PGS rammer. Crushed stone compaction coefficient - what is it? Factors and properties of construction sand

High rates of construction, accelerated development of residential areas, office buildings makes you think about the quality characteristics of concrete. Solid, strong foundation concrete mortar impossible to create. Concrete is the main connecting, structural material in construction. The quality of concrete directly affects the strength and service life of structures. It is possible to prepare a solution from sand and gravel mixtures, paying attention to the source of occurrence and observing the required ratio of components.

Appointment of ASG

Sand-gravel mixture, or in other words ASG, consists of gravel. The composition is prepared in two ways:

• natural;
• artificial.

The resulting mixture is in great demand and is used in industrial, road, housing construction:

• for ;
• for the manufacture of monolithic, iron concrete structures;
• as a drainage layer of the road surface;
• landscape alignment.

Types, mixture structure

Proportional content of sand, gravel in the mixture - main criterion gravmasses. Gravel should not be more than 75% of the total mass. Great importance is given to the size of the components, and also checked for compliance with standards. Based on the proportional content of the components, two types of sand and gravel soil are distinguished:

• Natural (PGS). The ratio of gravel in percentage in relation to the total mass is not less than 10, and not more than 95 - 1/5 of the entire composition. The classic composition is not subjected to additional processing. The gravel mass is mined in a quarry and immediately shipped to the buyer. Basically, the content of gravel is 10-20% of the bulk. The percentage can rise to 30 if the mixture was mined in reservoirs. The size of the elements reaches from 10 to 70 mm. With a separate agreement with the buyer, the size may be larger than the declared one, the maximum value is 10 cm.
• Enriched (opgs). The proportions of the components are as follows: sand 30%, gravel up to 70%. 3/4 of the entire enriched mass is gravel.

You can get an enriched composition through special preparation. Observing certain proportions, the necessary components are mixed. The result is oops. Given the percentage of gravel, five groups of enriched mixtures are distinguished.

• 1 group. The percentage of gravel from the total mass is 15-25%.
• 2 group. The amount of gravel is 25-30%.
• 3rd group. The content of the component is from 35 to 50%.
• 4 group. The percentage of gravel is 50-65%.
• 5 group. Gravel in an amount of 65 to 75%.

The greater the percentage of gravel contained in the solution, the harder the mass is obtained. depends on the amount of gravel specifications solution, operating parameters. The final cost of concentrated gravel compounds is affected by the amount and percentage of content natural stone.

According to the deposit and the original source of formation, natural gravel mixtures are divided into:

• Ravine (mountain) are characterized by an admixture rocks, the shape of the natural stone is acute-angled, the size is different. The heterogeneity of the structure of this type does not allow the use of the ravine-mountain type for the production of concrete. The mixture is widely used as a drainage during the repair of highways, pits and pits are filled up.
• River (lake). There is a small amount of clay, shell rock. The shape of the elements is rolled.
• Marine. Impurities are contained in a small amount, or absent. The shape of the stones is round, dense.

Lake-river, sea gravel mixtures are used for the manufacture of concrete mortar, which is necessary for buildings of special strength, pouring the foundation.

Features of the choice of mass

In all branches of construction: preparation of structures, pouring of any type of foundation, concrete is required. A responsible approach to the manufacture of concrete mortar ensures the reliability and strength of structures. An important role in the technological process is played by the ratio of components.

The main point is to buy correctly high quality products not worth saving. Concrete reflects how the material is extracted. Pay attention to various impurities, the structure of the mass should not contain them. The absence of foreign components increases the adhesion between gravmass and other components of the solution.

To work with the foundation, enriched mixtures are used, since the amount of gravel in them exceeds the sand content, which increases the density and reduces the friability of the solution.

Compaction degree

Transportation of bulk material leads to its compaction. Compression is controlled by regulatory building standards. The exponential value that determines the amount of reduced volume is called the tamping (compacting) coefficient. Compaction standards are fixed at the state level.

Compaction of the material is a natural process, the coefficient depends on the mass of the batch. Important points are the quality of the material and the method of transportation. The average compaction index is 1.2, according to the standards. For example, for sand, the tamping index is 1.15, for crushed stone - 1.1.

