WO2020101631A1 - Thermally insulating non-autoclaved cellular concrete - Google Patents

Abstract

The utility model relates to artificial, porous, rock-like materials of mineral origin which are used as additional (effective) thermal insulation of barrier constructions of buildings and structures. Proposed is a thermally insulating non-autoclaved cellular concrete of medium density in a dry state of from 110 to 170 kg/m3 and having a novel method of pore formation and a ratio of components.

Description

 Heat-insulating non-autoclave cellular concrete

The utility model relates to artificial porous rock-like materials of mineral origin, which, along with polystyrene foam and technical wool, are used as additional (effective) thermal insulation of the enclosing structures of buildings and structures.

 Non-autoclaved aerated concrete obtained from gas-porous mixtures based on Portland cement as a binder, blowing agent and additives that accelerate the setting and hardening of cement without using solid mineral aggregates in the mixtures is known from the prior art.

 A known mixture for the manufacture of non-autoclaved aerated concrete (Patent for invention RU Ns 2120926, IPC С04В 38/02, В28В 1/50, publ. 10/27/1998), which contains, May. hours: cement - 1, sodium chloride or calcium - 0.005 - 0.001, silica fume - 0.04 - 0.1, superplasticizer C-3 - 0.002 - 0.01, blowing agent - 0.0016 - 0.002, water - 0.3 -0.4.

 The known composition of the raw mix for the manufacture of cellular concrete (Copyright certificate SU 1491857), which contains, may. %: Portland cement - 50-55, lime - 3-5, aluminum powder - 0.03-0.05, sodium chloride - 1-2, semi-aquatic gypsum - 0.5-2, water-soluble preparation VRP-1 - 0.015-0.025 water is the rest.

A common feature of cellular concrete obtained by both of these technical solutions is the too high average density of the material in the dry state (from 492 to 512 kg / m ³ in the decision RU 2120926, from 300 to 360 kg / m ³ in the decision SU 1491857).

 A material with such a density can be considered heat-insulating among building materials of the construction group, but it is not effective thermal insulation in the understanding of the possibility of its use for additional thermal insulation of building fences.

For the same reason, any cellular concrete with a density higher than 200 kg / m ³ cannot be considered a substitute material for products that are massively used in construction due to low (in the range from 30 to 180 kg / m ³ ) bulk density (technical cotton wool and foam polymers).

 That is why the technical solutions cited, despite the authors' declarations regarding intentions to reduce the density and increase the thermal properties, do not contain among the characteristics the main indicator that characterizes the effective thermal insulation material - the thermal conductivity coefficient (the value of which for the materials of the corresponding group is not higher than 0.08 W / ( mK)). In addition, the goal of achieving the level of effective isolation by the authors of the known solutions was not stated or set.

 Therefore, in the context of the claimed utility model, the high density of cellular concrete obtained by the indicated technical solutions is a drawback.

Heat-insulating cellular concrete with a density of 140-155 kg / m is known under the commercial name Masa Lithopore (joint development of divisions of Masa GmbH and Luca Industries International GmbH, Germany, https: //www.masa- group.com/en/products/litho-pore /). The specified material, similarly claimed is non-autoclaved aerated concrete based on cement, however, it is produced using foam concrete technology, that is, the mixture is porized by mixing it with previously prepared foam.

 The disadvantage of this technical solution is the increased complexity and capital intensity of production associated with a two-stage technology for preparing the mixture and the need for additional heat and moisture treatment of products.

The technical task of the utility model is to obtain a gas-porous cemented concrete of natural hardening (aerated concrete) with an average density in the dry state in the range of values from 110 to 170 kg / m ³ by creating a new composition of the cellular concrete mixture in which the reduction in the number of dry components necessary to achieve the specified density level compensated by an increase in the expansion ratio of the mixture.

 The technical result is the discovery of new consumer properties of aerated concrete, which consists in the possibility of its use as an effective building insulation, as a flame retardant heat-insulating material of mineral origin, devoid of the main disadvantages of foam polymer insulation - combustibility, toxicity, vulnerability to the effects of real operational factors, a limited period of effective use etc.

