CZ309348B6 - Clay mixture for producing fired or unfired building products or materials - Google Patents

Abstract

Clay mixture for producing fired or unfired building products or materials containing brick clay and/or kaolinite clay and/or clay with carbonates and clay, additives, fillers and water, and also contains alkali-activated hybrid cement of 10 to 80% by weight of the total mixtures.

Description

Clay mixture for the production of fired or unfired building products or materials

Field of technology

The invention relates to a clay mixture for the production of fired or unfired building products or materials.

Current state of the art

Clay is one of the oldest known building materials. Products made of this material are used in the construction industry in both unfired and fired versions.

The return of traditional building materials, so-called earth building, such as adobe bricks or clay plasters, is motivated by the fact that thick walls made of earth accumulate heat in winter and, on the contrary, create a cooler environment in summer. A clay mixture usually consists of clay, sand, loess and water. Unfired clay building materials also have their disadvantages such as washability, friability and mold formation.

Products made of unburnt brick clay are among the most used building materials. These products, mostly in the form of bricks, brick blocks, blocks, etc., are made from brick clay, the so-called brick shard, which is mostly composed of clay, clays, slag, lightening agents and water.

One of the important characteristics of fired brick clay products as a building material is compressive strength, especially for products such as fired brick clay products containing lightening agents to increase the heat insulating properties of fired brick, which is currently used mainly in the form of brick blocks or blocks with cavities. However, the lightening of such masonry elements results in a reduction of their strength, which has a negative effect on the resulting load-bearing capacity of the masonry wall.

The aim of this invention is to improve the characteristics of building products or materials made of fired and unfired clay, especially in terms of compressive strength and while maintaining especially their thermal insulation properties.

The essence of the invention

The stated objective is achieved by a clay mixture for the production of fired or unfired construction products or materials, which contains brick clay and/or kaolinite clay and/or clay with carbonates and clay, additives, fillers and water, the essence of which is that it contains alkaline activated hybrid cement in the amount of 10 to 80% by weight of the total amount of the mixture.

The mixture according to the invention will significantly increase the compressive strength of the products, especially fired bricks in the form of brick blocks or blocks with cavities, while the thermo-technical parameters of the products will be preserved. In the case of fired clay products, the mixture according to the present invention allows to reduce the temperature and firing time of the products, which represents an advantageous reduction in production costs by reducing the energy consumption for firing. Reducing the firing time will also reduce CO2 emissions, increase the productivity of ceramic kilns and reduce the rate of shrinkage during the drying and firing times, thus reducing the formation of cracks.

- 1 CZ 309348 B6

An example of the implementation of the invention

For the preparation of one sample, the brick mixture used in the Pezinsk brickyard was used as the basic mixture for the production of products from brick clay. Alkaline-activated hybrid cement was added to this brick-making mixture in an amount of 15% by mass, relative to the total amount of the mixture. The amount of water in the brick mixture was at the level of 19.4% mass. This sample is further referred to as 15H in the text.

To prepare the next sample, alkaline-activated hybrid cement was added to the brickwork mixture, the same as in the previous case, in an amount of 30% by mass, relative to the total amount of the mixture. This sample is referred to in the text as 3OH.

In order to compare the effect of the added alkali-activated hybrid cement, reference samples, hereinafter referred to as REF, were also prepared at the same time. These reference samples were prepared only from the basic mixture, i.e. the brick-making mixture without the addition of alkali-activated hybrid cement.

In all three cases, the samples were prepared as follows. By homogenization and mixing, a "brick dough" was prepared from the raw materials, which was left to rest for 12 to 14 h, and then test samples were made from it by pressing at a pressure of 8 to 12 MPa. The test samples thus produced were placed on the grids for the time indicated in the table below as the hydration time. A series of samples were fired at temperatures of 700, 800 and 900 °C. Firing was carried out in an electric laboratory furnace with a regulated firing mode. The heating rate was 5 °C/min and the holding time at the given firing temperature was 120 min.

The table shows the monitored physical properties of the REF, 15H, 30H samples after firing at 700 °C, 800 °C and 900 °C, respectively. after firing and hydration in the case of 15H, 3 OH samples.

