It has been said that there are two types of concrete – concrete that has cracked and concrete that is about to crack. As Kryton is the only integral waterproofing company that has a fully integrated waterstop system we field lots of questions on joints. This will be the first of three in a series on joints.
Early in its life, concrete dries, shrinks and quite commonly cracks. In addition, fluctuations in temperature and moisture levels cause concrete to shrink and expand throughout its life, eventually leading to cracking. Different applied load weights can cause shear or bending, which increases the likelihood of breaks. The resulting cracks represent an easy path for water and chemical contaminants to enter the concrete and corrode the steel reinforcement inside. This is why preventive measures, such as proper jointing, are a crucial part of the construction process.
Joints are pre-planned cracks. Unlike random cracks that can lead to concrete deterioration, joints fortify structures by controlling and minimizing cracking.
Types of Joints
A crack-inducement joint is commonly referred to as a control or contraction joint. These joints create a purposeful weakness in the concrete so that straight line cracking will occur at that desired, pre-planned spot. Crack-inducement joints are most often used in sidewalks, driveways, pavements, floors and walls.
An isolation or expansion joint separates concrete slabs from structural elements such as walls, footings or columns. They allow the slabs and touching surfaces to move without causing cracks. These joints are typically used when separating driveways and patios from sidewalks, garage slabs or stairs.
Construction joints, also called cold joints, separate sections of concrete that have been placed at different times. They provide stopping places during construction and are often referred to as joints that “occur at the end of a day’s work.” These joints can align with or function as crack-inducement or isolation joints.
Coming up tomorrow – Addressing Joint Vulnerability.
