction of liquid tanks. In Egypt, asphalt was used in mummification, and some ancient doctors attributed medicinal properties to it.

The composition of asphalt is a mixture of bitumen, sand, gravel or crushed stone. In nature, it occurs in both liquid and solid form. Asphalt becomes soft and pliable when heated, then hardens again when cooled.

There are two types of asphalt.

• Natural - formed from oil as a result of natural chemical processes. It can be found at shallow depths in the form of strata deposits.
• Artificial - obtained industrially as a result of the distillation of crude oil in specialized factories.

Natural asphalt contains much more bitumen than artificial asphalt. Natural bitumen contains from 60% to 75%, artificial bitumen - from 13% to 60%.
The world's largest deposit of natural asphalt is located in the southwest of the island of Trinidad, a bitumen lake with an area of ​​40 hectares and a depth of more than 30 meters. At the current rate of use, the reserves of the asphalt lake will be mined for at least 400 years. The first asphalt, which appeared in the United States in 1876 during the construction of a road in Washington, was mined on the island of Trinidad. In Europe, asphalt was first used during the construction of the Royal Bridge in Paris in the thirties of the last century, as well as on the bridge over the Rhone River in Lyon. In Russia, the era of asphalt began in 1839, when the first sidewalks were laid in St. Petersburg.

The properties of asphalt have proven to be very practical for road construction. It lays flat, has a structure that provides good grip, and is easy to repair. Asphalt dries quickly and acquires sufficient strength, which made it possible to use roads immediately after it was laid.
IN modern production A mixture of asphalt and cement is used. This technology gives asphalt plasticity, the ability to withstand high pressure and temperature changes without collapsing. With the advent of multi-ton trucks and the development of aviation, as the load on the pavement has increased enormously, the demands on roads have increased. This forced asphalt manufacturers to improve production technology. For the construction of specialized objects that require an increased margin of safety, modifier additives are used - heavy-duty crushed stone and recycled old tires.

In which city did the first asphalt road appear?

Asphalt was the first petroleum product with which man became acquainted. Natural asphalt - one of the types of natural bitumen - is a viscous resinous substance formed from heavy fractions of oil as a result of long-term weathering. It is found in the form of strata vein deposits, as well as lakes in places where oil naturally comes to the surface of the earth. This is a hard, fusible mass of black color, containing 25–40% oils and 60–75% resinous-asphaltene substances. The word “asphalt” (from the Greek “asphales” - durable, strong, reliable) has been known since the time of Herodotus, who described Mesopotamian and Persian asphalt deposits in his “History”.
People found applications for natural asphalt at the dawn of civilization - in Ancient Egypt 5,000 years ago, the floors and walls of grain storage barns were covered with asphalt. In Babylon it was used as binder when laying stone walls- The Bible says that during the construction of the Tower of Babel, “earth resin” was used, as asphalt was called in ancient times. The same Babylonians, when constructing the famous Hanging Gardens of Babylon, used a layer of asphalt mixed with reeds for waterproofing. 400–500 BC in Media, the walls of fortresses, as the ancient Greek historian Xenophon testifies, were built from bricks held together with natural bitumen. In the same way, the first sections of the Great Wall of China were built on bitumen.
As for the more familiar road use of asphalt for us, natural asphalt was used in the construction of roads in America, more than half a thousand years before such use of asphalt was thought of in Europe and the USA. When in 1532 a detachment of Spanish conquistadors led by Francisco Pizarro entered the territory of the Inca Empire, they were, among other things, amazed at the magnificent asphalt roads there.
But the great civilizations of the past died, and asphalt as a building material was forgotten for centuries and millennia. Up to early XIX centuries the streets of all cities of the world in best case scenario paved with stones, and only then major cities A new era has begun - the era of asphalt. In 1832 - 1835 In Paris, the first work on paving city streets and sidewalks with asphalt was completed. Then, in 1835–1840, it was the turn of London, Vienna, Lyon, Philadelphia and some other cities.
IN Russian Empire The first experience of using asphalt was made in 1839, when in St. Petersburg almost 100 meters of one and a half meter wide sidewalk near the Tuchkov Bridge were covered with it. Asphalt was used on a somewhat larger scale in 1865, when the terraces were paved Winter Palace. But already in next year asphalt began to be used quite widely on ordinary St. Petersburg streets, squares and courtyards, and by 1880 it covered many streets in Kronstadt, Moscow, Riga, Kharkov, Kyiv and Odessa. True, the first asphalt plant was built in Russia only in 1873, several miles from Syzran, and before that asphalt was purchased abroad.
Since the middle of the 19th century, in France, the USA, Switzerland and other countries, road surfaces have been made from bitumen-mineral mixtures. In the United States, cast asphalt prepared using petroleum bitumen was first used in 1876. Then, in 1892, the first road structure with a width of 3 meters was built using an industrial method, and 12 years later, using a tarmacrator with the free flow of hot bitumen, 29 km of road were built.
New types were needed for the rapidly developing road network road surfaces, and the asphalt turned out to be the most suitable material. It can be laid almost perfectly evenly, it is a very low-noise coating, but at the same time it has the necessary roughness. Modern roads are covered with asphalt made from petroleum bitumen, obtained as a result of the oxidation of heavy oil distillation residues with air at a temperature of 239-340 ° C. This process was developed in 1896 and introduced into production in 1914.

