RU2600398C1 - Crude mixture for making autoclave foam concrete - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: invention relates to the industry of construction materials and specifically to compositions for production of heat-insulating autoclave foamed concrete and articles based thereon, which can be used for heat insulation of industrial plants and enclosing structures of buildings and structures. Crude mixture for making autoclave foam concrete contains, wt%: Portland cement 8-14, unslaked lime 12-18, quartz sand 37-40, polyfunctional gasifier based on aluminium paste and surfactants 0.15-0.40, dispersion of multilayer carbon nanotubes in a superplasticiser based on polycarboxylates activated by means of an ultrasonic disperser and containing 1-3 % of multilayer carbon nanotubes 0.005-0.02, water with the temperature of 45-55 °C 32-38.

EFFECT: optimization of processes of foaming and structuration of cellular concrete mass, lower density and heat conductivity of the obtained foamed concrete while maintaining strength properties.

1 cl, 2 tbl

Description

The invention relates to the building materials industry, and in particular to compositions for the production of heat-insulating autoclaved aerated concrete and products based on it, which can be used for thermal insulation of industrial plants and building envelopes.

A known raw material mixture for the production of autoclaved aerated concrete, including, wt.%: Portland cement 32.67-42.71, quartz sand with a fineness of grinding 3500-4100 cm ² / g 53.071-63.865, two-water gypsum 2.92-4.17 , aluminum powder or paste 0.095-0.119, mixing water at a temperature of 42-52 ° C in an amount corresponding to a W / T ratio of 0.55-0.63, while the final alkalinity of the raw material mixture is 26-32%. The above raw mixture contains non-additive Portland cement grade M500 D0, two-water gypsum with a calcium sulfate content of at least 95% (RU patent No. 2543249 dated 02.27.2015).

A disadvantage of the known composition is that the resulting aerated concrete has a high density (490-510 kg / m ³ ). The disadvantages include the absence of lime in the composition of the raw material mixture, the presence of which determines the completeness of the gas evolution reaction in the initial period of aerated concrete pore formation, and also contributes to a set of structural strength during the autoclave treatment of products.

The closest mixture of the same purpose to the claimed invention in terms of features is a raw material mixture for producing nanostructured autoclaved aerated concrete, including the following components, wt.%: Suspension of fine sand (dry matter) 62.5-72.5, lime-siliceous binder, when the ratio of components, wt.%: quicklime 75-85 and quartz sand 15-25, 25-35, gypsum 1.5-2.5, aluminum paste or powder 0.05-0.1, water to a density of 1, 75-1.80 kg / l (patent RU No. 2448929 from 04/27/2012). This composition is taken as a prototype.

Signs of the prototype, coinciding with the essential features of the inventive mixture - quicklime, quartz sand, aluminum blowing agent, water.

The disadvantages of the known composition adopted for the prototype are the high density and thermal conductivity of the resulting aerated concrete, which limits its use as an effective insulation.

The problem to which the invention is directed is to reduce the density and thermal conductivity of products from aerated concrete while maintaining strength quality indicators within the values allowed by GOST 31359-2007.

The technical result is the optimization of the processes of expansion and structure formation of aerated concrete mass.

The problem was solved due to the fact that the known raw material mixture for the manufacture of autoclaved aerated concrete, including quicklime, quartz sand, aluminum blowing agent and water, additionally contains Portland cement and a dispersion of multilayer carbon nanotubes in a solution of a superplasticizer based on polycarboxylates activated by ultrasonic dispersion containing 1-3% multilayer carbon nanotubes, and as an aluminum blowing agent - a multifunctional gas sample . Zovatel based on aluminum paste and surfactants, with the following ratio of ingredients, wt%:

Portland cement 8-14 quicklime 12-18 Quartz sand 37-40 water with a temperature of 45-55 ° C 32-38 specified aluminum blowing agent 0.15-0.40 the specified dispersion of multilayer carbon nanotube 0.005-0.02

Distinctive features of the inventive mixture from aerated concrete mass according to the prototype are: the presence of Portland cement in the mixture; the introduction of a dispersion mixture of multilayer carbon nanotubes (MWCNTs) in a solution of a superplasticizer based on polycarboxylates activated with an ultrasonic dispersant containing 1-3% MWCNTs; the use of a multifunctional gasifier based on aluminum paste and surfactants as an aluminum blowing agent; another quantitative ratio of the ingredients used, wt.%: Portland cement - 8-14; quicklime - 12-18; quartz sand - 37-40; water with a temperature of 45-55 ° C - 32-38; the specified aluminum blowing agent is 0.15-0.40; the specified dispersion of multilayer carbon nanotubes is 0.005-0.02.

The introduction of the Ful Vec multilayer carbon nanotube (MWNT) dispersion in a solution of a superplasticizer based on polycarboxylates activated with an ultrasonic dispersant containing 1-3% MWCNTs allows preserving the required material strength while reducing the grade in density from D300 to D200.

The content in the dispersion of multilayer carbon nanotubes in an amount of less than 1% does not significantly affect the properties of the claimed material.

The content in the dispersion of multilayer carbon nanotubes in an amount of more than 3% is impractical due to the high cost of this component, as well as the absence of a significant effect on the physicomechanical characteristics of the material.

