Modified additives such as ready-mixed mortar additives, cellulose ethers, coagulant, redispersible polymer powder, air entraining agents, early-strength agents, water-reducing agents, etc., which are added additional according to the needs of the project. They greatly improve the performances of ready-mixed mortars’physical and mechanical properties.
How does each additive work in dry-mix mortar?
1. Cellulose ether
In the ready-mixed mortar, cellulose ether is a main additive that has a very low addition amount, but can significantly improve the performance of the wet mortar and affect the construction performance of the mortar. Reasonable selection of cellulose ethers of different varieties, different viscosities, different particle sizes, different degrees of viscosity and added amount will produce and exert a positive influence on the improvement of the performance of dry mortar.
The production of cellulose ether is mainly made of natural fibers through alkali dissolution, etherification, water washing, drying, grinding and other processes. In the production of building materials, especially dry mortar, cellulose ether plays an irreplaceable role, especially in the production of special mortar (modified mortar), it is an indispensable and important part. Cellulose ether plays a role in water retention, thickening, delaying cement hydration power, and improving construction performance. The good water retention capacity makes the cement hydration more complete, can improve the wet tackiness of the wet mortar, increase the bonding strength of the mortar, and the time can be adjusted. The addition of cellulose ether to mechanical spraying mortar can improve the spraying or pumping performance of the mortar, as well as the structural strength. Therefore, cellulose ether is widely used as an important additive in ready-mixed mortar. The cellulose ethers used in ready-mixed mortar are mainly methyl hydroxyethyl cellulose ether and methyl hydroxypropyl cellulose ether. They account for more than 90% of the market share.
2. Redispersible polymer powder
Redispersible polymer powder(RDP) is a powdered thermoplastic resin produced by spray drying and subsequent processing of polymer emulsions. It is mainly used in construction, especially dry mortar to increase cohesion, cohesion and flexibility.
The role of the RDP in the mortar: the RDP forms a film after being dispersed and acts as a second adhesive to enhance the adhesion; the protective colloid is absorbed by the mortar system and will not be destroyed by water after the film is formed Or disperse twice; the film-forming polymer resin is distributed in the entire mortar system as a reinforcing material, thereby increasing the cohesion of the mortar.
Redispersible latex powder in wet mortar can improve construction performance, improve fluidity, increase thixotropy and sag resistance, improve cohesion, extend open time, enhance water retention, etc. It can improve the tensile strength after the mortar is cured. Tensile strength, increase bending strength, reduce elastic modulus, improve deformability, increase material compactness, increase wear resistance, increase cohesive strength, reduce carbonization depth, reduce material water absorption, and make materials have excellent hydrophobicity Water and other effects.
3. Air-entraining agent
Air-entraining agent, also called air-entraining agent, refers to the introduction of a large number of uniformly distributed tiny bubbles during the mixing process of the mortar, which can reduce the surface tension of the mixed water in the mortar, resulting in better dispersibility and reduced mortar mixing Additives for bleeding and segregation. In addition, the introduction of fine and stable air bubbles also improves construction performance. The amount of air introduced depends on the type of mortar and the mixing equipment used.
Although the amount of air-entraining agent is extremely small, the air-entraining agent has a great influence on the performance of the ready-mixed mortar. It can effectively improve the workability of the ready-mixed mortar, improve the impermeability and frost resistance of the mortar, and reduce the density of the mortar. , Save materials and increase construction area, but the addition of air-entraining agent will reduce the strength of mortar, especially compression mortar. Therefore, the amount of air-entraining agent should be strictly controlled. The air content, construction performance and The relative strength is used to determine the optimal addition amount.
4. Early Strength Agent
Early strength agent is an additive that can accelerate the development of early strength of mortar, most of which are inorganic electrolytes, and a few are organic compounds.
The early strength agent for ready-mixed mortar must be powdered and dry. The most widely used premixed mortar is calcium formate. Calcium formate can improve the early strength of the mortar and accelerate the hydration of tricalcium silicate, which has a certain water reducing effect. The physical properties of calcium formate are stable at room temperature. It is not easy to agglomerate and is more suitable for application in dry mortar.
Water reducing agent refers to an additive that can reduce the amount of water used for mixing while keeping the consistency of the mortar basically the same. Water-reducing agents are generally surfactants, which are classified according to their functions: ordinary water-reducing agents, high-efficiency water-reducing agents, early strength water-reducing agents, retarding water-reducing agents, retarding high-efficiency water-reducing agents and causing water-reducing agents, etc.
The water-reducing agent used for ready-mixed mortar is required to be powdery and dry. Such water-reducing agent can be evenly dispersed in the dry-mixed mortar without reducing the shelf life of the ready-mixed mortar. At present, the application of water-reducing agent in ready-mixed mortar is generally in cement self-leveling, gypsum self-leveling, batching mortar, waterproof mortar, putty, etc. The selection of water-reducing agent should be based on different raw materials and different mortar properties. Optional.
Additives for ready-mixed mortars include retarders, quick-setting agents, fibers, thixotropic lubricants, defoamers, etc., according to different types of mortars, different options are added. These additives are used in ready-mixed mortars. The improvement in performance is like a seasoning for cooking food. It is added to the dishes to brighten the color, increase the taste and lock the nutrition, so that different types of ready-mixed mortars can exert better quality capabilities. It is the ready-mixed mortar in the engineering A magic weapon for better use in the game.
Post time: Aug-20-2021