Dry powder mortar has been widely used at present. There is a bond strength index in dry powder mortar. From the perspective of physical phenomena, when an object wants to attach to another object, it needs its own viscosity. The same is true for mortar, cement +Sand mixed with water to achieve the initial bond strength, and then cured by additives and cement to finally achieve the bond strength required by the mortar. So what are the factors that affect the bond strength?
The effect of additives
Cellulose ether and rubber powder are indispensable additives in dry powder bonding mortar. The rubber powder in the mortar is generally water-soluble redispersible latex powder, which can be divided into rigid and flexible. Use the corresponding rubber powder according to the product needs; main functions It provides excellent adhesion and helps to improve the water resistance, heat resistance, plasticity and flexibility of the mortar.
The role of cellulose ether is mainly used for water retention in mortar to improve the constructability of the product; for example, when building a house before, many master craftsmen mixed cement and sand on the ground. After adding water and stirring, they often see the water flow away. When plastering the wall with this kind of mortar, not only should it be thick, but also a small amount should be slowly applied. Another situation is to wipe off while rubbing. Improvements in these conditions were immediate. Water is locked in the mortar and refuses to drain. When plastering the wall, it can be easily constructed like putty, and the thickness can also be controlled and reduced; the biggest advantage is that the drying speed of the mortar can be effectively controlled, and the cement can be fully hydrated, which is beneficial to the overall improvement of the mortar strength.
shrink
The shrinkage of mortar can be said to be complementary to the bonding strength, which can affect the actual bonding area, thereby forming hollow cracks and directly losing the bonding strength; therefore, we must have strict requirements on the gradation of cement and sand in the mortar , which not only controls shrinkage, but also contributes to the bond strength of the mortar. In addition, reducing shrinkage can also be mixed with active materials. Active materials generally refer to large amounts of activated silica and activated alumina. Does not harden or hardens very slowly when water is added. Its particle size is finer, which can replace part of the cement filling mortar, thereby reducing the overall shrinkage of the mortar.
Effect of waterproof and hydrophobic
In a sense, waterproofing and hydrophobicity are at odds with bond strength. For example, in the past, many people hoped to have waterproof properties in tile adhesives, which can reduce the construction process of kitchen and bathroom walls, but the feasibility is not high; first, if our mortar wants to achieve waterproof or hydrophobic effects, we must add hydrophobic agent. After the hydrophobic agent is mixed with the mortar, an impermeable film will gradually form on the surface. In this way, when the tiles are pasted, water cannot effectively penetrate into the tiles, the wetting ability is reduced, and the natural bonding force cannot be improved during the subsequent mortar maintenance.
The bonding strength refers to the maximum bonding force of the mortar acting on the bottom layer;
Tensile strength refers to the ability of the mortar surface to resist the tensile force perpendicular to the surface;
Shear strength means the strength determined by applying a parallel force;
The compressive strength means the maximum value at which the mortar fails, measured by applying a pressure.
Post time: Mar-06-2023