As a blowing agent, a multifunctional blowing agent based on aluminum paste and surfactants from ECKART "STAPA * Alupor No. 905" was used. The use of this blowing agent in the composition of the mixture in the claimed amount allows you to stabilize the process of structure formation of aerated concrete, which has a positive effect on the physico-mechanical and thermotechnical characteristics of the products.

It was experimentally established that the replacement of aluminum powders widely used in analog materials (PAP-1 and PAP-2) with the presented multifunctional blowing agent reduces the density and thermal conductivity of products from gas silicate by 40-55%. The consumption of this blowing agent is 0.15-0.4% by weight of all components. Excessive blowing agent leads to intensive expansion of the massif and its further shrinkage, which negatively affects the operational properties of aerated concrete. A decrease in the amount of blowing agent leads to insufficient expansion of the gas mass, which entails an increase in the density of the cellular concrete mass.

The introduction of Portland cement into the mixture allows to stabilize the set of plastic strength of aerated concrete in the pre-autoclave production period.

The use of water with a temperature of 45-55 ° C for mixing raw components makes it possible to intensify the processes of gas generation and expansion of the cellular concrete mass.

Additional strength and durability of the products of the proposed composition gives their autoclave treatment, which is the main process that turns a mechanical mixture of dissimilar components into chemical compounds (calcium hydrosilicates of various mineralogical composition) that bind sand grains.

The proposed technical solution allows to obtain an effective heat-insulating autoclaved aerated concrete, as well as reduce its density and thermal conductivity.

To obtain aerated concrete, the following components are used:

- Portland cement in accordance with GOST 31108-2003;

- quicklime according to GOST 9179;

- quartz sand according to GOST 8736;

- water with a temperature of 45-55 ° C in accordance with GOST 23732;

- aluminum gas blower from ECKART "STAPA * Alupor No. 905";

- dispersion of multilayer carbon nanotubes (MWCNTs) “Ful Vec” in a solution of a superplasticizer based on polycarboxylates activated with an ultrasonic dispersant containing 1-3% MWCNTs.

The raw material mixture for the manufacture of aerated concrete is obtained as follows.

At the initial stage of production, lime-silica binder (IQB) and sand slurry are obtained. The preparation of a lime-silica binder involves the co-grinding of lime and sand (15% of ICW) to a specific surface of 2700-2900 cm ² / g. The preparation of sand sludge is carried out by wet grinding of the siliceous component. To carry out wet grinding, water of a temperature of 45 ° C is introduced into the mill. As grinding media use metal balls. As a result of grinding, the density of sludge is 1.6-1.7 kg / l.

After preparing all the raw materials, the mixture is thoroughly mixed. Mixing sequence: separately prepare the dry component - cement and IKV, as well as the liquid component - blowing agent, water and dispersion of MWCNTs. Next, dry and liquid components are mixed.

In order to intensify the process of expansion, the temperature of the mixing water should be in the range from 45-55 ° C.

The uniformity of the mixture and the uniformity of its expansion is ensured by thorough mixing of the mass. Excessive mixing time is harmful, since the onset of gas formation is possible.

Before molding, the mobility (fluidity) of the mixture is determined using a Suttard viscometer.

The mixture is poured into a pre-prepared form (cleaned and oiled). The volume of the mixture to be poured is taken into account swelling at 2/3 or 3/4 of the height of the mold.

After pouring the aerated concrete mass, its intensive expansion begins, which lasts 10-15 minutes.

To prevent possible subsidence of the massif and the set of plastic strength by it, the mold is placed in a thermal holding chamber, the air temperature in which is 40-60 ° С.

Hydrothermal treatment of aerated concrete samples is carried out in an industrial autoclave at an excess pressure of 8 to 12 atm and a temperature corresponding to this pressure of 150-200 ° C.

According to the described method were prepared compositions of raw mixes with different ratios of ingredients.

The prepared formulations passed laboratory tests.

Table 1 shows the claimed compositions of the raw mixes and the known composition.

Table 2 presents the results of laboratory tests of samples made from the claimed and known compositions.

As can be seen from table 2, samples of autoclaved aerated concrete of the claimed compositions have quality indicators that in their value exceed the thermal characteristics of the prototype. In addition, the characteristics of the samples of the developed material comply with the requirements of GOST 31359-2007.

The advantage of the proposed technical solution is that it contributes to the development of autoclaved aerated concrete as an effective heater of the building envelope, and also allows the use of this material for thermal insulation of industrial plants.

Claims (1)

A raw material mixture for the manufacture of autoclaved aerated concrete, including quicklime, quartz sand, an aluminum blowing agent and water, characterized in that it further comprises Portland cement and a dispersion of multilayer carbon nanotubes in a solution of a superplasticizer based on polycarboxylates activated by an ultrasonic dispersant containing 1-3 % of multilayer carbon nanotubes, and as an aluminum blowing agent polyfunctional blowing agent based on aluminum pass you and surfactants, in the following ratio of ingredients, wt.%:
Portland cement 8-14 quicklime 12-18 quartz sand 37-40 water with a temperature of 45-55 ° C 32-38 specified aluminum blowing agent 0.15-0.40 the specified dispersion of multilayer carbon nanotube 0.005-0.02