RU2114091C1 - Method of concrete article making - Google Patents

Abstract

FIELD: building industry. SUBSTANCE: method involves mixing carbonate and silica-containing filling agents with the following acids: hydrochloric, sulfuric, nitric, acetic, hydrofluoric or liquid production waste containing one or some indicated acids followed by forming and hardening. Evolved gases are trapped and used for carbonization of the formed and hardened articles. Finely-dispersed quartz sand that can not be used for concrete making is used as silica-containing filling agent which is mixed with liquid acid-containing waste from chemical polishing glass articles. Gas evolving at mixing is used for treatment of concrete articles. Invention can be used for making concrete article used for above ground, underground and hydrotechnical constructions. EFFECT: improved method of making. 2 cl, 1 tbl

Description

 The invention relates to methods for the manufacture of concrete products based on clinker-containing cements and may find application in the industry of building materials and products in the manufacture of concrete and reinforced concrete products, structures for above-ground, underground and hydraulic structures.

A known method for the production of concrete products based on clinker-containing cements by surface treatment of hardened concrete with CO ₂ or SiF ₄ gases. This method is known under the name, respectively, of carbonization or coloring of the surface of products with gases under pressure in hermetically sealed containers [1 and 2].

Along with the positive technical solutions of this method (increased strength, corrosion resistance, water resistance of concrete) due to the binding of the soluble component of concrete Ca (OH) ₂ in water-insoluble products CaCO ₃ , CaF ₂ , there are also disadvantages:
heat-intensive technology for producing CO ₂ gas related to the process of burning coke in furnaces;
an expensive process for producing SiF ₄ gas by the action of scarce and expensive HF acid on silica sand, suitable for concrete as a fine aggregate or as a main component in glass production.

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образующиеся газы CO₂ выделяются в окружающую среду, что снижает ее экологию и ухудшает условия работающих;
отсутствует безотходная технология изготовления бетонных изделий, т.е. не предусмотрена возможность повышения дополнительной прочности бетонных изделий при такой технологии.Closest to the proposed method is the preparation of concrete mixture [3], which consists in pre-mixing carbonate-containing aggregates with cement and mineral hydrochloric acid, followed by mixing the resulting product with the rest of the mixture components

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the generated CO ₂ gases are released into the environment, which reduces its ecology and worsens the conditions of workers;
there is no non-waste technology for the manufacture of concrete products, i.e. the possibility of increasing the additional strength of concrete products with such a technology is not provided.

 The purpose of the invention is to improve the ecology of the environment through the disposal of industrial waste and waste-free technology for the manufacture of concrete products, and increase their strength.

To achieve this goal, in a known method of manufacturing concrete products, by mixing carbonate or silica-containing aggregates with acids, further mixing the resulting product with the other components of the mixture, molding and hardening, aggregates or part of them are mixed with acids of the type: CH ₃ COOH; H ₂ CO ₃ ; HCl; H ₂ SO ₄ ; HNO ₃ HF or with liquid production wastes containing one or more of these acids, gases released by mixing are captured and carbonized or / and stained with molded and hardened products. Fine silica sand unsuitable for concrete production can be used as part of a silica-containing aggregate, which is mixed with liquid acid-containing wastes of chemical polishing of glass products, and the concrete products produced are stained by mixing SiF ₄ gas.

 To implement the method, components with the following characteristic parameters were used.

Component Feature
1. Portland cement grade M400 (GOST 10178-85).

 2. Slag Portland cement M300.

3. Limestone crushed stone of the Gurovsky deposit (Tula region). Containing CaCO ₃ 98.1-98.7, the remaining impurities are SiO ₂ , clay, Fe ₂ O ₃ . Bulk density 1460 kg / m ³ , D _naib. = 20 mm, D _min. = 5 mm.

 4. Quartz sand with a particle size modulus of 2.1-2.3. In terms of grain size and chemical composition, it meets the requirements of GOST 8736-93, as applied to heavy concrete.

 5. Quartz sand with a fineness modulus of less than 1.1. It is a by-product of brown coal mining in open sections of the Moscow Region basin. By granulometric composition, sand is unsuitable for the production of cement concrete. In this experiment, sand from the Kimovsky brown coal section (Tula region) was adopted.

6. Liquid (sludge) waste from chemical polishing of glass products. Waste from the Dyatkovo crystal plant in the Bryansk region, which cannot be neutralized by lime, has been accepted. They contain 20-30% free hydrofluoric acid HF and 5-10% sulfuric acid H ₂ SO ₄ . The rest is fluorides and sulfates of alkali and alkaline earth metals.

 7. Liquid wastes of nitrocellulose production not subject to lime neutralization. In the experiment, wastes from the Aleksinsky chemical plant of the Tula region.

