12.2. Preparation and technology of plastering during restoration using lime mortar

The technology of applying lime plaster during restoration (continued)

Prepare the quenching boxes of boards measuring 3x4 or 2x3 meters, height about 0.5 meters. In the upper narrow part of the box arrange a drain hole with a latch and a metal grid with cells of at least 100 holes per 1 cm (references recommended). The quilting box is given a small slope in the direction of the pit, located under the quenching box. The dimensions of the pit in the plan are also 3x4 or 2x3 meters, and a depth of 1.5x1.7 meters. Walls and the bottom of the box strengthened with boards or stones, so that the water does not go into the ground and the lime does not clog the ground. The quenching box extends 20-30 cm in the direction of the pit above its edge. Lime pieces are placed on the bottom of the quencher box and poured with tap water or any clean water to extinguish "into the dough" (1: 4), preventing strong evaporation. This means that you need to pour abundantly (on the entire layer of lime at once) and then topping up to full volume. Lime while actively stirred and broken into pieces. Then add water until quenching "in milk" (l: 8), also actively mixing. After that, open the valve and, mixing, pour the “milk” into the pit.

It should be noted that sometimes the quenching box is recommended to be filled with lime by one quarter in the literature on plastering technology, that is, for slaking “into the dough”. It says that then add water to the consistency of "milk". But there is nowhere else to top up. So according to these recommendations, the quenching occurs "in the dough," and the "milk" does not work. The quenching time in the quenching box is unlimited, but it is logical to drain after the water begins to cool.

Heavier than hydrated lime, impurities, burnout and underburning remain at the bottom of the box and are thrown away. It is recommended to fill the pit in reference books during the day, so that the sediment does not stratify. There is no doubt that further mixing of the solution in this case is not provided.

Let us return to the “milk” in the quencher box. In reference books 1940-1950. It is recommended that the lime (intended for mass construction) be kept in a pit, covered with water for at least 2-2.5 months. About mixing it in the pit is not mentioned. After a certain time (2 months or 3 years) determined by the technologist (as agreed with the customer), diluted dough from the quenching pit, according to the recommendations in the same sources, should be filtered through a vibrating screen with 0.3 * 0.3 mm cells. Everything unnecessary remains on the screen and is thrown away. It is logical to filter into barrels or other containers that do not allow water to pass through. This lime is ready for mixing solution. Solution mixture with a high content of Ca (OH) - fat lime - requires a large amount of fine aggregate, in particular, sand. To avoid cracking the plaster, it is required to determine the content in the Ca (OH) test. . The most reliable results are chemical laboratories. But such an analysis is not always done.

More often use a more accessible technique. Strained dough is allowed to settle for 2-3 weeks. When the precipitate is compacted, about 3 liters of hydrated lime are taken from its thickness (without water). This dough is placed in a conical bucket of fixed sizes, and a cone of a certain shape and mass is submerged into it under its own weight. If the depth of the cone is less than 12 cm, the dough is diluted with water and the cone is dipped again. So continue until the dip of the cone is 12 cm. Such a dough is called a dough of normal consistency . The bulk of this test determines the grade of lime in the test. So, the following data is given in the reference book: the volume mass of lime of the first grade is 1300 kg / m , second grade - 1350 kg / m , the third grade - 1400 kg / m .

Next produce mixing solution. Clean sand is very important for the quality of the plaster. The presence of clay, silt inclusions, as well as the presence of particles of just earth, clearly leads to the destruction of the clothing of the building in 1-2 years. The content of clay, dust and silt particles should not exceed the value established by GOST.

There are river sand and sand from the quarries - mountain. River sand has more rounded grains; mountain sand has grains with sharper edges. The porosity of river sand is greater than that of mountain sand. The strength of the solution in the sand from quarries is greater than that of solutions with river sand.

The strength of the plaster, like any clothing, is not so significant - the material can be durable, but fragile. The main thing is that the clothes fulfill their functions: they are compatible with masonry, vapor permeable to the outside, waterproof, durable, frost-resistant, weather-resistant, etc.

For example, the tensile strength of lime-sand plaster is often about 0.4 MPa (4 gs / cm ). But it does not interfere with the use of such solutions at all times for durable clothing.

The selection of the particle size distribution depends on the function (purpose) of the clothes, on the clothing layer. For example, from the fact that it is a plaster of a dome under a painting or fresco, just a dome, internal walls, external walls, drums, socles, on what kind of layer it is: splashing, priming or covering.

The mortar mixture for the first layer of plaster - spray and for the outer layer - covering - should be more liquid than for the base layer - soil.

