Do-it-yourself paving slabs: production technology, making a vibrating table and molds

Composition of cement-sand mixture and technology of vibrocompression of paving slabs

The technology of vibrocompression of paving slabs is the small-piece production of concrete components for pavements and platforms from a semi-dry mixture using the molding method (vibratory shrinkage of the composition with further compaction under a special press). Schematically, vibrocompression is a sequential cycle of work:

• feeding semi-dry concrete into a matrix (mold) installed on a vibrating table;
• compaction of the mixture in the matrix with a punch (moving-pressing part of the matrix);
• parallel vibration of the table, squeezing air bubbles out of concrete;
• removing the pressed product onto a tray for complete drying.

The technology allows automation of most technological processes. It should also be noted that intermediate work processes also play a significant role in the production cycle - preparation of raw materials and production of the mixture in a mortar-concrete unit, cleaning and preparation of forms, accurate calculation of punch pressure, as well as stripping, drying and moisture treatment of finished products.

Each batch undergoes sampling (quality control), after which the transport package is formed, tied, labeled and stored before sending the finished product to customer construction sites.

Advantages of vibration compaction

The obvious “advantages” of producing vibropressed paving slabs are well known:

• automation and high speed of production processes;
• mass production of products with uniform quality and technical characteristics;
• increased strength and wear resistance of products;
• the ability to produce tiles with a colored front layer and a reinforced coating of granite and marble chips.

The products receive a stable, strict shape and clear geometry. The surface of the tile does not crack, lends itself well to grinding, polishing, bush hammering, and the color coating is extremely stable and retains its brightness and saturation for up to 25 years of use of the tile.

Vibro-pressed tiles are cheaper than vibro-cast tiles, have a rough surface, can withstand much greater loads and are more effective when paving sidewalks, technical sites, urban areas, warehouses at freight terminals, and transport stops.

Features of the process of vibrocompression of paving slabs

When creating a cement-sand mixture for vibratory pressing of paving slabs per 1 cubic meter of mixture, the following is used:

• high-quality Portland cement according to GOST 31108-2003 (I 42.5H) – up to 590 kg;
• Mkr sand - up to 1640 kg;
• water - 180±5 liters.

The concrete mixture has a minimum water content (7-11%) and is considered heavy (from 2000 kg/m3), remains quite dry and plastic. This allows you to significantly save on cement consumption and obtain high-density products that can withstand loads of up to 30-50 MPa (low abrasion) and at least 200 freezing/thawing cycles (minimum water absorption + B200).

• The volume of filling the finished mixture into the molds is regulated by level sensors depending on the swing of the box feeder and the duration of the vibration cycle (on average in a bunker - 0.1-0.43 m3).
• The compaction, depending on the composition of the mixture, is regulated by unbalanced shafts (oscillation frequency - up to 3000 revolutions).
• Pressure of raw material pressing by punches is not less than 0.2 MPa. This is sufficient for moving and stacking molded tiles.

The finished tiles are unloaded onto pallets and undergo a two-level heat-moisture (steam) treatment in TVO floor chambers: 5-8 hours at +20°C, then 8-9 hours at +50+55°C. An initial holding time of 1 hour is required, and once peak heating is reached, the temperature is gradually lowered.

Next, the finished tiles are packaged and tied on pallets, undergo technical control and transported to the warehouse.

Source

Compositions of concrete for the production of blocks using semi-dry vibrocompression:

Heavy concrete:

Lightweight concrete:

In the production of wall blocks, three main components are used: binder, aggregate and water. Cement and slow-hardening gypsum can be used as a binder, and sand, crushed stone screenings, expanded clay, slag, ash, sawdust, or any similar local materials capable of creating a durable composition after mixing with the binder and setting it, can be used as a filler. For the manufacture of construction products, all types of cements with a strength grade from 200 to 600 kg/cm can be used.