Who is who in the world of discoveries and inventions Sitnikov Vitaly Pavlovich

Who invented asphalt?

Who invented asphalt?

We are accustomed to asphalt, this nondescript gray material. It can be seen everywhere - under our feet, on the roofs of buildings, in canals and on the bottom of a tarred boat, and even in the paintings of great artists: the paints they used were based on a natural mountain resin called asphalt. This is how “mountain resin” is translated from Greek word"asphalt". It was introduced into use by the historian Herodotus, who told us in his “History” about this material and its location in Mesopotamia.

The ancient Romans called rock tar bitumen. In fact, it is one of the components of oil. In ancient times, asphalt-bitumen was used to seal amphoras containing wine, used it as a special glue, and tarred the bottoms of ships. It was used to cover the floors of grain storage facilities to protect them from moisture, to coat the joints between the slabs of temples, and to fasten bricks and stones together that were used to line the banks of reservoirs and irrigation canals.

This material was known not only in the ancient East and ancient states. Asphalt bitumen was also known to the ancient Incas, who created their civilization in America. When at the beginning of the 16th century the first European conquerors came to South America, amazingly wide and smooth highway roads, lined with huge stone slabs, the joints of which were coated with asphalt. Individual areas These roads serve as a reliable means of transportation for modern Bolivians.

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It is a multicomponent mixture based on sand, stone and bitumen binder. The “correct” name of the material is asphalt concrete, which does not prevent the term “asphalt” from being used even in specialized publications.

Asphalt consists of bitumen, sand, types of crushed stone or gravel, as well as mineral additives and fillers. The only constant component is bitumen, and the remaining components can be added in different proportions.

Functions of fine components of asphalt mixture

Sand, contained in asphalt, plays the role of a filler and a fine base, helping to distribute pressure from the road to the ground. Without sand, the bitumen binder would leak out and crushed stone would be squeezed out onto the top.

In the case of special asphalts containing cement, sand participates in the cementation process and gives the coating additional hardness.

Mineral filler– is a rock (sandstone, limestone or chalk) crushed to a dusty state, intended to fill residual voids. Sandstone is the most universal, as it is inert to almost any chemical exposure. Calcium carbonates (limestone and chalk) are commonly used on roads general purpose, while sandstone can be used near chemical plants.

Rubber– added to asphalt in the form of rubber crumbs (1-1.5 mm), it gives the coating high water resistance and plasticity. Asphalts treated with rubber are much less likely to crack, which increases the period between repairs. The disadvantage of such roads is high price, therefore their use is limited to laying the most critical sections of highways.

Change in asphalt structure when adding mineral filler

Classification

One of the main parameters is the size of the crushed stone used, dividing asphalts into the following groups:

1. dense– used for laying the top layer of coating and contains fine crushed stone. In the case of a crushed stone fraction of less than 5 mm, such asphalts are used for pavements with low loads (sidewalks and pedestrian crossings) and are called fine-grained. Larger fractions of crushed stone (5-15 mm) are suitable for creating the top layer of highways;
2. porous– used in the lower part of a multilayer pavement and contain less bitumen than dense asphalts;
3. highly porous– optimal quality bases for heavily loaded roads. In their production, the largest crushed stone of the 15-40 mm fraction is used. Such dimensions provide the necessary water permeability, creating drainage in lowlands and marshy areas. Larger coarseness reduces road base shear and indentation upper layer soil, reducing the risk of washout and subsidence of the coating.

Manufacturing technology

The basis of any asphalt production is the preparation of the initial components, mixing high temperature and storage in special heated bunkers.

It is important that the plant is located close to the construction site, since the material must be transported for installation in a heated state. If the mixture cools down, it will be very difficult to compact and the resulting coating will not be strong enough. Let's look at the stages of asphalt production.

Preparation of components from which asphalt is made

This includes drying and sifting. Sand, crushed stone and rock usually arrive at the plant in a wet or air-dry state. The presence of residual moisture is fraught with a decrease in the strength of the coating and splashing of the hot bitumen mixture when water gets into it.

To eliminate possible consequences, the material is dried at a temperature of 150-160? C - this temperature allows you to get rid of moisture adsorbed in the pores of the material.

Screening of crushed stone is carried out using a screen. The mineral filler is pre-crushed in a crusher, after which it is also subjected to fractionation. Depending on the production technology, drying can be single or double, repeated after crushing or sifting.

