Brick Clay

Overview

Brick Clay is composed of clay minerals with a diameter of <0.0039mm and a recrystallized diameter of <0.01mm, which are loose and have not yet solidified into a rocky soil-like sediment. It contains clay minerals, detritus and various associated minerals. Clay minerals are generally: kaolinite, sericite and dolomite; debris and associated minerals are: free sandy quartz, nodule clumps or dispersed calcite, dolomite, rhodochrosite, pyrite, limonite, pyrite, gypsum and hard gypsum and organic matter.

The main chemical composition of masonry clay: Al2O3, SiO2, Fe2O3, CaO, MgO, K2O, Na2O, moisture, organic matter, etc., the composition is more complex, but as long as its physical and chemical properties in line with the requirements, allowing a wide range of chemical composition changes. Clay for bricks and tiles has plasticity after mixing with water, maintains its original shape after drying, has rock-like hardness after baking, and has the properties of water absorption and adsorption. There are many types of clay that can be used for firing bricks and tiles, and the varieties required are also wider. Clay used for firing brick and tile, according to the different impurities contained in the clay, can be divided into common clay, sandy clay, iron clay, lime clay, loess, red clay and so on. In addition, clay shale or gangue can also be fired bricks and tiles.

Two, general industrial requirements

Brick clay, as the name suggests, is mainly used for firing bricks, tiles, in the construction industry is a traditional, dosage, wide range of industrial and civil construction materials. Despite the increasing number of new building materials, but it can not replace the traditional brick, tile, the vast majority of rural areas in particular. At present, China has no unified quality requirements and technical standards for brick clay raw materials, only general industrial indicators, including: chemical composition, particle composition, plasticity, impurities, moisture content and color. In general, where in the existing processing technology conditions, can be made into bricks, tile products of all the utilized clay, can be called brick clay.

1. Chemical composition of masonry clay

Brick, tile clay chemical composition and allowable fluctuations in the range of Table 3-28-1.

Table 3-28-1 chemical composition of masonry clay

2. Particle composition of masonry clay

Particle composition of the clay has a greater impact on the clay molding, drying. Domestic particle composition of clay is generally divided into three levels: clay level, particle size <0.005mm; dust or dust level, particle size between 0.005 ~ 0.05mm; silt or sand level, particle size > 0.05mm. Clay type and the content of each particle level is shown in Table 3-28-2.

Table 3-28-2 Clay type and content of each particle level

The clay type and content of each particle level

The clay type and the content of the particle level

There are many fine particles of fertilizer clay, clay, clay, and clay. More fine particles of fat clay and clay suitable for the production of tiles and thin-walled hollow products; sandy clay and clay suitable for the production of ordinary bricks. General masonry clay particle composition and content of the range of Table 3-28-3.

Table 3-28-3 general masonry clay particle composition and content

3. Plasticity of masonry clay

Plasticity is the basic performance of the clay, mainly depends on the nature of its solid and liquid phase, such as the solid phase of the chemical properties, dispersion, particle content and shape, etc., for the same kind of For the same kind of clay, the level of plasticity still depends on the type and quantity of adulteration and liquid. According to the plasticity index size, can be divided into three types of clay: high plasticity clay, plasticity index>15; plasticity clay, plasticity index 7 ~ 15; low plasticity clay, plasticity index <7.

General brick clay and sandy clay, plasticity index should be greater than 7. Because of the tile body is thin, the shape of the brick is more complex, the tile clay is more than the brick clay requirements are high, not only to fine particles, less impurities, plasticity index correspondingly should be greater than 7. Less impurities, plasticity index should be higher accordingly.

4. Dry shrinkage (air shrinkage)

Dry shrinkage refers to the shrinkage of clay blanks after air drying. The dry shrinkage of clay is directly proportional to the plasticity index, the general length shrinkage of clay is between 1.5% and 15%, while the clay used for bricks and mortar, its dry shrinkage is 3% to 12%.

5. Firing shrinkage

Completely dry clay products in the firing, the clay fusible substances melted into the glass phase material filled with particles in the interstices, resulting in the contraction of the volume of the products, known as firing shrinkage. Masonry clay firing shrinkage is generally 2% to 8%.

6. refractoriness

Refractoriness refers to the clay in the baking process began to soften the melting temperature. The production of masonry products generally use fusible clay with a refractoriness of less than 1350 ℃.

7. Other factors affecting product quality

Other factors affecting product quality mainly refers to the influence of common minerals or impurities in the clay, generally the following.

(1) quartz in the clay in the form of loose particles, or the formation of interlayers, lenticular body, quartz can reduce the plasticity of the clay, reduce the drying shrinkage.

(2) alumina often exists in the form of aluminosilicate minerals. more Al2O3 content, the clay roasting temperature is high, and refractoriness is also high.