When using a cement-based mixture, the finished products are aged from one (at a temperature of +15. +45 degrees C) to two (at a temperature of +5. +10 degrees C) days, after which they acquire strength sufficient for storage and transportation. 100% of the strength of the product is acquired after 28 days at a aging temperature of 20 degrees C. If the consumer has a steaming chamber, the products can be subjected to heat treatment for 6.8 hours at a temperature of at least + 50.75 degrees C. In this case, after cooling and drying they acquire 60.80% brand strength.

The selection of the compositions given below was carried out using Portland cement grade 400 (PTs M400). Data for 1 cubic meter of mixture. When using grade 300 cement, cement consumption should be increased by 15%. If it is necessary to increase the strength of products by 10 kg/cm (for example, from grade 30 to grade 40), the consumption of cement in concrete should be increased by 10..15%.

Mixture recipes for vibrocompression

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Compositions for the manufacture of products by vibration pressing

Options for preparing a solution for pressing per 1 m3 of mixture:

— In the “Number of components” column, the volume of filler in m3 is indicated before the brackets, and its weight in kg is indicated in brackets. Depending on specific local conditions (field, production method, etc.), the density of aggregates may differ from the average densities used in the compositions. In this case, the composition must be adjusted experimentally.

— In the column “Density of concrete” its density is indicated in kg/cubic meter. m. The column “Grade of concrete and solid products” indicates the brand (strength) of concrete or the brand of any solid products made from this concrete (brick stones, plinths, curbs, etc.) in kg/cm 2 .

— In the column “Brand of hollow stone” the brand in kg/cm2 of hollow wall stones measuring 390x190x188 mm and hollow partition stones is indicated. The strength of these products is lower than the strength of concrete due to the presence of voids.

— In sawdust concrete compositions it is allowed to use any sawdust untouched by rot, however, softwood sawdust is preferable to hardwood sawdust because swell less. To improve the preservation of sawdust in concrete, it is advisable to introduce the Proston D-18 accelerator into the compositions in an amount of up to 2% by weight of cement.

— Of the indicated compositions, concrete with a minimum density has the best thermal insulation properties: the “warmest” is concrete with a density of 880 kg/cu. m, the “coldest” - with a density of 2300 kg / cubic meter. m.

Cement-based compositions:

HEAVY CONCRETE

Concrete density kg/m3

Grade of concrete and solid block kg/cm2

Brand of hollow block kg/cm2

Concrete on sand and crushed stone.

Cement, kg Sand quartz m3 (kg) Water, l.

240 1,15 (1950) 90…130

Cement, kg Sand quartz. M3 (kg) Dolomite or limestone crushed stone, m3 (kg) Water, l

200 0,54 (920) 0,65 (980)

Cement, kg Dolomite or limestone screenings, m3 (kg) Dolomite or limestone crushed stone, m3 (kg) Water, l

200 0,3 (450) 0,8 (1200) 90…130

Cement, kg Dolomite or limestone screenings, m3 (kg) Water, l

Cement, kg Quartz sand, m3 (kg) Granite crushed stone, m3 (kg) Water, l

200 0,54 (920) 0,65 (1100) 90…130

Concrete on brick waste

Cement, kg Clay waste. Or silica. Brick fraction. 2…15 mm, m3 (kg) Quartz sand, m (kg) Water, l

230 0,9 (990) 0,32 (540) 90…130

LIGHTWEIGHT CONCRETE

Expanded clay concrete

Cement, kg Expanded clay, m3 (kg) Water, l

250 1,2 (720) 100. 150

Cement, kg Expanded clay fraction. 0.5 mm, m3 (kg) Expanded clay fraction. 5. 15 mm, m3 (kg) Water, l

220 0,65 (390) 0,6 (330) 90. 130

Ash concrete

Cement, kg Coal ash. or slate, m3 (kg) Water, l

200 1,2 (960) 90. 130

Cement, kg Coal ash or oil shale. m3 (kg) Quartz sand, m3 (kg) Water, l

220 0,9 (720) 0,32 (540) 90. 130

Cement, kg Crushed dolomite or limestone, m3 (kg) Coal ash. or slate, m3 (kg) Water, l ¦ 9O. 13O

