Online methods for testing asphalt concrete mixtures. Asphalt concrete testing laboratory

Materials used in construction must undergo tests that document the compliance of their properties with the requirements of GOSTs. After testing the material, technical documentation (certificate) is issued, which confirms the quality of the products. Asphalt is relatively simple to produce, but laboratory testing of asphalt concrete is also provided for in the regulations of the current legislation.

Asphalt production

The technology for producing asphalt concrete is quite simple. Private entrepreneurs are not afraid to invest their funds in this area. The big advantage of the material is that it can be produced not only in large industrial enterprises, but also in small mobile devices.

In general, the manufacturing technology is the same for all asphalt pavements:

measuring the dosage of constituent substances;
preparation of each ingredient;
mixing ingredients.

Technologies used

There are several technologies for laying asphalt concrete. Each of them is used in different climatic conditions.

Asphalt laying technologies:

Undoubtedly, each technology has its pros and cons. The choice of the right one depends on many factors: climatic, economic, assigned tasks, etc.

Sampling rules

Test work is carried out in accordance with GOST. The first stage is the selection of material samples. First, the mixture is prepared in accordance with the selected technology. Samples are formed from the finished asphalt to test strength, adhesion and swelling. There are two molding methods. They depend on the amount of crushed stone in the finished material.

Options for forming samples for testing asphalt concrete in the laboratory:

Crushed stone in the finished mixture is less than 35%. The sample is pressed under a pressure of 40 MPa.
More than 35% in the composition of asphalt. In this case, the material is compacted due to vibration, and only then pressing occurs. Press pressure - 20 MPa.

To test cold-produced asphalt concrete, compaction occurs under very low pressure - 0.5 MPa. This allows you to check the asphalt: whether it can last for a long time without deformation or destruction. All samples should be taken no later than half an hour after preparing the mixture.

When quality control of already laid asphalt occurs, samples are drilled (sometimes cut out). To do this, use a drilling rig or a pneumatic hammer.

Creating samples

When testing asphalt concrete for physical properties, cylindrical samples are selected. This happens by compacting the finished mixture in special molds.

Pressing order:

This is a generalized method of pressing asphalt concrete. For each manufacturing technology (cold, hot) it is slightly different.

Test methods

Any laboratory test occurs in three stages: preparation, testing and processing of the results obtained. There are several methods for monitoring indicators.

Indicator name	Instruments required for measurement	Essence of the test
Specific Gravity	Scales and vessel with a volume of 2−3 liters	The density is determined taking into account the porous part. First, the samples are weighed dry, then immersed in a vessel with water. Re-weighing is performed. Next, the sample is removed from the vessel and the weight is checked again. Laboratory test results are processed taking into account pores.
Definition of porous part	Not required	The pore volume is calculated as a percentage. Calculations are based on the obtained density data.
Swelling of asphalt	Not required	Produced by calculation based on previously obtained data.
Strength	Press, thermometer, containers	The maximum load threshold at which the sample begins to fail is determined. Using a press, the breaking load is calculated.

After all tests have been completed, a report table is drawn up. If the values fall within the range established by GOST, it means that asphalt can be used in the construction of new roads or the repair of old ones.

Asphalt concrete is a modern artificial one, produced by compacting an asphalt concrete mixture, mineral filler (, sand) and. In the Russian Federation, the nuances of assessing the quality of asphalt concrete and asphalt concrete mixtures are outlined in state standards. Since it is often not possible to independently distinguish good material from defects, when implementing any large ones, it is recommended to order laboratory testing of asphalt concrete and asphalt concrete mixtures from expert companies. One of the best representatives of the latter is our independent organization.

The state standard establishes that testing of asphalt concrete is carried out according to the following material parameters:

deformability;
shear resistance;
compressive strength;
splitting strength.

Testing of asphalt concrete involves laboratory determination of the following characteristics of the object:

average density;
compaction coefficient;
grain composition;
water saturation;
compressive strength.

The likelihood of encountering a product of unsatisfactory quality on the construction market at the moment is relatively small, but it is still present. And even if the buyer purchases a product with acceptable performance characteristics, he still often gets something completely different from what he expected.

