Type, composition and technical performance of plaster mortar
Plastering works, the construction process of applying the plastering mortar on the surface of the base material, which protects the base layer, increases the aesthetics and provides special functions for the building, is called the plastering project. The plastering project has two main functions. One is the protective function, which protects the wall from the erosion of wind, rain and snow, increases the ability of the wall to prevent moisture, weather, and heat, and improve the durability and thermal performance of the wall. ; The second is to beautify the function and improve indoor sanitary conditions. Purify the air, beautify the environment, and improve living comfort.
Plastering works are usually divided into general plastering and decorative plastering. The types of plastering mortars are divided into general plastering mortars, decorative plastering mortars and special plastering mortars according to the different functions of plastering mortars. According to different production methods, it is divided into on-site mixing plaster mortar and ready-mix plaster mortar.
Plastering mortar is composed of cementitious materials, and commonly used cementitious materials include cement, lime, polymer, and construction gypsum. Both cement and general-purpose Portland cement can be used to prepare mortar. The choice of cement type is related to the use of mortar. Generally, the strength requirements for plastering mortar are not very high, and generally the medium strength grade cement can meet the requirements. The strength of the plastering mortar should not exceed the two strength levels of the base material. The inner and outer walls of the facing bricks, the strength of the middle-layer plastering mortar shall not be lower than M15, and the cement plastering mortar is preferred. Clogging the side seams of doors and windows, scaffold eyes, and holes. Window sills and balconies should use M15, M2D cement mortar. The cement strength grade used for cement mortar should not be greater than 32.5; the cement strength grade used for cement mixed mortar should not be greater than 42 . Level 5. If the cement strength level is too high, shrinkage cracks will occur, which can be properly blended to avoid cracks.
Lime
Lime, in order to improve the workability of the mortar and save cement, an appropriate amount of lime is often beaten in the mortar. Lime includes quicklime and slaked lime (namely slaked lime). Two methods are commonly used for slaked lime on construction sites: slaked lime slurry method and slaked lime powder method. Depending on the amount of water added, lime can be matured into slaked lime powder or lime paste. The theoretical water requirement of lime slaked is 3zI e of the weight of lime in the quicklime. Evenly add water to obtain slaked lime powder with fine particles and uniform dispersion. If aging with excessive water, a lime paste with a certain consistency will be obtained. Lime paste has good water retention. If it is added to cement mortar and mixed into a mixed mortar, the workability of the mortar can be significantly improved. Lime generally contains overfire lime. Overfire lime slaked slowly, if it occurs after the lime slurry hardens Maturation will cause swelling and cracking due to the expansion caused by maturation.
In order to eliminate this hazard of overfired lime, the lime should be slaked. It should be “Chen Fu” about a week. During the hardening process, lime will evaporate a lot of water, causing significant shrinkage of the volume. Prone to shrinkage cracks.
Therefore, lime should not be used alone. Generally, it should be mixed with sand, paper tendons, hemp knives and other materials. In order to reduce shrinkage and increase tensile strength, lime should not be used in long-term damp and water-soaked environments. In many special occasions, polymer can be used as the cementing material of mortar to make polymer mortar.
Polymer mortar
The so-called polymer cement mortar refers to a new type of building material in which a polymer adhesive is added to the cement mortar to greatly improve the performance of the mortar. The polymer cement is used as an organic bonding material and the cement or mortar in the mortar. Inorganic bonding materials such as gypsum are perfectly combined to greatly improve the bonding strength of the mortar and the base layer, the deformability of the mortar, that is, the flexibility, and the cohesive strength of the mortar.
The type and penetration of the polymer largely determines the performance of the polymer cement mortar. Changed the technical and economic performance of traditional mortar. At present, various types of polymer mortars with excellent performance have been developed.
Building plaster
Building gypsum is also called dihydrate gypsum, and building azurite can be obtained by heating natural dihydrate gypsum under the piece. Compared with other cementitious materials, building gypsum has the following characteristics: fast setting and hardening. After the building gypsum is mixed with water, the slurry begins to lose its plasticity within a few minutes. The plasticity is completely lost within 3 minutes to produce strength. The volume expands when it sets and hardens. Gypsum slurry will produce micro-expansion in the initial stage of setting and hardening. This property makes the surface of gypsum products smooth, delicate, accurate in size, full body, and good in decoration.
Many decorative ornaments and decorative lines in architectural decoration projects take advantage of this feature, and building gypsum is widely used, with large porosity and low volume density. When building gypsum is mixed and hydrated. Large olive capillary pores are formed inside the building gypsum products, so the thermal conductivity is small, and the sound absorption is good. It is a light-weight insulation material. Has a certain temperature and humidity control performance.
Because a large number of capillary pores in gypsum products have a strong adsorption capacity for water vapor in the air, they have a certain adjustment effect on indoor air humidity, and have good fire resistance, poor water resistance, impermeability and frost resistance. The most commonly used fine aggregate for preparing mortar is Heran sand. The sand should meet the technical performance requirements of concrete sand. Because the mortar layer is relatively thin, the maximum particle size of sand should be limited. In theory, if it should not exceed the thickness of the mortar layer, medium sand should be selected, and the maximum particle size should not be larger. The thickness of the sand has a great influence on the cement dosage, workability, strength and shrinkage of the mortar.
The requirements for water mixing mortar and concrete mixing are the same. Both need to meet the “Concrete Water Standard” IJGJ admixture. In order to improve the various properties of fresh and hardened mortar or to give mortar some special properties, it is often mixed in mortar people add appropriate amount. For example, in order to improve the workability of the mortar and improve the crack resistance, frost resistance and heat preservation of the mortar, additives such as microfoaming agent and water reducing agent can be mixed; to enhance the waterproof and impermeability of the mortar, it can be penetrated Waterproofing agent, etc.; in order to enhance the thermal insulation performance of the mortar, an air-entraining agent can be added to increase the porosity of the mortar. Fiber In order to prevent the shrinkage and cracking of the mortar layer, it is sometimes necessary to add some fiber materials, or to make it have some special functions, it is necessary to select special aggregates or admixtures, such as paper reinforcement, hemp knife, glass fiber, paper reinforcement, hemp Knives and glass fibers are all fiber materials.
Fiber is a polymer that undergoes certain mechanical processing (traction, Lape shaping, etc.) to form fine and soft filaments to form fibers. Fiber has the characteristics of large elastic modulus, small deformation when subjected to force, and high strength. Fibers are generally divided into natural fibers, man-made fibers and synthetic fibers. The old hemp rope is beaten with a hemp machine or bamboo sticks into a flocculent hemp ball called hemp knife. Use rice straw, wheat straw or fiber material to process it into a paddle, called paper tendons.
According to the shape and length, glass fiber can be divided into continuous fiber, fixed length fiber and glass wool; according to the glass composition, it can be divided into non-children, chemical resistance, high child, medium alkali, high strength, high elastic modulus and alkali resistant glass Fiber etc. The combination of fiber technology and construction technology can play a role in crack prevention, impermeability, impact resistance and flexural resistance, and improve the quality of construction projects. Anti-crack mortar is the addition of fibers to polymer mortar.
