RU2246464C2 - Magnesia binder-based composition - Google Patents

Abstract

FIELD: manufacture of building materials.

SUBSTANCE: invention is meant for use in manufacture of slabs and panels destined for in-door and out-door facing of buildings, underwindow borders, staircase steps, as well as in manufacture of dry building mixes and construction of cast-in-place structures (floors and plasters). Composition of invention contains, wt %: caustic magnesite 20-30, high-activity amorphous silica 1.5-4.5, magnesium chloride solution (density 1.2-1.25 g/cm³) 15-25, additionally: fine magnesium hydrosilicate 1-3.5, and filler - the rest.

EFFECT: increased water resistance, frost resistance, and strength of magnesia binder-containing materials due to directed formation of structure.

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Description

The invention relates to the building materials industry and can be used in the manufacture of plates and panels for internal and external cladding of buildings, window sills, stair steps, as well as for the production of dry building mixtures and monolithic structures: floors, internal and external plasters.

It is known that obtaining materials and products on a magnesian binder with high strength, water resistance and frost resistance is impossible without the use of modifying additives, preferably mineral ones.

Known mass (RU 2098382, C 04 B 28/30, 1997) for the production of facing material, including components in the following ratio, wt.%:

Caustic Dolomite 20-60

Magnesium Chloride Solution 29-55

Calcium Magnesium Silicate 5-40

Surfactant 0.01-0.1

Pigment 0.5-5

Water rest

In this composition, calcium-magnesium silicate is used partly as a filler and partly in the form of a source of silicic acid, which helps to increase the strength and frost resistance of the resulting facing material. However, the effectiveness of this technique is not high enough. If the strength of the obtained material has doubled in individual compositions, an increase in frost resistance up to 25 ... 29 cycles does not solve the problem of the durability of the wall material used for exterior decoration. In addition, there is no data on the water resistance and crack resistance of the material when the humidity of the environment changes.

Known astringent (SU 1433924, 04 04 9/00), including components in the following ratio, wt.%:

magnesium oxide 25-45

Calcined Serpentine 47-67

magnesium chloride or sulfate

This binder provides excellent indicators of strength and linear shrinkage during hardening, according to no data on its water resistance and frost resistance. The disadvantages of the proposed solution can also include additional energy costs for firing serpentine.

Also known are methods of increasing the water resistance of magnesia stone by introducing mineral additives containing an increased amount of active SiO ₂ . These include slags, acidic ashes, dust collection products from furnaces and others, but there is no evidence that such materials are highly water- and frost-resistant.

The closest in technical essence to the invention is a composition based on a magnesian binder (RU No. 2163578 C1, 02.27.2001) containing caustic magnesite, highly active amorphous silicon dioxide, a solution of magnesium chloride and aggregate.

The invention solves the problem of simultaneously increasing the water resistance, frost resistance and strength of materials on a magnesian binder by the directed formation of their structure by introducing a complex modifying additive.

The essence of the invention lies in the fact that the composition based on a magnesian binder, including caustic magnesite, highly active amorphous silicon dioxide, a solution of magnesium chloride and aggregate, contains a solution of magnesium chloride with a density of 1.2 ... 1.25 g / cm and an additional finely dispersed additive of hydrosilicate magnesium in the following ratio of components, wt.%:

Caustic Magnesite 20-30

Highly active amorphous silica 1.5-4.5

A solution of magnesium chloride with a density of 1.2 ... 1.25 g / cm ³ 15-25

Magnesium Hydrosilicate 1-3.5

Placeholder else

The content of caustic magnesite in an amount of 20-30 wt.% Is necessary and sufficient to ensure the bonding of all the components included in the composition as a whole with minimal porosity and maximum strength.

The content of a solution of magnesium chloride with a density of 1.2 ... 1.25 g / cm ³ in an amount of 15-25 wt.% Is necessary and sufficient to create a workable mixture. A smaller amount of it in the composition will lead to an undesirable decrease in the mobility of the mixture, and a larger one will unnecessarily increase the mobility, which will lead to a decrease in strength and an increase in the porosity of the material due to delamination and air entrainment processes. In addition, vysolobrazovanie is possible, and this is undesirable for finishing surfaces.

