Sand fineness modulus: definition, what it is measured in, classification of sand and GOST | GC Respect

About brands and fractions of building materials

Depending on the degree of strength, bulk material of natural origin is conventionally divided into several grades:

1. Mark 800.
2. Mark 400.
3. Mark 300.

The above designations are necessary for marking the “binding product” when performing certain types of construction work:

• indoor use;
• external use;
• finishing of concrete structures.

One of the indicators that should be taken into account is the size of the material: its division into fractions. The gradations are distributed as follows:

1. Large particles. The size can vary between 0.2-5.0 millimeters.
2. The average size. Its dimensions range from 0.5 to 2.0 millimeters.
3. Fine grain with values ​​not exceeding 0.5 millimeters.

It is the size of the fractions that acts as the basis for the subsequent use of river material. Therefore, it is customary to divide natural materials into 2 classes: first and second.

Fine- and medium-fraction sand is more suitable for preparing working mixtures (solutions). A material of natural origin with a coarse fraction is used for preparing concrete mixtures for the construction of concrete structures. It is also used in the construction of buildings.

Acceptance rules

Sand, enriched sand and graded sand must be accepted by the manufacturer's technical control service.

To verify compliance of the quality of sand, enriched and graded sand with the requirements of this standard, acceptance inspection and periodic testing are carried out.

Acceptance control at the manufacturer is carried out daily by testing a combined replacement sand sample selected in accordance with GOST 8735. During acceptance control, the following is determined:

• grain composition;
• content of dust and clay particles;
• clay content in lumps;
• presence of contaminants.

During periodic testing of sands, the following is determined:

• once a quarter bulk density (bulk density at humidity during shipment is determined if necessary) and the presence of organic impurities (humic substances);
• once a year and with each change in the properties of the rock being mined, the true density of grains, the content of rocks and minerals classified as harmful components and impurities, the specific effective activity of natural radionuclides.

Periodic monitoring of the specific effective activity of natural radionuclides is carried out in specialized laboratories duly accredited for the right to conduct gamma spectrometric tests or in radiation metric laboratories of supervisory authorities.

In the absence of geological survey data on the radiation-hygienic assessment of the deposit and a conclusion on the class of sand, the manufacturer carries out a radiation-hygienic assessment of the mined rock sections using the express method directly at the mine face or in finished product warehouses (according to the alluvium map) in accordance with the requirements of GOST 30108 .

Acceptance and delivery of sand, enriched sand and fractionated sand is carried out in batches. A batch is considered to be the amount of sand established in the supply contract and simultaneously shipped to one consumer in one railway car or in one ship. When shipping by road, a batch is considered to be the amount of sand shipped to one consumer per day.

Selection and preparation of sand samples for quality control at the manufacturing plant is carried out in accordance with the requirements of GOST 8735.

When checking the quality of sand, the consumer must use the sampling procedure given below. If the results of the control check on the grain composition, the content of dust and clay particles and clay in lumps are unsatisfactory, the batch of sand will not be accepted.

The number of spot samples taken to control the quality of sands in each tested batch, depending on the volume of the batch, must be at least:

• with a batch volume of 350 m3 - 10;
• St. 350 to 700 m3 - 15;
• St. 700 m3 - 20.

From the spot samples, a combined sample is obtained that characterizes the controlled batch. Averaging, reduction and sample preparation are carried out according to GOST 8735.

To control the quality of sand shipped by rail, spot samples are taken when unloading wagons from the flow of sand on belt conveyors used to transport it to the consumer's warehouse. When unloading the car, five spot samples are taken at equal time intervals. Cars are selected according to the instructions of the consumer. If the batch consists of one wagon, five spot samples are taken during unloading, from which a combined sample is obtained. If conveyor transport is not used for unloading, spot samples are taken directly from the cars. To do this, the surface of the sand in the car is leveled and holes with a depth of 0.2-0.4 m are dug at the sampling points. The sampling points should be located in the center and in the four corners of the car, and the distance from the sides of the car to the sampling points should be not less than 0.5 m. Samples are taken from the holes with a scoop, moving it from bottom to top along the walls of the hole.

To control the quality of sand supplied by water transport, spot samples are taken when unloading ships. When belt conveyors are used for unloading, point samples are taken at regular intervals from the flow of sand on the conveyors. When unloading a vessel with grab cranes, point samples are taken with a scoop at regular intervals as unloading proceeds, directly from the newly formed sand surface in the vessel, and not from the holes. For control testing of sand unloaded from ships and placed on alluvial maps using hydromechanization, spot samples are taken in accordance with GOST 8735, paragraph 2.9.

