The composition of the mortar for the construction of stoves and fireplaces depends on many factors: the work site, the location of the stove, the type of brick and its surface. In the article we will give advice on the compositions and methods of preparing solutions, as well as perform an overview of ready-to-use dry mixtures for this type of work..
To fasten bricks into monolithic masonry, masonry mortars are used. The duration of the stove or fireplace depends on the strength of the seams, on the thickness of the seam (if the mixture is not heat-insulating) – heat losses, on the accuracy of the execution and structure of the solution – gas tightness and appearance of the entire structure.
Masonry mortar is a mixture of powdered materials (filler and binder) mixed with water and / or liquid glass (phosphoric acid) to increase plasticity, reduce mortar moisture and internal seam cracks, and reduce brick shrinkage after drying. Some mixtures are supplemented with plasticizers to obtain a thin, durable seam..
The composition and density of the solution should correspond to the type of bricks and the place of installation (the temperature regime of the furnace, blower, chimney – different, wood, coal, gas stove – different). In the firebox of a wood-burning stove, the temperature, as a rule, does not increase for full-fledged sintering of the solution on a clean chamotte mortar. In furnaces that are fired with anthracite, also not all places are heated with flue gases to the firing temperature.
A stove folded in a bath, a room fireplace, a Russian stove for cooking or a barbecue in the yard are in different operating and climatic conditions, which means that the solution must be selected based on the characteristics of the environment – for high humidity, frost-resistant, ecologically perfect.
The more precisely the geometry of each product is maintained, the thinner the seam can be obtained. Some craftsmen are of the opinion that a seam of 3-4 mm is an indicator of a quality lining. Others argue that too thin seams as a result of frequent heat changes do not sufficiently compensate for the thermal expansion of the masonry of domestic stoves. They recommend an average thickness of 6-9 mm. In many respects, the thickness of the masonry and the method of binding the bricks become decisive..
In this case, the solution should not be liquid (0.6 l per 1 l of dry mixture), but semi-thick (0.5-0.55 l / l) or thick (0.35-0.4 l / l), for ready-made water mixtures are usually required less. The thicker the mortar, the thicker the joint can be obtained. The amount of water also depends on the ability of the brick to absorb water: for example, for clinker masonry, there should be less water in the mortar.
It is better to lay, dry and light the stove in dry, warm weather. The oven can only be coated after drying and after a test firing..
Advice! When laying the individual parts of the furnace, try to take bricks of the same brand (dinas, chamotte, ceramic) and from the same batch. Thus, the rate of filling open pores with a solution, adhesion, drying time, volumetric and linear expansion for all bricks of one section of the furnace will be the same..
Types of masonry mortars
Depending on the binder, simple and complex mixtures are distinguished:
In the names of mixtures with a two-component astringent, the first word is determined by the main component, and through the hyphen – the auxiliary. So, lime-clay solution has lime as the main binder, and clay-lime mortar – clay. When describing the proportions of the compositions, an astringent is taken per unit volume, and the remaining components are indicated in proportion to it.
The most popular and common of the masonry compositions. However, such a solution is used when laying dry sections of the furnace, where moisture is excluded. Due to the low moisture resistance in outdoor stoves, foundations and outdoor chimneys, the strength of masonry on clay mortar will be short-lived. In this case, the seams should be quite thin, 3-5 mm, and the clay itself should be of high quality, normal fat content.
The determination of the fat content of the clay is carried out by the craftsmen before the start of work. The balls are made, dried and tested in the fall, the solution is monitored for adhesion to the trowel, the lump is checked under pressure, the flagellum is twisted and torn from the plastic mass. Oily clays need to be weaned by adding clean and sifted in dry weather quarry sand (fraction up to 1 mm), in lean ones – add oily clay.
The mineral composition of the clay, if possible, should be close to the composition of masonry bricks. Highly valued kaolin and blue Cambrian clays, as well as their mixtures.
The basic recipe for clay mortar includes:
- 1 part clay;
- 1 part of sand, options for the ratio 1: 0.1–4, depending on the fat content of the clay;
- 0.25 parts of water.
Before cooking, the clay is gradually moistened, allowing time to absorb moisture and soften – several hours, and sometimes days. Clay solutions must be thoroughly mixed, breaking lumps, removing pebbles, and bringing them to homogeneity and elasticity. Before work, the resulting mass must be filtered through a sieve with 3×3 mm cells. The correct solution slides off the shovel without spreading. If the mass is dry during operation, you can add water to it, homogenizing the composition and bringing the consistency to the thickness of the village sour cream.
