Cement-lime mortar: proportions and characteristics of grades. Features of cement mortars with lime

Mortars are characterized by three main parameters: density, type of binder and their purpose. Depending on the density (in the dry state), heavy (with a density of 1500 kg / m 3 or more) and light (with a density of less than 1500 kg / m 3) solutions are distinguished. For the manufacture of heavy solutions, heavy quartz or other sands are used; fillers in light solutions are light porous sands from pumice, tuffs, slags, expanded clay, etc. Light solutions are also obtained with the help of foaming additives - porous solutions.

By type binder mortars are divided into cement (on Portland cement or its varieties), lime (on air or hydraulic lime), gypsum (based on gypsum binders) and mixed (on cement-lime, cement-clay, lime-gypsum binder). Solutions prepared on one binder are called simple, and on several binders - mixed (complex).

According to their purpose, mortars are masonry (for masonry, installation of walls from large-sized elements), finishing (for plastering rooms, applying decorative layers to wall blocks and panels), special, with special properties (waterproofing, acoustic, X-ray protection).

The choice of binder depends on the purpose of the solution, the requirements for it, the temperature and humidity conditions of hardening and the operating conditions of the building. Portland cements, pozzolanic Portland cements, Portland slag cements, special low-grade cements, lime, gypsum binder are used as binders. To save hydraulic binders and improve the technological properties of mortars, mixed binders are widely used. Lime in mortars is used in the form of lime paste or milk. Gypsum is mainly used in plasters as an additive to lime.

The water used for mortars must not contain impurities that have a detrimental effect on the hardening of the binder. Suitable for these purposes tap water. If the solution is used in winter conditions, hardening accelerators are added to its composition, as well as additives that reduce the freezing point of water (calcium chloride, sodium chloride, potash, sodium nitrate, etc.)

The composition of the mortar denote the amount (by mass or volume) of materials per 1 m 3 of the solution or by the relative ratio (by mass or volume) of the initial dry materials. In this case, the binder consumption is taken as 1. For simple solutions consisting of a binder (cement or lime) and not containing mineral additives, the composition is denoted as 1:4, i.e. per 1 wt. hours of cement accounts for 4 wt. hours of sand. Mixed mortars consisting of two binders or containing mineral additives are indicated by three numbers, for example 1:3:4 (cement:lime:sand).

Quality mortar mixtures characterized by their workability - the ability to fit without special compaction on the base thin layer filling in all the imperfections. Workability is determined by the mobility and water-holding capacity of mortar mixtures.

Mobility- the ability of the mortar mixture to spread under the action of its own mass. Mobility is determined (in cm) by the depth of immersion in the mortar mixture of a reference cone weighing 300 g with a 30 ° apex angle and a height of 15 cm. The deeper the cone is immersed in the mortar mixture, the greater its mobility. The degree of mobility of the mixture depends on the amount of water, on the composition and properties of the starting materials. To increase the mobility of mortar mixtures, plasticizing additives and surfactants are added to them. The mobility of mortars, depending on their purpose and method of laying, should be as follows.

brick wall laying, concrete stones, stones from lungs rocks: 9-13.

Masonry walls made of hollow bricks, ceramic stones: 7-8.

Filling horizontal joints when installing walls made of concrete blocks and panels; jointing of vertical and horizontal seams: 5-7.

Rubble masonry: 4-6.

Filling voids in rubble masonry: 13-15.

Water holding capacity called the property of the solution to retain water when laying it on a porous base. If the mortar has a good water-retaining capacity, the partial suction of water compacts it in the masonry, which increases the strength of the mortar. The water holding capacity depends on the ratio constituent parts solution mixture. It increases with an increase in cement consumption, replacement of part of the cement with lime, the introduction of highly dispersed additives (ash, clay, etc.), as well as some surfactants.