 The chemical composition of the waste includes, wt.%: Nitrocellulose dissolved 0.2-0.24; undissolved nitrocellulose 0.10-0.16; sulfuric acid 0.84-0.91; nitric acid 0.42-0.45; soda 0.52-0.56, the rest is water.

 8. Limestone seeding with a size of less than 5 mm, obtained as a waste of stone crushing in a quarry upon receipt of explosive limestone crushed stone with a chemical composition given in paragraph 3.

 An example of the implementation of the manufacture of concrete products.

1. By the method of the prototype (experiment 1). 12 kg 700 g of limestone crushed stone, 0.114 kg of limestone seedlings (10% by weight of cement), Portland cement 3 kg 677 g and 1.5 l of hydrochloric acid solution containing 1.5% by weight of HCl cement were placed in the mixer. This mixture was stirred for 30 s, and then quartz sand was added. In this case, there was a violent reaction with the release of CO ₂ gas into the atmosphere in accordance with the chemical reaction, i.e.

.

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After 30 s, 6 kg 255 g of quartz sand was added and the mixture was further mixed for another 30 s. 10 pieces were formed from the resulting concrete mixture by vibration. samples of concrete products with a size of 10x10x10 cm. After a day of hardening, concrete samples were placed on 27 days of natural hardening in wet sand with t = 20 ± 2 ^o C. After hardening, they were tested for compressive strength. The test results are shown in the table (experiment 1 - prototype method).

Experience 2. Experience in the implementation of the proposed method was carried out according to the method of experiment 1, but with significant changes. Only carbonate aggregates (12 kg 700 g of limestone crushed stone and 0.114 kg of limestone seedlings) were pre-mixed with hydrochloric acid for 30 s, and the CO ₂ gases emitted in this case were captured and placed in a rubber hermetically sealed container. Then Portland cement 3 kg 677 g and 6 kg 255 g quartz sand were added to the mixer and stirring was continued for another 30 s. Molded 10 pcs. samples of concrete products (after 1 day of hardening in air) were placed for 24 hours in a chamber with trapped CO ₂ gas, and then for 26 days they were placed in a natural hardening medium at t = 20 ± 2 ^o C and relative humidity more than 90%, t .e. into the wet sand. After 28 days of solidification (1 day in air + 1 day in CO ₂ and 26 days in wet sand), the samples were tested for strength. The results are shown in table. (experience 2).

Experience 3. In the mixer was placed 12 kg of 700 g of limestone crushed stone, 0.114 limestone sowing and 1.5 l of acidic waste production of nitrocellulose. The mixture was mixed for 30 s in a hermetically sealed mixer equipped with a rubber hose through which CO ₂ gas was transported into a closed rubber container. CO ₂ gas was released due to a chemical reaction, the interaction of CaCO ₃ aggregates with mineral acids (H ₂ SO ₄ and HNO ₃ contained in acidic liquid waste. Then 3 kg 677 g of cement, 6 kg 255 g of silica sand were added to the mixer and stirring was continued another 30 s. Next, the manufacture of 10 pieces of prototypes of concrete products was carried out according to the method of experiment 2. The test results are given in table. (experiment 3).

Experience 4. In two mixers, carbonate and silica-containing aggregates were treated: in the first mixer, 1 liter of hydrochloric acid containing 1.5% HCl by weight of cement was added to the limestone crushed stone, and 0.114 kg of substandard fine sand were mixed with 0 in fine rubber in the second mixer. 5 l of waste from chemical polishing of glassware. CO ₂ gas was captured from 1 mixer, and both gases were accumulated from the second SiF ₄ in one rubber bottle. The products processed in two mixers for 30 s were placed in one mixer and 3 kg of 677 g of Portland cement, 6 kg of 255 g of silica sand were added to them and stirring was continued for an additional 30 s. Formed by vibration 10 pcs. concrete samples 10 × 10 × 10 cm in size withstood 1 day in air, 2 days in a gas environment of SiF ₄ and CO ₂ and the next 26 days in a medium of wet sand at t = 20 ± 2 ^o C and relative humidity of more than 90%. Hardened samples were tested. The test results are given in table. (experience 4).

.When carbonate or part of silica fillers or parts of them are mixed with acids, reactions occur (spontaneous processes) with the release of CO ₂ or SiF4 gases into the atmosphere in accordance with the chemical equations:

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 In the examples, all possible options of the proposed method for producing concrete products are not exhausted.

As can be seen from the table during the preliminary processing of limestone crushed stone and seeding with hydrochloric acid (prototype method), the concrete strength increased from 25.3 to 32 MPa, i.e. 26.48%, and CO ₂ gas was released into the environment during processing (example 1).