If the stove is not supposed to be finished, then the water for the solution should be rain or drinking settled, so that efflorescence will not appear on the surface of the seams. If you plan to plaster, then salt can be added to the solution for the fortress, up to 150 g per bucket. For the strength of the seams, Portland cement is sometimes added – 0.5-1.0 kg / bucket.
The predominant use of clay mortar in the construction of stoves and fireplaces is also explained by the high maintainability of masonry based on it. The stove can be shifted, repaired, disassembled to clean the smoke channels.
Lime-based mortars are used for the construction of foundations, outdoor chimneys, outdoor ovens. For strength, a little cement is added to it (in a ratio of 0.5: 1, and sand and cement are mixed before adding lime).
The dough is made from slaked lime. Lime-boiling water must be poured with water in a creative container until the process stops, then drained into a suitable container (built-in wooden box) and stored without air access. Over time, the quality of hydrated lime improves. It is advisable to use it not earlier than after a month, it is even better to withstand it longer. You can extinguish lime using the fast, slow and medium method. The intensity of the process depends on the amount of water.
Basic composition of lime mortar:
- 1 part lime dough;
- 2-3 parts of sand.
If the dough was too thick, it must first be diluted with water. Before mixing the ingredients, the sand is sieved through a 3×3 mm sieve, and then the lime dough is filtered through the same sieve and mixed thoroughly. To determine the quality of the composition, the solution is stirred for five minutes with a wooden flat instrument and checked:
- sticking does not occur – the solution is skinny, you need to add lime dough;
- sticks in clots and / or covers with a uniform layer of 2-3 mm – normal;
- a layer thicker than 2-3 mm – greasy solution, you need to add sand.
The finished mass can be stored and used for several days.
Such a solution is also used in the construction of foundations and chimneys above the roof level. The quality and properties of the binder in this case are standardized, therefore the recommended composition of the mortar can be written on the packaging, especially when using Portland cement for refractory masonry. It is important to use the solution quickly. Self-curing in air, it may no longer be suitable for work after 0.75-1 hours. The strength of the solution depends on the brand of cement – composition, additives, refractory properties, quality work.
The basic composition of the cement mortar:
- 1 part of strong cement (M400, M500);
- 5 parts of sand (from 1: 1 to 1: 6 – options).
Cement with sand is sieved through a 3×3 mm sieve, mixed, and sieved again, and then water is poured into the dry mixture. The thickness of the seam depends on the density of the resulting mass. Some craftsmen (with good cement) make seams up to 15–18 mm thick. Sometimes expanded clay, broken refractory bricks are added to the solution as a filler – the larger the fraction, the thicker the seam. For heat-resistant concrete elements, finely ground chamotte powder or ZSA backfill is used as a filler..
Table 1. Recommended formulations for mortars with sand and clay (under load)
Cement grade Mortar grade (cement-clay and cement-sand), kgf / cm2 one hundred 50 25 ten 4 400 1: 0.2: 3.5 1: 0.7: 6.5 1: 1.9: 12.5 – – 300 1: 0.1: 2.5 1: 0.4: 5 1: 1.3: 10 – – 200 – 1: 0.2: 3.5 1: 0.7: 6.5 1: 2: 16 – 150 – – 1: 0.3: 4.5 1: 0.8: 7 – one hundred – – 1: 0.1: 3 1: 1.5: 10.5 1: 1.8: 13 50 – – – 1: 0.2: 3.5 1: 1: 9
Ready dry mix
For the preparation of solutions, ready-made mixtures are often used, which are sometimes called mortars. At the same time, the operating temperature, the thickness of the joint, the similarity with a certain brand of brick depends on the type of mixture. Mixture data and recommendations for use are applied to the packaging. It indicates: storage conditions, purpose, proportions of water during preparation, time of setting and hardening, shelf life of the prepared solution, recommended brands of bricks and layer thickness, mortar consumption for different joint thickness and brick size (one-and-a-half brick needs less than an ordinary one, ), maximum application temperature, fire resistance (150–250 ° C higher than the operating temperature).
There are mixtures for masonry and finishing works, frost-resistant (winter), for outdoor work, moisture-resistant, fire-resistant, heat-insulating. In addition to the main components – binder and filler, such compositions contain special additives that provide the specific characteristics of the entire structure.