Sample Hydration time [hours] Am weight loss [%] Density [g/cm ³ ] Open porosity [%] Compressive strength [MPa] REF - 700 °C 25.97 1.6501 36.5 11.53 15H-700°C 69 23.32 1.7042 35.16 >26.11 30H - 700°C 44 21,27 1.7974 31.59 >26.11 REF - 800 °C 27.31 1.6327 38.12 14,15 15H- 800 °C 93 23.85 1.6998 36.79 >26.11 30H- 800 °C 68 21.52 1.7898 33.86 >26.11 REF - 900 °C 27.05 1.5935 42.07 15.02 15H-900°C 45 23.79 1,695 39.67 18.69 30H - 900°C 20 21.48 1.7566 38.2 >26.11

The compressive strength of all fired samples was determined under the same testing conditions on a LOYD Instruments LR5K plus device (with a maximum load of 5000 N). In the case of samples with alkali-activated hybrid cement, it was not possible to determine the exact value of the strength, because the maximum force that can be achieved by the device (5000 N) was not sufficient to break the test bodies of the samples.

The strength of reference samples, REF, from brick clay increases slightly with firing temperature. At a temperature of 900 °C, a strength of 15 MPa was achieved (a value comparable to the strength of traditional bricks on the market). The commonly used firing temperature of classic bricks is -900 °C. The REF - 900 °C sample can therefore be considered as a reference for determining the influence of the addition of alkali-activated hybrid cement on sinterability and mechanical properties. All samples with the addition of alkali-activated hybrid cement have a strength of at least 74% higher than REF - 900 °C.

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A mixture for the production of burnt roofing was prepared, where bricklayer's clay with 20% by mass, ground recycled burnt roofing and alkaline activated hybrid cement in the amount of 15% by mass were used for the total amount of the mixture. Firing took place in a tunnel furnace fired with natural gas at a temperature of 900 °C. the consumption of natural brick raw material was reduced by 20%, the bending strength remained the same as that of a traditionally fired covering, the CO2 emission was reduced by min. by 5% and the scrap rate of production decreased by min. by 30% due to smaller volume changes.

A mixture was prepared for the production of fired covering, where brick clay with 10% by mass, saliva with a carbonate content of over 30% and alkaline activated hybrid cement in the amount of 10% by mass were used for the total amount of the mixture. Firing runs in a tunnel furnace fired with natural gas at a temperature of 900 °C. The consumption of high-quality brick clay was reduced and there were no volume changes of the product due to the effect of the alkali-activated hybrid cement.

A mixture for the production of ceramic paving was prepared, where kaolinite clay with 10% by mass, recycled ceramic tiles and alkaline activated hybrid cement in the amount of 10% by mass were used for the total amount of the mixture and the firing took place in a roller kiln at 800 °C. Significantly reduced energy consumption min. by 20%, the paving properties reached a hardness of 5 to 8 on the Mohs scale as in traditional production, while the productivity of the kiln increased by at least 5 to 10%.

A mixture was prepared for the production of clay plaster, where clay, sand, straw cuttings and alkaline-activated hybrid cement were used in the amount of 15% mass, for the total amount of the mixture. Clay plaster was used in the exterior and interior, improving the strength, adhesion to the wall, which made it possible to increase the roughness of the plaster for better heat-insulating properties, reducing the volume changes and reducing the number of cracks, reducing the washability of the exterior plaster and the friability of the interior plaster, while the antibacterial effect of alkaline-activated hybrid cement was manifested by lower mold formation.

A mixture of brick clay with 15 to 30% mass of alkali-activated hybrid cement was prepared. Alkaline-activated hybrid cement contains alkaline salts that improve the thermal energy accumulation of the final product, for example brick blocks produced by extrusion. Firing took place in a tunnel kiln at a temperature of 700 to 900 °C in order to achieve the highest bulk density with the lowest possible porosity. Bricks were used as a ceramic battery to store thermal energy with subsequent regulated output via a heat exchanger.

A mixture of clay with a CaCO content above 30%, e.g. saliva or limestone with a CaCO content, + MgCCh above 50%, was prepared and used as a replacement for part of the fine sand in the fireproof plaster with an admixture of 20 to 80% by mass of alkali-activated hybrid cement. This mixture is suitable for the protection of steel, wooden and concrete structures.

During a fire reaching a temperature of around 800 °C, the carbonates decompose and release diffusible CO2, which has an extinguishing effect, multiplying the effect of the mixture. Free CaO + MgO reacts with alkali-active hybrid cement and fine sand to solid compounds with additional structural protection.

The given examples of execution serve only to illustrate this invention. These examples do not describe all possibilities, combinations and ranges in the composition of the mixture according to the present invention, which can be prepared in the sense of the essence of the present invention.

Claims (1)

1. A clay mixture for the production of fired or unfired building products or materials, containing brick clay and/or kaolinite clay and/or clay with carbonates and clay, additives, fillers and water, 5 characterized by the fact that it contains alkaline activated hybrid cement in an amount 10 to 80% by weight, based on the total amount of the mixture.