How is asphalt concrete tested?

The methods used can vary greatly depending on the qualities and properties that the asphalt concrete test is aimed at identifying.

The average density of asphalt concrete involves step-by-step weighing of pre-selected samples. First, the mass of the object in its normal state is determined. Then the material is placed in water for half an hour, after which it is taken out, cleaned of excess moisture using a rag and weighed again. Based on the results obtained, experts calculate the average density of the object.

Why should I order an asphalt concrete test?

The likelihood of encountering a product of unsatisfactory quality on the construction market is currently relatively small, but it is still present, so testing asphalt concrete is a very relevant service. And even if the buyer purchases a product with acceptable performance characteristics, he still often gets something completely different from what he expected.

Some suppliers ignore the requirements for building materials by current regulatory documentation. Wanting to save money in production, they can in every possible way adjust the composition of the goods they offer. This problem becomes especially relevant in the construction market during the warm seasons, when most projects for the construction of new buildings are activated. Then, trying to satisfy the sharply increased demand, the manufacturer can often set priorities on quantity, which will inevitably affect quality.

An incomplete solution to the problem is possible if you order goods directly from specialized factories. However, they only work with large purchases. In addition, they require pickup. The option is good, but not always suitable.

Moreover, neither the relevant certificates nor the famous name of the manufacturer can fully guarantee quality. Firstly, defects periodically occur almost everywhere - including even among the most conscientious manufacturers. Secondly, the low quality of the mixture may be due to incorrect storage or transportation conditions, so the problem often does not even come from the manufacturer as such.

The trouble is that potential problems do not end with the manufacturer and distributor of the product. It is also necessary to control the direct contractor of the construction work. A contractor can purposefully purchase low-quality asphalt concrete on the construction market at low prices, while the reporting documentation will indicate an expensive and good material. It is also not uncommon for a particular contractor to artificially simplify the technology for manufacturing the final product - due to greed, saving time, or even simple laziness. It is clear that all this cannot have a favorable effect on strength, durability and, as a consequence, safety. So it turns out that you can’t do without third-party control.

Therefore, the only effective and reliable way to ensure the quality of the material is to order laboratory testing of asphalt concrete from an independent company with the appropriate specialization. For example, in our expert organization.

What are the purposes of testing asphalt concrete?

Testing of asphalt concrete has the following main goals:

carry out a thorough analysis of the quality of asphalt concrete, confirm or refute the compliance of its properties with state standards, detect and record discrepancies between the declared and actual characteristics of the product;
conduct a comprehensive study of low-quality asphalt concrete in order to identify the reasons for a significant deterioration in its characteristics, find the culprit for the unsatisfactory condition of the final product - the supplier, contractor or third party;
form, based solely on a comparison of objective data obtained as a result of research procedures, with current state standards.

Laboratory testing of asphalt concrete can be carried out not only to get an answer to the question of the suitability of the building material for further use. The expert opinion provided to the client upon completion of the research is a legally binding document. You can operate it in conflict situations related to the quality of asphalt concrete. We are also talking about court proceedings, where the expert opinion of our organization will become one of the main arguments of the customer when justifying his point of view. Often, however, the very fact of the presence of this document saves the client from the need to transfer the case to the judicial level: not wanting to get involved in a deliberate a losing conflict, the unscrupulous supplier satisfies all the demands placed on him. For this reason, testing of asphalt concrete, offered by our expert organization, is not only a way to obtain objective information regarding the quality of a building material, but also an effective mechanism for protecting one’s rights and legitimate interests.

Some suppliers ignore the requirements for building materials by current regulatory documentation. Wanting to save money in production, they can adjust the composition of the goods they offer in every possible way. This problem becomes especially relevant in the construction market during warm seasons, when most projects for the construction of new buildings are activated. Then, trying to satisfy the sharply increased demand, the manufacturer can often set priorities on quantity, which will inevitably affect quality.

Why should I order asphalt concrete testing from your company?