200 0,5 (750) 0,53 (420) 90. 130

Expanded clay concrete

Cement, kg Expanded clay fraction. O. 5 mm, m3 (kg) Expanded clay fraction. 5. 15 mm, m3 (kg) Coal ash. or slate. m3 (kg) Water, l

200 0,65 (390) 0,55 (300) 0,44 (350) 90. 130

Cinder concrete

Cement, kg Granulated slag, m3 (kg) Water, l

200 1,3 (720) 90. 130

Cement, kg Granulated slag, m3 (kg) Quartz sand, m3 (kg) Water, l

200 0,9 (500) 0,32 (540) 90. 130

Cement, kg Boiler slag, m3 (kg) Water, l

200 1,2 (1080) 90. 130

Cinder concrete

Cement, kg Boiler slag, m3 (kg) Quartz sand, m3 (kg) Water, l

200 0,8 (720) 0,32 (540) 90. 130

Ash and slag concrete

Cement, kg Boiler slag, m3 (kg) Coal ash. or shale, m3 (kg) Water, l

200 0,8 (720) 0,4 (720) 90. 130

Sawdust concrete

Cement, kg Sawdust, m3 (kg) Quartz sand, m3 (kg) Water, l

260 0,6 (150) 0,65 (1100) 100. 150

Cement, kg Sawdust, m3 (kg) Quartz sand, m3 (kg) Water, l

280 0,4 (100) 0,8 (1350) 100. 150

Cement, kg Sawdust, m3 (kg) Quartz sand, m3 (kg) Lime paste, m3 (kg) Water, l

230 0,9 (220) 0,3 (500) 0,04 (50) 100. 150

Expanded clay sawdust concrete

Cement, kg Cramsite, m3 (kg) Sawdust, m3 (kg) Water, l

280 0,7 (420) 0,6 (150) 100. 150

Composition of concrete for paving slabs - main components and manufacturing details

The problem of road paving has faced people of all eras. Changes of seasons, rains and sub-zero temperatures quickly rendered any coating unusable. Natural stone remains the most resistant to weather changes, but its use requires significant investment and does not guarantee an ideal road surface.

Artificial stone allows you to get not only a durable, but also a very attractive coating, which is why concrete paving elements are in great demand. The composition of concrete for paving slabs determines not only the operational features of the products, but also the aesthetics of the future coating. Concrete sidewalks are in demand both in the design of city streets and in private areas.

Performance comparison

Many buyers are interested in which paving slabs are better. The answer depends on the area in which the slabs will be used. If a large load will be placed on the coating, you need to choose durable products with a long service life.

The performance characteristics of paving stones depend on what production technology was used. All slabs are made from the same raw materials, but the proportions of concrete are different. The time required to form products differs. The quality of coloring depends on the technology chosen.

Vibrocast tiles

Such slabs have a smooth surface. It is slippery, so manufacturing companies apply notches to the surface of products or make a figured ornament. The material is easy to cut with a stone disc and can be chipped with a pick. The service life of the slabs is 5-8 years, but much depends on the operating conditions.

The coating fades quickly. Tiles crack when impacted and often break when cleaning sidewalks in winter. The quality of the product depends on how strictly the manufacturer followed the technology. Therefore, it is better to buy products from large companies.

Vibropressed

Such slabs are more expensive than vibrocast slabs, but their performance is higher. Paving stones have stable dimensions, making them easier to work with. But the products are durable, so they are more difficult to process, chip and cut.

Tiles made by vibration pressing have a rough front side. It is more convenient for pedestrians to move along it.

The paving stones are laid on a flat, compacted base. Quartz or river sand is used to fill the joints.

Hyper-pressed

Hyperpressed tiles are more expensive than other products, but they last a long time even in difficult conditions. The slabs have an attractive design and are durable, although thinner. It is comfortable for pedestrians to walk on such paving stones; shoes do not slip even in winter.