Strength of the hardened mortar depends on the activity of the binder, the water-cement ratio, the duration and conditions of hardening (temperature and humidity environment). When laying mortar mixtures on a porous base capable of intensively sucking out water, the hardening strength of the solutions is much higher than the same solutions laid on a dense base. The strength of the mortar depends on its brand, which is set according to the compressive strength after 28 days of hardening at an air temperature of 5-25 ° C. There are the following brands of solutions: 4, 10, 15, 50, 75, 100, 150, 200 and 300.

Frost resistance solutions are determined by the number of cycles of alternate freezing and thawing until the loss of 15% of the original strength (or 5% of the mass). According to frost resistance, solutions are divided into grades Mrz from 10 to 300.

The choice of brand and composition of the solution depends on the type of building, its operating conditions, as well as on the planned degree of durability (Table 4). Buildings located above the ground with a relative humidity of up to 60% inside, as well as underground structures in soils with a low level of humidity, are laid on cement-lime and cement-clay mortars. In this case, the solutions must have a ratio of the volume of lime (clay) dough to the volume of cement not exceeding 1.5: 1. If the humidity inside the building is more than 60%, or the ground has high humidity, this ratio should not exceed 1:1. Lime and clay are not used in mortars when masonry is located below the groundwater level.

Table 4 Marks of mortars for masonry.

Cement-lime and cement-clay mortars in summer conditions are used in the construction of buildings whose height does not exceed three floors. The brand of clay mortar used in a dry climate is 10, in a moderately humid climate - 2, and for a mortar with additives - 4. The consumption of binders depends on the composition of the mortar (Table 5), as well as the brand of binder and mortar (Table 6).

Table 5 Compositions of mortars for masonry (in parts by volume).

For laying walls from dry and porous stone materials, mortars with greater mobility are used, for laying from wet and dense materials, with less.

Table 6 Consumption of binders depending on the brand of mortar.

Cement- mortar- a mixture with high adhesion, strength and elasticity. It has proven itself as a masonry mortar for building blocks and bricks, as well as for plastering various surfaces indoors and outdoors. The scope of application is not limited to finishing work, this also includes laying pipes, processing reinforcing mesh, pouring monolithic floors. One of the most important advantages of such a composition is reliability and moisture resistance.

In addition to the above properties, lime is also characterized by bactericidal properties that prevent the formation of fungi and molds. It is worth noting, unlike cement mortar, the ability of the material to pass moisture, which has a positive effect on the level of humidity inside the room. Hence resistance to temperature extremes up to 65 °C and frost resistance down to -50 °C.

Good adhesive properties make it possible to work with any materials, even with wood. The mixture is easy to lay, filling even the smallest cracks and bumps. The increased plasticity of the lime mortar makes it possible to extend the drying time up to three hours, thereby avoiding cracking.

According to the characteristics of fat content, the following lime compositions are distinguished:

1. normal - with an optimal degree of plasticity, practically do not crack and shrink when dried;

2. skinny - used for any facing work, as they have minimal shrinkage;

3. fatty - highly plastic material with big amount binders, therefore it is well used in the form of masonry mortar.

Fat content can be adjusted by adding various components. So, to lower the value, porous sand is added, and lime increases the fat content back.

According to the ratio of density, solutions are divided into:

• low density - up to 1500 kg/m3;
• medium density - from 1500 kg / m3.

The ratio of the components of the solution determines the scope of its application. The most popular brands are M75 and M50. For example, the M75 mixture proved to be the best as a reliable masonry mortar for bricks. Whereas for a wider area of ​​use, as well as for carrying out plastering works digest M50.

With regard to plaster mixtures, they are conditionally divided into:

1. basic - for rough leveling of the surfaces of walls and ceilings;

2. decorative - having decorative elements in the structure or due to prolonged drying, they are easily subjected to textured processing with subsequent painting;

3. special - are of a technical nature to improve the moisture-proof properties, sound insulation and insulation.