The asphalt concrete tests you order will be carried out only by highly qualified specialists who have not only an impressive theoretical base, but also extensive experience in solving relevant problems.
All asphalt concrete tests are carried out in modern, equipped with new and high-precision equipment.
You get reliable results in the fastest possible time.
And all of the above is available at the most reasonable prices!…

When planning the arrangement of road surfaces, it is important to choose high-quality materials for laying. This need is due to high loads during operation and various climatic conditions. To be sure of the quality of materials, order an asphalt concrete test. Our construction laboratory has been conducting similar events for many years, and can guarantee the quality and reliability of the results to each client.

Make an order

From 2 to 4 days

№ n/n	Name of tests, characteristics	Units	Cost, rub; without VAT	Test timing	Requirements Document
7. Roads mixtures of asphalt concrete road, airfield and asphalt concrete. mixtures of asphalt concrete and asphalt concrete crushed stone-mastic.					SP 34.13330.2012 SP 78.13330.2012 SP 42.13330.2016 SP 82.13330.2016 GOST 9128-2013 GOST 31015-2002
7.1	Sampling of asphalt concrete mixture for testing	1 sample	800,00	1 day	GOST 12801-98;
7.2	Preparation of samples from asphalt concrete mixture (cores)	1 sample	2650,00	1-2 days	SP 78.13330.2012
7.3	Determination of shear resistance characteristics and coefficient of internal friction at 50	1 sample	2100,00	1-2 days	GOST 12801-98;
7.4	Determination of the grain composition of the mineral part of the asphalt concrete mixture (by burning method)	1 sample	2700,00	3-4 days	GOST 12801-98;
7.5	Determination of binder flow rate	1 sample	1100,00	1-3 days	GOST 12801-98;
7.6	Determination of average density and water saturation of mixture samples	1 sample	1550,00	1-2 days	GOST 12801-98;
7.7	Compressive strength at temperatures: at 50	1 sample	1180,00	1 day	GOST 12801-98;
7.8	Compressive strength at temperatures: at 20	1 sample	1180,00	1-2 days	GOST 12801-98;
7.9	Determination of water resistance	1 sample	2000,00	1-2 days	GOST 12801-98;
7.10	Determination of water resistance during long-term water saturation	1 sample	2500,00		GOST 12801-98;
Cutting and testing cores from the coating: Determination of compaction coefficient, water saturation coefficient, thickness of asphalt concrete in coatings and bases.
7.11	Sampling cores from asphalt concrete pavement to measure thickness	1 core	1000,00	1 day	GOST 12801-98; SP 78.13330.2012
7.12	Sampling cores from asphalt concrete pavement	1 sample (3-4 cores)	1800,00	1 day	GOST 12801-98; SP 78.13330.2012
7.13	Preparation of coating samples and marking	1 sample	500,00	2-4 days	GOST 12801-98; SP 78.13330.2012
7.14	Determination of average density and water saturation in cores	1 sample	1550,00
7.15	Warming up and reshaping cores	1 sample	2650,00
7.16	Determination of average density and water saturation of remolded samples	1 sample	1550,00
7.17	Determination of the compaction coefficient of mixtures in structural layers of road pavement	1 sample	200,00
Increasing price coefficients in the price list: -2.0 work on weekends and holidays; -1.5 extraordinary accelerated execution of work *Depending on the volume of work, prices may be adjusted

Characteristics of asphalt concrete

The main components of such material are crushed stone, sand, bitumen and mineral powder. Asphalt concrete has the form of a compacted mixture. One of the direct purposes is the arrangement of roads and other surfaces.

Asphalt concrete is characterized by:

type of coarse aggregate (may be a predominance of crushed stone, gravel or sand);
level of hardness and viscosity of bitumen;
size of crushed stone/gravel granules;
main purpose.

What are asphalt concretes used for? Each type has its own purpose. Roads cover main streets, sidewalks and driveways. Airfields are equipped with runways and sites. Garages and roofs of industrial buildings are covered with industrial asphalt concrete. There are also decorative ones. They are used to decorate city squares and cover dividing strips.