The only drawback is that such slabs are difficult to lay on radius sections and on a winding surface. The declared high characteristics will only be available for those products that were produced by enterprises that strictly adhere to the technology.

Basic properties and production methods

Concrete paving slabs, like any other paving element, must comply with the requirements of GOST 17608-91. According to the standard, all types of products must:

• made of heavy or fine-grained concrete;
• have a strength class of B22.5;
• have a tensile strength in bending of at least 3.2 MPa;
• have frost resistance of at least F100 and water absorption of no more than 6%.

In addition, in the production of paving slabs, technologies are used that make it possible to produce products in one or two layers, with or without the use of pigment.

Composition requirements

Cement should not contain mineral additives exceeding 5%, as well as tricalcium aluminate exceeding 8%. The water-cement ratio cannot exceed 0.4, and the amount of air in the mixture should be within 4 - 5%. To ensure high frost resistance, special additives with an air-entraining effect are introduced into the concrete mixture.

Such requirements leave a significant imprint on the composition of artificial stone. The recipe for concrete for paving slabs largely depends on the production technology and materials used. Thus, the main methods of manufacturing paving elements are vibration pressing and vibration casting.

Advantages of vibropressed tiles

MadbotFORUMHOUSE Member

I want to put paving stones under the parking lot. I read a bunch of sites and topics. I still don’t understand for myself:

1. Is vibrocast still less durable than vibropressed?
2. Does vibratory casting have any operational advantages? Or just brighter colors?
3. Builders say that with a vibrocast it is easier to wash off dirt with the same Karcher, plus, they say, they have had one for many years and nothing. But I see that in the city it is often split (although vibropressed too). In principle, I wouldn’t say that I definitely want a “glossy” surface, so maybe I’ll stick with a vibropressed one and not worry about it? But for myself, I want to figure it out, maybe vibratory casting has some advantages (besides the appearance, which someone likes).​

Elena Maslova

1) Vibro-cast tiles are less durable and dense than vibro-pressed tiles because:

• A) it does not contain crushed stone (the main component responsible for the strength and durability of the concrete product).
• B) its production requires a high content of water, which, when the concrete mixture hardens, evaporates and leaves behind large pores and connecting capillaries. During winter operation, they are saturated with precipitation water and salt reagents; when freezing, the water expands in volume and the concrete is destroyed. In the case of vibration compaction, the pores formed in the concrete are scattered and closed; water cannot penetrate into them from the outside.
• C) with vibratory casting technology, the concrete of a product is compacted under the influence of vibration; with vibrocompression technology, compaction occurs simultaneously under the influence of both vibration and punch pressure, the density of the concrete of a freshly molded product is significantly higher.

– 2) Only bright colors. In general, it is believed that vibro-cast paving slabs are more attractive to the buyer due to the variety of shapes and colors in full color. With the maximum permissible dosage of dye, colored vibrocast tiles turn out duller due to the high water-cement ratio during production. Therefore, manufacturers add more pigment to achieve brighter and richer shades.

However, few people know that high dosages of coloring pigment negatively affect the strength of the finished product.

In addition, vibropressing technology began to use high-quality granular pigment, which has high light resistance, does not fade at all, can be used in low dosages, and produces a bright, beautiful product.

– 3) Of course, dirt is washed off much better from a smooth surface, but with a Karcher you can perfectly wash off dirt from the surface of vibropressed tiles. You can actually find cracked vibropressed tiles in urban public spaces. This is due to the fact that there are two methods for producing vibration-pressed tiles - single-layer pressing and two-layer pressing. With a single-layer method, the main components of the concrete mixture are cement and sand, with a two-layer method, the main layer is cement, sand and crushed stone, the front layer is cement and sand. The main layer of concrete is responsible for the strength and durability of the entire structure, and the front layer is responsible for the aesthetic appearance and wear resistance. These are two different structures, which only in a single integrity provide all the requirements for concrete.