Manufacturers and prices

Another plus is the affordable cost of the material compared to the cement-sand mortar. Its low consumption (1 m2 layer in 1 mm - 1.5 kg of the mixture) determines the economic benefits. Lime mortar can be bought from manufacturers ready-made or in the form of a dry mix packaged in bags. Construction manipulations inside the premises are allowed to be carried out powder formulations, while for outdoor work, especially under conditions of high humidity, it is recommended to entrust the preparation to professionals.

The cost depends on the quality of the raw materials used, the ratio of ingredients. An approximate price range is shown in the table below.

The line of manufacturers of ready-made dry mixes is quite extensive. All of them have their own characteristics, features in the composition and scope. Below are the most accessible and common.

Do-it-yourself solution preparation

In addition to ready-made production options, it is possible to make lime mortar yourself. Buy all the necessary high-quality elements and carefully observe the proportions to achieve a high-quality result with savings Money. The main ingredients used are cement, sand, lime and water.

The ratio of ingredients determines the brand and specifications.

Water consumption during preparation is usually 0.8 parts per 1 hour of cement. In practice, the amount of liquid is determined visually by the consistency of the solution - normally, the mixture should look like thick sour cream.

Lime, as a building material, is used only in extinguished form, otherwise as a result chemical reaction finished material may bulge or rupture altogether. For preparation, you will need a separate container. The process differs depending on the rate of quenching.

1. Fast-extinguishing lime is poured into a barrel of water until completely immersed. After the appearance of soaring, more water is added and mixed. Extinguishing takes an average of 8 minutes.

2. Medium-extinguishing lime is poured into a container and filled with water in double volume. When steaming, water is also added and mixed. The process continues for approximately 25 minutes.

3. Slow-extinguishing lime is only moistened with water. The reaction is accompanied by a threefold increase in volume and an increase in temperature. Takes over 25 minutes.

The prepared material is diluted with water in a ratio of 1: 1 to the state of milk of lime. Often, for the final extinguishing, it is poured into a special pit, sprinkled with a layer of sand and earth and aged in this way for 15-20 days. The composition acquires a creamy consistency and is now called lime dough or paste.

For cement-lime plaster mortar most commonly used as a binder cement:

• type I Portland cement with a minimum amount of additives and a high setting rate;
• Type II Portland cement grades M500-400 with additives up to 35%.

As practice shows, three-layer plastering is most often used at construction sites. The proportions of the solution (water-sand-lime-cement) in this case will depend on the layer of plaster.

• draft layer - spray - 2.2: 6.7: 1.5: 1;
• middle layer - soil - 2.8: 9: 2.2: 1;
• finishing layer - covering - 4:13.5:3:1.

For the preparation of masonry cement mortar, it is more expedient to use a concrete mixer, since in practice it is required more than plaster. The latter, in turn, is prepared in improvised containers using a construction mixer.

Part of the water is poured into the concrete mixer, then cement, lime and sand are alternately introduced into required proportion. After thorough mixing, the mixture is closed with the remaining water.

In the case of manual preparation, there are two types of procedures:

1. The lime dough is passed through a sieve with a mesh diameter of not more than 3 mm. Then sand and cement are added in portions to it, everything is thoroughly mixed until the required fat content of the solution is obtained.

2. A dry mixture of sand and cement is prepared in desired ratio. Milk of lime is gradually poured into it, if necessary, diluted with water to achieve the required consistency.

To increase the stability of the solution to factors external environment, slowing down the hardening process, the following are added to the finished mixture:

• plasticizers;
• frost-resistant additives;
• setting retarders and others.

The Portland cement used in the composition also brings a number of positive characteristics material:

1. in combination with the action of hydraulic additives, it provides resistance to leaching, and therefore to long-term exposure to ground and sea waters;

2. Attaches cement high level anti-corrosion protection;

3. lime mixtures with Portland cement are not prone to destruction even with a seasonal change in freezing and thawing regimes.