The consistency of the mixture of each layer is determined by the amount of immersion of the standard cone.

Manual mixing of the solution with small amounts of work is performed as follows. Liquid or thick dough is drained into the work, pre-filtered through a vibrating screen with 0.3x0.3 mm cells. Add small amounts of sifted sand, mixing each time, until a homogeneous mixture is obtained. Sifted cemyanka enter through a sieve. The amount of sand, a certain particle size distribution and cement, as well as water per batch is established by technologists. For large volumes of work for mixing the solution using mixers of various types.

After mixing, the mortar mixture is sifted for spraying and soil through a sieve with 3x3 mm cells, and for covering with a 1.5x1.5 mm sieve. .

Putting plaster. Surface preparation is no less important for durability than the quality of the solution. If the masonry is not made “into the wasteland”, then the mortar should be removed from the joints by no less than l cm. In the old recommendations, the old plaster to be removed is recommended to be knocked off in the old way. To facilitate this work is possible using a detachable machine. To remove the old paint, dirt, soot and lichen, you can use a power drill with a rubber disc, which holds the sanding pelt with the largest grain possible. You can also use a construction dryer.

It is believed that the adhesion of the mortar to the brick is carried out by “as if needles” penetrating into the surface layer of the brick. This means that the particles of the “dough” penetrating into the pores harden there and crystallize, which is confirmed by modern knowledge. Therefore, the pores need to be cleaned, released. Therefore, in addition to the mechanical cleaning mentioned above, it is necessary (without fail) to rinse the walls well - to remove layers of dust, dirt, etc. In some cases, mainly from the outside, it is effective to rinse the walls with a stream of water under a pressure of up to 2 to 4 atmospheres.

Before applying the plaster layer to the wall must be moistened. A brick that is not moistened until it is completely saturated with water also sucks in water along with the binder, but more slowly, longer, without drying the solution. As the long experience of builders shows, in this case there is a stronger adhesion of the mortar to the brick. Undoubtedly, by old masters it was established experimentally that five to six times the surface was wetted enough that the plaster would not crack.

Old masters (XVIII century) considered it necessary to mix it thoroughly immediately before applying the mixture.

As indicated in the special literature, coatings up to 7 mm thick are performed at one time without bleeding with a plastic mixture. When the thickness of clothing is about 1 cm, it is done in two steps: spraying and primer In external plasters with a layer thickness of 1 cm, a covering 3 mm thick is sometimes used to inject pigment or as a basis for painting work. External coatings 2 cm thick are often performed without a covering. Layers of soil should be no more than 7 mm.

Plastering works in the premises begin with plastering of the ceilings, and then proceed to the plaster of the upper part of the walls.

The technological process of plastering (tasting) consists of applying on the base of the soil, soil and covering layer. At one time, thick layers of the solution should not be applied, since it can slip in the process of work, and after drying it can crack.

The first layer of stucco - spray - should completely cover the surface to be plastered, firmly connect with it, fill all its irregularities to obtain a larger area of ​​adhesion and ensure the solidity of the plaster layer with the base. The thickness of the layer of spray varies depending on the base. On wooden bases - up to 10 mm, including the thickness of the splitting, on brick and concrete - up to 5 mm.

Before applying a layer of spray, the surface of the base must be well moistened so that after plastering the water contained in the solution is not absorbed and the strength of the plaster does not decrease. For a better filling of the unevenness of the base, the plaster for the spray is prepared more mobile (liquid) - creamy than for the subsequent layers. The solution from the falcon throw a trowel for plastering. The applied layer of spray does not level, but only removes the hanging parts of the solution. The exception is when thin plaster is being made (grouting on concrete). After setting the layer of spray can apply a layer of soil.

For soil use a thicker solution than for splashing. The soil is the main layer of plaster. It levels the surface to be plastered and forms the basic thickness of the plaster. The thickness of each layer of soil should not exceed 7 mm when using lime and lime-gypsum solutions, and 5 when using cement mortars   mm The average thickness of the plaster for simple plaster is no more than 12 mm, for improved - no more than 15 mm, for high-quality - no more than 20 mm.

After the start of setting, each layer of plaster, except for spraying, must be leveled with a wooden scraper. Each subsequent layer of plaster can be applied after the external signs show that the solution of the previous layer is somewhat cured, does not sprinkle under your finger (when pressed on it), whitening of the solution is noticeable, which indicates its drying and the beginning of hardening, etc. The average aging times for the plaster layers are given in Table 12.4. The given periods in the summer and with good ventilation are reduced by half, and in cold weather, on the contrary, they increase to two times. The plaster layer should not be allowed to harden completely and be dried out, as this will aggravate the adhesion of the new layer to the old one.