Compression ratio - important point in construction. At the start of work, preparatory stage, during which the thickness, level, quantity and other indicators necessary for subsequent work are determined. The acceptance of the final result is affected by the compaction factor.

When compacting the soil by tamping, the main rules are observed. Differences in the depth of the dug trench are leveled by compaction from the highest marks, gradually moving to lower ones. Compaction is carried out until the density is reached, which is prescribed by the regulations. At the time of work with the mixture, freezing of materials is not allowed, the humidity corresponds to the norm. The process is considered completed when the number of strokes does not exceed the established limits. The so-called "two control strikes" rule.

Concrete preparation process

During individual construction, the mixture is prepared by hand. With small volumes of construction, there is no need to hire expensive construction equipment. Before starting work, it is worth determining the structure, calculating the mass, preparing the appropriate components.

For self-kneading, you will need the following consumable and tools:

• supply of cement of the required grade;
• clean warm water;
• opgs;
• container for kneading;
• (concrete mixer);
• bucket.

Properly matched components affect the quality result. For an enriched look, it is worth making the ratio of parts 8 to 1, where the first is a mixture, the second is cement. This coefficient was determined by trial and error, and is currently actively used. experienced craftsmen. How much water to add is an individual matter. It is worth focusing on the dryness of the components, gradually add liquid until the desired consistency of the solution is reached.

Cement for mortar is used in grades that provide the desired strength. These are m300, m500, m600. Recently, Portland cement has become popular, which has excellent astringent properties. With a small amount of work, concrete m400 is used, taking into account the fact that ready mix Worth spending two hours.

Quality concrete made from PGS is affected by the size of natural stone. The solution acquires the necessary strength with a gravel size of 8 cm. The necessary proportions are maintained: 6 - mixture, 1 - cement.

Why the sand compaction coefficient is needed, and what significance this indicator plays in construction, probably every builder and those who are directly related to this non-metallic material know. The physical parameter has a special meaning, which is expressed through the value of Buy. The calculation parameter is necessary in order to be able to compare the actual density of the material on a certain area of ​​​​the site with the required values ​​\u200b\u200bthat are prescribed in the regulations right on the spot. Thus, the sand compaction coefficient according to GOST 7394 85 is the most important parameter, on the basis of which the required quality of preparation for work at construction sites using bulk non-ore substances is assessed.

Basic concepts of compaction factor

According to generally accepted formulations, the sand compaction coefficient is the density value that is characteristic of a particular type of soil in a certain area of ​​​​the site to the same value of the material that is transferred by standard compaction modes in laboratory conditions. Ultimately, it is this figure that is used in assessing the quality of the final construction work. In addition to the above technical regulations, to determine the coefficient of sand compaction during tamping, GOST 8736-93 is used, as well as according to GOST 25100-95.

At the same time, it must be remembered that in the working process and production, each type of material can have its own unique density, which affects the main technical indicators, and the sand compaction coefficient according to the SNIP table is indicated in the relevant technological regulation SNIP 2.05.02-85 in part of Table No. 22. This indicator is the most important in the calculation, and these values ​​\u200b\u200bare indicated in the main project documentation, which range from 0.95 to 0.98 in the project calculation range.

How does the sand density parameter change?

Having no idea what the required sand compaction coefficient is, it will be difficult during the construction process to calculate the required amount of material for a particular technological process work. In any case, you will need to find out how the state of the material was affected by various manipulations with non-metallic matter. The most difficult calculation parameter, as the builders admit, is the sand compaction coefficient during the construction of the SNIP road. Without clear data, it is impossible to do quality work in road construction. The main factors that affect the final result of material readings are:

• Method of transportation of the substance, starting from the starting point;
• The length of the sand route;
• Mechanical characteristics affecting sand quality;
• The presence of third-party elements and inclusions in the material;
• Ingress of water, snow and other precipitation.

Thus, when ordering sand, you need to thoroughly check the sand compaction coefficient in a laboratory way.