To control the quality of sand shipped by road, spot samples are taken when unloading vehicles. If belt conveyors are used for unloading sand, point samples are taken from the flow of sand on the conveyor. When unloading each vehicle, one spot sample is taken. Cars are selected according to the consumer's instructions. If the lot consists of less than ten cars, sand samples are taken from each car. If conveyor transport is not used when unloading cars, spot samples are taken directly from the cars. The surface of the sand in the car is leveled, a hole 0.2-0.4 m deep is dug in the center of the body. Sand samples are taken from the hole with a scoop, moving it from bottom to top along the wall of the hole.

The amount of sand supplied is determined by volume or weight. Sand measurements are carried out in wagons, ships or cars. Sand shipped in wagons or cars is weighed on truck scales. The mass of sand shipped in ships is determined by the vessel's draft. The amount of sand from units of mass to units of volume is recalculated based on the bulk density of sand, determined by its moisture content during shipment. The supply contract specifies the calculated sand moisture content accepted by agreement of the parties.

The manufacturer must accompany each batch of supplied sand with a quality document indicating:

• name of the manufacturer and its address;
• number and date of issue of the document;
• name and address of the consumer;
• batch number, name and quantity of material;
• numbers of invoices and vehicles;
• grain composition of sand, enriched sand;
• grain composition of a mixture of fractions or the size of narrow fractions (for fractionated sand);
• content of dust and clay particles, clay in lumps;
• content of harmful components and impurities;
• presence of contaminants;
• bulk density and filtration coefficient (at the consumer’s request) in sand and enriched sand;
• specific effective activity of natural radionuclides;
• designation of this standard.

Types and characteristics of material: its classification

There are a number of indicators that characterize river material of natural origin:

• fineness module;
• filtration coefficient;
• volumetric and bulk density;
• additional characteristics.

To fully understand the gradation of the product, we will consider each indicator separately.

About size

The particle size module is data on the size of fractions, which includes such definitions as:

• Fine sand with a grain size of 1.5 - 2.0 mm.
• A natural product of medium size with a fraction of 2.0 - 2.5 mm.
• Natural material with coarse grain: 2.5 – 3.0 mm.
• Product with increased grain size: 3.0-3.5 mm.
• Very coarse sand with a grain size of 3.5 mm or more.
• Dusty product with a grain size of 0.5-0.14 mm. Sand in this category is divided into several subtypes: – with a low proportion of moisture; – wet; – a material of natural origin, saturated with moisture.

What is filtration coefficient

This indicator makes it possible to understand the physical and technical properties. This parameter indicates the volume of liquid required to infiltrate 1 m3 of sand in 60 minutes. This indicator is affected by the porosity of the product.

A few words about bulk and volumetric density.

The value of this indicator is within the range of 1300-1500 kilograms per meter. As the moisture content of the sand changes, its volume changes accordingly. This affects the bulk density of the naturally occurring product. There are certain requirements that you should start from and adhere to - these are GOST 8736-93.

What is included in the concept of additional characteristics

Additional features include:

1. What class of radioactivity does the product belong to?
2. The presence of materials (their types), such as clay, an admixture of silt and other natural components.

How to make sure that river sand will be delivered to you at the order stage

You can try to determine the type of sand at the order stage. Of course, at this stage it is impossible to be 100% sure of the type of material. But if you do not skip this stage and follow the instructions below, then the likelihood of you being deceived by unscrupulous suppliers will be minimized.

So, what you need to do when ordering and how to understand that they will bring you river sand:

