RU2801720C2 - Method for manufacturing, storing and transporting concrete products - Google Patents

Abstract

FIELD: concrete products.

SUBSTANCE: invention can be used in factories producing reinforced concrete products and structures, as well as in warehousing, storage, transportation and laying of products at the workplace. The method includes vacuuming the concrete components before mixing, during their mixing and turning into a liquid concrete mix. Lay the mixture for curing. Vacuum and carry out power intermittent compression of it with an overpressure of 10 atm. A freshly moulded concrete product is placed for 15-20 hours in a thermo-moist treatment chamber with a temperature of 17-23°C and relative humidity 90-100%. The product is covered with a wide-band airtight material made in the form of a sleeve or half-sleeve of any size, obtained by soldering two or more rolls of packaging material with an ultrasonic sealer having a metallized outer layer for a period of at least 30 days. The cavity formed between the product surface and the inner surface of the packaging material is vacuum-treated. The product is transported to the workplace, the packaging is removed before the product is placed on the workplace. At the same time, concrete components are mixed, concrete is prepared, it is moulded, and the moulded concrete product is thermo-moist treated under medium vacuum conditions.

EFFECT: reduced porosity of concrete, uniform drying and hardening of the concrete product for 30 days regardless of the atmospheric pressure and humidity of the surrounding air, elimination of shrinkage cracks on the surface of the concrete product, increased density, strength and safe operation period of the concrete product.

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Description

The invention relates to the manufacture, storage, transportation and laying of concrete products and can be used in factories of reinforced concrete products and structures, as well as in warehousing, storage, transportation and laying of products at the workplace.

A known method of manufacturing a product from a concrete mixture, including mixing cement, sand, silica fume, pigment, superplasticizer C-3 and water to form a concrete mixture, subsequent laying the concrete mixture in a steel mold with a polyurethane embossed insert, placing the mold on a molding plate, compacting concrete using vibration for 1-2 seconds, then using vibration and pressure of 10-15 ATM for 6-15 seconds, after which the freshly molded product is placed in a thermo-wet treatment chamber with a temperature of 17-23 ° C and a relative humidity of 90-100% and incubated for 15-20 hours (RU 2254987).

The disadvantage of the known method is the narrow scope, low efficiency, accuracy and safety, since the method is not intended for warehousing, storage and transportation of products.

The absence in the known method of hermetic packaging of the product excludes the uniformity of drying and uniformity of hardening of the concrete product at all stages of storage and transportation, since the drying and hardening of concrete products lasts from 5 to 30 days (How long does concrete harden? https://eren.kz/ru/ poleznye-stati/item/372-skolko-vremeni-tverdeet-beton.html).

The fact is that in the known method, the product is removed from the mold and remains open already 20 hours after pouring liquid concrete into the mold, since the method does not provide complete and hermetic packaging of the product for up to 30 days. Therefore, in the known method, the product remains fully or partially open for an indefinite period. Under these conditions, moisture penetrates into the concrete along with the air soluble in it, which contributes to the porosity of the concrete. Regardless, exposed parts of the product surface, such as ribs, corners, and end ends, are more exposed to sunlight and wind than accidentally covered parts, and therefore dry faster, especially in windy, warm, and dry weather.

Uneven drying of a concrete product leads to uneven hardening and changes in volume. As a result, shrinkage cracks form in the surface layers of the exposed parts of the products, which reduce the quality, strength, durability and safety of concrete products and structures, lead to premature and unexpected destruction, to injuries to injured people and animals and to victims (Types of defects in concrete structures and their causes occurrence.

A known method for manufacturing a concrete floor, including the production of a molding frame made of plastic, pouring liquid concrete into a prepared mold, covering the upper concrete surface with a polyethylene film, which is repeatedly removed every 3 days, and the open upper surface of the concrete is poured with water, and the film is finally removed after 20 days

The disadvantage of the known method is the narrow scope, since the method is not intended for the manufacture of transportable concrete and reinforced concrete products, for their storage, storage and transportation to the workplace.

In addition, the disadvantage of the known method is its low efficiency and safety, since the method does not provide timely sealed vacuum packaging of the product for up to 30 days. Therefore, the method does not provide long-term evacuation of the product and stop the flow of atmospheric air under atmospheric pressure into the water present inside the concrete mass, since the water in the concrete in the first 28-30 days after its manufacture will not all take part in the chemical interaction with cement. Under these conditions, the known method does not exclude the gassing of water and concrete, the formation of porosity and capillarity of concrete, which reduces its strength, durability and contributes to premature destruction, which, in turn, can lead to casualties and / or injuries to people and animals.

