Building binders

There are a significant number of different binders. However, only some of them are used in construction. They are called building binders and are divided into two main groups: inorganic (mineral), the main of which are Portland cement and its varieties, lime, gypsum and others, and organic, of which the products of oil and coal distillation (bitumen, tar), often called "black" binders, are most often used.

Building mineral binders are called powdery materials that, after mixing with water (and in some cases with solutions of some salts), form a mass that gradually hardens and turns into a stone-like state. Almost all mineral binders are obtained by coarse and fine grinding of raw materials and intermediates, followed by heat treatment at different temperatures. Under these conditions, various physical and chemical processes take place that ensure the production of a product with the required properties. The burnt material is subjected to fine grinding.

Most mineral binders harden as a result of the appearance of hydrate neoplasms when the binder interacts with water. Only in some cases, hardening occurs as a result of the interaction of a binder, for example, slaked air lime, with air carbon dioxide and simultaneous recrystallization of calcium hydroxide.

Mineral binders are used in the vast majority of cases in a mixture with water and with so-called aggregates-mineral (and sometimes organic) materials consisting of individual grains, pieces, and fibers of different sizes. Binders mixed with fine aggregate (sand) give solutions, and concretes mixed with fine and coarse aggregates (gravel, crushed stone, etc.). Sometimes binders are used only in the form of mixtures with water without aggregates.

The use of binders mixed with aggregates is due to two main reasons. The first reason is of an economic nature — the cost of binders is relatively high, so to reduce the cost of a product or design, they must be manufactured with minimal binder consumption. For each type of products and structures, the binder consumption is determined by a number of requirements that provide for the necessary structural strength, reliability and durability of a particular structure. The second reason is technical. The fact is that binders in the form of dough without fillers show an increased tendency to shrink and swell both during hardening and under the influence of heat and humidity changes. This often leads to the formation of cracks and accelerated destruction of structures and structures.

The production of binders is a complex of chemical and physical-mechanical effects on raw materials, carried out in a certain sequence.