Asphalt concrete according to gost: classification and

In this article we will talk in detail about what is included in the composition of asphalt concrete. In addition, we consider the classification of these materials, their technical and operational properties. The topic of the article is of considerable interest, since the scope of asphalt affects a variety of areas, starting with the device of public roads and ending with the manufacture of floor screed in industrial buildings.

And it is precisely on how well the asphalt mixture is prepared and subsequently used that the strength, durability and price of these coatings depend. So, we will study what asphalt concrete is and what caused its demand.

Main features and composition

Asphalt concrete is a wide list of materials manufactured in accordance with the requirements given in GOST 9128. During the preparation process, thorough mixing and subsequent compaction of the mixture of mineral aggregates and heated bitumen is performed.

The finished mixture has a relatively uniform consistency without large-sized inclusions, without cavities, with the same degree of density throughout the entire thickness of the stacked layer.

The structure of asphalt concrete is largely determined by the composition of the ingredients used.

The traditional composition includes:

• mineral materials (crushed stone or gravel, crushed or natural quartz sand, fine mineral powder);
• organic binders (bitumen and emulsions based on it).

To obtain the desired consistency, all the ingredients that make up the mixture are mixed warmed to the desired temperature.

Application features

Due to high manufacturability, ease of installation, variety of modifications, tight deadlines for brand strength and other advantages, asphalt concrete mixtures have become common as material for construction and repair:

• motorways, designed for increased mechanical loads;
• public roads, sidewalks, ramps, ramps, etc .;
• squares, grounds, car parks;
• foundations of industrial, storage and commercial facilities;
• runways of airfields.

Of course, this is only a brief list of areas in which building mixtures made using bitumen and mineral aggregates can be used. However, the high popularity of the material is not surprising, since these coatings are characterized by high transport and economic indicators.

Asphalt concrete, which has gained brand strength, wears out slowly in comparison with other building materials. In addition, asphalt coatings demonstrate high resistance to the negative effects of environmental factors, including precipitation, sudden temperature changes, long-term exposure to sunlight and excessive humidity.

Classification

The current GOST for asphalt concrete involves the following classification of mixtures - based on mineral aggregate and bitumen.

In accordance with the type of bitumen used and its temperature of heating, the following modifications differ:

• hot mixtures based on liquid and viscous oil road bitumen with a temperature when laying the coating is not less than +120 ° С;
• cold mixtures based on liquid petroleum road bitumen with a laying temperature of not less than + 5 ° C.

Based on the parameters of mineral aggregate, asphalt concrete is divided into:

• crushed stone mixtures;
• gravel mixes;
• sand mixtures.

In accordance with the maximum grain size of the mineral aggregate, asphalt concrete is divided into the following categories:

• coarse-grained with a particle size of not more than 40 mm;
• fine-grained with a particle size of not more than 20 mm;
• sandy with a particle size of not more than 10 mm.

Important: Modern cold mixes are made using fine-grained or sandy aggregate.

An important parameter, according to which the classification of asphalt concrete is carried out, is the residual porosity. This parameter with reference to hot mixtures is calculated as a percentage ratio of the number of pores to the volume of compacted material.

In accordance with the parameters of residual porosity asphalt concrete is divided into the following types:

• highly porous (10.0-18.0%);
• porous (5.0-10.0%);
• dense (2.5-5.0%);
• high density (1.0-2.5%).

Important: Cold mixtures after a set of brand strength should be characterized by residual porosity in the range of 6.0-10.0%.

Hot asphalt mix, in accordance with the content of crushed stone or gravel aggregate, is divided into the following categories:

• asphalt flytip (50-60%);
• type "b" (40-50%);
• type "in" (30-40%).

The crushed-stone asphalt concrete, prepared on the basis of a cold mixture, according to the content of mineral aggregate corresponds to types “B” and “B”. To indicate the type of mixture, in addition to the type designation, the letter “x” is indicated, that is, cold.

Sand filled materials, both hot and cold, are divided into the following categories:

• Type "G" - prepared using sand obtained in the process of crushing and subsequent fractionation of rocks.
• Type "D" - prepared using natural sand or from a mixture of natural sand with residual materials.

Asphalt grades

In accordance with the physico-mechanical parameters, the following grades are assigned to asphalt:

• Mark 1 - this category includes a wide range of different coatings, starting with porous and ending with dense asphalt concrete. For example, asphalt concrete grade 1 type A is used in the construction and repair of roads, landscaping, etc.

Important: Materials with high porosity are not advisable to use as an independent coating. Porous mixtures are used for arranging the bases for the subsequent laying of more dense materials.

