Reasons for cracking caused by the use of expanded polystyrene board for external insulation of glass fiber mesh
(1) The density of the polystyrene board is too low: the polystyrene board below 15kg/m2 is used as the material of the wall insulation layer. Due to the low density, easy deformation and poor impact resistance, the insulation wall is cracked.
(2) The aging time is not enough: the polystyrene board should be aged for 42 days under natural conditions or in 60C steam for 5 days. In order to catch up with the production period, it will go to the construction site. As a result, the dimensional stability of the polystyrene board is not enough. After the system is completed, it continues to shrink and deform, causing the thermal insulation wall to crack.
(3) Material pulverization: Due to the long construction period or construction every other year, the surface of the polystyrene board is pulverized. As a result, the polystyrene board is not firmly pasted or the plastering sand case is not firmly bonded, causing accidents such as the falling off of the insulation layer and the cracking of the plastering mortar.
(4) Thermal shrinkage: The polystyrene board will undergo irreversible thermal shrinkage when heated, causing cracking and hollowing of the thermal insulation surface.
(5) The thermal conductivity of the plastering mortar directly applied to the polystyrene board is too different from that of the polystyrene board, and the flexibility index of the anti-cracking material of the opposite layer should be higher. Otherwise, cracks are prone to occur, which is common in severe cold areas with large temperature differences. The thermal conductivity of the expanded polystyrene board is 0.042W/(m* K), and the thermal conductivity of the anti-cracking mortar is 0.93W/(m. K), and the thermal conductivity of the two layers of materials is 22 times different. When the anti-crack mortar is on the surface, since the anti-crack mortar is only 3mm, when the thermal conductivity of the thermal insulation layer material is lower, its ability to block thermal insulation is stronger, so that the temperature of the anti-crack mortar rises sharply, and the surface temperature will be as high as 50~70 One, in case of sudden rainfall, the temperature will drop to about 15T, and the temperature difference can reach 40~65C. Such a temperature difference change and the influence of the outdoor temperature during the night and the season will lead to a large N difference in the deformation of the surface layer, and crack-resistant mortar is easy to produce.