Binders are known for their wide use in the construction industry for the preparation of concretes and mortars used in the construction of buildings, structures and other structures. There are many varieties of them, and today we will briefly touch on the main existing subgroups.
Classification of binders
By origin, they may belong to an organic or inorganic group. The first includes all kinds of bitumen, resins, tar and pitches. The main scope of their application is the manufacture of roofing, which can be rolled or piece type, asph alt concrete and a wide variety of waterproofing materials. Their main distinguishing quality is hydrophobicity, that is, the ability to soften and take on a working state during heating or when interacting with any organic liquid.
The second group - inorganic binders - consists of lime, gypsum and cement. All of them are in demand in the process of preparing concrete and a variety of mortars. Appearance of inorganic bindersIt is represented by a finely ground material, which, in the process of mixing with water, turns into a liquid-plastic pasty mass, hardening to the state of a durable stone.
What characterizes them
The main properties of binders of inorganic origin are hydrophilicity, plasticity when interacting with water and the ability to pass to a solid state from a semi-liquid pasty. This is what they differ from the representatives of the first group.
According to the method of hardening, inorganic binders are considered air, hydraulic, acid and autoclave hardening. This division depends on the ability to long-term resistance to natural climatic factors.
Air binders harden by interacting with water and, having formed a durable stone, can remain in this state in the air for a long period of time. But if the products and building structures made with their use are regularly moistened, then this strength will be lost quickly enough. Buildings and structures of this type are easily destroyed.
What is included in this group? This traditionally includes gypsum magnesia binders - clay, air lime. If we consider their chemical composition, then this entire group, in turn, can be divided into four more. This means that all air binders are either lime (based on calcium oxide), or magnesia (which include caustic magnesite), or gypsum.binder, created on the basis of calcium sulfate, or are liquid glass - potassium or sodium silicate, existing in the form of an aqueous solution.
Going to "water" materials
Now let's look at another group - hydraulic binders. They tend to harden, as well as to retain strength characteristics for a long time in an environment not only in air, but also in water. Their chemical composition is quite complex and is a combination of various oxides.
This large group, in turn, can be divided into cements of silicate origin, which contain about 75% calcium silicates (mainly Portland cement with its varieties, this group forms the basis of the range of modern building materials) and another subgroup - aluminate cements based on calcium aluminate (the most famous representatives are all varieties of aluminous cement). Romancement and hydraulic lime are included in the third group.
What binders are acid-resistant? It is an acid-resistant quartz cement that exists as a finely ground mixture of quartz sand and silicon. Such a mixture is closed with an aqueous solution of sodium or potassium silicate.
A characteristic feature of the group of acid-resistant binders is their ability, having passed the initial stage of hardening in air, to counteract the aggressive influence of various acids for a sufficiently long time.
Organics in construction
The other big sub-group is organicbinders (consisting, as already mentioned, mainly of varieties of asph alt and bituminous materials) has a completely different nature. The same asph alt can be artificial or natural. As part of it, bitumen is mixed with representatives of minerals in the form of limestone or sandstone.
In the construction industry, asph alt is widely used in road construction and airfield construction as a mixture of sand, gravel or crushed stone with bitumen. The same composition has asph alt used in the form of waterproofing.
What is bitumen? This is an organic substance (either natural or artificial), which includes high-molecular hydrocarbons or their derivatives containing nitrogen, oxygen and sulfur. The scope of application of bitumen is very wide and varies from road and housing construction to enterprises of the chemical industry and the paint and varnish industry.
Tar is understood as astringents of organic origin, which include aromatic high-molecular carbohydrates and their derivatives - sulfuric, acidic and nitrogenous.
Their beneficial qualities
The main requirement for the organic group of binders is to have a sufficient degree of viscosity at the moment of contact with a solid surface, which would allow high wetting and enveloping properties to form a waterproof film. Another requirement is the ability to retain quality data over a long period of time.