Another disadvantage of the known method is its low accuracy, since the known method does not provide the exact time of the first covering of the product with a film, removing the film from the product, re-covering the product with a film, pouring water. The known method does not contain an indication of the exact volume of water used for pouring concrete, the exact duration of pouring concrete with water, the exact indication of the technology for pouring concrete with water, the exact thickness of the water layer on the concrete surface before re-covering with a film. All this reduces the standardizability and repeatability of the technology for the production of concrete products, reduces the strength of concrete and contributes to the development of porosity in it, which reduces the durability of products and the safety of their operation.

In addition, the known method does not accurately indicate the quality of the polyethylene film used in the first, second and subsequent times of covering the concrete surface and does not indicate the pressure inside the cavity formed by the film and the concrete surface. In this regard, the method does not exclude the use of defective film, low-quality film, previously used film, old polyethylene film and holey film at the very beginning of its use. This reduces the quality of concrete and the safety of using concrete products and structures.

A known method for the manufacture of automobile concrete roads, which consists in compacting concrete with aggregates from local road-building materials, including vacuuming cement, local road-building materials that are part of concrete, vacuuming the concreted surface before laying concrete on it, force compression and simultaneous vacuuming of concrete laid on a concreted surface (RU 2336387).

The disadvantage of the known method is the narrow scope, since the method is not intended for the manufacture of finished concrete and reinforced concrete products and structures in factories and enterprises, where they are stored and temporarily stored in warehouses and only then transported to their destination, sometimes over considerable distances. In particular, the method is not intended for the manufacture of railway sleepers used in the construction of railways, for the manufacture of road slabs, paving slabs, curbstones used in the construction of roads, footpaths and sidewalks, for the manufacture of reinforced concrete piles, trusses, floor slabs, railings and gratings used in the construction of bridges, pedestrian overground and underground passages, as well as for the manufacture of foundation blocks, wall panels, floor slabs, lintels, poles, well rings and other products used in the construction of buildings and structures.

In addition, the known method has low efficiency, accuracy and safety, since it does not provide high strength due to the lack of sealed packaging of concrete products. The absence in the known method of hermetic packaging of the product excludes the uniformity of drying and hardening in it for several days and weeks after the manufacture of the products, regardless of the magnitude of atmospheric pressure and humidity of the surrounding air. The fact is that the known method does not provide complete packaging of the finished concrete product, so it remains open still in its raw form, that is, in a state when the concrete has not yet dried and not completely hardened. In turn, the exposed parts of the surface of the product, such as ribs, corners and end faces, are often more exposed to sunlight and wind, and therefore dry faster, especially in windy, warm and dry weather. Uneven drying of a concrete product leads to uneven hardening and changes in volume, which, when hardening concrete, leads to its uneven shrinkage. Therefore, the exposed parts and surface layers of concrete products made by the known method harden faster than the inner layers. And that is why shrinkage cracks form in the surface layers of the exposed parts of the products, which reduce the quality, strength, durability and safety of concrete products and structures (Hardening of concrete, http://hardstones.ru/tverdenie-betona.html).

A known method of vacuum packaging of predominantly large-sized items, which consists in wrapping the item with a wide-band air-vapor-tight material, the outer layer of which is pre-metallized by spraying metal powder or using metal foil, the material can be made in the form of a sleeve or half-sleeve of any size, obtained by soldering two or more rolls packaging material with an ultrasonic sealer, the cavity formed by the surface of the product and the inner surface of the packaging material is evacuated by pumping out air (RU 2678868).

The disadvantage of the known method is the narrow scope, low efficiency, safety and accuracy, since the method is not intended for the manufacture of concrete and reinforced concrete products and structures.

In addition, the known method does not provide timely packaging of concrete products and structures, so air can penetrate the concrete and cause its porosity, which reduces the strength and durability of concrete products when used outdoors, especially in northern latitudes.

The objective of the invention is to expand the scope, increase efficiency, accuracy and safety due to the manufacture, molding of concrete, thermo-moist treatment of molded concrete products under medium vacuum, packaging products in sealed vacuum packaging for a period of at least 30 days, storage and transportation of concrete products in it and unpacking before placing the product on the workplace.

