Deep analysis of the causes of cracks in the external wall insulation mortar layer

In recent years, China's thermal insulation building materials market has developed rapidly, but there are also some problems. The investigation found that there were continuous cracking and shedding events of thermal insulation mortar of external wall thermal insulation layer, local cracking and shedding, and large area shedding phenomenon. Since the dry density of the thermal insulation mortar layer is 20kg/m3, if it falls from tens of meters, the damage to people or things on the ground is very huge. Today, Tianjin Sanxing Mortar Factory will give you a deep analysis of the causes of cracks in the mortar layer of the external wall insulation system.
Cause Analysis of Cracks in Plaster Mortar Layer of Exterior Insulation System Caused by 1. Material Factors
1 Insulation board density is too low
At present, the density of the insulation board used for external wall insulation is mainly 18~22kg/m3. However, in the construction process, the construction unit often uses shoddy insulation boards below 18kg/m3, which are easy to cause cracking of plastering mortar layer due to low density, easy deformation and poor impact resistance.
2 insulation board aging time is not enough
The self-shrinkage and deformation time of the insulation board in the natural environment is as long as 60 days. However, due to factors such as capital turnover and cost control of production enterprises, the production is usually determined by sales. The insulation board used in a large number of projects has been installed on the wall within 7 days of natural aging. As a result, the polymer mortar continues to shrink after the insulation board is installed on the wall, and the shrinkage stress of the reinforcement mortar is concentrated at the board joint, the tensile stress on the plaster mortar layer adhered to the insulation board causes the plaster mortar layer to crack.
3 insulation board material powder
Under normal conditions, the insulation board is pulverized at a speed of l ~ 1.5mm per year. In actual construction, due to factors such as long construction period or construction in the following year, the surface of the insulation board is pulverized, and the pulverization interface seriously affects the bonding between the plastering mortar and the insulation board, which easily leads to weak bonding of the insulation board or plastering mortar, causing the insulation layer to fall off or cracking of the plastering mortar layer.
4 The thermal conductivity of the plastering mortar and the insulation board is too large
The lower the thermal conductivity of the material, the stronger the ability to block heat, the thermal conductivity of the expanded polystyrene board is 0.042W/(m?K), the thermal conductivity of the anti-cracking mortar is 0.93W/(m?K), and the thermal conductivity of the two layers is 22 times different. When the sun shines directly on the surface of the plastering mortar in summer, the temperature of the plastering mortar will rise sharply, and the surface temperature will reach 50~70 ℃. In case of sudden rainfall, the temperature will drop to about 15 ℃, and the temperature difference can reach 35~55 ℃. Such temperature difference changes and the influence of outdoor air temperature in day and night and season will lead to large deformation difference of the plastering mortar layer, and the plastering mortar is easy to crack.
5 Incompatibility and mismatch between bonding material and bonded material
The bonding material is incompatible with the bonded material and does not match, resulting in poor bonding of the insulation board and cracking of the plaster mortar layer.
6 bonding material bonding force, high strength, large shrinkage
The bonding force of the bonding material is large, the strength is high, and the shrinkage is large, and the insulation board will be cracked, causing the plaster mortar layer to crack.
Analysis of the causes of cracks in the mortar layer of the external insulation system of external walls caused by 2. construction factors
Exterior wall insulation system is completed in the construction site of the construction project, the quality of the adhesive mortar construction quality is related to the overall quality of the insulation system, but also an important factor in the cracking of the insulation plaster mortar layer.
1, the surface of the base level flatness deviation is too large, the use of adhesive thickness adjustment, the use of multi-layer board adjustment, the use of surface grinding leveling adjustment and other methods, these will lead to the quality of insulation quality defects.
2. The surface of the base layer contains dust and other substances that hinder the paste, and there is no interface treatment when pasting.
3. The bonding area of the insulation board is too small, which does not meet the requirements of the specifications and construction plans, and cannot meet the quality requirements of the bonding area.
4. The embedding depth and anchoring quantity of the anchoring nails of the insulation board do not meet the requirements of the design and construction plan.
5. The lap width of alkali-resistant glass fiber grid cloth does not meet the specification requirements, and cracks are formed at the lap position.
6. The four corners of the door and window openings are the positions where the stress is concentrated. Alkali-resistant glass fiber grid cloth is not added along the 45 ° direction of the door and window openings, and cracks often occur.
7, in the sun exposure or high temperature weather for plastering mortar layer construction, water retention performance is insufficient, resulting in surface water loss too fast caused by plastering mortar layer cracks.
In recent years, China's thermal insulation building materials market has developed rapidly, but there are also some problems. The investigation found that there were continuous cracking and shedding events of thermal insulation mortar of external wall thermal insulation layer, local cracking and shedding, and large area shedding phenomenon. Since the dry density of the thermal insulation mortar layer is 20kg/m3, if it falls from tens of meters, the damage to people or things on the ground is very huge. Today, Tianjin Sanxing Mortar Factory will give you a deep analysis of the causes of cracks in the mortar layer of the external wall insulation system.