 Another technical result is the production of artificial porous stone of low density, suitable for use as an effective building insulation, economically less expensive than the technology of autoclaving gas silicates, by way.

An additional technical result is the possibility of producing non-combustible mineral building insulation as a commercial product at regional mini-enterprises with affordable for small businesses, the level of investment, as the only alternative to technical watts obtained today in capital-intensive industries with a high concentration of production capacities and an appropriate level of investment.

 Given the real thermophysical characteristics of common types of building insulation (thermal conductivity in the range of 0.038-0.050 W / (m-K)), the competitiveness in this regard of aerated concrete directly depends on the possibility of reducing its density to a level that provides commensurate performance. Other properties of cellular concrete as a full-fledged building material of inorganic origin — fire resistance, safety for humans and the environment, cheapness and ease of preparation — are a convincing basis for the use of effective cellular concrete insulation in mass construction.

Heat-insulating cellular concrete of an open porous structure of medium density in the dry state from 110-170 kg / m ³ in the form of small-sized slabs or blocks can be used for thermal insulation (warming) of flat building surfaces, as well as a moisture-accumulating element of walls and ceilings.

The essence of the utility model is the modification of the well-known gas-expandable cement cellular concrete (aerated concrete) in the direction of excluding any aggregates from the raw mix for its preparation, while increasing the degree of mixture porosity by increasing the amount of blowing agent per binder unit. A feature of the cellular concrete obtained in this method is the formation of the structure (solid phase) of the material solely due to the crystalline hydrates of the cement clinker, that is, the finished material is actually a porous cement stone. The utility model is implemented using the technology of gas-porous cementitious cellular concrete without additional heat and moisture treatment using intensifying and modifying additives.

 The problem is solved by using a raw material mixture with a subsequent composition of the components to obtain gas-porous non-autoclaved aerated concrete in mass fractions with respect to cement: cement - 1, water-soluble salt - 0.0075-0.175, alkaline component - 0.001-0.05, gasifier - 0.0063-0.0080; water 0.78-0.94.

 In this case, Portland cement grade 42.5 R is used as cement, the water-soluble salt is more preferably calcium chloride, or sodium chloride, or potassium chloride, or a mixture thereof, or iron chloride, or aluminum chloride, less preferably calcium nitrate, or sodium nitrate, or sodium formate, or mixtures thereof, or sodium sulfate or aluminum sulfate, the precursor powder is more preferably ground lime, caustic soda is less preferable, and aluminum paste or aluminum powder is more preferable as a blowing agent, ferrosicilium powder is less desirable.

 At the same time, in order to intensify the setting of Portland cement, the mixture may additionally contain soda ash in an amount of 0.002-0.003 wt.h.

 At the same time, in order to increase the strength of products by reducing the need for mixing water without reducing the mobility of the mixture, it may additionally contain a plasticizer or superplasticizer in an amount of 0.0001-0.05 wt.h.

At the same time, in order to increase the strength of products, the mixture may additionally contain highly active metakaolin in an amount of up to 0.07 parts by weight. At the same time, in order to increase the strength of the products, the mixture may additionally contain limestone flour in an amount up to 0.03 parts by weight.

 At the same time, in order to strengthen the structure of cement stone by initiating the formation of an additional amount of calcium hydrosilicates as a result of the reaction of silicon dioxide with lime, such as the source of which is cement hydration, and additionally introduced, the mixture may additionally contain silica fume in the amount of 0.04- 0.10 parts by weight

 At the same time, in order to exclude the appearance and development of shrinkage cracks of products, the mixture may additionally contain polypropylene fibers in an amount of 0.003 to 0.005 parts by weight.

 At the same time, in order to increase the strength of the material in the early stages of hardening, the mixture for its preparation may additionally contain a colloidal suspension of two-water gypsum, made on the basis of semi-water gypsum in an amount of 3 to 5 grams of semi-water gypsum per 1 gram of blowing agent.

 The feasibility of choosing a particular reagent as a component of the mixture, or the use of one or another additive, depends on the type and origin of cement, the mineralogical composition of clinker, the conditions of hardening of products, and also, if necessary, the achievement of certain physical and technical indicators.