This goal is achieved by mixing all the components of concrete with each other, molding and thermo-moist treatment of the liquid concrete product under medium vacuum conditions, subsequent packaging of the product in sealed vacuum packaging for a period of at least 30 days, storage and transportation of the product in vacuum packaging and unpacking before laying the product on the workplace, which ensures the absence of dissolved air in the water inside and on the surface of the product, minimizes the air porosity of the finished concrete, increases the strength of the concrete product and extends its safe operation.

The technical result is a reduction in the porosity of concrete, uniformity of drying and hardening of the concrete product for 30 days, regardless of the value of atmospheric pressure and humidity of the surrounding air, the absence of shrinkage cracks on the surface of the concrete product, an increase in the density, strength and service life of the concrete product.

The essence of the method of manufacturing, storing and transporting concrete products, including vacuuming the concrete components before mixing, during their mixing and turning into a liquid concrete mixture, laying the mixture for curing, evacuating and intermittent power compression with an excess pressure of several atmospheres, placing a freshly molded concrete product for 15-20 hours in a thermo-moist treatment chamber with a temperature of 17-23°C and a relative humidity of 90-100%, fitting the product with a wide-band air-vapor-tight material made in the form of a sleeve or half-sleeve of any size, obtained by soldering two or more rolls of packaging material with an ultrasonic sealer having a metallized outer layer, evacuating the cavity formed between the surface of the product and the inner surface of the packaging material, and transporting the product to the workplace, consists in mixing the concrete components, preparing concrete, shaping it, carrying out thermo-moist treatment of the molded concrete product under conditions of medium vacuum, after which the product is packed in sealed vacuum packaging for a period of at least 30 days, stored and transported in it, the packaging is removed before the product is placed in the workplace.

In the claimed method, due to the production of concrete, concrete molding, wet treatment of a concrete product in medium vacuum, accuracy, efficiency and safety are increased, since the medium vacuum ensures the degassing of water and all dry concrete components before they are mixed with each other, during mixing, in the process production of liquid concrete, as well as in freshly molded concrete products. The fact is that it is the average vacuum (negative pressure from 1 to 25×10 ^-3 mm Hg) that provides almost complete degassing of water (Yermolaev E.A. Obtaining water ice by layer-by-layer freezing under vacuum conditions. Abstract of the thesis. Candidate of Technical Sciences, Moscow, 2009. -16 p.).

The absence of gases in the aqueous phase of liquid concrete and in the molded concrete product eliminates its porosity of the concrete product, which increases its strength and safety of the concrete product during operation in extreme conditions and increases the safety of concrete products, as it excludes their premature destruction.

Medium vacuum ensures the absence of air in the water, both inside the concrete and on its surface. The absence of air in water eliminates the appearance of air pores in concrete when water interacts with cement. This standardizes the technology of manufacturing concrete products, increases their strength, safety and safety during operation.

Packing the product in sealed vacuum packaging for at least 30 days, storing and transporting it and removing the packaging before placing the product on the workplace expands the scope, improves efficiency, safety and accuracy. The fact is that inside such a package, the dissolution of air in the water remaining inside the concrete is excluded due to the fact that it has not completely reacted with cement, and the microclimate is standardized, which standardizes the completion of the concrete hardening process in the product to the calculated value, regardless of the value of atmospheric pressure. and humidity of the surrounding air.

The method is carried out as follows. All concrete components are mixed, concrete is prepared, it is molded, and the molded concrete product is thermo-moist treated under medium vacuum conditions. The resulting molded and thermo-moist treated concrete product is packed in sealed vacuum packaging for a period of at least 30 days. The packaged product is stored and transported in a package. Remove the packaging before placing the product on the workplace.

Example. In the middle latitudes of Russia in the summer at an atmospheric pressure of 760 mm Hg. Art. and outdoor temperature at noon +19°C and at midnight +15°C was used known and claimed methods.