When capturing CO ₂ gas during the preliminary processing of limestone gravel and seedlings (the proposed method) and processing the hardened concrete samples with this gas, the strength additionally increased from 32 to 35.6 MPa, i.e. an additional 11.25%, and CO ₂ gas was not released into the environment, because it was captured and CO ₂ gas was processed; the surface of hardened products was carried out in a hermetically sealed chamber; moreover, CO ₂ gas was adsorbed onto the concrete surface and realized by the formation of a water-insoluble concrete product — CaCO ₃ .

As can be seen from experiments 3 and 4, the strength of the treated samples with CO ₂ and SiF ₄ gas also increased, respectively, by 10-15% with respect to the prototype method.

The physicochemical nature of the technical achievement of the goal, i.e., increasing the ecology of the environment and additional strength due to waste disposal and waste-free concrete manufacturing technology, is explained by the following factors:
1. The evolved gases CO ₂ or SiF ₄ during mixing carbonate (CaCO ₃ ) or silica-containing (SiO ₂ ) aggregates with acids of the type: CH ₃ COOH, H ₂ CO ₃ , HCl, H ₂ SO ₄ , HNO ₃ and HF or liquid waste containing one or more of these acids are purposefully disposed of during the carbonization or staining of products manufactured using this technology, and in the known method, CO ₂ or SiF ₄ gases are released into the atmosphere, which leads to a decrease in the environment ecology.

2. As a result of the daily residence of samples of hardened products in a gas medium of CO ₂ , SiF ₄ or (CO ₂ + SiF ₄ ), reactions of the concrete corresponding to Ca (OH) ₂ formed during hydration of the alite (3 CaO • SiO ₂ ) - cement clinker occur and gases CO ₂ (carbonization process) or SiF ₄ (coloring process) with the formation of water-insoluble components CaCO ₃ , CaF ₂ , SiO ₂
Ca (OH) ₂ + CO ₂ = CaCO ₃ + H ₂ O (carbonation)
Ca (OH) ₂ + SiF ₄ = CaF ₂ + SiO ₂ + H ₂ O (coloring)
Insoluble components in water CaCO ₃ , CaF ₂ , SiO ₂ settle in the pores of concrete, increasing its density and, accordingly, strength.

3. Thanks to the capture of gases CO ₂ and / or SiF ₄ , which are released during the preliminary processing of carbonate or silica-containing aggregates or parts thereof, a waste-free technology for the production of concrete products is ensured. In addition, slag-formed wastes, due to chemically spontaneous complex processing processes, become environmentally friendly additives for concrete, and positively affect the strength of concrete. The latter contributes to the improvement of environmental protection, as liquid acid-containing waste, limestone sowing, sands substandard for concrete are utilized.

The proposed method in comparison with the known has the following technical and economic advantages:
working conditions for workers manufacturing concrete products are improved, as CO ₂ or SiF ₄ gases are captured;
by increasing the additional strength, the consumption of cement is saved, because instead of the concrete grade 100-300, a grade of 150-350 is obtained with the same cement consumption per 1 m ^{3 of} concrete, and at W / C = const;
saving lime consumption, which is currently used to neutralize waste from chemical polishing of glassware and waste from the production of nitrocellulose, because instead of lime, quartz sand and limestone seeding substandard for concrete were adopted;
no coke consumption is required to produce CO ₂ gas for the carbonization process, the latter is obtained in the manufacturing process of concrete products;
To obtain SiF ₄ gas, it is required to expend scarce acid HF and sands suitable as aggregate for concrete. The role of the latter is performed by waste from chemical polishing of glassware and quartz sands substandard for concrete;
waste from chemical polishing of glassware, emitted gases CO ₂ , SiF ₄ and substandard quartz sands are utilized;
due to the above advantages, the cost of concrete is reduced by 20-25%.

Claims (2)

1. A method of manufacturing concrete products by mixing carbonate or silica-containing aggregates with acids, further mixing the resulting product with the remaining components of the mixture, molding and hardening, characterized in that the aggregates or part of them are mixed with acids of the type CH ₃ COOH; H ₂ CO ₃ ; HCl; H ₂ SO ₄ ; HNO ₃ ; HF or liquid production wastes containing one or more of these acids, gases released during mixing are trapped and they carbonize and / or stain molded solidified products. 2. The method according to p. 1, characterized in that as part of the silica-containing aggregate, finely dispersed silica sand unsuitable for concrete production is used, which is mixed with liquid acid-containing wastes of chemical polishing of glassware, and formed during the mixing with SiF ₄ gas, the molding of solidified products is stained.

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