These binders have found their use in laying roads and city streets, they coverairfields and highways, arrange sidewalks and floors in basements and industrial buildings.
Consider now the main types of building materials belonging to the two listed groups. Recall again - the inorganic group is mainly divided into those that harden in air and those that are able to do this in an aquatic environment.
Binders - building materials
The well-known clay is one of the most common air-curing binders. It has found its application in the construction of a variety of buildings. It is a clay sedimentary rock that exists as a mixture of dust-like particles of microscopic size with sand and small clay inclusions. The smallest of them are called finely dispersed. It is their presence that allows, when it enters a humid environment, to turn into a pasty substance. After drying, this plastic mass easily hardens in the form given to it.
If such a form is burned, then the resulting stone of artificial origin has a sufficiently high strength. Like other mineral binders, due to the different composition of the clay, there can be a variety of shades. From solutions based on them, fireplaces, stoves are laid, and bricks are also molded. They can be skinny, fat and medium. Clay-chamotte has refractory qualities, so it is indispensable for the construction of fireplaces and stoves.
What is lime
Another very famous and widely usedthe binder is called air building lime and is obtained from rocks, namely chalk, dolomites, limestones, shell rock. The main oxide in it can be different, depending on this, air lime is usually divided into dolomitic, magnesian, calcium. All three varieties are obtained by kilning limestone of the respective origin.
Can be air lime either quicklime or slaked (or hydrated). The latter is formed in the process of extinguishing one of the three above.
If you look at the existing lime fraction, you can attribute it to lumpy or powdery. Quicklime is a fairly large porous lumps. In the process of quenching with water, a lime paste is formed from it. In order to “extract” powdered lime from lumpy lime, it is necessary to carry out the process of hydration (quenching), or grind the lumps. It can be used with or without additives. Slags, active minerals and sand of quartz origin serve as additives.
All about plaster
The next material is alabaster, aka gypsum. It is obtained by thermal processing of crushed gypsum stone. Gypsum hardens through three intermediate steps consisting of its dissolution followed by colloidation and then crystallization. During the passage of the first stage, a saturated solution of two-water gypsum is formed. Hardening, it increases in volume and acquires a smooth white surface.
Using coloring pigments, it is possible to givegypsum products any color shades. The setting process of this binder normally begins after 4 minutes from the start of mixing. The end of curing occurs between 6 and 30 minutes later.
In the process of setting, the mixture of gypsum and water must not be mixed and compacted in order to avoid the risk of loss of astringent qualities. There are quite a few grades of gypsum, they are designated by various numbers characterizing the degree of compressive strength.
It is sold packaged in bags of different sizes. Gypsum has found the widest application in the interior design of residential buildings and public buildings. It has long been customary to cast a wide variety of curly shapes from it. It should be stored exclusively in a dry room, and the shelf life is limited due to the possible loss of strength as the main useful quality.
And more about plaster
Gypsum plaster looks like a grayish to bright white powder. If you mix it with water, a characteristic reaction begins, and the mixture heats up. It is customary to add special materials to gypsum called retention additives, the purpose of which is to improve consistency and adhesion to the surface during plastering, as well as slightly prolong the curing time.
To increase the volume of the material without loss of working properties, fillers are introduced (for example, from expanded perlite or mica). Special high-strength gypsum is fired at high temperatures, in the process, crystal water is removed from it. Its hardening time has been increased to 20 hours, andhardness is much greater than other varieties.
Plaster gypsum is impregnated and marbled (bright white, slowly hardening and used for plastering internal surfaces) is obtained, and various fillers and holding additives are introduced into it during manufacture. The main purpose of most of these additives is to serve as a setting retarder. In order to produce internal plaster, it is prepared in plastering machines with the possible addition of certain fillers, such as sand.
Dry plaster or plasterboard building boards are also obtained from it, and gypsum is also used to fill the joints between them. There is putty gypsum with similar properties.