Features of backfill calculation

To calculate the data, the so-called “soil skeleton” is taken, this is a conditional part of the structure of a substance, with certain parameters of friability and moisture content. The calculation process takes into account the conditional volumetric weight of the considered “soil skeleton”, takes into account the calculation of the ratio of the volumetric mass of solid elements, where water would be present, which would occupy the entire mass volume occupied by the soil.

In order to determine the compaction coefficient of sand during backfilling, it will be necessary to carry out laboratory works. AT this case moisture will be involved, which in turn will reach the necessary indication criterion for the condition optimal humidity material at which the maximum density of the non-metallic substance will be achieved. When backfilling (for example, after a dug pit), it is necessary to use tamping devices that, under a certain pressure, allow you to achieve the required sand density.

What data is taken into account in the process of calculating the Purchase?

At any project documentation on the construction site or the construction of the roadway, the coefficient of relative sand compaction is indicated, which is necessary for quality work. As you can see, the technological chain of delivery of non-metallic material - from the quarry directly to construction site changes in one direction or another, depending on natural conditions, methods of transportation, storage of material, etc. builders know that in order to determine the required amount of the required volume of sand for a specific job, it will be necessary to multiply the desired volume by the value of the Purchase specified in the project documentation. The extraction of material from the quarry results in the material having loosening characteristics and a natural decrease in weight density. This important factor will need to be taken into account, for example, when transporting a substance over long distances.

Under laboratory conditions, a mathematical and physical calculation is made, which will ultimately show the required sand compaction coefficient during transportation, including:

• Determination of the strength of particles, caking of the material, as well as the size of the grains - the physical and mechanical method of calculation is used;
• With the help of a laboratory determination, the parameter of relative humidity and the maximum density of non-metallic material is revealed;
• Under conditions of natural location, the bulk density of a substance is determined empirically;
• For transportation conditions, an additional method for calculating the density coefficient of a substance is used;
• Climatic and weather characteristics are taken into account, as well as the influence of negative and positive parameters of the ambient temperature.

“In each project documentation for the implementation of construction and road works, these parameters are mandatory for keeping records and making a decision on the use of sand in production cycle.»

Compaction parameters during production work

At any working documentation you will be faced with the fact that the coefficient of the substance will be indicated depending on the nature of the work, so below are the calculation coefficients for some types of production work:

• For backfilling of the pit - 0.95 Kupl;
• For backfilling of the sinus regime - 0.98 Kupl;
• For backfilling trench pits - 0.98 Kupl;
• For restoration work underground equipment everywhere engineering networks located near the carriageway of the roadway - 0.98 Kupl-1.0 Kupl.

Based on the above parameters, we can conclude that the tamping process in each case will have individual characteristics and parameters, while various equipment and ramming equipment.

“Before carrying out construction and road works, it is necessary to study in detail the documentation, where in without fail the density of the sand for the production run will be indicated.”

Violation of the requirements of the Purchase will lead to the fact that all work will be recognized as of poor quality, and will not comply with GOST and SNiP. Supervisory agencies in any case will be able to identify the cause of the defect and the poor quality of the work, where the requirements for sand compaction were not met during a specific area of ​​production work.

Video. Sand compaction test

When choosing crushed stone, it is important to take into account such an indicator as the compaction coefficient. This criterion shows how much it is possible to reduce the volume of material, while maintaining the same mass due to tamping or natural shrinkage. This indicator is used to determine the amount of aggregate, both upon purchase and directly during the construction process.

In view of the fact that after ramming the bulk density of crushed stone of any fraction will increase, it is necessary to immediately take into account the stock of material. And in order not to buy too much, a correction factor is needed.

The compaction coefficient (Ku) is a very important indicator, which is necessary not only for the correct ordering of materials, but also in order to provide for further shrinkage of the gravel layer after its loading. building structures. Moreover, knowing the compaction coefficient, it is possible to predict the stability of the construction objects themselves. Due to the fact that the tamping factor is, in fact, the degree of volume reduction, it can vary depending on 4 factors:

1. Loading method and parameters (for example, from what height backfilling is performed).
2. Features of the transport by which the material is delivered to the object, and the distance to the construction site - after all, even a stationary mass gradually compacts as a result of subsidence under its own weight.
3. Fractions of crushed stone and the content of grains of smaller size than the lower limit of a particular class of crushed stone.
4. Flakiness - needle-shaped stones shrink less than cuboid ones.