(3) iron oxide Common minerals are limonite, aqueous hematite and so on. Iron oxide in clay is a flux, but also the coloring agent of clay. When iron oxide is roasted under oxidizing or reducing conditions, the products are red or gray-black to black, respectively.

(4) calcium oxide, magnesium oxide to carbonate (calcite, dolomite) minerals endowed with clay, powder or crumbs to nodule agglomerates. Dispersed carbonates can reduce the refractoriness of the clay, increase the firing contraction, weaken the coloring power of iron, if the presence of fragments or nodules, after roasting to generate quicklime, hygroscopicity into quicklime, thereby expanding the volume of the product to blow up.

(5) potassium oxide, sodium oxide often feldspar particles state in the clay. Feldspar can be regarded as a melting agent and can reduce the refractoriness of clay.

(6) organic matter mainly formed by plant decay, it makes the clay coloring, fired products increased porosity.

Brick clay is mostly locally sourced, there is no requirement for mining technical conditions, the general test items include the following. ① basic chemical analysis: SiO2, Al2O3, Fe2O3; ② combination of analysis: SiO2, Al2O3, Fe2O3, CaO, MgO, burn loss, K2O, Na2O, SO3; ③ physical properties test: particle size analysis, plasticity index determination, pottery test.

Three, brick clay resources and development and utilization

China's brick clay resources are rich, widely distributed throughout the country. From the distribution characteristics, Northeast and North China to yellow loam, Northwest and some parts of North China to loess, South to red loam. The main layer is the loose clay mineral layer of the fourth system, and the thickness varies greatly. China's clay deposits can be divided into two categories, residual clay and sedimentary clay, according to the generation conditions. Quaternary clay is mainly residual clay, residual clay is called primary clay, clay minerals piled up in situ, is the main type of clay used for bricks and tiles. Sedimentary clay, also known as secondary clay, which contains clay minerals by handling and then deposited, mainly refers to the Quaternary before the formation of clay, such as clay shale, gangue, etc..

Clay brick and tile products is China's current large-scale production of wall materials, brick and tile with a great demand for clay, in line with the local materials, the principle of nearby sales, the production of ordinary brick and tile manufacturers all over the country, the main mining of the Quaternary loose clay layer. With the development of science and China's requirements for the protection of arable land, new wall materials are being promoted, and gradually will replace part of the loose clay mining, enterprises should actively work toward this, the more mature technology: clay shale, gangue, fly ash and other production of wall materials, technical specifications and industrial requirements can be referred to the relevant manufacturers indicators. In addition, in the lack of soil and sand in the mountains, hills, beach areas can be sand production gray sand brick. The main process is to take 85% of the fine sand, add 15% of the lime, and then add a small amount of coagulant with water mixing, after ablation after pressing molding, and then high-pressure saturated steam maintenance into. This brick production cost is low, good quality, high strength, can meet the requirements of 8 to 12 layers of brick wall construction.

Henan brick clay resources amounted to hundreds of millions of cubic meters, mainly in the Quaternary in the Pleistocene and the upper Pleistocene. The middle Pleistocene clay is brownish-red and brownish-yellow, and the upper Pleistocene is grayish-yellow and brownish-yellow clay and sandy clay. There are generally no or few gravel layers and calcareous nodule interlayers within the ore body. The thickness of the ore body is large, up to 10-30 m in the plain area and 2-10 m in the hilly area, and the ore body has no cover layer and is exposed. Clay quality varies greatly, according to the Hebi City, the main minerals contained in the clay are: kaolinite, illite, montmorillonite, quartz, feldspar, calcite, iron-containing minerals and so on. Chemical composition: SiO2 is 57.6%～71.5%, Al2O3 is 10.76%～13.98%, Fe2O3 is 4.8%～5.23%, Na2O+K2O is 1.41%～4.16%, SO3 is 0.042%～0.11%. Liquid limit is 25.5%~34.2%, plastic limit is 16%~21%, plasticity index is 9.3%~15%, which is in line with the general indicators of bricklaying clay.

Henan Province, brick and tile clay products manufacturers scattered, according to the 1998 data, the province's state-owned, collective, individual brick and tile products enterprises 3,233, the annual consumption of 30.85 million m3 of clay resources, the production of bricks 60.16 billion, 2.202 billion pieces of tiles, the annual gross industrial output value of 824.5 million yuan, employment of 111,700 people, the development of the national economy has a non-negligible impact, especially the vast rural areas of Henan Province, the impact of the countryside, especially in the production of bricks and tiles. The impact of the majority of rural areas in Henan Province, in particular, still use clay bricks and tiles as building materials, the market is very broad. Application of new materials to make wall brick manufacturers also have some, most of the coal mines, power plants discarded gangue, fly ash and other waste materials.