CS250768B1 - Composite cement mix of increased chemical resistance - Google Patents

Abstract

The solution concerns a composite cement mixture against an external aggressive solid, liquid or gaseous medium, at least of an acidic nature. The essence of the solution is adding steel and cast iron granules and chips or waste resulting from surface treatment (e.g. cutting, blasting) to cement mixtures, as well as adding freely dispersed steel reinforcement to cement mixtures with steel and cast iron granules and chips or waste resulting from surface treatment. The action of the aggressive medium on the added steel and cast iron admixtures or steel dispersed reinforcement causes corrosion of the added metal admixture associated with the formation of rust. The formation of iron corrosion products seals the capillaries and pores in the cement mixture. This process also dulls the aggressive medium and increases the diffusion resistance to its penetration. The solution can be used to increase the resistance of cementitious building materials and structures made from them, especially concrete and reinforced concrete, against the effects of acidic aggressive environments and environments that cause corrosion of steel reinforcement of concrete.

Description

250768 3 4

The present invention relates to an incompatible cementitious mixture of enhanced chemical resistance against the effect of an acid aggressive environment.

Furthermore, it is an object of the present invention to increase the resistance of cementitious compositions to the opposite kind of aggressive environments which, in addition to the corrosion of the cementitious stone, also cause corrosion of the steel reinforcement.

Podlá čs. No. 197,164 and No. 239,206, an increase in the chemical strength of inorganic binders can be achieved by the addition of powders that contain metal iron. The admixture of the iron powder inorganic binders occurs with some aggressive media, such as carbonated and acidic water, wet acid gases, and the like, a process for rusting metal iron particles.

Products of corrosion of metallic iron, oxides of iron, resp. their hydrates and hydroxides collapse in the hardened binder of the capillary of apores. When the aggressive environment comes into contact with the metallic iron particles, the aggressive medium is also agitated.

Until now, iron mechanical powders and wastes with a softness have been used to increase the anticorrosive strength of the binder mixtures, so that they can contain up to 15% by weight of particles larger than 0.5 mm amine. 1 ° / o of particles smaller than 0.125 mm with metallic iron content (Fe) min. 5% by weight. Investigation of the influence of fineness, dose and content of metallic iron in steel and cast granules, crushers and wastes reveals that coarser particles, up to 5 mm in size, can also be used to produce a protective effect. It will be appreciated that the rate of formation of metal corrosion-rust corrosion products that is formed in the surface layer of the composite cement mixture by the reaction with the active aggressive medium, which is the essence of the anticorrosive active compounds, is highly dependent on the size of the particles. In mixtures with a particle size of less than 100 μΐη, the corrosion products begin to form within a few days, while in the case of particles of 5 mm in size, the formation of a thick layer lasts, depending on the dose, months to years. A further improvement in the properties of the composite cement mixtures has been achieved when the formation of a protective layer instead of the previously used ferrous powders is used as a loose dispersed steel reinforcement. It has been found by observation that the steel fiber corrosion products have been generated in particular in fibers which, when forming the cementitious composite mixture of the present invention, have reached the surface or just below the surface into a max. able to overwhelm the medium aggressively.

The drawbacks of the iron powders and wastes of the added admixture mixtures used so far are their cost and energy demands, the possibility of cracks due to mechanical stress and low abrasion resistance of hardened binders.

The above disadvantages of ferrous mechanical powders and wastes are eliminated by the composite cementitious mixture of enhanced chemical resistance of the invention. It is based on the fact that besides cement, iron powder, modifying additives and admixtures it contains per part by weight of cement min. 0.01 and max.5 parts by weight of steel and / or cast iron granules and / or chippings and / or rubbish and steel wastes in which the metallic iron content is not less than 5 per cent by weight and the particle size is not more than 5 mm.

Further, the shortcomings of cementitious compositions containing iron mechanical powders and wastes are eliminated by the composite cementitious compound of increased chemical resistance, which contains from 0.01 to 0.5 parts by weight of free scattered steel reinforcement with a slenderness ratio of 50 to 250 parts per 1 part by weight, part of loose scattered steel is min. 0.05 and max. 20 parts by weight of steel and / or cast iron granules and / or rubble and / or cast iron aocel waste.

The demonstration of the protective properties of the composite cement composition according to the invention and the possibilities of its use show the following examples of use. Example 1

In order to demonstrate the anticorrosive effects of the compositions according to the invention, a casting alloy according to ČSN 42 9823 of this granulometric composition was used:

Size (mm) Residues on the screen (% by weight) 4, 2.0 3 78.5 2 14.5 1 4.9 0.5 0.1 Total 100.0

The iron (Fe) content of the cast iron was 99.0% by weight. With the use of water, cement, water and water, 4 X 4 X 16 cm, 1 set (3 pieces) of the mixture of this composition were made: Portland cement tr. 400Wet 450 g sand smooth granulome smooth 450 g sand smooth granulometrious 450 g cast iron 450 g water 225 ml 250768 6