Over the past decades, the use of cement-lime mixtures in construction and decoration has remained at the same level. But this is not due to a lack of new materials and technologies, but only because this composition meets all modern requirements for building materials. Cement-lime mortar remains relevant and in demand.

Main advantages

Cement-lime mortar is a durable and plastic material that is excellent as a binder in construction and for finishing works.

• It can be used as a masonry mortar or plastering material. In the form of a masonry mixture, it reliably connects blocks or bricks used in construction. As a plaster, it can be used for interior and exterior finishing work.
• It is excellent for pouring monolithic floors, due to its characteristics. Lime, which is part of the solution, increases the period of its solidification. The increase in the hardening time and the viscosity of the composition help to avoid the formation of cracks, help to more evenly distribute the putty over the surface.

penetrating power

Cement mortar with lime has a high degree of adhesion to the surface. It is able to easily fill small cracks and depressions, which increases the adhesion strength to any materials to which it is applied.

Such a solution is characterized by a high degree of adhesion, so it can be used even when working with wood. Plaster on shingles ( wooden crate) is produced with just such a solution.

The increased characteristics of strength, elasticity and moisture resistance make it possible to use the mixture for any interior finishing work, even with high humidity, since dampness and precipitation do not destroy the finished coating. The solution can be used, for example, for finishing work in bathrooms, on facades or on foundations, even in the part where it is directly adjacent to the blind area and, as a result, is exposed to moisture.

Specifications

The composition of such a solution necessarily includes cement, sand, slaked lime and water. It is worth paying attention to what needs to be added exactly slaked lime. Otherwise, the quenching reaction will begin in the solution itself when water is added, and the bubbles, formed already inside the solution, will lead to cracking of the plastered surface. This blistering process will result in poor mortar quality and brittleness after it dries.

Thanks to the lime that is part of the material, pathogenic bacteria and fungi do not develop on it, in addition, lime prevents the penetration of rodents and various pests into the dwelling.

Construction mixtures, their composition and properties are regulated by various GOSTs. This is necessary for the standardization and regulation of norms in construction. GOST 28013-98 is the main regulatory legal act regulating technical requirements to mortars and the materials included.

This standard also includes characteristics of quality indicators, acceptance rules and conditions for transporting ready-made solutions. It contains qualitative and quantitative characteristics masonry mortars, materials for plastering and for internal works used in various conditions operation.

Properties

The main properties of cement-lime mortars:

• mobility;
• the ability of the solution to retain water should be from 90%;
• the stratification of the prepared mixture should be up to 10%;
• application temperature up to 0 degrees;
• average density;
• humidity (this parameter applies only to dry mortar mixes).

The composition of the mixture is selected depending on the type of material on which it will be applied, and on the conditions for further operation of the finished coating.

There is such a thing as the fat content of the finished mixture. Fat content depends on the amount of astringent included in the composition.

Cement-lime mortars are divided into three categories of fat content.

• Normal- these are solutions with such plasticity, which is most universally suitable for use in various conditions. Solutions with such a fat content do not shrink and, as a result, crack the finished coating.
• Skinny- These are solutions with minimal shrinkage. They are ideal for tiling work.
• fatty- these are mixtures with a high degree of plasticity, which is due to the large number of binders that make up the composition. This material is best used for masonry work.

The fat content category can be adjusted by adding components to the composition that can change the plasticity of the solution. For example, porous sand reduces fat content, while lime, on the contrary, can increase it.

Thus, it is easy to adjust the plasticity of the finished solution and adjust its properties to specific operating conditions.

Density and grades

The components that make up the cement-lime mortar have direct influence for its density. The ratio of these components also plays an important role.

As a result, solutions of the following types can be distinguished:

• low density or light - up to 1500 kg / m³;
• high density or heavy - from 1500 kg / m³.