In the first series of experiments, cement, sand, microsilica, pigment, superplasticizer C-3 and water were mixed with each other in the open air until a liquid concrete mixture was formed. After 5 minutes, the concrete mixture was placed in 5 identical steel molds, made in the form of rectangular tubs, with a polyurethane embossed insert. The molds were placed on the mold plate, then the concrete in each mold was compacted with vibration for 2 seconds, and after 2 minutes the concrete in each mold was recompacted with vibration and overpressure of 10 ATM for 10 seconds. After that, the freshly molded products were placed in a thermo-moist treatment chamber with a temperature of +19°C and a relative humidity of 100% for 20 hours. They took the concrete products out of the molds, placed them on an iron grate and exposed them to the open air in direct sunlight for 30 days. Then, on the 31st day, the open products were loaded into the back of a truck, and on the same day, all 5 products were transported in the open form along a country road for a distance of 10 km in dry sunny weather. Then we examined the products. It turned out that the upper surfaces of all 5 products were covered with a layer of road dust. On the upper surface of one of the items, there was a zigzag shrinkage crack 4 cm long, up to 0.5 mm wide, and up to 1 mm deep. After that, the volume of each product was measured by the volume of water displaced during drowning in it. The results obtained were statistically processed, analyzed, and the average value of the product volume was taken as 100%.

In the second series of experiments carried out on a similar summer day in the same area at an atmospheric pressure of 760 mm Hg. st. and at a temperature of +19°C at noon, concrete products were manufactured, stored and transported by the claimed method. For this, a calculated portion of cement, a sand-gravel mixture and an estimated volume of water placed in an open iron bath of the minimum mold type, and 5 empty molds for molding products into a specially prepared vacuum container were added. Then this container was closed hermetically and a negative pressure of 25×10 ^-3 mm Hg was created inside it. Art. To create a medium vacuum, a two-rotor machine of domestic production with a capacity of 150 l/s was used. The residual pressure in the sealed container was measured with a Mini-Convectron combined-type electronic vacuum gauge with a liquid crystal display showing the current pressure in the range of 10 ^-4 -10 ^-3 mm Hg. Art. After the pressure inside the container has dropped to 20×10 ^-3 mm Hg. Art., mixed the components of concrete with each other inside the container to the state of liquid concrete. After 5 minutes inside the container under medium vacuum conditions, the prepared liquid concrete was poured into 5 empty molds in the form of rectangular baths, similar to those used in the first series of experiments and subjected to thermo-moist treatment for 20 hours at a temperature of +19 ° C and 100% humidity. After that, the container was opened, the molded and processed concrete products were taken out, and each product was packed in a sealed vacuum package. The products in the package were placed on an iron grate and exposed to the open air under direct sunlight. After 30 days, the products were loaded into the open body of a truck and taken along a country road in dry sunny weather to a rural settlement, where they removed the packages from each product and studied their condition. The results of the inspection showed that all products were very clean, their surfaces did not have cracks.

After that, the volume of each product was measured by the volume of water displaced during drowning in it. The results obtained were statistically processed, analyzed and the average value of the volume of the product was determined, which was compared with the average value of the volume of the concrete product obtained by the known method in the first series of experiments. The result was expressed as a percentage. It turned out that the claimed method provided a decrease in the value of the volume of the concrete product by an average of 0.41%.

Thus, the claimed method ensured the absence of shrinkage cracks, dust and dirt on the surface of concrete products during transportation and storage while reducing their volume, which confirms the degassing of water, cement paste, liquid concrete and indicates the minimization of the porosity of concrete products.

Consequently, the developed method for the manufacture, storage and transportation of concrete products makes it possible to reduce the volume of concrete products, which indicates the absence of air in them. The absence of air in concrete products minimizes the porosity and capillarity of concrete in them and increases its density, which increases the strength and safe operation of concrete products.

Claims (1)

A method for manufacturing, storing and transporting concrete products, including evacuating the concrete components before mixing, during their mixing and turning into a liquid concrete mixture, laying the mixture for curing, evacuating and intermittent power compression with an overpressure of 10 atm, placing a freshly molded concrete product on 15-20 hours in a thermo-moist treatment chamber with a temperature of 17-23°C and a relative humidity of 90-100%, fitting the product with a wide-band air-vapor-tight material made in the form of a sleeve or half-sleeve of any size, obtained by soldering two or more rolls of packaging material with an ultrasonic sealer, having a metallized outer layer, evacuating the cavity formed between the surface of the product and the inner surface of the packaging material, and transporting the product to the workplace, characterized in that the concrete components are mixed, the concrete is prepared, it is molded, and the molded concrete product is thermo-moist treated under medium vacuum conditions, after which the product is packed in sealed vacuum packaging for a period of at least 30 days, stored and transported in it, the packaging is removed before the product is placed in the workplace.