After 1 day of storing the mortar bars with a relative humidity of 100%, the deformed bars were placed in a carbon-aggressive solution containing approximately 70 mg / l of aggressive carbon dioxide. A few months of exposure to the bars in this solution appeared rust stains and corrosion products of cast iron crumb with carbon dioxide from an aggressive solution that took 10% of the total surface of the beam-metal. Example 2

In order to demonstrate the anticorrosive effect of the waste steel pulp on the production of 4 X 4 X 16 cm mortar shavings, steel sawdust resulting from the cutting of conventional rolled sections on machine saws was used. The sawdust used is small with this granulometric composition:

Sew Size (mm) Residues per (° / o wt. 2, 2.0 µl 21.3 0.5 48.2 0.25 21.3 µ, O45 6.2 Overflow over 0.045 1.0 Total 100.0

The metallic iron content, determined magically, was 99.0% by weight. Before using cement mortars, sawdust was degreased. The dose of steel sawdust was chosen from 20 to 40% by weight of cement. A total of 2 types of mortar bars were prepared with 2 sausages (6 pieces), 1 set (3 pieces) for each type of mortar.

Steel sawdust mixture 20% cement weight: Portland cement tr. 400 'wet 450 g steel sawdust 90 g sand continuously] granulometry fine 450 g sand continuously] granulometry' medium 380 g sand continuous granulometry thick 450 g water 225 ml

Steel sawdust mixture 40% cement weight: Portland cement tr. 400

Wet 450 g steel sawdust 180 g sand continuous granulometry fine 450 g sand continuous granulometriestred 270 g sand continuous granulometrygreen 450 g water 225 ml

After one day of wet deposition with a relative humidity of 100%, de-molding was carried out and the bars were placed in a carbon-aggressive solution containing 70 mg / l of aggressive CO2 per lime and into a solution of hydrochloric acid at pH = 4. exposing the trays to carbon dioxide steel filings from the solution on the beams were about 20% of the weight of the cement and about 80% of the total surface of the trays at a weight of 40%. For a period of time, exposing the trays to corrosion of the sawdust-steel-sawdust pH-4 from the solution to the surface framings occupied 90% of the total surface of the trays at a dose of 20% by weight of about 60 ° / o. Example 3

In order to demonstrate the anti-corrosive effect of the o-whole fibers, concrete bars of 7 x 7 X 28 cm were made in 2 sets (6 pieces). The concrete mixture had this composition per 1 m3 of finished concrete: Portland cement tr. 400Wet steel fiber length 30 mm and diameter 0.3 mm aggregate 0/4 mmkamenivo 4/8 mmkamenivo 8 / 16water 450 kg 45 kg870 kig'350 kg525 kg200 1

After 1 day of storage in the damp, the mold was removed and one set (3 pieces) of shim-metal was placed in a hydrochloric acid solution pH = 4 and the second set (3 pieces) of carbon dioxide-containing water was aggressive to lime of about 70 mg / l. After three months of exposing the strings to the steel fiber, the steel fiber corrosion products at the surface of the strips that diffused into the stone were observed in both types of aggressive media.

According to the invention, industrial products as well as wastes can be used as a source of granules and pulps added to the composite cementitious mixtures. For the purposes of the invention, steel and cast iron granules according to ČSN 42 9823 can be used for the purposes of the invention. Steel fibers produced, for example, for the Kefar industry or other types of steel filaments can be used as a dispersed fibrous filling.

Claims (2)

Instead of the relatively expensive manufactured cast-iron chips, granules and fibers, industrial wastes can be used for the purposes of the present invention. These wastes are produced by priming the machining of steel or lithium products. They are especially the ones created by sawing, cutting and blasting. However, when using waste materials, it is important to consider the nature and content of the impurities therein, since if these operations are carried out with the addition of emulsions, oils, pastes or other preparations, these can significantly impair the properties of the concrete. O 8 8 can be used especially for those types of concrete structures that are exposed to the effects of an acid corrosive environment and an environment that causes corrosion-reinforcing reinforcement. Suitable objects for the use of the cementitious composite according to the invention are concrete structures of chemical plants, floors of chemical stores, reservoirs, chemical substrate stores, handling areas in agrochemical areas, handling of feed areas, feed troughs in agriculture, navigable troughs in sugar-cookery and elsewhere. OBJECT 1. A composite cementitious mixture of high temperature resistance, comprising a cement, an iron powder, a filler and / or a modifying agent and an admixture, characterized in that a minimum of 1% by weight of the cement is present. 0.01 and max. 5 parts by weight of steel and / or cast iron granules and / or chippings and / or cast iron and steel wastes in which the inventive iron content is less than 5% by weight. and the particle size is not greater than 5 mm. í2. 2. A composite cementitious composite of enhanced chemical resistance according to claim 1, wherein from 0.01 to 0.5 wt. loose scattered steel reinforcement with a slimness ratio of 50 to 250. Severografla, n. p., race 7, Most Price 2,40 Kčs