Also, solutions according to the ratio of components are divided into grades from M4 to M200 according to GOST 28013-98. For example, for masonry the best way solutions of grades M100 and M75 are suitable. They are characterized high performance moisture resistance and strength. The components that make up these materials are more homogeneous, since, unlike concrete of similar grades, they do not include crushed stone.

Ready mortar grade 100 or grade 75 is suitable for the construction of civil and industrial facilities. To prepare solutions of these grades, it is necessary to mix cement, lime and sand in a certain proportion. So, for mortar M100 when using cement brand 500, the proportions will be 1: 0.5: 5.5. And for the M75 mortar using a similar brand of cement, the proportions will already be different - 1: 0.8: 7.

For plastering, mortars M50 and M25 are very popular. They have such undeniable advantages as cheap and easy to prepare.

Solutions of brand 50 and brand 25 can be used when the humidity in the room is above 75%. This allows them to be used in the construction of baths and other premises where high humidity preserved long time. Also, the lime included in the composition prevents the formation of any type of fungus on the plastered surface, which, of course, is an advantage of such a coating.

Diversity

Plaster mixtures can be divided into several types.

• Basic- are used for initial, rough leveling of the surface and sealing large flaws and holes;
• Decorative- such options may contain decorative additives, such as pigment for coloring, crushed mica to create a shimmering effect, plasticizing and hydrophobic additives;
• Special- used to improve technical properties of the processed room, they can serve for moisture-proof, sound-proof and heat-insulating tasks.

Dry mix or do-it-yourself composition?

Undeniable dignity of this material is its value. It is significantly cheaper than similar cement-sand mortar. The benefit is due to the economical consumption when applied to various surfaces in comparison with analogue. The sandy solution is less plastic due to the disparate fraction of sand and the absence of a plasticizer. It has less adhesion and is worse distributed over the surface.

Cement-lime mortar can be purchased as a dry mix from various manufacturers, or you can make your own. There is now a wide range of manufacturers ready mixes with their characteristics and applications.

Should be addressed Special attention on the markings on the packaging to find the optimal mixture suitable for the type of work you need.

To use such a mixture, add water in accordance with the instructions on the package, mix thoroughly to acquire a uniform texture. For these purposes, you can use a construction mixer or, in the old fashioned way, knead the composition with a trowel and a shovel.

In the event that you decide to make the mixture yourself, then this is not difficult to do. Enough to buy everything necessary ingredients(cement, lime, sand) and mix them in the proportion of the appropriate brand you want to get.

When making a cement-lime mortar, it is necessary to add hydrated lime, but if you only have quicklime available, you can extinguish it yourself.

Comments:

Despite the leaping leaps and bounds of scientific and technological progress, cement mortar is still an integral part of any construction. It is the main link that ensures the strength of the foundation and brickwork. Therefore, any mistake in its preparation significantly reduces the life of the building built on it.

Cement - basic connecting link, which ensures the strength of the foundation or brickwork.

Grades of cement mortars

First, two clarifications need to be made.

First: in construction, a whole group of binder mixtures is called cement, despite significant differences in their composition. Portland cement, pozzolanic Portland cement, Portland slag cement, and alumina cement are the most widely used. This group includes expanding cement and many other mixtures.

Second: non-professionals often confuse cement and concrete compositions. This is a mistake, since the cement mortar is prepared by mixing cement and sand in certain proportions, and for the preparation of concrete, gravel or crushed stone is added to the composition.

Good cement should have good binding power. In the vast majority of cases, the M200, M300, M400, M500, M600 grades are used to prepare cement mortars. The higher the grade, the prepared cement mortar will be of better quality and strength.

Depending on the cement used and the amount of sand added to the mixture, cement solutions are also divided into grades. In private construction, grades 15, 25, 50, 75, 100, 150 and 200 are usually used. In industrial construction, cement mortar M300 is sometimes used to give the structure being built extra strength.

