Mortars: general technical conditions, composition, application, GOST

For the sphere of construction services, such a concept as construction solutions is typical and habitual. GOST 28013 (approved and put into effect by the decision of the USSR State Construction Committee No. 7 in 1989. It was replaced by a similar GOST approved by the Gosstroy of Russia Decree No. 30 of 1998 and enacted since July 1999) treats the concept as a set of terms "Mortar mixture", "dry mortar mixture", "mortar" and defines uniform requirements for general technical characteristics regarding their preparation, acceptance and transportation and quality indicators.

As a note: these standards do not apply to hot and chemically resistant building solutions.

What is a mortar?

The composition of the solution is properly composed and thoroughly mixed to a homogeneous mass constituents: astringent, small aggregate and a shutter. If necessary, special additives can be added to the solution. Traditionally, cement, gypsum or lime acts as an astringent, giving the solution elasticity. The filler, as a rule, is sand, the builder is water.

Not requiring hardening, completely ready for use after the connection of the necessary components, the mortar is called a mortar. The solution mixture can consist of dry components mixed in the factory. This is the so-called dry solution. It is covered with water before use.

The hardened mass, reminiscent of an artificial stone, in which the astringent binds sand particles together, thereby reducing friction, is called a solution.

Building solutions: general specifications

Construction mortars are classified as follows.

Depending on the binder used in the composition, the following are distinguished:

1. Simple single-component - cement, lime or gypsum. As a rule, they are designated by the ratio 1: 2, 1: 3, in which 1 - the part (share) of the binder, the second number - how many parts of the aggregate is added to the part of the binder.

2. Complex, mixed, multicomponent. This, for example, cement and limestone, limestone and gypsum, clay and straw, limestone and ash and others. They are indicated by three digits: astringent core, astringent, filler.

A lot depends on the quantitative ratio of astringent and sand. There are mortars:

1. Normal . Characterized by the optimal ratio of binder and aggregate.

2. Fatty . Characterized by an excess of binder, give a large shrinkage when laying, cracks (when applied in a thick layer). Determined by immersing the stick in the solution - the fat mixture envelops it in a thick layer.

3. Skinny . Characterized by a lack of, a small amount of binder, virtually no shrinkage, are optimal for lining. Determined as follows: when the stick is immersed in the solution, the mixture does not adhere to it.

Based on the properties of astringent mortars, the building is divided into:

- air - their solidification takes place in air in dry conditions (gypsum);

- hydraulic - the processes of solidification begin in the air and continue in a moist environment, for example, in water (cement).

Depending on the sand used, whether ordinary natural, mountain, river or light porous (expanded clay, pumice, tuff), there are heavy (density in the dry state of 1500 kg / m3) and light (up to 1500 kg / m3) mortars. The quality of the aggregate directly affects the strength of the final product. So, in comparison with slag, mixing of binder with building sand without impurities (mineral salts, impregnations of clay rocks) increases the strength of the mortar to 40%.

The quantitative ratio of water also plays a significant role in the preparation of solutions: when it is deficient, the solution is characterized by rigidity, with excess - by stratification, as a result of which the quality characteristics of strength decrease.

Acknowledgment that the building mortar (GOST 28013-98) is prepared correctly, according to the quality standards and the correct ratio of the required components, is its workability. Movable, plastic composition is able to fill all the voids, tightens well, is rammed, does not crumble, does not crumble, does not slip along the walls. With a minor addition of the binder and the shutter, the solution becomes more ductile, but this leads to more shrinkage of the building material upon solidification and, accordingly, to the formation of cracks.

Let us dwell in more detail on the technical features of solution mixtures and solutions, all parameters of which are controlled by the current standards.

