RU2287505C1 - Molding mixture for foam concrete - Google Patents

Abstract

FIELD: building materials, raw mixtures.

SUBSTANCE: molding mixture for foam concrete comprises the following components, wt.-%: Portland cement, 30.0-77.0; metal-containing carbon nanotubes, 0.001-2.5; frothing agent, 0.4-0.7, and water, the balance. The mixture can comprise 0-30 wt.-% of quartz sand as a filling agent additionally. Invention provides decreasing energy consumptions in manufacturing building articles, minimal shrinkage and enhancing heat-physical properties of heat-insulating articles. Invention can be used in manufacturing foam concrete articles of different designation.

EFFECT: improved and valuable technical properties of mixture.

2 cl, 1 tbl, 1 dwg, 4 ex

Description

The invention relates to building materials, namely to raw mixes, and can be used in the production of foam concrete products for various purposes.

Known raw mix for the manufacture of lightweight concrete (copyright certificate SU No. 1588734, 1990), consisting of: Portland cement 12.0-20.0, slag stone aggregate 47.0-52.0; refractory production waste 8.0-13.0; ash of power plants 5.0-9.0; wood saponified resin 0.035-0.45; metallurgical lime waste 1.0-3.0; the rest is water.

The disadvantage of this mixture is its high thermal conductivity, since slag pumice gravel is used, which has a high density.

The closest analogue to the claimed invention is a raw material mixture for foam concrete, including, wt.%: Cement 33-77, carbon clusters of the fulleroid type 0.0001-2.0, water - the rest, as well as a foaming agent (RF patent No. 2233254, 27.07. 2004).

An object of the invention is to reduce the energy consumption of building products and the creation of a molding mixture with a composition that allows to reduce shrinkage to a minimum and increase the thermal properties of thermal insulation products.

The essence of the invention lies in the fact that the molding mixture for foam concrete containing cement, water, a foaming agent, carbon nanotubes, contains carbon nanotubes metal-containing in the following ratio of components, wt.%: Cement 30.0-77.0, foaming agent 0.4-0 , 7, carbon metal-containing nanotubes metal-containing 0.001-2.5, water - the rest. The mixture may additionally contain a filler - silica sand 0-30 wt.%.

The introduction of a foaming agent into the structure of the cement stone creates hollow regions in the form of bubbles with air; these nanotubes are located on the surface of the bubbles and serve as a framework for the formation of cement crystalline hydrates, i.e. strengthen walls of hollow areas. The walls of the bubbles become strong and do not shrink, and also increase thermal insulation properties. The use of quartz sand increases the density of the mixture and strength.

The drawing shows the microstructure of foam concrete samples obtained with and without the use of carbon metal-containing nanotubes.

It is clearly seen that the microstructure of the foam concrete sample in the presence of an additive has become more uniform, the pore size is approximately the same, as a result, the effect of "collapse" of air bubbles does not occur, and the thermal conductivity of the structure decreases. The claimed invention is illustrated by examples.

Example 1

Cement is poured into the apparatus for the production of foam concrete mixture, then water is poured. In a separate container, foam is prepared by mixing a foaming agent and water. After that, the foam is combined with a cement solution, carbon metal-containing nanotubes are added and mixed in a gentle mode (up to 600 rpm). Then, the resulting mixture is fed under pressure into metal molds of cubes with a side of 100 mm. Carbon metal-containing nanotubes are used obtained from a mixture of polyvinyl alcohol with copper chloride (I) or (II), taken in molar ratios (20-1): 1, heated to 300 ° C. Examples 3 and 4 - samples were obtained, as in example 1, but with a different content of nanotubes.

Example 2 (control)

Samples were obtained, as in example 1, but in the absence of carbon metal-containing nanotubes.

The prepared molding mixture has minimal shrinkage after laying it in the mold, since carbon metal-containing nanotubes have a high specific surface and high strength properties. In addition, metal-containing nanoparticles are a structure-forming element, as a result of which, being located on the surface of the bubble film, they are a material comparable in size, a “template”, for further arrangement of the main structure-forming elements of cement binder crystalline hydrates, which also increases the resistance of the foam concrete mixture and helps to reduce shrinkage , increase the strength of foam concrete and, as a consequence, increase the coefficient of thermal conductivity.

For experimental verification of the effectiveness of the claimed mixture were prepared four composition of the molding sand. All formulations, including the prototype, are given in table 1. The test results of each composition, namely the values of the shrinkage of the mixture after holding the products in natural conditions for 24 hours, the coefficient of thermal conductivity at 28 days after natural hardening, are given in table 1.

Table 1
Comparative characteristics of foam concrete samples Composition No. 2 (C) one 3 four The composition of the samples wt.% cement - 68.3 blowing agent - 0.43 water - 31.27 cement - 68.3 foaming agent - 0.43 carbon metal-containing
nanotubes - 0.001 water - 31.269 cement - 68.3 foaming agent - 0.43 carbon metal-containing nanotubes - 0.025 water - 31.245 Cement - 68.3 Foaming agent - 0.43 carbon metal-containing nanotubes - 0.05 Water - 31.22 Shrinkage of samples,% 3.8 1,1 1.3 0.9 The average density, kg / m ³ 330 300 300 300 The coefficient of thermal conductivity, W / K · m 0,065 0,052 0,049 0,045

From the above data it is seen that the foam concrete products obtained from the proposed mixture compositions have low shrinkage during hardening and reduced thermal conductivity. Using the invention allows to obtain foam concrete products of non-autoclave hardening without the use of such an energy-intensive process as autoclave processing.

Claims (2)

1. The molding mixture for foam concrete containing cement, foaming agent, water and carbon nanotubes, characterized in that it contains carbon nanotubes metal-containing, in the following ratio, wt.%: Cement 30.0-77.0 Foaming agent 0.4-0.7 Specified Nanotubes 0.001-2.5 Water Rest 2. The molding mixture according to claim 1, characterized in that it additionally contains 0-30 wt.% Aggregate - quartz sand.