It should be remembered that the strength of concrete structures, foundations of buildings and roads directly depends on the accuracy of determining the degree of compaction. However, one should also not forget that tamping on the site is often carried out only on the top layer, and in this case the calculated coefficient does not always correspond to the actual shrinkage of the base. Especially often this happens when construction is not done by professionals, but by amateurs. In accordance with the requirements of the technology, each layer of backfill must be rolled and checked separately.

Another parameter that must be taken into account is that the degree of compaction is calculated for a mass that is compressed without lateral expansion, that is, it is limited by walls, which prevents it from spreading. At the site, such conditions for backfilling any fraction of crushed stone are not always created, so a small error remains. This fact should be taken into account, first of all, when calculating the settlement of large structures.

Transport seal

It should be noted that finding some standard value for compressibility is actually not easy, as too many factors affect it. (All of them are listed above). The supplier may indicate the crushed stone compaction factor in the accompanying documentation, although GOST 8267-93 does not directly require this. However, when transporting gravel, especially its large batches, there is often a significant difference in volumes when loaded and at construction site where it was delivered. Therefore, the correction factor, which takes into account the compaction of crushed stone, must be entered into the contract and controlled at the reception point. The only mention in the current GOST: the compaction coefficient, regardless of the fraction, should not be higher than 1.1. Suppliers are certainly aware of this and are trying to keep a small stock in order to avoid returns. Measurements are often resorted to during acceptance, when crushed stone is delivered to the construction site, since it is ordered not in tons, but in cubic meters. To do this, the truck body with the crushed stone in it must be measured from the inside with a tape measure, then calculate the volume of delivered gravel, and then multiply it by a factor of 1.1. Such a calculation will allow you to approximately determine how many cubes were filled into the back of a truck before shipment. If the figure obtained taking into account the compaction is less than that indicated in the accompanying documents, then the car body was underloaded. Equal to or greater than indicated in the documents - you can safely unload crushed stone.

Site compaction

It should be noted that the above figure - 1.1 - is taken into account only during transportation. At a construction site where crushed stone is compacted artificially, using a vibrating plate or a roller, this coefficient can increase to 1.52. At the same time, performers need to know exactly the degree of shrinkage of the gravel backfill. Usually this parameter is listed in the project documentation. However, if there is no need for an exact value, they use the average indicators that are indicated in SNiP 3.06.03-85:

Crushed stone of fraction 40-70, as a rule, has a compaction of 1.25-1.3 (if its grade is not lower than M800). Up to M600 - from 1.3 to 1.5. For small and medium classes of 5-20 and 20-40 mm, these indicators have not been established, since they are often used only when buckling the upper bearing layer of grains 40-70.

Laboratory research

It is customary to calculate the compaction coefficient on the basis of laboratory test data, during which the mass of crushed stone is subjected to ramming and testing on various devices. There are several methods here: volume substitution (GOST 28514-90); standard layer-by-layer compaction of crushed stone (GOST 22733-2002); express methods using one of three types of density meters: static, water balloon or dynamic.

The results are obtained either immediately or after 1-4 days, depending on which method for the study is chosen. The cost of one sample of the standard test is 2500 rubles. In total, at least five such tests must be carried out. If data is needed urgently, for example, during the day, express methods are used based on the results of selecting at least 10 points. The cost of each point is 850 rubles. In addition, you will have to pay for the departure of the laboratory assistant to the site - about 3 thousand rubles more. However, one cannot do without accurate data on the construction of large facilities. In addition, a reputable construction organization must have official documents, which confirm that the contractor complies with the requirements of the project.

Is it possible to find out the degree of tamping yourself?

Yes, the coefficient can be determined both in the field and for the needs of private construction. To do this, you must first find out the bulk density for each size: 5-20, 20-40, 40-70. It directly depends on the mineralogical composition of the material, but only slightly. Crushed stone fractions have a much greater influence on the volumetric weight. For the calculation, you can use averaged data:

More accurate density data for a specific fraction of crushed stone can be determined in the laboratory or by weighing a known volume of building crushed stone, followed by a simple calculation:

Bulk weight = mass / volume.

