LV10010B - Composition of producing of gypseous products - Google Patents

Abstract

The invention applies to civil engineering and may be used in the production of wired separating constructions. The object of the invention is a mixture, which consists of plaster binder, sodium salts of naphthalene sulfonic acid, lignin sulfonic acid and formaldehyde condensation products and alkali or slate ashes. It is offered to insert lime and 100-1,000cm<2>/g specific surface crystalline silica to the mixture to increase the water alkalinity in consolidated plaster's pores, which reduces the corrosion of metallic armature mounted inside the plaster. It is offered to prepare the mixture as follows:plaster binder - 100;sodium salts of naphthalene sulfonic acid, lignin sulfonic acid and formaldehyde condensation products - 0.2-0.5;alkali - 0.5-1.6;or shale ashes - 5-15;lime - 10-20;100-1000 cm<2>/g specific surface crystalline silica - 20-100.

Description

COMPOSITION FOR THE MANUFACTURE OF GYPSUM ARTICLES

The invention relates to the building materials industry and can be used in the manufacture of reinforced enclosures, exterior or interior.

There is a prior art gypsum binder-containing composition that reduces corrosion of reinforcement: 'puculan portland cement, potassium bichromate filler additive and sulfate-yeast roast / 1 /. However, the use of Portland cement admixtures in gypsum compositions can lead to destructive phenomena, especially when the free CaO-binding activating additive is insufficient.

The most preferred composition corresponds in technical terms to a composition containing (in units of mass): gypsum binder-1, S-3, alkali 0.0002-0,0004 or shale ash 0.05-0.10 / 2 /. The disadvantage of this composition is that the alkalinity of the pore fluid is insufficient in hardened gypsum designs. This can be explained by the fact that for said mixture / 2 /, the high pH of the solvent water (as determined by the KOH additive in admixture water) is significantly lowered (pH not exceeding 7) by the formation of a mixture of hydrates and gypsum, i. the hydroxyl ions 0H ~ are consumed after interaction with other components of the formation. As a result of the strong alkalinity reduction of the gypsum concrete pore fluid, corrosion of the metal reinforcement built into it occurs.

Crystalline silica and lime are added to the recommended gypsum binder composition without the components already mentioned. The total weight ratio of the ingredients in the composition is as follows:

1. gypsum binder - 100,

2. S-3 - 0.2-0.5,

3rd alkali - 0.5-1.6,

Lime 4 - 10-20,

5. Crystalline silica having a specific surface density of 100-1000 cm / g - 20-100.

The main difference between the recommended technological solution and the already known is the addition of lime and crystalline silica with a specific surface area of 100-1000 cm ² / g, which gives a significant increase in alkalinity and its stable retention in the pore liquid of gypsum products.

In addition, the recommended composition differs from the prototype with a higher alkali content and lower (total weight) acidic S-3 concentration (sodium salt of formaldehyde and condensation products of lignosulfonic acid).

This effect cannot be achieved by directly increasing, for example, the alkali additive, since over time the acid resulting from hydrolysis of calcium sulphate (gypsum) neutralizes the alkali / 3 /.

Therefore, even with the initial mixing water, the alkalinity of the water (pH more than 10) after 3-4 days the gypsum concrete pore fluid pH drops to 7. This effect, i.e. Increasing the alkalinity of the gypsum concrete porous fluid and its stable retention over time can only be achieved through synergistic increases in the alkalinity of the porous fluid: increasing the lime and alkali mixtures alone does not lead to a similar result.

Lime, together with silicon crystalline oxide, plays a poly-functional 1 ohm:

- increases the alkalinity of the pore fluid;

participates in the formation of the structure and compacts the gypsum-containing materials by filling the crystalline gypsum framework with alkaline growths which remain stable over time;

- further plasticizes the mixture and thus achieves uniform plasticity at lower concentration of S-3 sodium salts;

- lowers the residual moisture of post-hydration gypsum products.

In addition, the complex injection of alkali and lime regulates the setting time of the composition, as the alkali accelerates the binding, while the lime «

slows down, but they both allow to regulate the necessary technological process of gypsum products.

Crystalline silica with a specific surface area of 100-1000 cm ² / g improves the deformation properties of gypsum products. Addition of crystalline silica in the composition leads to a new effect - lowers

2agresivo, for metals, the concentration of SO 4 ions (in total mass). Silica, when deposited in the pores of the gel, reduces capillary porosity and serves as a specific buffer that protects the reinforcement from corrosion. Crystalline silica with a specific surface area of 100-1000 cm ² / g does not increase the water consumption of the composition.

Examples.

To obtain the composition, compositions are prepared with the optimum boundary conditions for the incoming components (compositions 1-3, la-3a, lb-3b), as well as outside (4.5) and prototype (6.7) (see Table 1). .

First, the sodium salts of the crystalline sulphonic acid with formic acid aldehyde and the condensation product of lignin sulphonic acid are mixed with water in the blender and then lime with silica and alkali is added. As the last plaster binder is introduced and then all this mix is mixed for 50-60 s. water shall be drawn up in such a quantity that the mixture has a run-out of 18 cm on a Suttard viscometer.

Pre-weighed steel (T-3) reinforcing bars (diameter 5 mm, length 120 mm) are molded into 4x4x16 cm composite bars in one piece each. Six such samples are prepared from each mixture and then placed in desiccators for 90 days at a humidity of 0,6 and ψ '= 1,0. The samples are then disintegrated, the reinforcing bars removed and their condition evaluated: appearance, loss of metal mass, maximum depth of grooves, etc.

The physico-chemical and technological properties of the recommended composition as well as the results of reinforcement corrosion studies for the composition of the specified compositions are shown in Table 2.

The test found that the corrosion of the reinforcement is significantly reduced compared to the prototype using the components of the recommended composition. Also, the loss of durability during cyclic saturation and drying of the recommended composition is less than that of the prior art compositions, and there is a possibility of varying the binding time, which indicates the technological advantages of the recommended compositions.

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The use of the recommended composition allows prolonged shelf life of enclosed structures and articles due to the elimination of internal stresses and reduced corrosion.

Excluding reinforcement corrosion protection operations from the production cycle of gypsum plastered structures with special coatings significantly simplifies their production process, reduces labor-intensive reinforcement dyeing, production area spaces (paint baths, drying frames, etc.), and has a positive impact on working conditions and environment, since most anti-corrosive substances that are harmful to health do not need to be used.

Sources of information

1. USSR Author Certificate No.893932, st.kl.C04B 11/00, B 48.81.

2. Application for Russian Patent No. 5015326, with priority dated 28.11.1991.

3. rwnc. HaroTūBJGHMe μ πεμηθηθημβ γμποοβηχ οτροΜΤβΛίιΗωχ MaTepiiaaoB,

ΓΚ'Ρ. C HGH. H. CTP0WM34aT, 1981.

Claims (1)

Invention Formula » The composition of gypsum products consisting of sodium salts of gypsum binder, naphthalene sulphonic acid and condensation products of lignin sulphonic acid and alkali or shale ash differs in that, in order to increase the alkalinity of the liquid in the pores of the hardening gypsum products, and crystalline silica having a specific surface area of 100 to 1000 cm / g and the component ratios by weight are as follows: gypsum binder - 100; sodium salts of condensation products of naphthalene sulphonic acid, formaldehyde and lignosulphonic acid 0.2-0.5; alkalis - 0.5-1.6; or ash - 5-15; · Lime - 10-20; crystalline silica having a specific surface density of 100 to 1000 cm 2 / g 20-100.