 Obtaining aerated concrete of medium density within the stated range is carried out through the use of such an amount of blowing agent that allows you to fill a given volume of forming equipment with a mixture of a given volumetric weight.

At the same time, the following factors are limiting in the number of the main components of the mixture: the content of water-soluble salt in an amount less than 0.0075 parts by weight does not provide the minimum tangible acceleration of the hardening of Portland cement, the excess content of water-soluble salt indicator of 0.175 wt.h. entails the risk of the phenomenon of shrinkage of cellular concrete;

 the alkaline component content is below 0.001 parts by weight does not create sufficient for effective gas formation of the alkalinity of the liquid phase of the mixture, the excess content of the alkaline component level of 0.05 wt.h. leads to an unreasonable proportional decrease in the strength of cellular concrete;

 the content of the blowing agent in an amount less than 0.0063 wt.h. does not allow to achieve porosity of cellular concrete sufficient to ensure the upper boundary of a given range of its density. The content of the blowing agent in an amount higher than 0.0080 wt.h. increases its porosity above the level necessary to maintain the minimum required strength of the material;

 the water content in an amount less than 0.78 wt.h. does not provide sufficient mobility of the cellular concrete mixture, the excess of water-cement ratio of the level of 0.94 wt.h. negatively affects the strength characteristics of the material.

 The formed cellular concrete mass is maintained under natural conditions and hardens due to: a) self-heating of concrete, both as a result of hydration of the cement itself, as well as interaction with it, and between the additives; b) limited heat loss due to increased thermal protection of the tooling (thermal insulation of the molds) and low thermal conductivity of cellular concrete of high porosity.

The array is kept in molds for the time necessary to achieve its strength sufficient to free the array from rigging and cut into products of a given shape (at least 6:00), and the finished cellular concrete products are subjected to technological sludge in natural conditions for 7-14 days to achieve their tempering (brand) strength.

 The composition of the raw mix of the declared insulating cellular concrete is illustrated by an example.

 Example 1

 To obtain aerated concrete, Portland cement grade 42.5 R, calcium chloride, quicklime, ground powder and aluminum paste were used. Aerated concrete mixture was prepared and tested according to DSTU-N B B.2.7-308: 2015 “Guidelines for the manufacture of cellular concrete products”, DSTU B V.2.7-164: 2008 “Thermal insulating products from cellular concrete. Technical conditions. "

All dry components of the mixture were weighed in the required amount. Water with a temperature of 40 ° C and dry components were loaded into a high-speed turbulent mixer according to the following loading sequence: water, calcium chloride, Portland cement, quicklime powder. The formed mixture was mixed for 4 minutes. Next, a pre-prepared aluminum suspension was introduced into the mixture and stirred for 1.5 min. The resulting aerated concrete mixture was poured into a mold measuring 153x121x110cm. The formed cellular concrete array was freed from form-fitting (formwork) a day later, after which the array was wrapped in a polymer film and kept for the purpose of hardening in a production room and at ordinary ambient temperature for 7 days. Subsequently, samples selected according to regulatory requirements were dried to constant weight and subjected to physical and mechanical tests. The test results, as well as other examples of the composition of the proposed and known cellular concrete mixtures (from the materials of patent RU 2120926 and copyright certificate SU 1491857) are shown in Table 1. In the examples given, the average density of the finished material is the total weight composition of dry components - Portland cement, water-soluble salt, alkaline component and blowing agent, as well as the estimated amount of chemically bound water at the rate of 10% by weight of cement.

 The joint presence in the mixture of the proposed composition of these substances in the specified ratio ensures the production of non-autoclaved aerated concrete with fundamentally distinctive characteristics in terms of average density, which ultimately provides the material with thermal conductivity indices necessary and sufficient for its use as additional (effective) thermal insulation of building structures.

 The claimed heat-insulating non-autoclave aerated concrete allows you to expand the scope of cement non-autoclave cement aerated concrete (aerated concrete); expand consumer choice in the market of effective building insulation; to obtain a new heat-insulating building material of mineral origin, suitable for use as a non-combustible effective insulation of building fences, with a set of advantages that are not available for substitute materials.