Mixing of the solution is usually carried out in portions, with a construction mixer or an electric drill – this way the composition will be more homogeneous, with optimal moisture content and density. The use of ready-made mortars allows you to simplify the work, save time for preparing the solution, and in some cases for drying. The stability of the composition is one of the advantages of using them.
The prices of mixtures vary in a wide range, but the specific consumption of material in the production of masonry must be taken into account. For a comparative analysis, we have prepared a summary table of large packaged mixtures from various manufacturers – Russian and foreign. Prices shown in the table are valid for September 2016.
Table 2. Solutions, mixtures for chimneys, fireplaces, stoves
Manufacturer Name Appointment Packaging Mixture consumption Recommended layer thickness Operating temperature Refractoriness Price, rub. Plitonit, Russia Plitonit mortar Super fireplace Refractory yellow masonry 20 kg 4 kg / m2 3-4 mm 1200 ° C 1200 Heat-resistant mortar Plitonit Super fireplace Thermal layer gray masonry 20 kg 6 kg / m2 4-6 mm 400 ° C 449 Mortar for finishing stoves and fireplaces Plitonit Superfireplace Thermal plaster white finishing 25 Kg 2 kg / m2 with a layer of 2 mm 1–2 mm 400 ° C 559 Ogneuporsnabservice Refractory masonry mix masonry 25 Kg 3-8 mm “Pechnik” Furnace mix masonry 18 Kg 650 Fireclay mortar for refractory brick laying masonry 20 kg 1690 ° C 750 “Terracotta”, Russia Masonry mix for outdoor use masonry, waterproof 25 Kg 25 kg / 50 bricks up to 12 mm 400 ° C 493 Highly plastic mortar mix 20 kg 3-8 mm 1780 ° C 350 Clay-fireclay masonry mixture masonry 20 kg 322 Clay-chamotte mixture with a kaolin clay content of 99.9% masonry 20 kg 20 kg / 40 bricks 3-12 mm 1300 ° C 350-750 Dry mixture Clay-fireclay masonry masonry 20 kg 3-12 mm 1300 ° C 685 Heat-resistant white grout finishing 20 kg 1.5 kg / m2 934 BorRoss, Russia Refractory mixture 25 Kg 25 kg / 40 bricks 3 mm 1750 ° C 240 Furnace mixture 25 Kg 25 kg / 40 bricks 3 mm 850 ° C 225 “Borovichi Refractories Plant” Masonry kiln mix Termix masonry 25 Kg 185 Refractory masonry mixture Termix masonry 25 Kg 185 “Prospectors” Masonry mix for stoves and fireplaces masonry 25 Kg 25 kg / 50 bricks 3-8 mm 247 Bossnab Furnace mix OPTIMA masonry 20 kg 0.29kg / brick 4-5 mm 500 ° C 550 Refractory mortar MAXIMUS masonry 20 kg 0.22kg / brick 2-3 mm 1400 ° C 620 Refractory mortar masonry 25 Kg 0.27kg / brick at? 5 mm 320 KBS, Russia Refractory mixture (BS-103) masonry 20 kg 20 kg / 30 bricks 1600 ° C 215-265 Weber-Vetonit, France + Russia Refractory mortar for masonry furnaces and fireplaces ML Tuli masonry 25 Kg 0.25 kg / brick at? 13 mm 1200 ° C 2,200 RATH, Austria Universal Hafnermortel furnace mortar 25 Kg 3.2 kg / m2 up to 5 mm 1300 ° C 1560 EMA furnace solution 25 Kg 2.5 kg / m2 at? 2 mm 1100 ° C 1,053 ORTNER, Austria AUSBAUMORTEL solution masonry 20 kg 1200 ° C 1885 Blend HAFTMORTEL Das Original masonry, finishing 20 kg 1.3 kg / m2 at? 1 mm 2-50 mm 1100 ° C 5 330 HAFTMORTEL CREME Blend masonry, finishing 20 kg 1.0 kg / m2 at? 1 mm up to 50 mm 1000 ° C 5 655 Binder solution VERSETZMORTEL NK masonry 20 kg 1.3 kg / m2 at? 1 mm 1200 ° C 2 301 Wolfshoher Tonwerke, Germany Universal mix Universal HM on a hydraulic binder for laying fireboxes and outer walls of stoves and fireplaces 20 kg 6 600 Universal mixture Universal HKM on ceramic binder 25 Kg 3740