Unlike concrete mix, which, with large volumes, is more rational to buy ready-made at specialized factories, the cement mortar is almost always prepared on construction site. To get the desired grade, it is necessary to mix cement and sand in a certain proportion.

For example, to prepare the M100 composition, you can use M300 cement and sand in a ratio of 1: 3, when using M400 cement, these proportions will be 1: 4, and when using M500 cement, 1: 5. To prepare a solution of M200, these proportions will be as follows: when using M400 - 1: 2; when using M500 - 1: 2.5; when using the M600 - 1: 3.

In the above examples, it is easy to see that the consumption of cement, regardless of its brand, always remains the same, and only the amount of sand consumed changes. Therefore, observing the necessary proportions, it is easy to cook cement mixture almost any brand. It is very important not to get hung up on the brand of binder used for the preparation, but to achieve desired brand final product.

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Types of cement mortar

In addition to dividing into brands, the prepared composition, depending on the final result, can turn out:

• skinny;
• normal;
• bold.

It turns out such a separation due to non-observance of the proportions of the binder and aggregate in it. In a lean composition, insufficient consumption of cement and an excess of aggregate - sand. It is very inconvenient to work with such a composition, and the masonry laid on it will not be securely tied and, accordingly, will not be strong enough.

There is too much binder and too little filler in the fatty composition. Despite the greater than necessary consumption of cement, it is also not suitable for high-quality work, it quickly sets and hardens, but after hardening it becomes covered with cracks and crumbles. The masonry laid on it will be short-lived.

A normal cement mortar is a composition where all the necessary proportions are observed and all components are mixed correctly. Such a composition seizes and hardens more slowly in comparison with a greasy one, but it does not crack or crumble, and the masonry laid on it is durable and durable.

To determine the type of mixture, it is enough to carefully examine the mixing tool. If ready composition does not stick to the instrument, but only slightly stains it, then it is skinny.

If the prepared composition sticks to the removed tool, hiding it under its own layer, then it is greasy.

Properly prepared composition working surface tool should stick in separate lumps.

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Preparation and use of cement mixture

The cement mixture can be prepared either in a pure cement-sand composition, or with the addition of some lime. To prepare it, you will need tools:

• a concrete mixer or a container replacing it;
• shovel;
• buckets.

To prepare a clean mixture, cement and sand are first dry mixed in the desired proportion. It is necessary to mix until its components form a homogeneous product. Then water is added to the resulting mixture (approximately 8-9 liters for each bucket of cement), and again everything is thoroughly mixed until the mixture turns into a pasty composition of the desired consistency.

If the result of the work is a lean solution, then it needs to be redone, adding a little cement to it. If the mixture turned out to be oily, then you need to add sand and water to it in small portions. This process should continue until a normal solution is obtained, which is convenient to work with.

But you need to remember that you need to use the prepared cement-sand composition in just an hour and a half, after preparation, and then it will begin to harden and it will be difficult to work with it. For grouting small cracks in the masonry, it is completely unsuitable. Therefore, professional masons prefer to perform such work with a cement-lime mixture.

It is prepared in the same way as the pure composition, but instead of water, the prepared dry mixture is diluted milk of lime. Such a solution has increased plasticity, good strength and adhesion, and practically does not crack. To work with such a mixture is usually given from 3 to 4 hours. This mixture is used for finishing brickwork, as well as for fine finish ceiling and floor.

The use of the prepared solution must obey certain patterns.

The ideal option would be to use in the masonry the composition of the brand that corresponds to the brand of material used for masonry.

Those. if brick grade 100 is used for masonry walls, then the composition used for masonry should be of the same grade. In this case, the masonry is almost homogeneous.

But for high grades of brick, this is an unacceptable luxury. For example, if masonry is made of 350 bricks, then the use of the M350 composition will be impractical in practice and too expensive financially. Therefore, when distilling brickwork, M400 cement and sand are usually used in a ratio of 1: 3.5. The result is a composition of approximately M115.