The advantages of non-autoclave heat-insulating cellular concrete in comparison with autoclave concrete are lower capital and energy consumption of its production, as well as the possibility of organizing such production at small enterprises of a regional level with little technological complexity and investment volume. The advantages of cellular concrete insulation made using the proposed mixture in comparison with substitutes - representatives of the non-combustible tile insulation segment of the building are increased environmental friendliness, resistance to the effects of real operational factors, in particular the absence of destructive effects of moisture, as a result of an almost unlimited useful life.

The products obtained according to the utility model can be used for thermal insulation of building envelopes of buildings and structures, as an insulating element of facade systems of buildings, as a water-absorbing element of building envelopes, and also as an element for construction using elements of full factory readiness.

Table 1

Claims

Formula

1. Heat-insulating non-autoclave aerated concrete of medium density in the dry state from 110 to 170 kg / m ³ containing cement, a water-soluble salt, an alkaline component, a blowing agent and water, characterized in that it contains a blowing agent as a blowing agent, in the following ratio of components, May . h

 - cement - 1;

 - water soluble salt - 0.0075-0.175;

 - alkaline component - 0.001-0.05;

 - gas blowing agent - 0.0063-0.0080;

 - water - 0.78-0.94.

 2. Aerated concrete according to claim 1, characterized in that the cement is Portland cement grade 42.5 R.

 3. Aerated concrete according to claim 1, characterized in that the water-soluble salt is calcium chloride or sodium chloride, or potassium chloride, or a mixture thereof in an amount of 0.02-0.027 wt.h.

 4. Aerated concrete according to claim 1, characterized in that the water-soluble salt is iron chloride, or aluminum chloride in an amount of 0.0075-0.025 wt.h.

 5. Aerated concrete according to claim 1, characterized in that the water-soluble salt is calcium nitrate, or sodium nitrate, or sodium formate, or a mixture thereof in an amount of 0.02-0.027 wt.h.

 6. Aerated concrete according to claim 1, characterized in that the water-soluble salt is calcium nitrate or calcium nitrate, or calcium formate in an amount of 0.02-0.027 wt.h.

7. Aerated concrete according to claim 1, characterized in that the water-soluble salt is sodium sulfate or aluminum sulfate in an amount of 0.01-0.03 wt.h.

8. Aerated concrete according to claim 1, characterized in that the alkaline component is quicklime powder in an amount of 0.01-0.05 wt.h.

 9. Aerated concrete according to claim 1, characterized in that the alkaline component is caustic soda in an amount of 0.001-0.009 wt.h.

 10. Aerated concrete according to claim 1, characterized in that the blowing agent is aluminum paste, or aluminum powder, or ferrosicilium powder.

 11. Aerated concrete according to any one of claims 1 to 10, characterized in that the mixture for its preparation further comprises soda ash in an amount of 0.002-0.003 wt.h.

 12. Aerated concrete according to any one of claims 1 to 10, characterized in that the mixture for its preparation further comprises a plasticizer or superplasticizer in an amount of 0.0001-0.05 wt.h.

 13. Aerated concrete according to any one of claims 1 to 10, characterized in that the mixture for its production additionally contains highly active metakaolin in an amount of up to 0.07 wt.h.

 14. Aerated concrete according to any one of claims 1 to 10, characterized in that the mixture for its production additionally contains limestone flour in an amount up to 0.03 wt.h.

 15. Aerated concrete according to any one of claims 1 to 10, characterized in that the mixture for its production additionally contains silica fume in the amount of 0.04-0.10 wt.h.

 16. Aerated concrete according to any one of claims 1 to 10, characterized in that the mixture for its production additionally contains hydrochloric acid in an amount of 0.015-0.025 wt.h.

17. Aerated concrete according to any one of claims 1 to 10, characterized in that the mixture for its production further comprises polypropylene fibers in an amount of 0.003 to 0.005 parts by weight.

18. Aerated concrete according to any one of claims 1 to 10, characterized in that the mixture for its preparation further comprises a colloidal suspension of two-water gypsum, made on the basis of semi-water gypsum in an amount of 3 to 5 grams of semi-water gypsum per 1 gram of blowing agent.