Two-layer tiles are denser, more durable and frost-resistant than single-layer tiles, and even more so than vibro-cast ones. Typically, a single-layer tile can crumble if the production technology is not followed, however, there are also cases that the front layer of a two-layer vibro-pressed tile can fly off during operation. The reason is a violation of the manufacturing technology: incorrectly selected moisture content of the front and main layers of concrete. But this is rare; as a rule, the technology of two-layer vibrocompression provides for complete automation of the process and the influence of the human factor in this case is minimized.

Specifics of pressing with simultaneous vibration

The most common method in the industrial production of paving slabs is vibropressing. This technology makes it possible to obtain a significant volume of production per work shift, but requires extensive experience of workers and the operator responsible for the production of the concrete mixture.

Features of the recipe

The recipe for artificial stone for vibrocompression is characterized by the absence of inert aggregates with a particle size of more than 5 mm. The technology involves compaction by pressing the mixture with simultaneous vibration, which affects the requirements for water content.

The composite for vibrocompression must be homogeneous, but rigid to prevent delamination during compaction.

To create such a system, coarse aggregate is contraindicated, since it requires a larger amount of moving mortar part for uniform distribution.

That is why the proportions of cement, sand or screenings, water, pigments and additives differ significantly from the classic ones for heavy artificial stone. This material is called fine-grained concrete.

Basic proportions

The specifics of compaction of the mixture do not allow the production of such tiles at home, because it is very difficult to ensure the proper load with your own hands. Most often, the proportions of cement and fine aggregate are taken to be 1:3 or 1:4, respectively, and the amount of water does not exceed 30% of the mass of cement. To color products, mineral and organic pigments are used with a dosage ranging from 1 to 3% of the weight of cement.

Vibropressing is a modern method of producing paving stones

From the same raw materials (cement, sand, gravel, modifiers and water), modern factories produce paving slabs using the vibration pressing method. The method is very similar, but the use of automation allows you to put production on stream:

• Automation accurately doses the composition of the concrete mixture.
• The shaped forms are filled with a semi-dry composition - less water, shorter hardening time.
• Within a batch, all tiles are the same thickness.
• A vibropress compacts the concrete mixture under the combined influence of static and dynamic loads, which reduces the likelihood of cavities and other molding defects.
• Simple unmolding of blanks.
• It is possible to produce one- or two-layer products with higher strength characteristics.
• Flow production with minimal manual labor makes it possible to produce large quantities of goods.

There is a clear advantage of paving stones obtained by vibrocompression.

Vibration casting technology

This production method is not particularly productive, but allows the production of products with complex geometries and designs. Thanks to the use of a moving mixture and moderate compaction, the composite fills all the curves of the form, so a pattern of any complexity appears clearly and practically without flaws.

Composition of the solution

The composition of the mixture for paving slabs made by vibration casting is characterized by a large amount of filler, as well as the possibility of using crushed stone with a grain size of 3 - 10 or 5 - 20 mm. In this technology, it is important to achieve mobility of the mixture, so the recipe is distinguished by the presence of effective plasticizers and stabilizers.

In addition, when introducing crushed stone from dense rocks, such as granite, the amount of cement can be reduced, because the stone frame will ensure a dense and durable concrete structure.

In fact, the composition of the composite and the main proportions of raw materials in the production of paving slabs using vibratory casting technology are very close to the recipes for classic heavy concrete. If special forms are available, such products are easy to produce at home, and the mixture can be easily made with your own hands using a gravity mixer.

Additional production equipment

Plastic molds for embossed paving slabs
It was already mentioned above that the types of production of tile material can be different, but no matter what production technology you choose, in addition to the main equipment, the enterprise must have additional equipment:

• Molds for tiles. These molds are made from a variety of materials: there are plastic, polyurethane, silicone, rubber, mold-plastic molds. You need to know that some types of forms are categorically inapplicable in large-scale production of the product; it is better to purchase them for use in a small private enterprise. As for this method of manufacturing tiles, such as vibration pressing, it uses special steel molds;
• Mixer. Tile production is impossible without concrete mixers. These units help prepare high-quality concrete solution for the production of paving slabs. Concrete mixers come in various types, but in the process of producing tiles, gravitational and forced devices are more often used. The more tiles the enterprise must produce, the larger the unit required for the production process;
• Sieve. Another type of equipment that cannot be dispensed with during tile production is vibrating screens. Using this tool, bulk components are sifted to make a mixture.

