The raw material composition of dry-mixed mortar. Dry-mixed mortar is also called premixed (dry) mortar, also known as dry powder, dry mix, etc. It is a semi-finished mortar made by accurate ingredients and uniform mixing in the factory. Just add water and stir at the construction site to use. There are many types of dry-mixed mortar, and its composition is relatively complex. In summary, it is composed of cementing materials, fillers, mineral admixtures, admixtures and other materials. (1) Cementing material. Commonly used cementing materials for dry mixed mortar are: Portland cement, ordinary Portland cement, high alumina cement, calcium Portland cement, natural gypsum, lime and mixtures of these materials. Portland cement (usually type I) or Portland white cement are the main binders. Floor mortar usually also requires the use of some special cement. The amount of cementing material accounts for 20% to 40% of the dry mix product quality. (2) Filling. The main fillers of dry mixed mortar are: yellow sand, quartz sand, limestone, dolomite, expanded perlite, etc. These fillers are crushed, dried, and then screened into three categories: coarse, medium, and fine. The particle size is: coarse filler 4mm ~ 0.4mm, medium filler 0.4mm ~ 100mm, and fine filler below 100mm. Products with very small particle size need to use fine stone powder and sorted limestone as aggregate, and the limestone should be as white as possible. Ordinary dry mortar can use either crushed limestone or dried and screened sand as aggregate. If the sand is of sufficient quality for use in high-grade structural concrete, it must meet the requirements for the production of dry mixes. The key to producing dry-mixed mortar with reliable quality lies in the control of raw material particle size and the accuracy of the feed ratio, which is achieved in the automatic production of dry-mixed mortar. (3) Water-retaining and thickening materials. Mortar thickening powder is commonly used as a water-retaining and thickening material in dry-mixed mortar. It achieves the purpose of thickening and retaining water through physical adsorption of water molecules. It is safe, non-toxic, non-radioactive and non-corrosive. (4) Mineral admixtures. The mineral admixtures of dry mixed mortar are mainly: industrial by-products, industrial waste and some natural ores, such as slag, fly ash, volcanic ash, fine silica powder, etc. The chemical composition of these admixtures mainly contains calcium oxide. Silica hydrochloric acid is soluble in water and has only high activity and hydraulic hardness. (5)Admixtures. Admixture is a key part of dry-mixed mortar. The type and quantity of admixtures and the adaptability between admixtures are related to the quality and performance of dry-mixed mortar. In order to increase the workability and adhesion of dry-mixed mortar, improve the crack resistance of the mortar, reduce the permeability, and make the mortar not suitable for bleeding and separation, thereby improving the construction performance of dry-mixed mortar and reducing production costs.
The production process of dry mixed mortar The production process of dry mixed mortar includes preparation of raw ingredients, drying and screening of quartz sand, and possible crushing and grinding of limestone. Cement and fillers are generally fed into raw material silos pneumatically, and additives can be manually thrown into small raw material silos or tanks through a hoist. Most of the current production forms are vertical "tower" shapes. In the new dry-mixed mortar production plant, a unique powder flow technology is used for feeding, and the original horizontal feeding equipment is abandoned. It has the characteristics of large capacity, high precision and good flexibility.
Comparison with traditional mortar Traditional mortar is mixed and used at the construction site, which requires a certain amount of space, and the powder layer will cause certain environmental pollution to the site. At the same time, the materials are piled on the mud floor in the open, resulting in more impurities, including The amount of mud is large, the ingredients are inaccurately measured, the workability is difficult to control, and the aggregate screening is random, resulting in high void ratio, large dry shrinkage rate, and poor impermeability of the mortar, which may eventually lead to voids in the plastering of the exterior wall. Drums, cracks and penetrations occur. In comparison, all the ingredients of dry-mix mortar are accurately measured and fully mixed in the production workshop, and then water is added and mixed at the site according to the determined water-cement ratio. It overcomes many problems such as inaccurate metering of ingredients, environmental pollution, and excessive mud content. It has the characteristics of low bleeding, low dry shrinkage, strong bonding, crack resistance and permeability, and can basically meet the requirements of new wall materials. .
Socioeconomic benefits Dry-mixed mortar is currently a new product with the fastest development and great development potential in the field of building materials. In Europe, there are almost two dry-mix mortar production plants for every city with a population of 1 million. Only a small part of the gypsum and mortar used in construction is still mixed and prepared on site. Calculated according to this standard, taking Jiangsu Province as an example, the province has a population of 74 million and requires at least 148 dry-mix mortar production plants to meet market demand. At present, there is almost no large-scale dry-mix mortar production plant in Jiangsu. The development of dry-mix mortar products has only just begun. In the next few years, the growth rate of domestic dry-mix mortar will be unprecedentedly high.
Now, the production, promotion and application of domestic construction dry mortar has formed a new industry, creating new growth points for residential industrialization. Dry mortar generally uses industrial waste such as fly ash as raw materials, and the recycling of waste has brought huge benefits to society. Since dry-mixed mortar is a revolution against traditional mortar, it is inevitably hindered by the forces of habit. Therefore, government decision-making and support are very important. With the collaborative efforts of scientific research, production, and construction, we believe that dry-mixed mortar production will be a new industry. Industry will take root, blossom and bear fruit.
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