- Purpose of sand
- Dependence of laboratory quality on the method of extraction
- Quartz sand
- Sand impurities
- Sandy loam
This article presents the main indicators of the quality of sand and its performance properties. You will learn how to determine the impurity in the sand, how it is mined and where the varieties of this rock are used. We will tell you about the features and uses of quartz sand.
Sand is a rock and one of the oldest and most demanded building materials, it can vary in properties and consistency. It is not independent, although it is part of most of the known solutions (except gypsum) and concrete.
Purpose of sand
In construction, this material is used for the following works:
- As a fine aggregate for cement mortars and concrete.
- As a backfill when leveling the bottom of pits, trenches, roads.
- Other options: abrasive in sandblasting machines, filters, weight, casting mold, etc..
The quality of this material is regulated by GOST 8736-93 “Sand for construction work”. In private construction, it is not necessary to expect an analysis for compliance with GOST, therefore it is better to learn how to independently determine the quality of sand for the corresponding work.
The fraction of sand is determined in laboratory conditions and ranges from 0.1 mm (fine) to 3.5 mm (very coarse). In its natural form, all fractions are mixed to a homogeneous mass, but the sand is classified according to the predominant fraction. As a rule, this is an average fraction of 0.5-1.5 mm, suitable for any work and mortar in private construction.
Dependence of laboratory quality on the method of extraction
Sand is obtained in many different ways, which leave their “imprint” on the composition of the mass and the structure of the grain itself.
Sea sand.It is extracted by mechanical or hydraulic (pumps) lifting from the seabed, or by stripping the banks. Since there is no intense current at the bottom of the sea, the grains of sand have an acute-angled shape. This makes the adhesion to the mortar more reliable, and the products made of such concrete more durable. Sea sand is distributed only near the seas and lakes – closer to the place of extraction, since its transportation to remote areas is unprofitable. The volume of sea sand in production and sale – about 10%.
River sand.Due to the intense flow in the rivers, grains of sand have a polished surface and a round shape. Therefore, it is considered the least reliable in the manufacture of products. However, the spread of rivers makes the extraction of river sand almost ubiquitous, and transportation costs are reduced. River sand accounts for up to 5% of the total market volume.
Quarry washed sand.It is mined in quarries as the main or accompanying (in the development of sandstone) material. Initially, the raw material has many impurities – clay, silty rocks – so it is washed with water until it meets the requirements. In quarries, about 15% of all sand is washed.
Quarry seeded sand.It is extracted in special sand pits, where the quality of the deposit is explored in advance. Screens are built near the quarries, on which the rock is sifted. Such sand is of good quality – pure composition of the mass (without impurities) and sharp corners of the grain of sand. 40% of the mined sand comes from quarry screenings.
Artificial sand.It is formed by the screening of granite, marble, crushed stone. Represents the screening of these materials. Has the highest quality and price. The grains of sand are sharp, since they are formed as a result of rupture, fracture of the mass. Artificial sand accounts for up to 30% of the market.
In private construction, it does not matter where the sand came from and how it was obtained. The main requirement for it is purity, absence of organic matter and impurities. Clean, good sand can be found in a pine forest or on a wild lake beach.
There are types of sand that are not used in construction. Quartz sand, which has extremely valuable properties, should be especially noted. It is obtained by processing (crushing and sieving) milk quartz. Its scope is quite wide:
- With its high silicon (silicate) content, it becomes the object of keen interest of glass-makers and speculators. The sand is melted and molded into glass, adding additional additives to the mass.
- Highly purified sand – washed and disinfected – itself becomes a cleaning element. It is used in water filters. Intergranular porosity and adsorption properties are used to remove manganese and iron oxides from water.
- Sand of a stable fraction from 0.5 to 0.8 mm is used in sandblasting machines for cleaning surfaces under pressure.
- Any product based on quartz sand – concrete, plaster, element – in addition to strength, acquires an interesting appearance. The concrete has a pastel shade, and the plaster casts in the light.
This is only a small part of the “work” of quartz sand, available to the common consumer. It is widely used in industry in a wide variety of qualities..
Impurity in this context should be understood as the content of finer (fine) particles in the sand mass. A mass with a fine sand content of more than 20% is subject to additional sieving, since fine inclusions worsen the properties of the product (in solution and concrete) and slow down the passage of liquid (in filters). The most common admixture is clay. In this regard, there are two subspecies of rock – sandy loam and loam.
The prefix su- means “close”, that is, the composition of the sandy loam is close to sand. Falls under the classification of GOST 25100–95 (2011) “Soils. Classification”. Depending on the percentage of clay, there are:
- Light sandy loam. 10-15% clay in sand. Suitable for drainage dumping with relatively low water flow. It is applicable in private construction for finishing and road works. Not suitable for critical concrete structures.
- Heavy sandy loam. 15–20% clay in sand. Suitable for filling non-drainage layers, walling outbuildings, preparing wood concrete (sawdust concrete). Not suitable for load bearing plaster.
You can visually distinguish sandy loam from pure sand – the mass has a brownish tint. When wet, a liquid substance appears like dirt – a finely dispersed impurity dissolves. In general, sandy loam can be called “dirty sand”, since an admixture of clay and other substances negatively affects the quality of solutions with the addition of cement.
Rock containing up to 35% clay. The presence of such an amount of clay gives the mass properties different from those of sand. The main one is waterproofing. Some cases of optimal use of loam:
- A layer of compacted bedding will serve as a water barrier.
- Plaster, prepared on loam with sawdust, has exceptional durability and vapor permeability.
- Suitable for wood concrete, cement consumption is less.
- By increasing the percentage of clay, a “historical” building material is obtained – adobe. Loam with more than 50% clay is kneaded on straw and formed into blocks, or laid on the floor.
- Perfect for filling the sinuses of the foundation, well, sealed cesspool, caisson. Improves thermal and waterproofing by separating the structure from the ground.
- Ideal filling under the road or blind area.
The loam is almost brown in color and clumps together in the hands. An old heap of this rock is difficult to mine with a shovel..
It’s hard to imagine our life without sand. Almost everything that we see was created with his “participation”. At the same time, it continues to be one of the most demanded materials, which means that it has no analogues yet..