Also, a large tile production enterprise will require a device such as a stacker. With the help of this device, manufactured products can be easily stored. We have already said that tile production can be carried out in two ways - vibration casting and vibration pressing. What is the difference between the technologies? Let’s figure it out together by studying in detail the indicated manufacturing methods.

Selection of the basic ratio of components

When producing paving slabs on your own, it is best to move away from the classical scheme. So, if you increase the mobility of the mixture, you can reduce the intensity of vibration, which greatly simplifies the manufacture of products at home. With this approach, the composition of concrete should be slightly modified.

The main proportions of concrete used for pouring paving slabs can be represented in the following diagram:

• 1 mass part of cement;
• 1.5 – 1.7 parts by mass of sand;
• 2.5 – 3 mass parts of crushed stone;
• 0.35 – 0.4 parts by mass of water;
• plasticizer + pigment.

As the class of concrete increases, cement consumption increases proportionally and the proportions of aggregates decrease. As a result, the composition of the composite changes, but the artificial stone retains its dense structure and the entire set of properties.

Selection of materials

To create paving slabs with high strength, frost resistance and water resistance, it is important to select materials of appropriate quality.

Cement

The main element of any concrete is cement. For the manufacture of paving elements, you should choose medium-aluminate cements with a mineral additive content of no more than 5%, as well as with a strength class of 42.5. The packaging of such a binder indicates the grade CEM I 42.5 N or B. Medium aluminate cements include binders with a C3A content of 5 to 8%. You can find out the aluminate content from the seller by asking for the cement passport.

Fine aggregate

As a fine aggregate, it is best to use washed quarry sand with a particle size modulus of 2 - 2.5.

This material belongs to construction sands of the first class; when used, the concrete composition is characterized by lower consumption of binder and low cost with higher quality indicators.

Coarse aggregate

When using coarse aggregate, it is best to purchase granite crushed stone with a grain size of 3 – 10 mm. Such material will provide increased strength and durability with high mobility of the mixture. But its cost is high, so you can purchase a standard mixture of grains with a diameter of 5 - 20 mm and adjust the recipe, reducing the content of coarse aggregate.

This approach will ensure high mobility and uniformity during the formation of the stone frame in the body of the composite.

Self-production

The production of sidewalk elements with your own hands must begin with preparing a place for molding and storing products. Even with high mobility of the resulting mixture, after filling the molds, they must be compacted. Submersible or homemade vibrators are suitable.

Compaction should be carried out for no more than 5–10 s, otherwise the mixture will stratify and the appearance of the pavement elements will deteriorate.

Standard recipe

When producing a composite with strength class B25, you can use the following composition per 1 m3:

• cement = 390 – 420 kg;
• sand = 700 – 750 kg;
• crushed stone = 1000 – 1050 kg;
• water = 155 – 165 kg;
• plasticizer + pigment (if desired, color the products).

Mixing technology

When mixing the components, sand is first loaded, then water with additives and cement, and lastly crushed stone. Mixing is carried out for at least 2 - 3 minutes until a homogeneous material is obtained.

Paving slabs made of concrete of this composition will have intense hardening kinetics, so it is very important to prevent moisture loss from its surface.

Advantages and disadvantages

The advantages of vibrocast tiles include:

• beautiful appearance, variety of shapes and colors;
• high strength;
• glossy surface, which ensures easy cleaning and cleaning;
• the lowest cost of all types of paving stones;
• ease of installation and high maintainability.

The good thing about it is that it is affordable, beautiful, environmentally friendly and durable. It has proven itself excellent in the construction of pedestrian paths in private construction, where there are no heavy loads from transport or a large number of people.