Research and analysis on the causes of cracks in mortar layer
1. insulation board density is too low
At present, the density of thermal insulation board used for external wall insulation is mainly 18 ~ 22kg/m3, and the thermal insulation board below 18kg/m3 is adopted. Due to low density, easy deformation and poor impact resistance, it is easy to cause the surface mortar layer cracking.
2. The aging time of the insulation board is not enough: the self-shrinking and deformation time of the insulation board in the natural environment is as long as 60 days. If the natural aging time of the insulation board is short, it will cause the wall to continue to shrink, and the reinforcement mortar will shrink. The stress is concentrated at the joints of the board, which generates tensile stress on the plaster mortar layer adhered to the insulation board and causes the plaster mortar layer to crack.
3. thermal insulation board material powder: thermal insulation board under normal conditions at the rate of l ~ 1.5mm per year powder, powder interface will affect the plaster mortar and thermal insulation board bond, it is easy to lead to the thermal insulation board or plaster mortar bond is not firm, causing insulation layer fall off or plaster mortar layer crack.
4. The bonding material and the bonded material are incompatible and do not match, resulting in the unstable bonding of the insulation board and the cracking of the plaster mortar layer.
5. the adhesive strength of the bonding material, high strength, large shrinkage, will also pull the insulation board crack, cause plaster mortar layer crack.
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