Joints in concrete floors. Part 1 - Construction joints

Autor: Ramon Planas Masip

An essential element, to a greater or lesser extent depending on the design, of any concrete floor are the joints, both constructive and retraction, as well as the perimeter.?The joints are the elements of the slab that give more problems at the maintenance level, as the pavement ages. In this article are going to focus on the first ones: the constructive joints.

A constructive joint is one that divides the floor with the basic function of finishing in a functional way with the concreting of the day. There are several considerations to keep in mind:

• They are that shape the slab
• They are the joints that open the most, although there is contraction cuts, the constructive are the ones that absorb the most movement.
• Due to this opening, they are most susceptible to being damaged by traffic.

There are different ways to design this type of joints, which we list below:

• Simple joint conformed with the formwork: Consists of stopping with a rule the pour and remove formwork the next day to continue with the process. As there is no passing element, this solution is so susceptible to warping and differential sinking due to the load change that is practically obsolete today.
• Assemble joint: In this case the formwork has a shape that allows the transmission of loads; however, a large opening disables the solution.
• with metallic dowells: If this elements are subject to a calculation, we can ensure the transmission of loads and a good behavior before warping, but we still have two important problems:

1. Horizontal movements are blocked by retraction of the slab. This is something that can be solved by placing dowells rhombus or trapezoidal.
2. The edge of the joint, like in the previous ones, are left unprotected to the traffic, for being a living concrete edge, very little resistant to wear by wheel arches. This is something that can be solved by placing steel angles to protect these edges.

• Pre-formed Joint: These joints have several advantages:

1. They do not require disassembly; they are lost in the concrete.
2. They allow a perfect alignment and leveling placed with the appropriate squad for this purpose.
3. They protect the edges of the joint with a metallic reinforcement.

4. They have integrated trapezoidal dowells for the transmission of loads.

• Preformed joints of optimized geometry: These joints, of more recent release in the market, have the advantages of the preformed joint, adding a geometry in the form of a zigzag that practically does not exist the blow of the wheel. For this reason, they are ideal for high traffic logistics.

For several decades, the firm Permaban has been manufacturing various preformed joint solutions. For more information: https://www.permaban.com/about-permaban/english