Qualitative characteristics of mortar mixtures

Important quality indices of solution mixtures are medium density, ability to retain water, mobility and delamination. The lower the binder consumption with the requirements for mixtures, the better. If the mixture has time to grasp or it has been thawed, it is strictly forbidden to add a shutter to it. To achieve the desired properties, it is important to properly prepare the solution mixtures, dose, adjust the substances in them. It should be a mixer of a cyclic (continuous type), gravitational (forced) action. At the same time, an error of up to 2% is allowed with respect to astringents, a preserver, dry additives, up to 2.5 - with respect to the aggregate. For winter conditions, the temperature of the solution should be equal to or greater than 5 ° C. The optimum temperature of the water for mixing is up to 80 ° C.

Depending on the rate of mobility, several grades of solution mixtures are isolated:

1. Pc4 - characterized by a mobility norm of 1-4 cm. It is used in vibrating butovy masonry.

2. Pc8 - the fork of variations in mobility is based on the range from 4 to 8 cm. It is relevant for conventional butovy (from hollow stones and brick) masonry, facing works, wall mounting (large-block, large-panel).

3. Pc12 - mobility above 8 and up to 12 cm. It is used for masonry from ordinary brick, plastering, facing, pouring voids.

The ability of freshly prepared mortar mixtures to retain water is also one of the most important indicators. The index of quality in the laboratory is a mark of 90% in the winter, 95% - in the summer. At the production site, it should exceed 75% of the water-holding capacity determined by laboratory data. The higher the density, the higher the water resistance index. For factory dry mortar mixtures, moisture content up to 0.1% by weight is acceptable.

With regard to delamination and medium density, in both respects an error of 10% is allowed, not higher. If air-entraining additives are added to the mortar mixture, the indicator decreases relative to the average density to 6% of the value set by the project.

Quality standards for solutions

Average density, resistance to frost, compressive strength - the main quality indicators of solutions. Thus, there are several brands that determine the index of strength for axial compression: M4, M10, M25, M50, M75, M100, M150, M200.

F10, F15, F25, F35, F50, F75, F100 are grades characterizing frost resistance index of the solution, which is subjected to alternate freezing and defrosting. The frost resistance index has one of the primary values for concrete, masonry, plaster solutions, when it comes to exterior plaster. All grades of solutions are controlled.

The density of building solutions (GOST 28013) is divided into heavy and light, the plug of deviations in the indices can not be more than 10% of the established by the project. The most difficult is a concrete mix. It is used when laying foundations, the construction of basement floors. The higher the density, the stronger, harder the solution.

Quality standards of substances included in solutions

As the substances used for the preparation of solutions, cement, lime, gypsum raw materials, sand, including slag from thermal power plants, are used for blast furnace slag. All these components, as well as water for mortar, must meet certain requirements, presented both in accordance with GOST 28013, and with quality standards applied to each component.

Aggregate

For each individual mortar, depending on the purpose, a certain filler of the required moisture content is needed. So, for finishing works suitable for construction sand with the size of grains of sand up to 1.25 mm, for soil - up to 2.5 mm, when plastering grains of sand can reach 1-2 mm, when plastering the finishing layer - no more than 1,25 mm (possible Deviation of up to 0.5% by weight, but the solution should not contain sand with grains over 2.5 mm). If sand and ash are used, then there should not be ice, frozen lumps. When heated, the temperature of the building sand can not exceed 60 ° C. Light mortars mean the mixing of binder with porous sand (schungite, vermiculite, expanded clay, perlite, slag pumice, aglonite, fly ash and others). Decorative solutions are made of washed quartz sand, crumbs of rocks with the size of grains of up to 2.5 mm (granite, marble, ceramics, coal, plastic). Colored plastering of facades involves the use of 2-5-millimeter granite, glass, ceramic, coal, slate, plastic crumbs. Colored cement-sand plastering is carried out by adding color cement, natural or artificial pigments to the standards in the solution.

Chemical additives

Preparation of mortars often involves adding to their composition various quality improving products of chemical additives that prevent delamination, promote greater mobility, strength, and increase the frost resistance of the mixture. These are the so-called superplasticizing, plasticizing, stabilizing, water-retaining, air-entraining, accelerating hardening, retarding setting, antifreezing, compacting, hydrophobizing, bactericidal, gas-forming complexes. The last four are designed for use in special cases.