Mixing components

Crushed stone and sand are fed onto a conveyor belt, which transports them to a common bunker. Mixing with filler and bitumen can occur simultaneously or be carried out after achieving a homogeneous crushed stone-sand mass.

After adding bitumen, the temperature is maintained at 160-170? C. After reaching the required consistency, the mixture (now asphalt) enters a storage bin, where it can remain heated for up to 4 days. During this period it must be shipped to the consumer to avoid loss of strength characteristics.

Asphalt modification with additives that impart useful performance properties is carried out simultaneously with asphalt mixing. When creating a rubber-asphalt mixture, crumb rubber is added to a heated, ready-to-use product.

Delivery

Transportation of asphalt concrete to the construction site is carried out by motor transport. Most often, conventional dump trucks with a body resistant to hot asphalt are used. For transportation over long distances, kochers - vehicles with special heat-saving containers - can be used. They are designed to preserve the properties of asphalt concrete for 2 days.

The video will tell you how asphalt is made at a factory and whether it is possible to make it yourself:

How to check the parameters of the road surface and raw materials for its production

To avoid purchasing low-quality asphalt concrete, you should ask the seller for a certificate of product conformity. It is issued only after passing a set of tests corresponding to GOST or SNiP (depending on the scope of application).

In the quality control market, there are a number of regional laboratories that conduct sampling and testing of asphalt pavements. During the study, an average sample is selected from the total mass of the material. Analysis of the road surface is carried out by examining a core, which is an asphalt core obtained by drilling the road with a special hollow drill.

DIY cold asphalt

Let’s immediately make a reservation that cold asphalt is only laid independently, and its production is carried out only at the factory. The technology itself differs from traditional coating in lower operating temperatures (70-110 °C) and the addition of a complex of protective and polymer additives to its composition. The latter are necessary to impart greater strength and form a protective antioxidant film on the surface of the bitumen.

Despite the name, cold asphalt will still have to be heated in cold weather in order to convert the bitumen into a plastic state. At the same time, you need to use a burner to heat the place where the asphalt will be laid. Depending on the manufacturer, work with cold mixtures can be carried out even with negative temperatures(up to -20...-10 °C).

The advantage of cold asphalt is long term storage Unlike classic asphalt concrete, it does not need to be used immediately after purchase. The disadvantages include lower strength, which is almost 2 times less than that of hot asphalt.

To compact the coating, use a vibrating plate or improvised means - thick wooden beam, car wheel. The final finishing of the surface occurs after repeated passage of vehicles. It is not recommended to make entire sections of the road from cold asphalt, since they are destroyed under the pressure of a vehicle weighing over 3.5 tons.

Modified cold asphalt:

Recycling old asphalt

The high cost of creating a road forces us to look for ways to save money. One of them is recycling - the processing of waste asphalt in order to reuse. Processing is carried out in stationary conditions or in mobile recyclers.

The process is carried out in several stages:

• Removing a layer of old asphalt is done with a remixer, which removes the road surface by milling;
• crushing the milled layer to the size of crushed stone. The resulting product is called granulate and can be used for laying roads and preparing crushed stone-sand building mixtures;
• heating in an oven without direct contact with fire (to avoid ignition);
• adding a fresh portion of bitumen and polymer additives, if necessary.

Recycling technology is of industrial importance and is usually used in the construction of urban and intercity highways. If the opportunity arises to buy recycled asphalt for private purposes, do not hesitate - there is no difference in performance properties, while the price will be significantly lower.

Mobile asphalt recycling plants

Installation No. 1 Installation No. 2

Modernization of asphalt concrete pavements

Despite being quite practical, road surfaces can be improved. One way is to use special mastics for asphalt. They contain bitumen or bitumen emulsions containing rubber polymer additives.

Regular bitumen mastics are used hot, and emulsions are used cold. The principle of operation of mastics is to seal cracks and pores on the surface of the canvas. This prevents water from getting inside the road and destroying it - water contributes to cracking of the coating during freezing and water hammer when vehicles pass.

Advantages and disadvantages of the material

It is worth noting the following:

1. For light-duty applications, asphalts are not very expensive, unlike the multimillion-dollar cost of laying highways;
2. With proper quality, asphalt is irreplaceable in any weather.
3. Numerous defects that are clearly visible to pedestrians are rarely visible from a car window;
4. The production of heated and viscous mixtures is not a simple task, despite the automation of the process;
5. The difficulty of using heated mixtures is partly compensated by the appearance of cold asphalt;
6. Asphalt paths in the garden are not made precisely for the reason unpleasant odor bitumen, although over time the mixture hardens and causes inconvenience only in hot weather.

Existing alternatives to asphalt are currently too expensive and not as practical. Unlike others building materials, the improvement of asphalt occurs not through the development of new materials, but through the modernization of old ones.

The widespread introduction of polymer modifiers makes it possible to fundamentally improve the properties of road surfaces and expand the limits of their technological application, which is confirmed by numerous tests of the material.

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