To improve adhesion with subsequent layers, the freshly applied soil is cut by mutually intersecting grooves 3 mm deep at a distance of 40 mm from each other.

The last layer of plaster - nakryvochny. It is applied after setting the last layer of soil. The thickness of the covering layer after leveling and grouting with graters should be 2 mm for ordinary plaster. The coating solution is applied more fat.

Before applying the covering layer, moisten the primer with water using a brush. After the covering layer dries out a little, grouting should begin. Grout produce circular movements graters, and then razdragka

In the process of grouting, the dried surface is moistened with water, spraying it with a brush.

Table 12.4.

When carrying out plastering work, special attention should be paid to edges and corners (places of interface surfaces). The edges must be exactly vertical or horizontal, and the corners are carefully filled with mortar. This operation is carried out with the help of angular semi-blacks - husks (for internal corners) or enlarged (for external corners).

Plastering window and door slopes should be after carefully fixing the boxes. The gaps between the boxes and the brickwork are punctured with tow, felt or tow, antiseptic sodium fluoride solution. The tow or other materials moistened with gypsum mortar should be compacted and buried in such a way that there is a space of 20-30 mm left up to the surface of the box, which is filled with plaster. If the gaps are caulked flush with the box, then a crack forms between it and the plaster of the slope. With a thick plastering intent (more than 50 mm), nails are woven into the seams of the masonry and boxes after the pro- blade, which are braided with wire.

Internal slopes plastered with a bevel from the boxes to the surface of the walls. The corners of all slopes should be the same.

Plaster slopes in the following sequence: first, the upper slope on the horizontal rails, then bauxite on the vertical.

Rules-slats fasten with nails, plaster or inventory rake holders.

The solution applied with a trowel or a falcon on the slopes is spread with wooden beads, carved from boards in the shape of a slope and bound with sheet steel. Having filled the slopes with soil (with a large thickness - in several layers of 5-7 mm), apply a covering layer, which is leveled with a scraper and rubbed with a float. After grouting, remove the rules or slats and grease the “Usenka”. Blinds between window boxes are plastered the same way as slopes. After leveling and setting the solution, the bottom plugs are ironic.

For plaster applied to the wall, care is needed. If a mixture of cemyanka is added to the mixture, then a compound on a hydraulic binder is obtained. Such compounds, hardening in conditions of high humidity, at least do not shrink (during hardening slightly increase in volume), and therefore do not form cracks. Therefore, the hardening mixture must be moistened. Already started to set the composition should be slightly wetted, better spray. Excess water in this case is harmful, because it will wash out the binder. The first day (especially in hot weather) the solution is moistened several times as it dries, and in the next 5-7 days at least once a day. If air lime without hydraulic additives is used, then the mortar mixture should not be allowed to dry. Carbonation occurs only in a humid environment.

For the above purposes, the walls are sometimes covered with any wet cloth (burlap, matting). When performing plastering work in premises, you should avoid drafts, ventilation, etc., in order to keep the solution moist.

In any case, the care is performed in order to prevent the hardening mortar from drying out. Otherwise, shrinkage cracks may appear. The greatest shrinkage is observed in the first days, especially in the first days.

It should be noted that in plaster thickness of about 3 cm in the XIX century. and previously introduced pieces of charcoal up to 10 cm long at a distance from each other from 20 to 30 cm, the purpose of which is not explained. In addition, in such clothes sometimes in the stitches of the masonry at a distance of about 40 cm from each other, hammered hammered nails with wide caps, which were interconnected with wire.

To answer the naturally emerging question of why to apply antediluvian methods in the 21st century, consider the example of a brick. In the monograph by V.V. Inchika (1998) on efflorescence and salt corrosion of brick walls a modern brick of industrial production is compared with an old, artisanal brick.Clay for the manufacture of the latter was subjected to long-term staying and freezing under the open sky. As a result, soluble salts were washed out of clay and “beneficial” redox processes took place. Such processing of clay made it possible to obtain a brick of higher quality: “No matter how perfect the methods of processing clay are by mechanical means, they still cannot equal the effect of atmospheric factors during the weathering of clays.”

