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In-depth analysis of the causes of cracks in the external wall insulation mortar layer

In-depth analysis of the causes of cracks in the external wall insulation mortar layer

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  • Time of issue:2020-12-29
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(Summary description)In recent years, China's insulation building materials market has developed rapidly, but some problems have also appeared.

In-depth analysis of the causes of cracks in the external wall insulation mortar layer

(Summary description)In recent years, China's insulation building materials market has developed rapidly, but some problems have also appeared.

  • Categories:Company News
  • Author:
  • Origin:
  • Time of issue:2020-12-29
  • Views:0
Information

       In recent years, China's insulation building materials market has developed rapidly, but some problems have also appeared. The investigation found that there were frequent occurrences of cracks, cracks and shedding of the thermal insulation mortar of the external wall insulation. There were local cracks and shedding, as well as large-scale shedding. Since the dry density of the thermal insulation mortar layer is 20kg/m3, if it falls from a height of tens of meters, the damage to people or objects on the ground is very huge. Today, Tianjin Sanxing mortar manufacturer will analyze the causes of cracks in the plastering mortar layer of the external wall external insulation system for you.

1. Material factors cause cracks in the plastering mortar layer of the external wall insulation system

1 Insulation board density is too low

       Anti-crack mortar is currently used for exterior wall thermal insulation with a density of 18-22kg/m3. Yes, but in the construction process, the construction unit often shoddy, using insulation boards below 18kg/m3, due to low density, easy deformation, and poor impact resistance, it is easy to cause the surface mortar layer to crack.

2 Insulation board aging time is not enough

       The thermal insulation board shrinks and deforms for up to 60 days in the natural environment. However, due to factors such as capital turnover and cost control of the production company, it is usually sold on a fixed production basis. The insulation board used in a large number of projects has naturally aged less than 7 days On the wall, the polymer mortar results in continued shrinkage after the insulation board, and the shrinkage stress of this reinforced mortar is concentrated at the board joints, which causes tensile stress on the plastering mortar layer adhered to the insulation board, causing cracking of the plastering mortar layer .

3 Pulverization of insulation board material

       Under normal conditions, the insulation board is pulverized at a rate of l~1.5mm per year. In actual construction, due to factors such as long construction period or construction every other year, the surface of the insulation board is pulverized, and the pulverization interface seriously affects the bonding of the plastering mortar and the insulation board. It is easy to cause the insulation board or the plastering mortar to be weakly bonded, causing the insulation layer to fall off or the plastering mortar layer to crack.

4 The thermal conductivity of the plastering mortar and the insulation board is too different

       The lower the thermal conductivity of the material, the stronger the ability to block heat. The thermal conductivity of expanded polystyrene board is 0.042W/(m?K), and the thermal conductivity of crack-resistant mortar is 0.93W/(m?K). The thermal conductivity of the layer materials differs by 22 times. 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 be as high as 50~70℃. In case of sudden rainfall, the temperature will drop to about 15℃, and the temperature difference can reach 35~55℃. The change in temperature and the influence of day and night and seasonal outdoor air temperature lead to a large difference in the amount of deformation of the plastering mortar layer, and the plastering mortar is prone to cracks.

5 The bonding material is incompatible and mismatched with the bonded material

       The bonding material and the bonded material are incompatible and mismatched, which causes the insulation board to be weakly bonded and causes the plastering mortar layer to crack.

6 The bonding material has high bonding strength, high strength and large shrinkage

       The bonding material has high bonding force, high strength, and large shrinkage, which will also pull the insulation board and cause cracks in the plastering mortar layer.

2. Construction factors cause cracks in the plastering mortar layer of the external wall external insulation system

       The external wall insulation system is completed at the construction site of the construction project. The quality of the bonding mortar construction is related to the overall quality of the insulation system and is also an important factor in the cracking of the insulation plaster mortar layer.

       1. The flatness deviation of the surface of the base layer is too large. The use of adhesive thickness adjustment, multilayer board adjustment, surface polishing and leveling adjustment and other methods will lead to quality defects in the insulation quality.

       2. The surface of the base layer contains dust and other substances that hinder the pasting, and there is no interface treatment for it when pasting.

       3. The bonding area of ​​the insulation board is too small, does not meet the requirements of the specification and construction plan, and does not meet the quality requirements of the bonding area.

       4. The embedding depth and the number of anchoring nails of the insulation board do not meet the requirements of the design and construction plan.

       5. The overlap width of alkali-resistant glass fiber mesh cloth does not meet the specification requirements, and cracks are formed at the overlap position.

       6. The four corners of the door and window openings are where the stress is concentrated, and the alkali-resistant glass fiber mesh is not added along the 45° direction of the door and window openings, and cracks often appear.

       7. When the plastering mortar layer is constructed under the sun exposure or high temperature, the water retention performance is insufficient, which causes the surface layer to lose water too fast and causes cracks in the plastering mortar layer.

       In recent years, China's insulation building materials market has developed rapidly, but some problems have also appeared. The investigation found that there were frequent occurrences of cracks, cracks and shedding of the thermal insulation mortar of the external wall insulation. There were local cracks and shedding, as well as large-scale shedding. Since the dry density of the thermal insulation mortar layer is 20kg/m3, if it falls from a height of tens of meters, the damage to people or objects on the ground is very huge. Today, Tianjin Sanxing mortar manufacturer will analyze the causes of cracks in the plastering mortar layer of the external wall external insulation system for you.
 

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Time of issue:2020-12-29 13:52:21

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