Let's talk about cements
What other properties do hydraulic binders have? The process of their hardening, which began in the air, continues in the water, and their strength is maintained and even increases. The characteristic and best known representatives of the family of hydraulic binders are, of course, cements. They are marked depending on the strength, and the brand of a particular sample is determined by the establishment of the ultimate load on bending and compression. Moreover, each of the samples must be made in the accepted proportion of cement and sand and pass the test for a certain period of 28 days.
The setting speed of cement can also be different - slow, normal or fast. Similarly, depending on the rate of hardening, any cement can be conventional, quick-setting, orespecially fast hardening.
An example in this group is Portland cement, which exists in the form of a fine gray powder with a slight greenish tint, with the possible introduction of additives, which can be from granulated slag (Portland slag cement).
About curing speed
Quality testing (as well as production) of binders is carried out in compliance with numerous standards. For each of the existing groups, restrictions have been developed that determine the standard time for the start and end of setting, counting from the moment of water mixing.
Another cement - aluminous - is a fast-hardening hydraulic binder. In appearance, it is a fine powder of brown, gray, greenish or black color (depending on the processing method and initial components). It is slightly finer than Portland cement and requires slightly more water.
Mixed types of binders - those that can harden in both air and water and are used in the production of only non-reinforced concrete or mortar.
Bitumens and their scope
As for the most popular organic binders, their family includes a variety of bitumen and tar, ranging in color from black to dark brown. The traditional area in which such binders are used is waterproofing work. This building material is waterproof, waterproof, weather resistant and highly resilient. Soften and liquefycondition of this group of binders can be heated. As the temperature drops, their viscosity increases and may be completely lost.
This group primarily consists of bitumen of natural origin, as well as those obtained during oil refining. Their chemical composition is compounds of molecules of oxygen, hydrogen, sulfur and nitrogen. Petroleum bitumen (liquid, solid and semi-solid) is in demand in construction.
According to their purpose, they can also be classified into one of three groups - roofing, construction or road. An impregnating composition is prepared from roofing materials, roofing felt and many different mastics are produced.
Industrial bitumens of hard and resilient-hard grades are produced by the high-vacuum method with additional processing steps in which the oil boils at high temperatures. Especially resistant to heat and cold are oxidized. There are also mixtures of bitumen with polymers that affect the degree of their viscosity. A characteristic feature of all species is the ability to change the consistency depending on the temperature, and different phases can alternate repeatedly. The adhesive properties of the family of bituminous binders are based on it.
How valuable they are
The degree of expansion of bitumen under the influence of high temperatures is 20-30 times greater than that of mineral materials. Their valuable qualities are water resistance, resistance to s alts, alkalis, aggressive acids and drains. An example is s alt, which is sprinkled on the snow in winter on the streets to melt.
The resistance of bitumen is reduced by organic solvents, oils and fats, from light, heat and air oxygen, which oxidize their constituent parts. When heated, the soft particles evaporate and the bitumen surface hardens.
Their advantages are low flammability, that is, this material is not flammable. Petroleum bitumen is not a he alth hazard and is not classified as such. Other properties include thermoviscosity, high thermal insulation, good wetting.
The hardness of bitumen is determined by the depth of penetration of the needle immersed in them (it is measured in hundredths of a millimeter) at a normalized load for a certain time at a specific temperature. The transition between a solid and a liquid state is sliding in nature and is determined by the softening point at low temperatures. In addition, they are characterized by the so-called breaking point - this is the term for the temperature at which the bitumen layer to be bent cracks or breaks.
Other content
What other organic binders can you name? Coal tar pitches, which are a viscous or solid black substance and serve as a product of tar distillation, are impregnated with roofing felt. This material is quite dangerous and can cause burns if it comes into contact with the skin. It works best on overcast days or in low light.
Coal tar is a substance that is released as a by-product during coke production. He foundits use in the manufacture of mastic for roofing and road construction.