Researching

Our laboratory tests asphalt concrete to ensure compliance with various government requirements and standards. A detailed list can be found in the “Information” section of the website and the “GOST” subcategory. In addition, during the inspection the goal is to establish the reasons for the deterioration of performance if deviations are identified.

Our testing center conducts independent laboratory tests of the quality of asphalt concrete. In addition, we have our own road laboratory, which makes it possible to quickly go to the work site and take samples by cutting out cores.

At the request of the customer, we can also conduct research and give an opinion on already selected asphalt concrete samples provided for inspection.

IC "LSK" studies the following indicators:

layer thickness;
water saturation;
resistance to frost;
average density and others.

High accuracy of test results is possible due to the laboratory being equipped with modern equipment. In addition, the center’s specialists are experienced people who have been working in this field for many years. All this allows us to carry out high-quality tests of asphalt concrete and asphalt concrete mixtures in the shortest possible time and provide you with a full report on the quality of the building material.

Stages of work execution

Regulated and implemented on the basis of the following standards -

SNiP 306.03.85 and GOST 12801–9.8.

During the construction/repair of the roadway, there is a constant need to monitor the condition of the pavement - the quality of asphalt concrete according to samples obtained at 3 points over a laying area of 7000 m2.

Cores/cuts should be taken in layers from hot/warm mixtures 1-3 days after completion of the coating compaction work, and from cold mixtures - after 15-30 days.

Preparatory work

Before sampling, the area of asphalt concrete pavement on which work is to be performed must be cleared of dust. The selected core/cutting sample must have a solid appearance and shape, and must be missing.

If the coating has more than one layer, then sampling is carried out over the entire thickness, up to the upper layers of the base.

To select cores, select an area at a distance of at least half a meter from the edge of the pavement or the axis of the roadway with a size of no more than 0.5 * 0.5 m.

Main works

Selection is carried out in the form of square cuttings using, or cylindrical cores with a core sampler.

The dimensions of the cutting and the number of cores from one point are set to max. the size of crushed stone grains and the number of samples required for testing.

The mass of cuttings/cores must be at least 1 kg for sand mixtures, 2 kg for fine-grained mixtures, 6 kg for coarse-grained mixtures.

The diameter of the cores must be at least 50 mm - for samples of sandy asphalt concrete; 70 mm - for fine-grained;

100 mm - for coarse grain.

The obtained samples are marked, assigned numbers, a core sampling report is filled out, in which the construction/repair object is indicated, the name of the contractor who performed the work, and the number of the picket where the sampling was carried out is indicated.

Upon completion of the selection, the resulting holes in the asphalt concrete pavement are filled to the full depth (with a specially prepared mixture of bitumen, stone material and solvent). Filling occurs with some margin, so that a small protrusion up to 10 mm high (reserve) is formed on top of the hole. After this, it is enough to compact the roller protruding above the hole with your foot, and the rest of the compaction will occur over time naturally under the wheels of cars.

Multilayer cores are separated in the laboratory and recorded in a special test log; the selection report records the time of their delivery. The full cycle of sample testing is carried out within three calendar days.

The main difference between AB and many other building materials is the need for quick application of the finished product. Otherwise, it loses viscosity, becomes brittle and is not suitable for use. So, let's look at the basic schemes and technologies for the production of asphalt concrete.

This video will tell you more about the features of asphalt concrete production:

Technologies

The finished product is divided into 3 groups according to the manufacturing method:

cold– solid ingredients are dried, but not heated, warmed before adding. This material is best suited for patching, filling and patching. It is allowed to work with it at a temperature not lower than - 10 C;
hot and warm– solid ingredients are dried and heated, bitumen is heated to a higher temperature. Hot AB is more viscous and is not suitable for operation at sub-zero temperatures. However, it is precisely this that is used to build roads.

The only significant difference for the organization of production is the stage of preheating the ingredients. For the formation of a production line, the more fundamental question is the type of production: cyclical or continuous.

