Main structural features of EPS concrete block walls
At present, it is stipulated in severe cold regions that newly built residential and public buildings should meet the requirements of 65% and 50% energy saving external wall heat transfer coefficient limits, respectively. The corresponding thermal parameters of autoclaved aerated concrete block walls are shown in Tables 4 and 5, respectively. Among them, when the body coefficient Sc≤0.3, the heat transfer coefficient limits of the main parts of the external wall for 65% and 50% energy saving are 0.45 and 0.50 W, (mz·K), respectively; after calculation, if ordinary plastering mixed mortar is used inside and outside (insulation masonry mortar remains unchanged), and the density level and thickness of EPS concrete blocks are appropriately adjusted, the requirements of the corresponding external wall heat transfer coefficient limits can also be achieved.
Strengthened insulation measures should be taken on the outside of reinforced concrete beams and columns in EPS concrete block walls. For example, a 60mm thick flame-retardant EPS board is pasted on the outside of thermal bridges such as frame columns or special-shaped frame columns, and then a 100nlm thick (or 150 mm thick) EPS concrete block wall is covered and built; the joints between the external wall columns and the aerated blocks are reinforced with one cloth and two slurries (1 layer of alkali-resistant glass fiber mesh cloth, 2 layers of polymer mortar), and the extension is extended deep into the block wall to be fixed; the block wall at the reinforced insulation part should maintain a smooth and consistent appearance with the outside of the EPS concrete block wall body (300-450 mm thick). Near the door and window openings above the EPS concrete block wall, the outer sides of the upper and lower parts of the opening should be sprayed with 30 mm thick polyurethane rigid foam or 25 mm thick polystyrene particle insulation slurry, one cloth and two slurries (window additional net does not need to be turned over), and the appearance should be kept flat and consistent with the exterior of the EPS concrete block wall below the opening; at the same time, the reinforced concrete window lintel above the opening should also adopt the same enhanced insulation measures as the outer side of the above-mentioned frame column or special-shaped frame column, and keep the appearance flat and consistent with the exterior of the main body of the EPS concrete block wall.
When EPS concrete blocks are laid, their moisture content should be less than 30%, and the size of the block masonry mortar joint should be about 10 mm. When the length of the EPS concrete block wall is greater than 5 m, 3Φ4@150 full-length steel bars should be set in the middle of the height of each wall. The exterior of the EPS concrete block wall must adopt an appropriate finishing protective layer, and the layout and construction should be carried out according to the design plan of the building unit, that is, the exterior wall should not be made of clear water wall.
Before plastering the inside and outside of the EPS concrete block wall, an interface agent (EVA emulsion with a solid content of 7%) should be applied for treatment. The amount of cement used in preparing the plastering mortar should not be too much, otherwise it may cause cracks in the plastering layer. If the block wall uses dry powder insulation masonry mortar (its thermal conductivity is less than the thermal conductivity of the masonry material), the mortar joint influence coefficient is taken as 1.00. If ordinary masonry mortar is used, the mortar joint influence coefficient is taken as 1.25, thereby increasing the thermal conductivity and heat storage coefficient of the block material and the heat transfer coefficient of the block wall. The matching WB-5 dry powder insulation masonry mortar is mainly composed of cementitious materials, lightweight fine aggregates (ceramic sand and vitrified microspheres), fine fillers, wood fibers, EVA redispersible latex powder, cellulose ether and other raw materials, which are mixed evenly. The technical indicators of masonry mortar, internal mortar and external mortar specially used for dry powder insulation are shown in Table 6. Image