The presence in the composition of highly active powdered amorphous silicon dioxide promotes the formation of water-resistant magnesium hydrosilicates. Its content in the composition, less than 1.5 wt.%, Is not enough to complete the task, and more than 4.5 wt.% Is simply unnecessary, the excess will remain in a free state and will contribute to the swelling of the material and reduce its crack resistance.

The presence of finely divided magnesium hydrosilicate initiates the crystallization of modified hydrated neoplasms, which are stable magnesium oxychlorides and the products of the interaction of highly active finely divided silica with magnesium oxide.

This provides additional compaction of the structure of magnesia stone with water-resistant crystalline phases, causing an increase in strength, water resistance and frost resistance of the resulting materials and products. The content of the crystallization initiator of magnesium hydrosilicates in the composition of less than 1 wt.% Is not sufficient for the targeted crystallization of the desired neoplasms. An increase in the content of magnesium hydrosilicate additive over 3.5 wt.% Will lead to an increase in the consumption of a binder and a cinder, the most expensive components, as well as to a decrease in the strength of a magnesia stone.

Aggregate is necessary to save the binder and create a strong mineral skeleton. As rocks, any rocks of sedimentary, magmatic and / or metamorphic origin can be used.

A composition for the manufacture of construction products is prepared as follows.

Caustic magnesite, aggregate, amorphous finely divided silica and finely divided magnesium hydrosilicate are mixed dry, then the resulting dry mass is thoroughly mixed for 1 ... 3 minutes with an aqueous solution of magnesium chloride with a density of 1.2 ... 1.25 g / cm ³ in the amount providing molten mobility of the magnesia mixture. The resulting composition is poured into molds and kept for 4 ... 5 hours.

The prepared compositions of the compositions are presented in tables 1 and 2. From the obtained characteristics of the compositions it is seen that the use of complex additives allows to obtain waterproof products with sufficient frost resistance and strength at low binder costs.

Increasing the strength of the proposed material allows the use of organic aggregate to obtain effective heat-insulating concrete, and when using special aggregates with high hardness characteristics abrasives.

Table 1 N mixture Additives,% by weight of cement Compressive Strength (28 days) MPa Water resistance coefficient *, 28 days Frost resistance in accordance with GOST10060.1, Cycles 1 No 46.5 0.51 twenty 2 Magnesium Hydrosilicate 5 53,4 0.65 25 3 Magnesium Hydrosilicate 10 39.3 0.68 35 4 Silica fume 15 38.3 0.83 95 5 Silica fume 8 40.3 0.80 60 6 Magnesium hydrosilicate 5, Silica fume 8 48.0 0.90 200 7 Magnesium Hydrosilicate 10 Silica fume 10 53.5 0.93 230 * The coefficient of water resistance was determined by the ratio of the strength of the sample saturated with water for four days, according to GOST 10060.0, to the strength of samples hardened in natural conditions.

table 2 N mixture Caustic magnesite,% Solvent,% Placeholder,% Additives,% by weight of the composition Compressive Strength (28 days), MPa Softening coefficient 1 twenty fifteen 65 not 33.5 0.55 2 thirty 25 45 not 45.0 0.60 3 17.5 fifteen 65 magnesium hydrosilicate 1.0 amorphous silica 1.5 45.0 0.91 4 22 25 45 magnesium hydrosilicate 3.5 amorphous silica 4.5 53,4 0.90 5 19.5 twenty 55 magnesium hydrosilicate 2.5 amorphous silica 3.0 58.3 0.96

Claims (1)

A composition based on a magnesian binder containing caustic magnesite, highly active amorphous silicon dioxide, a solution of magnesium chloride and an aggregate, characterized in that it contains a solution of magnesium chloride with a density of 1.2 - 1.25 g / cm ³ and an additional finely divided magnesium hydrosilicate in the following ratio of components, wt.%: caustic magnesite 20-30 highly active amorphous silicon dioxide 1.5-4.5 the specified solution of magnesium chloride 15-25 magnesium hydrosilicate 1-3,5 placeholder else