Общеизвестно, что при массовом строительстве качество производимой продукции ухудшается. Это относится и к штукатурным работам. Не следует задавать автору или кому-либо вопрос о том, сколько нужно гасить известь и можно ли использовать для штукатурки составы массового применения. Это должен решать заказчик волевым порядком. За качество нужно платить временем, трудом, деньгами, нервными клетками. Нет возможности – «по одежке протягивай ножки». Кроме того, можно хорошо загасить известь, но не процедить ее или неправильно хранить. Соответствующий результат скажется в течении одного-двух лет. Можно так же использовать грязный песок, нанести штукатурку на плохо подготовленную поверхность, неудачно подобрать состав раствора, не обеспечить уход за одеждой, ввести в смесь какой-нибудь полимер, который «забьет» поры и т. п. И результат не заставит себя ждать.

Необходимо отметить, что нельзя предсказать, на сколько десятилетий дольше продержится штукатурка, выполненная традиционными «старыми» методами по сравнению с растворами массового применения, как по вышеизложенным причинам, так и потому, что не обладает требуемыми статистическими данными. Если заказчик принял решение получить качественную одежду для своего объекта, то ниже очень кратко излагается последовательность его действий. Эта схема является продолжением вышеизложенного материала и ее следует рассматривать как информацию или просто сведения.

Готовиться нужно начинать заранее, не менее чем за год, ведь «вскачь не пашут».

– Исходя из удобства выполнения работ, подъезда, доставки смеси на объект или объекты, необходимо выбрать место расположения ямы и гасильного ящика.

– Запроектировать конструкцию гасильного ящика и ямы с укрытием. Особенное внимание уделить технике безопасности. Ограждения и технологические обустройства – проходы, мостки – должны обеспечивать удобство работ и их безопасность. Негашеную известь не напрасно называют едкой. Стены и дно ямы должны быть выложены булыжником на гидравлическом растворе. Можно укрепить стены и дно ямы досками (осиной, дубом).

– Закупить необходимые для изготовления этих конструкций материалы, инструмент, инвентарь.

– Изготовить гасильный ящик (ящики) и яму (ямы). Разработать проект производства работ (ПIIP).

- Get familiar with commercially available lime. You should look for calcium crushed air lime of 1st grade. The grade of lime is determined according to GOST 9179 - 77. “Building lime. Technical conditions. The seller must have a certificate (passport) of the goods. The certificate data is compared with the data of GOST. Lump lime is shipped in bulk. Therefore, you should pay attention to the conditions of its storage. Most likely, the lump, even not crushed, especially freshly calcined lime will not be on sale. In this case, the material must be ordered at the factory by a certain date. As far as we know, most often in Petersburg quality material is obtained from the Uglovsky lime factory.

- When everything is ready for quenching, it is necessary to quench the calcium oxide by the above rules. Drain the “milk” into the pit. Non-passing particles from the bottom of the box should be discarded. Put out the next batch and pour the “milk” into the pit. Continue until the pit is full. Mix. Let the “milk” stand for several days until a film appears on the surface of the water. Remove the film, drain or pump out the water. Pour clean water. Stir the "milk". Let stand. After the appearance of the film, repeat all actions until the end of quenching. The optimal time for such intense quenching is unknown to the author. The number of outstanding particles and impurities can be determined by laboratory.

If the lime in the pit is not “lean” and is not “washed”, the duration of quenching is significantly increased. At the same time, small lumps (about 2-3 mm in size) are formed outside of the dough (most likely colloidal clots of calcium oxide hydrate). Therefore, such a dough should be drained all the more through a vibrating screen with 0.3x0.3 mm cells.

In reference books 1940-1950. The “dough” (when the “milk” has settled and compacted is already a “dough”) is recommended to be kept in the pit for at least 2-2.5 months. At the same time, lime is not “emaciated” and is not “washed”. Strained liquid "dough" is ready for mixing the solution.

- Depending on the purpose of the mortar mixture, on the particle size distribution and the porosity of the fillers, on the additives, on the thickness of the dough, technologists select the composition.

- Completion of the selection of the composition of the production of trial cards, the size of not less than 0.5 x 1 m. As a result of monitoring the trial cards, if necessary, the composition and technology. At the workplace, the dosage of the components is given in units of volume per batch - in liters, buckets. A further sequence of technological operations is partially set forth above. The full technique of plastering works is described in the special and reference literature. This technique is owned by every qualified plasterer. With large volumes of finishing work, technological maps are drawn up with a detailed description of the entire technological process: a list of mechanisms, inventory, sequence of operations, dosage of components, time spent on each stage of work, number, specialty and qualification of workers, etc. are given.

In conclusion, it should be noted once again that in order to create good and reliable plasters, one should at least qualitatively realize the physicochemical processes of the work of buildings' clothes and the technologies for their manufacture.