How to adjust the plasticity of raw materials?

In order to overcome some shortcomings caused by raw materials in the production process, it is often necessary to increase or decrease its plasticity to meet the requirements of the technical conditions of the product.

(1) Ways to improve the plasticity of raw materials

In the production of sintered tiles, weathering, aging and batching methods are generally used to improve the plasticity of raw materials such as clay, shale and coal gangue.

①weathering

In order to destroy the natural structure of clay, shale and coal gangue, it is subjected to atmospheric action.——Weathering and freezing, especially in the use of difficult to loosen the colloidal clay and fat clay is more necessary. The purpose of this is to make the natural wet raw materials disintegrate (mainly volume change) and become fine particles under the repeated action of wind, rain, sun, snow, water absorption, drying, cold and heat, expansion and contraction. At the same time, many chemical and physical changes occur in the weathering process of raw materials, causing organic matter to decay, soluble salts to be leached, and sulfides to be oxidized. The original composition is changed and the technical performance of the raw material is improved.

The raw materials of some brick factories in China have been weathered and their performance has been significantly improved. For example, the raw materials of the first brick factory and the second brick factory in Changsha, Hunan Province are mountain soil. The newly excavated raw materials have coarse particles, low plasticity, difficult molding and poor quality of finished products. However, after one year of weathering, the particles become finer and the plasticity is greatly improved, thus fully meeting the production requirements. Therefore, both factories emphasize the use“alternate year soil”,"The next year" is a winter to spring after a freeze-thaw. It should be noted that the water present in the air will expand in volume after freezing.9%, Producing huge expansion stress, the effect of thinning the raw material particles is obvious.

However, weathering often makes the natural moisture content of raw materials greatly increased, easy to make crushing, crushing, screening equipment and silo and other sticky blocking.

②Aging

Aging is the broken, crushed and water after the raw materials stored in a closed room. in the water“splitting”Under the action of the raw materials to further loose, uniform water distribution, so that the content of organic and inorganic components of the colloid increased, so as to improve its plasticity, improve its technical performance.

Raw material of a certain factory3After the day aging, the dry strength of the brick blank is increased.50%.

• Refinement

Fine grinding of raw materials is good for improving plasticity. That is, no plastic raw materials, if fine grinding, can also obtain a certain degree of plasticity, but do so need to invest a larger cost.

• Ingredients

In actual production, high plasticity of raw materials are often mixed with low plasticity of raw materials, with plasticity of more appropriate raw materials.

When using this method, we should attach great importance to the uniformity of the distribution of two kinds of raw materials with different plasticity in the mixture, because the raw materials with low plasticity are easy to loosen in water than the raw materials with high plasticity.

If the mixing is not uniform, the green body after molding is not homogeneous, which will cause a lot of waste loss in the process of drying and firing.

⑤ Steam (hot water) heating

The mud is heated with steam (hot water) and formed by hot extrusion. After the steam (hot water) heats the mud, the moisture is evenly distributed in a short time and penetrates into the voids of the mud particles at a faster rate, thereby greatly improving the plasticity of the mud.

⑥ Vacuum treatment

The air contained in the mud will reduce its plasticity, causing blistering, delamination and cracking of the formed body. The use of vacuum extrusion molding can not only overcome the above defects, improve the plasticity of the clay, but also increase the strength and compactness of the green body.

(2) Ways to reduce the plasticity of raw materials

Generally, sand, slag and fly ash are mixed into raw materials.and clinker powder (e. g. waste brick powder)and other barren materials to reduce their plasticity. Especially after the internal combustion brick-burning method has been widely used, the best effect is the admixture of combustible components in the raw materials, which is both a lean agent and an internal fuel.

If sand is mixed, quartz sand is generally selected, and limestone sand is not suitable, because the incorporation of limestone sand will reduce the quality of bricks.

When mixing all kinds of barren materials into the raw materials, there is also the problem of whether the mixed materials are evenly distributed in the raw materials. Experience has proved that if the admixture is not evenly distributed in the raw material, it will bring bad consequences to the product, reduce the strength and serious.WhenCracks are generated.