After that, the mixture is rolled to the state in which it will be used on the site, and measured with a tape measure. And then they again calculate the formula above, resulting in 2 different densities - before and after tamping. By dividing both numbers, we get the compaction coefficient for a particular material. With the same sample weight, you can simply find the ratio of the two volumes - the result will be the same. It should be noted that if the indicator after tamping is divided by the initial density, then the number obtained in the answer will be more than one- in fact, this is the material safety factor for sealing. In construction, it is used if the final parameters of the gravel pad are known and for ordering it is necessary to determine the amount of crushed stone of the selected fraction. The reverse calculation results in a value less than one. However, these figures are equivalent and in the calculations it is important to understand which one should be taken.

Coefficient of compaction (ramming) of ASG, sand, crushed stone, soil.

Compaction factor (Kupl)- this is the normative number, which is determined by GOSTs and SNIPs, taking into account how many times the bulk material (namely, sand, crushed stone, soil, etc.) is compacted (hence, its external volume has also decreased) during transportation and ramming. Its value ranges from 1.05 - 1.52: The compaction coefficient is taken into account from the volume of supplied bulk material (soil, sand, sand, crushed stone, expanded clay, etc.), as well as from the compaction mechanism (rammer). The very quality of the inert material is of great importance. For example, ASG (sand-gravel mixture) may contain different gravel content (from 10% to 90%), and hence change To upl. Based on this, the data in the table are averages.

The compaction coefficient is a dimensionless number showing the degree of reduction in the external volume of loose granular building material during its transportation by transport or ramming. It is used in relation to sand and gravel mixtures, sand, crushed stone, soil.

Each type of crushed stone has its own marking, specified in the accepted standard. (GOST 8267-93). It also describes methods for determining the compaction factor. Manufacturers must indicate this parameter in the marking of crushed stone of one kind or another. The degree of compaction is also determined experimentally by specialists. Results can be received within 3 days. The amount of crushed stone compaction is also measured by express methods. For this, static and dynamic density meters are used. The cost of measuring the value of the coefficient in the laboratory is much lower than directly on the construction site.

Why do you need to know the value of the compaction factor?

Knowledge exact value Ku (crushed stone compaction factor) is required to determine: a) the mass of the purchased building material; b) the degree of further shrinkage of crushed stone in construction work. In both cases, errors cannot be made.

The mass of crushed stone (in kg) can be calculated by multiplying the values ​​​​of 3 quantities:
— filling volume (in m3);
— specific gravity (in kg/m3);
- compaction coefficient (in most cases it ranges from 1.1 to 1.3).

Experts use tables medium weight crushed stone depending on the faction. For example, in 1 m3 rubble fits 1500 kg fractions 0-5 mm and 1470 kg fractions 40-70 mm.

Work with bulk materials is also associated with such a value as bulk density. Its accounting is mandatory in the process of buckling, laying rubble, calculating the composition of concrete. Its value is determined empirically using special vessels (volume up to 50 liters). To do this, the difference between the masses of an empty and a vessel filled with rubble is divided by the volume of the vessel itself.

Wedging- dense laying of the crushed stone base with the help of grains of various fractions. The essence of the technology is the filling of large voids between large grains with small pieces.

Rammer- one of mandatory conditions strengthening the foundation of roads or foundations of buildings. Carried out using special equipment(mechanical roller, vibrating plate) or manual tamper. The quality of the seal is controlled by a special device. The amount of compaction (ramming) can be determined by several methods. In particular, by the method of dynamic probing.

Compaction factor also used in the calculation required amount bulk materials for planning the site with rubble. Let the laying thickness be 20 cm. How much screening do we need for 1 m2 of land? Multiplying the area by specific gravity(1500 kg/m3) and compaction factor (1.3), we get 390 kg.

It should be remembered that different fractions of crushed stone have different compaction coefficients. This setting gets great importance when performing design work on the basis of crushed stone.