Change in temperature, humidity, climate in general, seismic and dynamic loads are factors that often lead to structural deformation. So that changes in the volume of building materials (expansion or contraction due to temperature differences) or subsidence of elements (due to errors in the calculation of the foundation or insufficient soil reliability) do not lead to the destruction of the entire structure, it is advisable to use an expansion joint.
Types of expansion joints
Depending on what type of deformation is needed to be prevented, the joints distinguish between temperature, shrinkage, anti-seismic and sedimentary.
Expansion joint is applied to prevent horizontal changes. When calculating an industrial building with a frame structural scheme, seams are located at least every 60 m for heated and 40 m for unheated buildings. As a rule, expansion joints affect only above-ground structures, while the foundation is less affected by temperature differences.
The settling expansion joint is necessary in order to prevent the appearance of cracks in structural elements as a result of the fact that the load is unevenly distributed or the soils are weak and some elements sag. Unlike the temperature seam, the sedimentary seam also separates the foundation.
Anti-seismic expansion joints in buildings located in an area with increased seismic activity are practically necessary. At their expense, the building is divided into blocks that are essentially independent of each other, and therefore, in the event of an earthquake, the destruction or deformation of one block will not affect the others.
If your structure consists of cast-in-situ reinforced concrete walls, a shrinkage expansion joint is required. The fact is that concrete tends to shrink and shrink in size - that is, a wall poured directly at the construction site, and not assembled from reinforced concrete panels, will certainly decrease in volume, forming a gap. For the convenience of further work, a shrinkage seam is made before pouring the next wall, and after the concrete dries, the seams and gaps are sealed.
Sealing and insulating seams
This aspect is very important to pay special attention to: the seams must be well protected from external factors. For this, various types of insulation and filler are used. Polyurethane or epoxy sealants are a good option: they have high hardness and are not very flexible; another option –
usepolyethylene foam cord, followed by sealing with sealant. Another option is to fill the expansion joint with mineral wool. And the expansion joint in the wall, filled with mineral wool, must be sealed with an elastic mass that is resistant to weather conditions and protects the filler from moisture and dampness. In addition to fillers, the seam can be protected with a profile or plank of the appropriate size.
Seam sizes
The width of the expansion joints varies from 0.3 cm to 100, depending on the type of joint, as well as the operating conditions of the building. Expansion joints reach 4 cm (narrow), and shrinkage joints are medium (4-10 cm) and wide (10-100 cm).