Cyclic method involves the production of AB with a capacity of 100 to 300 tons per day. An undoubted advantage is the ability to quickly change the recipe: each batch can be made with a different composition. However, such a line is less mobile due to the large dimensions of the mixing tower.
Continuous way ensures the production of asphalt concrete in a much larger volume - from 50 to 600 tons per day. Production starts literally 3 days after relocation. However, the absence of a fractionation stage here may cause a violation in the recipe. The solution to the problem is to install a separate screen for preparing solid ingredients.

Cyclic

The main part of production is occupied by the supply system for solid ingredients - inert. Before this, the material is dosed according to the recipe of the produced AB. Mixtures with different compositions are stored in bunkers, from where they are transported to the line.
Solid components are fed cold by a conveyor into a drying drum, where they are dried and heated by air flows.
The material is then transferred to a vibrating screen, where it is separated into different fractions based on grain diameter. This is done using a sieve system.

It is considered more economical to use a drum screen, since in this case the clogging of the pores in the sieves with dust and screenings is eliminated.

Under the screen there are bunkers for hot solid ingredients - for each fraction. From here, a dose of material is loaded into the weigh hopper according to the recipe. The composition of the mixture is set by the program.
Bitumen and mineral dust are loaded into their own hoppers: bitumen from the bitumen storage facility, mineral powder from the silo. Dosing is carried out using the dynamic weighing method.
All components are transferred to the mixing chamber. The mixing cycle leaves 45 s.
The finished battery is stored in horizontal, vertical or mobile tanks. Loaded into dump trucks.

Continuous

In many ways, the technological line here is the same, however, there are differences.

The principle of storage in bunkers is also used here.
The shipment of solid cold ingredients is also carried out from dispensers. But if with the cyclic method they acted as pre-dosers, since the mixture was shipped from hot ingredient bins, then with the continuous method, it is this device that measures the dose for the mixture, and therefore is much more accurate - within 0.1%.
Cold solid ingredients are loaded onto a conveyor equipped with an oversized screen, which is removed at this stage.
The stone then goes to a weigh bridge, where the material is not only weighed, but data on its compliance is transmitted to the weighing system. This allows you to dynamically adjust the composition of the mixture and prevent violations in the recipe.
The material that comes in for inspection is fed into the drying and mixing drum, where it is also dried with air.
Here the stone is mixed with sand, mineral dust, and bitumen.
Asphalt concrete is stored in round silos.

Equipment

The equipment used depends on the method of producing asphalt concrete and the nature of the plant - a stationary or relocating enterprise. For example, for a continuous cycle production line the following units will be needed:

hoppers acting as a dispenser with high precision;
collecting conveyor and conveyor with humidity control;
mixing drum, where ingredients are dried and mixed;
a hopper for the old battery and a supply line for the latter into the dispenser;
vacuum cleaner-fan for removing gases and dust;
dust collector and dust silo;
mineral powder silo;
bitumen tank;
storage bunker – thermally insulated or heated.

Read on to learn how asphalt concrete production is regulated in terms of waste.

Waste

The production of asphalt concrete is of a conditionally waste-free type, since most of the dust generated during fraction separation and preparation is captured and used as part of the mineral powder. For this purpose, the line includes a dust collector and a silo for its storage.

Gases - nitrogen and carbon oxides, sulfur dioxide, and sulfur dioxide - pose a great danger to the environment. To reduce harmful effects, enterprises provide a two-stage cleaning system.

Sample testing

Test methods for asphalt concrete according to GOST

are the object of laboratory research. Moreover, both the ingredients of the mixture, the AB after mixing, and samples of the finished coating are tested.

The purpose of the study is to assess the compliance of the parameters of the prepared AB with GOST standards.

Sample preparation

At the first stage, samples are prepared.

Laboratory– dried stone and sand are heated and dosed according to the recipe. Dehydrated bitumen is heated, all ingredients are mixed manually and then in a laboratory mixer. Temperature and time are respected.
Samples from mixers are selected immediately after unloading the product - 3-4 portions from each batch. Samples are pooled and mixed to obtain an average sample.