The necessary quantity of chemical additives is determined by mixing in laboratory conditions. Produced in accordance with standards, they do not cause destruction of materials, corrosive effects on the buildings and buildings in operation. Classified by type, brand, they all have a symbol, as well as designations of standard and technical conditions. Thus, sodium sulfate (CH, GOST 6318, TU 38-10742), to the antifreeze urea (urea, M, GOST 2081), to water-retaining carboxymethylcellulose (CMC, TU 6-05-386) can be classified as accelerating additives. . A complete list of additives is specified in the appendix to GOST 28013. A cement mortar is produced with the addition of organic (micro-foaming agents) and inorganic (clay, lime, cement dust, fly ash and others) plasticizers.

Technical quality control

The enterprise, which is engaged in the manufacture of mortar mixes, without fail carries out technical control of the dosing of the necessary components and the preparation of the actual solution mixture. Control is carried out once per shift. Mortar mixtures of the same composition, produced for a shift, are surrendered in lots. In this case, control samples are sent to the laboratory (selected according to GOST 5802) to determine all technical characteristics.

If the customer is specified other than those specified in GOST 28013 , the quality of the product is subject to control as agreed by the manufacturer with the consumer.

Test mortars are carried out in laboratory conditions by the manufacturer, from whom the consumer has the right to request control samples of the mortar mixture and solutions. The solution is dispensed by volume, the dry mortar mixture by weight.

Regarding the characteristics of the mortar mixture for the ability to delaminate and retain liquid, and the solution for frost resistance, verification is carried out when selecting or changing the composition or characteristics of the components of the solution. Then the products are subject to inspection every six months. If, in the event of a check, there are inconsistencies with the current standard, the whole lot is rejected.

What should be contained in the documents for the goods?

In documents supporting the quality of products and endorsed by the representative of the manufacturer responsible for technical control, the following information should be recorded:

- name and address of the manufacturer, exact date and time of mixture preparation;

- grade of solution;

- type of binder;

- quantity, mobility of the goods;

- name and quantity of chemical additives;

- an indication of this standard, which is a guarantee of compliance of ready-to-use products with technical data.

If porous aggregates are used, the average density in the dried state is additionally recorded. For a dry mixture, the volume of the zither is prescribed so that the mixture acquires the necessary mobility. Also, the documents must contain the warranty period of storage of the mixture in dry form, which is calculated from the date of preparation until the expiration of six months.

Transportation of mortar mixes

When transporting mortar mixtures, it is important to exclude the loss of cement milk. It is permissible to transport products by truck, as well as in tubs (bunkers) by cars and on railway platforms. At the same time, the temperature of the transportable solution must be checked, which is fixed when the technical thermometer is immersed to a depth of 5 cm.

In dry form, the mortar mixes are transported in cement carriers, containers or packaged up to 40 kg (paper packaging) and up to 8 kg (polyethylene packaging). At the same time in paper bags, transportation is carried out on wooden pallets, in polyethylene - by placing the bags with the mixture in special containers. Storage of the mixture in bags is allowed at a temperature of 5 ° C in closed dry rooms. After transportation, the solution mixture is discharged into a mixer or other containers.

Application of mortars

The sphere of application of mortars is diverse. Construction concretes and mortars on cement binding material as a structural material are widely used both in private and in industrial construction with the erection of strong bearing bases, horizontal, vertical, inclined structures, structures, ceilings, under capital and current repairs, reconstructions, restorations .

It is generally accepted that in the construction of stone buildings, the consumption of mortars reaches a quarter of the total volume of the building. Many of us have ever purchased lime, plaster, mixed mortars for plastering walls in apartments or private households (these are so-called finishing compounds). Also, someone had to purchase masonry solutions for installation works, cladding, masonry, fireproof. On the construction market, one can now find building solutions (GOST 28013), which have superiority in properties of thermal insulation, sound absorption, heat and fire resistance.