Dry mortar refers to the dry screening of the aggregate (such as quartz sand), inorganic cementing materials (such as cement) and additives (such as polymers) and a certain percentage of physical mixing made of a granular or powder , In the form of bags or bulk shipped to the site, add water after mixing can be used directly with the material. Also known as mortar dry powder, dry mix, dry mix powder, some building adhesives also belong to this category. Dry mortar in the construction industry to play a thin layer of bonding, liner, protective and decorative role, construction and renovation works are widely used.
At present, the main dry mortar varieties:
Finishes categories: interior and exterior wall putty, decorative color powder, powder coating.
Bonding categories: porcelain plate adhesive, sealing agent, insulation board adhesives;
Other functional materials: dry mortar, self-leveling material, repair mortar, hardening the ground, and so on:
Compared with the mortar formulated in the construction site, dry mortar has the following advantages:
(1) stable and reliable quality, to meet the different functional and performance requirements, improve project quality
(2) improve the efficiency, is conducive to the application of automated construction machinery, traditional construction to change the backward way
(3) of the new wall materials have a strong adaptability, is conducive to the promotion and application of new wall materials "
(4) easy to use, easy to manage
First, the dry powder mortar of raw materials
1, inorganic adhesive: ordinary portland cement, high alumina cement, special cement, gypsum, anhydrous gypsum
2, organic adhesives: redispersible powder is spray-dried by a special water-based emulsion, mainly based on vinyl acetate-ethylene copolymer and the system out of the polymer adhesive. Such powdered organic binders, when mixed with or dispersed in water, return to their original aqueous emulsion state and retain the typical properties and functions of the machine adhesive, and are therefore referred to as redispersible powders. After partial evaporation of water, the polymer particles through the coalescence to form a layer of polymer film, play a role in adhesive. According to the different ratio, using redispersible polymer powder for dry mortar modification, can improve the bonding strength with a variety of substrates, and improve the flexibility and flexibility of mortar, bending strength, abrasion resistance , Toughness, cohesive force and density as well as water retention capacity and workability.
3, aggregate Most aggregates are ordinary particle size quartz sand, limestone sand or white sand, and sometimes also use light aggregate.
4.1 Cellulose ether Cellulose ether is used as a thickener and a water retaining agent. Although the addition rate is very low (0.02% -0.7%), but the role is very important. The cellulose ethers used in the dry mortar are methylhydroxyethyl cellulose ether (MHEC) and methyl hydroxypropyl cellulose ether. Referred to as MC, MC characteristics: adhesion and construction of the two factors that affect each other; water retention, to avoid the rapid evaporation of water, making the mortar layer thickness can be significantly reduced
4.2 Other additives
1, starch ether can increase mortar consistency
2, air-entraining agent through the physical role of the introduction of micro-bubble in the mortar, reducing the density of mortar, better construction. Mainly fatty sodium sulfonate and sodium sulfate addition ratio of 0.01% -0.06%.
3, coagulant use it to get the desired setting time. Commonly used calcium formate, adding the ratio of 0.5% -2.5%
4, retarder is mainly used in gypsum mortar and gypsum-based jointing compound. Mainly acid salts, usually in the 0.05% -0.25%
5, the fiber is divided into long fibers and short fibers. Long fibers are mainly used for reinforcement and reinforcement; short fibers are used to influence the performance and water requirements of improved mortars
6, defoamer is mainly used to reduce the air content of mortar. Mainly with the inorganic carrier on the hydrocarbons, polyethylene glycol and other additives are pigments, thickeners, plasticizers, etc.
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