• Grade 2 - assigned to materials with a wide range of density with different content and percentage of gravel and sand. For example, asphalt concrete grade 2, type B, are the most common mixtures that are commonly used for the construction of various types of roads and squares, parking devices, etc.
• The brand of asphalt concrete 3 is assigned to materials that do not contain gravel or crushed stone. Instead of these mineral aggregates, sand and mineral powders are used. Mixtures of this type are characterized by a high density of concrete and are mainly used during seasonal patching of road surfaces.

Asphalt production

After we have figured out what the asphalt concrete mixtures are and what their technical and operational characteristics are, consider how these materials are made.

Important: Regardless of production volumes, you will need special equipment. Therefore, to make a full-fledged asphalt mixture with your own hands for arranging the territories adjacent to the house will not work. On the other hand, having a compact mobile ABZ, you can organize a profitable business.

Let's take a closer look at what are the features of the production process.

Manufacturing features

As already mentioned, asphalt concrete is made from solid or bulk mineral fillers and a viscous binder. The essence of the preparation of the finished material is the thorough mixing of the components in order to obtain a homogeneous consistency and optimal density parameters.

It should be noted that new technologies for the manufacture of asphalt pavements are permanently developed. For example, abroad, to reduce the cost of the finished product and simultaneously increase the strength characteristics of concrete, rubber is added to the composition. As a rule, the waste produced in the process of recycling tires.

In addition, foreign manufacturers integrate special pigments into the mixture to improve the aesthetic parameters of the material. Today, some domestic manufacturers try to make colored decorative asphalt, but such coatings have not received much popularity for a variety of reasons.

Despite the variety of technological innovations, let us dwell on the features of the manufacture of mixtures in accordance with the requirements of GOST 9128-97.

ABZ and their varieties

Asphalt production is carried out at specialized enterprises of asphalt concrete plants (ABZ).

In accordance with the mechanism of production, ABZ are divided into modifications of cyclic and continuous action.

• ABZ cyclic actions are the enterprises calculated on regular production of average and small volumes of road mixes. Therefore, such enterprises are located near large populated points where there is a permanent need for materials for the construction and repair of pavement.

The uniqueness of such plants lies in the possibility of changing the composition of their products several times per shift without compromising the quality of the mixtures.

Cyclic ABZ are equipped with a full set of equipment for receiving the filler and mixing it with a binder component. As an additional specific equipment, plants can be equipped with a screen, crushing and screening vibrating screen and tanks for storing finished products.

The use of the screen makes it possible to achieve a high quality of the finished asphalt, since the bulk components are divided into fractions before they get into the mixer. The presence of containers for storing the ready mix allows you to make products with a small margin.

• ABZ continuous action, in contrast to cyclic analogs, are equipped with only the necessary equipment. Such a constructional feature allows producing compact complexes adapted for transportation from one object to another.

The production of asphalt mix at such ABZ is carried out continuously, that is, the ingredients are fed into the bunker, processed there and sent to silos as a ready mix.

A significant disadvantage of continuous-action complexes is the absence of a screen in the basic configuration. As a result, the aggregates are not thoroughly processed, and the mixture is not sufficiently homogeneous.

Often, due to large-sized inclusions, asphalt concrete prepared on such equipment does not meet the requirements of GOST. On the other hand, due to compact dimensions, the equipment can be used by small specialized enterprises.

Production technology

Instructions for the manufacture of asphalt mixes in accordance with GOST 9128-97 involves the implementation of the following steps:

• Evaluation of the quality of components of the future mixture - this stage is especially important, since most of the operational characteristics of the finished product depend on it.
• Processing of mineral aggregates, during which the grinding and sieving of components to obtain the desired fraction.
• Component supply to heating hopperwhere under the influence of high temperatures excess moisture evaporates and in parallel the heating of the binder component is carried out.
• Combining components in a mixer. Due to long-term mixing, excess air is removed from the composition, therefore, the number of voids is minimized and the mixture acquires a uniform consistency.
• Supply of finished product in temporary storage tanks (silos). Due to the special design, containers are able to maintain a high temperature of the material for several days.

Methods for determining the quality of the finished asphalt

Modern methods for determining the quality of pavement are divided into methods used in laboratory conditions, and methods used outside the laboratory.

To determine the quality of asphalt concrete outside the laboratory, portable devices are used, such as, for example, the asphalt concrete density meter PA MG4.

As the name implies, the device determines the density of the coating. According to the research results, it is possible to get an idea of ​​such parameters as resistance to mechanical loads and water saturation of asphalt concrete.

Laboratory tests can provide more detailed and accurate data on the quality of the material. For laboratory tests, a sample is taken. Subsequently, on special stands, the sample is subjected to the stresses that in their natural environment affect asphalt concrete.

Conclusion

Now you have a general idea of ​​what constitutes asphalt concrete, according to what parameters it is classified, how it is made and how you can check its quality. You can find more useful information by watching the video in this article.