1. Ask what deposit the material is from. In the Sverdlovsk region it can be Mikhailovsky sand, as well as Kamyshlovsky and Kamensk-Uralsky. The last two are mined using the alluvial method, but, nevertheless, in our region they are also considered river and are not inferior to them in terms of characteristics.
2. Find out about the availability of documents for sand. The documents include a certificate of conformity and a laboratory test report. They are the ones who confirm the quality of river sand. If you are shown these documents, be sure to check the date and stamps. The certificate and protocol must not be expired. If they tell you that sand is not certified, then you should think about it. The fact is that sand certification is, of course, a voluntary and not free procedure. That's why not everyone does it. But conscientious manufacturers who monitor the quality of the material undergo this certification regularly. But even here there are pitfalls. First of all, you need to understand that the mere fact of providing a certificate cannot be a 100% guarantee that the sand will be brought from exactly that deposit. After all, many certificates are freely available. However, this stage should not be ignored. The more attentive and meticulous the buyer, the less likely he is to be deceived.
3. Ask to send you a photo of sand or see samples in person. Conscientious suppliers always have photos of samples of the raw materials they sell. If there are none, we advise you to think several times before ordering from such companies. It’s even better if you can come to the supplier’s office and personally see the sand that they offer to bring you. This way you will not only be able to see the samples with your own eyes and evaluate them, but also make sure that the company exists.
4. Pay attention to the price Extraction of river (as well as alluvial) sand involves the use of expensive equipment and takes place in several stages. In addition, the total cost includes delivery costs. For example, alluvial Kamyshlovsky sand is mined 140 km from Yekaterinburg. Therefore, a priori, it cannot cost less or at the same price as epoxy or quarry materials.

If at this stage all points have been completed and the supplier’s actions are beyond doubt, feel free to order river sand. The next step is to check it on site upon delivery.

Types of sand of natural origin

Of the known natural materials, such as river, sea, ravine or mountain sand, river sand is considered the cleanest. It is mostly used for preparing various mortars. It is valued for its uniform structure and small particles, the average of which is 1.5-2.2 mm. One of the problems with a naturally occurring product is its high price. Therefore, river sand is often replaced with quarry sand.

Characteristics of river sand

Presence of clay

In addition to dust, sand may contain clay impurities. It is characteristic of quarry sand and sand from crushing screenings. The reason for this is as follows: clay deposits are located very close to sand and crushed stone deposits. Thus, clayey soil contaminates the rock.

Testing sand for the presence of clay is very simple - you just need to take a handful and squeeze it in your hand. The clay will leave a dirty mark on the palm.

There is only one way to get rid of it - washing. No other method (screening, sifting, enrichment) helped to clean the material from clay.

Application area

This material is used in various industrial fields at different stages of the construction process:

1. When preparing cement mortars for masonry, plastering and cement screeds.
2. When installing walls and pillows under the foundation.

Sand is also used in the production process:

• asphalt and concrete mixture;
• borders;
• bricks;
• various adhesives;
• concrete;
• paving slabs;
• paints;
• dry mixtures;
• and reinforced concrete products.

Note! During the preparation of various solutions, sand constantly settles. Therefore, the mixture must be stirred regularly.

Presence of large inclusions

Large inclusions in sand usually mean pebbles, large grains, pebbles, and gravel. They are visible immediately. For some jobs these inclusions are not important, but for others they are extremely undesirable. For example, if you need sand for backfilling, foreign inclusions will not bother you. If the material is taken for paving slabs, bricklaying or plaster, the sand must be additionally sifted so that large pebbles do not interfere with construction work.

Inclusions of this type are characteristic of almost all sandy materials. Thus, pebble and gravel are found in river, lake, alluvial and quarry sands, and shell rock is found in sea sand. The screenings contain coarse grains of rock. The exceptions here will be fine sands - ephelium and quartz. This is due to the fact that these materials are carefully ground, deliberately not leaving large inclusions.

How is a natural product obtained?

The naturally occurring product is lifted from river beds using floating pontoons using centrifugal pumps and earthen shells. The suction power of the pumps ranges from 100 to 600 m3 per hour. The most common are 2 methods of extraction:

1. Using special equipment: excavators, scrapers, dredgers.
2. Hydromechanized method for raising river sand.

Both methods have their advantages and a certain technology for lifting a product of natural origin, which may contain shades of yellow, white and gray.

Extraction of sand from water with a brief description of the process

Sand is extracted from deep rivers using a dredge, which is secured to a barge. Such dredgers are equipped with special hydromechanical equipment, with powerful pumps, tanks and sieves for dividing sand by composition.

Rippers lowered to the river bottom mechanically suck in sand. The sand is transported through a slurry pipeline to the surface and deposited on a barge platform called a hydraulic dump. It has a device for draining water. The sand is then dry-cleaned and loaded onto another barge.

Extraction of river sand from dry river beds is similar to quarrying. All sand received must have a certificate of conformity.

In the video: an amphibious excavator dredger washing up sand at 400 m: