Abstract：Dry powder mortar is a semi-finished mortar made of raw materials that are accurately batched and uniformly mixed in the factory. It can be used only by adding
Dry powder mortar is a semi-finished mortar made of raw materials that are accurately batched and uniformly mixed in the factory. It can be used only by adding water and stirring at the construction site. Due to the variety of dry powder mortar, it is widely used. One of its biggest features is its thin layer to play the role of bonding, decoration, protection and cushioning. For example, the mortars mainly used for bonding function mainly include masonry mortar, wall and floor tile paste mortar, jointing mortar, anchoring mortar, etc.; the mortars mainly used for decoration and repair effects mainly include various plastering mortars, internal and external wall putty, color decorative mortar etc. There are waterproof mortars, various corrosion-resistant mortars, ground self-leveling mortars, wear-resistant mortars, thermal insulation mortars, sound-absorbing mortars, repair mortars, mildew-proof mortars, shielding mortars, etc.
Therefore, its composition is also relatively complex. In summary, it is composed of binders, fillers, mineral admixtures, pigments, admixtures and other materials.
Composition of dry powder mortar
1. Cementitious material
Commonly used cementitious materials for dry mortar are: Portland cement, ordinary Portland cement, high alumina cement, calcium Portland cement, natural gypsum, lime, silica fume and mixtures of these materials. Portland cement (usually Type I) or Portland white cement are the main binders. Some special cements are usually used in the floor mortar. The amount of binder used accounts for 20% to 40% of the dry mix product quality.
2. Filler
The main fillers of dry powder 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 fillers 4mm-2mm, medium fillers 2mm-0.1mm, and fine fillers below 0.1mm. For products with very small particle size, fine stone powder and sorted limestone should be used as aggregates. Ordinary dry powder mortar can use crushed limestone or dried and screened sand as aggregate. If the sand is of sufficient quality to be used in advanced structural concrete, it must meet the requirements for the production of dry mixes. The key to the production of reliable dry mortar is the control of the particle size of the raw materials and the accurate feeding ratio, which is realized in the automatic dry mortar production line.
3. Mineral admixtures
The mineral admixtures of dry mortar are mainly: industrial by-products, industrial wastes and some natural ores, such as: slag, fly ash, pozzolan, fine silica powder, etc. The chemical composition of these admixtures is mainly calcium oxide-containing silicon Aluminum hydrochloric acid, with high activity and hydraulic properties.
4. Additives
Admixture is the key link of dry mortar. The type and quantity of admixture and the adaptability between admixtures are related to the quality and performance of dry mortar. In order to increase the workability and cohesive force of the dry mortar, improve the crack resistance of the mortar, reduce the permeability, and make the mortar difficult to separate by bleeding, thereby improving the construction performance of the dry mortar and reducing the production cost. Such as polymer rubber powder, wood fiber, hydroxymethyl cellulose ether, hydroxypropyl methyl cellulose, modified polypropylene fiber, PVA fiber and various water reducing agents.
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