Since some tests require compaction of the sample, it is performed on a press:

with a crushed stone share of up to 35% - by pressing at 40 MPa;
with a crushed stone share of more than 35% - vibration at 0.03 MPa. and additional compaction at 20 MPa;
cold samples are compacted in a press at 40 MPa.

Cores are used to control the behavior of the finished product. They are obtained by cutting with a pneumatic hammer or by drilling through the entire thickness of the coating.

This video will tell you about sampling for testing asphalt concrete:

Laboratory tests

First of all, the average density of the AB is established:

the prepared samples are weighed in air;
Places in water for half an hour;
weighed in water;
wiped and weighed again in the air.

The results are calculated as the arithmetic mean of the density of at least 3 samples.

True Density

Determination of true density, that is, without taking into account pores, by the pycnometric method:

an average sample of the mixture or core is crushed to a maximum grain size of;
weigh a portion of the mixture and place it in a flask. Fill 1/3 with distilled water with surfactant;
the flask is placed in a vacuum cabinet under a pressure of no more than 2000 Pa;
the flask is filled with water to the mark, the pressure is reduced to 1 atm and the sample is again left for half an hour;
weighed in water.

The result is the arithmetic mean based on at least 2 samples.

Water saturation

Determination of water saturation, that is, an assessment of the volume of water that the AB absorbs under given conditions. The test examines the same samples on which the average density was measured:

samples are placed in a container and filled with water - no less than 3 cm;
the container is placed in a vacuum device under a pressure of 2000 Pa. The holding time for hot and warm mixtures is 1.5 hours, for cold mixtures – 30 minutes;
the pressure is lowered to normal. The holding time for hot and warm mixtures is 1 hour, for cold ones – 0.5 hours;
samples are removed from the container, wiped and weighed.

Tensile strength

Assessing the tensile strength comes down to determining the load at which the battery will begin to collapse. The studies use samples that have been tested for water saturation:

samples of the hot and warm mixture are kept in a water bath for 1 hour, samples of the cold mixture are kept in an air environment for 2 hours. Ice water is used for cooling;
The sample is placed in the middle of the asphalt concrete testing press plate, the top plate is lowered until the distance to the sample reaches 1.5–2 mm. Then turn on the electric motor;
the maximum value of the force meter is taken as the destructive load.

Water resistance coefficient

Water resistance coefficient - the ratio of the strength of dry AB to the strength of the material subjected to prolonged water saturation - 15 days:

the sample is weighed in air and water;
saturate with water in a vacuum device according to the method described above;
water-saturated samples are transferred to a container and kept for 15 days at a water temperature of 20 C;
samples are removed, wiped and subjected to tensile strength testing.

Bitumen adhesion assessment

Assessment of the adhesion of bitumen to mineral ingredients:

Two samples are prepared from the laboratory or prepared mixture: one serves as a control sample, the other is tested;
A 15% solution of table salt in a beaker (2/3 volume) is brought to a boil;
the mesh with the sample is immersed in the solution so that it covers the sample with a layer of 30–40 mm;
stand for 30 minutes if the bitumen is viscous and 3 minutes if it is liquid;
the sample is removed, the salt is removed and dried on filter paper;
The measurement is carried out after complete removal of moisture.

In addition, GOST regulates testing to determine the composition of the mixture: the proportion of bitumen; granulometric composition of the stone part and so on.

Equipment

To test asphalt concrete, standard chemical laboratory equipment is used.

dishes - flasks, glasses, droppers, porcelain cups, pestles, etc.;
sand and water baths;
press with hydraulic or mechanical drive. Must be equipped with any type of force meter;
chemical thermometer;
laboratory scales 4th accuracy class;
scales for hydrostatic weighing;
vacuum device or vacuum drying cabinet;
laboratory extraction nozzle;
set of sieves for granulometric analysis;
consumables - cotton wool, filter paper, etc.

The production of asphalt concrete is an indispensable part of the road construction industry. Moreover, the organization of work here is such that it is not difficult to obtain different mixtures for different needs.

This video will tell you how the quality of asphalt is checked in the laboratory: