RU2243190C1 - Method of manufacture of variatropic cellular concrete articles - Google Patents

Abstract

FIELD: manufacture of building materials; manufacture of wall panels and blocks.

SUBSTANCE: foam concrete mix is poured into mold, after which additional ingredient is introduced into mixture and layer is mixed. Used as additional ingredient is foam and cement.

EFFECT: extended functional capabilities; improved quality of articles.

5 cl, 1 ex

Description

The proposal relates to the building materials industry and can be used in the manufacture of enclosing elements - wall panels and blocks, floor and floor slabs, designs of thermal units, etc.

Variatrop products are known [1], characterized by a smooth change in the properties of the material, for example, density, along some geometric axis. Such enclosing elements have a number of advantages in comparison with similar homogeneous products.

Known methods for the manufacture of variastropic cellular concrete products, in which on the surface of the structural element creates a layer of concrete of variable density. This is achieved by various influences — mechanical [2, 3, 4], thermal [5], chemical [6], electrophysical [7], and others. The disadvantage of these methods is that they are more applicable in aerated concrete technology, but not foam concrete, those. there is a certain limitation of technological capabilities.

A known method of manufacturing variatropic cellular concrete products, applicable in the technology of foam concrete and disclosed in the sources [8, 9]. The method consists in the following: a foam concrete mixture is poured into the mold for the manufacture of the product, then an additional ingredient is introduced into the surface layer of the poured mixture, the role of which is a dispersed solid additive, and this ingredient is mixed with the foam concrete mixture in the surface layer of limited thickness, and the product is of variable chemical composition with a compacted surface layer. This method is adopted as a prototype.

The disadvantage of the prototype is that a denser layer is formed near the upper plane of the product, and in some cases this is not optimal. For example, the greatest damage to the roof of the furnace is observed on its lower plane, which is exposed to maximum temperatures, and it is known that the higher the density of concrete of a given composition, the higher its resistance to high temperatures. Since the temperature in the arch of the furnace naturally decreases, with distance from the lower hot plane, the variatropic structure of the arch is optimal, in which the density of concrete on the lower plane is maximum, and higher it gradually, without sharp transition boundaries, decreases. Such an internal structure is also suitable for coating plates with symmetrical reinforcement used in heated residential premises: the increased density of concrete near the lower edge eliminates unwanted accumulation of condensate in the plate and reduces the consumption of finishing materials.

The objective of the proposed method is to develop such a set of operations, techniques and operational parameters, in which a variastropic cellular-concrete enclosing element is produced at the lowest cost, characterized by increased density near its lower plane and a smooth, gradual, decrease in density when moving away from the lower plane.

The inventive foam concrete mixture is poured into a mold intended for the manufacture of a cellular concrete product, then an additional ingredient is introduced into the surface layer of the poured concrete mixture poured into a limited thickness and this layer is mixed with a limited thickness, a feature of the method is that as an additional ingredient use foam. The method is also characterized by optional features:

a) the foam concrete mixture is poured into the mold at 20-90% of the mold depth, after the introduction of the additional ingredient (foam) and its mixing, the volume of foam concrete increases;

b) an additional ingredient - foam - is introduced into the surface layer of the foam concrete mixture no later than 20-60 minutes after pouring the mixture into the mold, until the foam concrete mixture begins to set;

c) for mixing the surface layer of the mixture with foam, metal drive brushes with needles of different lengths are used, which increases the effect of the variatropic structure of the molded product;

d) after introducing the foam and mixing the layer of limited thickness, reduce the thickness of the mixed layer and replace the added additional ingredient - instead of the foam, dispersed solid material, for example cement, is introduced, mixing it with a foam concrete mixture in a surface layer of 5-10 mm thick, due to this, the open surface heavily porous aerated concrete is protected by a layer of expanded concrete;

e) if the furnace coating element is manufactured by the proposed method, the problem of reinforcement arises: the bending element must certainly be reinforced, and the reinforcement should be located in the stretched section zone, i.e. near the lower face of the element, where foam concrete has a high density and, accordingly, high thermal conductivity, which does not allow protecting the reinforcement from overheating and loss of strength, in principle, the coating of the furnace can be made curved, i.e. have the shape of a vault and then it is not necessary to reinforce it, but you cannot make a curvilinear element in the way described above, for this case the following sequence of operations is proposed: perform all the actions provided for in the “essence of the invention” section (with or without optional features), but the product is molded on a flexible pallet with a removable tool holder, the molded product is held for 1-24 hours, then the tool is removed, the product with the pallet is bent to the specified deflection boom and maintained in this Ide before hardening (at normal or elevated temperature). Similarly, it is possible to produce curved elements of prefabricated chimneys or shells for thermal insulation of hot pipelines.

A foam concrete product similar to that produced by the proposed method can, for example, be obtained by repeatedly pouring foam concrete mixes of different densities into the form of layers. However, at the same time, the complexity of the process increases incommensurably, the manufacturing cycle of products is lengthened, and most importantly, sharp transition boundaries still remain between the layers of foam concrete of different densities, which are the site of stress concentration and subsequent structural failure, i.e. it does not become variatropic.

Effect: expansion of technological capabilities in relation to the choice of the structure of the resulting products, reducing the complexity of the process, reducing the production cycle, improving the quality of products.

An example of the method. 1. The composition of the porous solution: Portland cement brand 400 400 kg / m ³ ; fine aggregate 150 kg / m ³ ; silica fume 30 kg / m ³ ; water with a temperature of 40 ° C 130 l / m ³ . 2. The composition of the foam: water with a temperature of 25 ° C 110 l / m ³ ; foaming agent 3,5 kg / m ³ . 3. The composition of the foam: a solution of 100%, foam 60%. The mold is filled with foam concrete mixture at 55% of its depth, then foam is fed into the mold and it is mixed with the foam concrete mixture in a layer with a thickness of 40-50% of the mold depth, mixing is carried out using a device consisting of a drill with different working bodies, which are rods with blades fixed on them, propellers, metal brushes with needles of different lengths. The intensity of mixing (duration, speed of rotation of the working body) vary with the depth of the processed layer. The properties of the resulting varied foam concrete: average density 500-600 kg / m ³ , maximum density in the bottom layer 800-820 kg / m ³ , minimum density 390-430 kg / m ³ , compressive strength 1.5-5 MPa, thermal conductivity 0.2-0.35 W / (mK). The obtained characteristics are quite satisfactory for the designed facility.

Sources of information:

1. Chernov A.N. Variatropia. - M., 1992.

2. Description of the invention to ed. testimonial. 141423, B.I. No. 18, 1961.

3. Description of the invention to ed. testimonial. 175862, B.I. No. 20, 1965.

4. Description of the invention to ed. testimonial. 324150, B.I. No. 2, 1972.

5. Description of the invention to ed. testimonial. 263456, B.I. No. 7, 1970.

6. Description of the invention to ed. testimonial. 263457, B.I. No. 7, 1970.

7. Description of the invention to ed. testimonial. 353921, B.I. No. 3O, 1972.

8. Description of the invention to ed. testimonial. 340536, B.I. No. 18, 1972.

9. Description of the invention to ed. testimonial. 379392, B.I. No. 20, 1973.

Claims (5)

1. A method of manufacturing variastropic aerated concrete products, including pouring into the form of a foam concrete mixture, introducing an additional ingredient into the surface layer of a filled foam concrete, limited in thickness, and mixing this layer, characterized in that foam is used as an additional ingredient, after which foam is introduced and mixed layer of limited thickness, cement is additionally introduced into the surface layer with a thickness of 5-10 mm. 2. The method according to claim 1, characterized in that the foam concrete mixture is poured into the mold at 20-90% of the mold depth. 3. The method according to claim 1, characterized in that the additional ingredient is introduced into the surface layer of the foam concrete mixture no later than 20-60 minutes after pouring the mixture into the mold. 4. The method according to claim 1, characterized in that for mixing the surface layer of the mixture with the foam, metal drive brushes with needles of different lengths are used. 5. The method according to claim 1, characterized in that the product is molded on a flexible pallet with a removable tool holder, the molded product is held for 1-24 hours, then the tool kit is removed, the product with the pallet is bent to the specified deflection boom and held in this form until hardening at normal or elevated temperature.