The Characteristics of Waterproofing Agent and How to Choose

May 25, 2021

Cement waterproofing agent is a chemical admixture that is added to cement. When the cement hardens, it expands in volume, compensating for shrinkage and tensioning steel bars to produce prestress and fully filling the cement gap. Waterproofing agent, also known as waterproofing agent, plugging king, plugging spirit, is a new type of waterproof material, divided into organic and inorganic, and is a new high-tech waterproof product. The high-grade fatty acid mortar waterproofing agent has the characteristics of long waterproof life, wide application range, simple construction, low cost, safety and environmental protection (up to oral non-toxic level), and the implementation standard: JC474-2008 (mortar, concrete waterproofing agent) standard. Frequently used Some water-repellent agents such as calcium stearate are difficult to mix with cement mortar quickly and evenly, so it is not a suitable water-repellent additive for dry-mixed mortar, especially for mechanically applied plastering materials.

Technical characteristics
1. The calcium sulfoaluminate expansion agent component of this product has the effect of compensating the shrinkage of concrete to achieve crack resistance; concrete curing in water for 14 days limits the expansion rate of ≥0.015%, while the general waterproofing agent can only impermeate but not crack.
2. The high-efficiency water-reducing agent component of this product can reduce the concrete-water-binder ratio, increase the workability and compactness of the concrete, further reduce the shrinkage rate of the concrete, fill the internal porosity of the concrete, and achieve the improvement of the impermeability level and the high compressive strength The role of.
3. Depending on the construction season, this product has a compound retarder and other components, which can reduce the heat of hydration of the concrete and reduce the temperature difference cracks, so as to pour large-volume concrete, summer construction concrete, or mix with early strength agent or antifreeze agent. Early-strength anti-freezing and anti-cracking concrete in winter.
4. Using this product to compensate shrinkage concrete to construct reinforced concrete structures above 60m, post-pouring belts can be omitted, and expansion-reinforcing belts can be used instead of post-pouring belts to continuously pour the concrete. It can solve the troubles caused by the cleaning and chiseling of the post-pouring joints; it can solve the disadvantages of the post-pouring joints that must be poured 60 days later, the construction period is long, and there are many hidden dangers of leakage.

Features of waterproofing agent:
Water-repellent/water-proof functions of varying degrees are indispensable for many dry-mixed mortar products, such as surface mortar for thin-plaster external insulation systems, tile grout, color finish mortar and waterproof trowel for external walls Gray mortar, exterior wall putty, waterproof slurry, powder coating and certain repair materials, etc. The water-repellent function of the mortar can be solved by adding water-repellent additives. It can also be used in conjunction with other admixtures such as water-reducing agents to further improve the water-repellent capacity of the mortar, while keeping the mortar in an open state to allow Diffusion of water vapor. The performance of this additive can be evaluated by capillary water absorption test methods.
Types and performance There are not many types of powdery water-repellent additives. There are roughly three types of water-repellent additives for dry mortar products on the market:
(1) Fatty acid metal salt. Such as calcium stearate, zinc stearate and so on. The unit cost of these products is relatively low, but the main disadvantage is that it takes a long time to mix the mortar with water evenly. The typical dosage is 0.2% to 1%.
(2) Silicone-based water repellent. Silane-based powder water-repellent additive. The product not only exhibits high water repellency, but also has the ability to mix with mortar quickly and evenly. There are different types of powdered silicone water repellents available on the market, but the main difference is whether the product can be quickly mixed with the mortar evenly. Silane forms a highly durable bond with the hydration products of cement in an alkaline environment to provide long-term water repellency. The typical dosage is 0.1 to 0.5%.
(3) The special hydrophobic redispersible polymer powder can provide good hydrophobicity, but the required dosage is higher, and the typical dosage is 1-3%. These polymers can improve the adhesion, cohesion and flexibility of the mortar

Features The water-repellent additives used in dry-mixed mortar products should have the following features: 1) It should be a powder product; 2) It has good mixing performance; 3) Makes the mortar hydrophobic as a whole and maintains a long-term effect; 4) There is no negative effect on the bonding strength of the surface; 5) It is environmentally friendly. Some commonly used water-repellent agents such as calcium stearate are difficult to mix quickly and uniformly with cement mortar, so it is not a suitable water-repellent additive for dry-mixed mortar, especially for mechanically constructed plastering materials. Silane-based powder additives are high-performance water-repellent agents that can meet the above requirements and can help users develop dry mortar products with water-repellent properties. The product is a powdery silyl product obtained by spray-drying a protective colloid and an anti-caking agent that are easily soluble in water and encapsulating the silane. When the mortar is mixed with water, the protective colloid shell of the product quickly dissolves in the water and releases the encapsulated silane to be dispersed into the mixing water. In the highly alkaline environment after cement hydration, the hydrophilic organic functional groups in silane hydrolyze to form highly reactive silanol groups. The silanol groups continue to irreversibly react with the hydroxyl groups in the cement hydration product to form a chemical Bonding, so that the silane connected together by cross-linking is firmly fixed on the surface of the hole wall in the cement mortar. Since the hydrophobic organic functional groups face the outside of the pore wall, the surface of the pores is hydrophobic, thereby bringing an overall hydrophobic effect to the mortar.