as Sand consider friable mix of grains (fineness from 0,14 to 5 mm) of various minerals which turns out as a result of aeration of rocks. Such sand call natural. Exist, including, and artificial sand which get when crushing solid izverzhenny, metamorphic or dense carbonate sedimentary rocks with the durability of 40 MPas. Though from the economic point of view receiving this sand is unprofitable as it is much more expensive, than natural. Apply it in case of lack of good natural sand. As a rule, in construction natural sand is applied.
Sand carry to friable detrital breeds and subdivide into rough sand (the size of grains more than 3 mm), coarse sands (the size of grains of 0,5 - 2 mm), average sand (the size of grains of 0,35 - 0,5 mm) and small sand (the size of grains of 0,14 - 035 mm). Also dusty sand which represent fine sandy dust (the size of grains of 0,01 - 0,14 mm) come across.
Dusty sand, or as they are called still, alevrita (microsand), are divided into large and fine sandy dust. To such sand it is possible carry silt (the thinnest deposits put with water) and the loess - the deposits of the smallest grains of quartz, limestone and other minerals put with wind. Sand classify by the field and mineralogical structure.
Formation of sand happens in various conditions - in the seas, the rivers, lakes and on the land.
In the sea they arise in coastal part and consist of well rounded grains of sand of one size with a smooth surface.
River sand are sorted worse. The part of kernels has the angular form.
In deserts sand are well sorted. They have no impurity clay, gravel particles. It is explained by the fact that sand of deserts turned out generally from the river deposits transferred wind. The constant winds blowing in deserts promoted that there was a certain sorting of the detrital deposits brought from the river. It turned out that wind lifted in air and carried away the easiest clay particles. Larger gravel grains remained on the former place. Sandy particles were cleared of impurity and, gathering in very large volumes, were distributed on the huge square.
Natural sand are divided by mineralogical structure on quartz, polevoshpatovy, calcareous and dolomitic. application In construction, especially at production of heavy concrete, quartz sand are widely applied. Other sand possess low firmness and durability.
What is quartz sand? By geological definition, it is melkooblomochny not hardpan rock from rather well sorted and rounded grains of quartz of 0,05 in size - 1 mm. Besides quartz at sand there can be grains of feldspar, mica (usually white mica), fragments of siliceous breeds and grain of steady minerals. Quartz sand have white color of different shades, depending on impurity. Apply quartz sand in the building, ceramic, glass and foundry industry.
Quartz sand are suitable also for concrete of any brands. Dry and friable quartz sand - the main raw materials in the glass industry. Detailed information on quartz sand will be given in the section on mineral raw materials.
Ochenchasto the sand applied at production of heavy concrete is called by small filler. Before use it is carefully cleared of clay and dust-like impurity by means of washing with water in peskomoyka. Impurity in sand reduce durability and frost resistance of concrete. Quality of sand is checked in the laboratory way.
Sand is also used for ballast in railway construction. But not any sand can be applied in these purposes. For example, small - and fine-grained sand are not suitable for ballast. The preference is given to the sand and gravel having the angular form and a rough surface of grains. It promotes the coupling of particles increasing stability of a ballast prism. Content of impurity has to be minimum. Best of all is peschano suitable for a bed - gravel mix, and also gravel mix with crushed stone from gravel, boulders and rocky breeds.
Durability of many construction materials which receive on the basis of cement depends on quality of the applied sand. Production of a large number of construction products demands use of the enriched sand i.e. which are washed out sorted both by the size of grains, and by mineralogical structure or in addition crushed (tonkomoloty).