Räppähdyssiteet

Räppähdyssiteet, also known as "snap ties" in English, are a crucial component in modern concrete construction, particularly for forming walls. They are a system of prefabricated metal ties designed to hold concrete formwork in place at a specific distance apart, ensuring uniform wall thickness.

The primary function of räppähdyssiteet is to resist the outward pressure exerted by the wet, uncured concrete. They connect opposite sides of the formwork, preventing the forms from bowing or collapsing under the weight and hydrostatic pressure of the concrete pour. Once the concrete has hardened sufficiently, the räppähdyssiteet are typically broken off or snapped at a designated weak point, leaving a small indentation or hole in the finished concrete surface, which is often later patched.

There are various types of räppähdyssiteet, with common designs including "cardboard tube ties" and "metal rod ties." Cardboard tube ties, for instance, consist of a paper or plastic tube that acts as a spacer, with metal rods passing through it and threaded into plates that attach to the formwork. Metal rod ties are simpler, often consisting of a single metal rod with forged ends that engage with the formwork. The choice of tie depends on factors such as the wall thickness, the type of concrete, and the required strength.

The use of räppähdyssiteet allows for efficient and consistent construction of concrete walls. They simplify the setup and stripping of formwork, reduce labor costs, and ensure dimensional accuracy of the finished structure. Proper installation and removal of these ties are essential for the structural integrity and aesthetic finish of the concrete.