Concrete Expansion Joints What are concrete expansion joints? Concrete as a building material has inbuilt characteristics of contraction or expansion in a slight manner during the curing process. This contraction or expansion results in the appearance of small surface cracks that appear during the curing process. The need for concrete expansion joint arises in order to eliminate the intermediate cracks in the concrete structure by creating planes of weakness in order to predetermine the location of contraction cracks.
Purpose of concrete expansion joints The Concrete Expansion Joints main purpose is to allow expansion and contraction of concrete slab without causing any potential damage to the slab itself or to the surrounding structures. Any changes in weather conditions also lead to the expansion or contraction of concrete and therefore the purpose of concrete expansion joints is to accommodate such movement at predetermined locations with proper joint applications that prevents the development of stresses leading to rupture of the concrete. The concrete expansion joint together with the isolation joints helps in managing the movement of concrete. The right positioning of concrete expansion joints helps in keeping the position, texture, strength and effectiveness of the concrete foundations.
Types of Concrete Expansion Joints There are different types of concrete expansion joints and these help in an easy momentum of concrete structures when faced with environmental changes. The importance of concrete expansion joints is felt more in case of earthquakes or other natural calamities when pressure accumulates within the concrete structure that causes cracks to look up on the top of the concrete structures. Basically there are two different types of concrete expansion joints and these are doweled and nondoweled ones. Some of these types are mentioned below
1. Asphalt Expansion Joint The asphalt expansion joint is made up of a mixture of asphalts, mineral fillers, and vegetable fibers formed under the heat and pressure between two asphalt saturated liners. These types of concrete expansion joints are waterproof, flexible, selfsealing and permanent.
2. Sponge Rubber Expansion Joint This type of concrete expansion joint is produced from top quality blown sponge rubber with a uniform thickness and density. These can be easily compressed having a recovery rate of 95% or more of the original thickness and having a density of not less than thirty pounds per cubic foot.
3. Cork Expansion Joint A concrete expansion joint of this type is produced from granulated cork bonded with a phenol resin. This type of concrete expansion joint recovers to about 95% of its original thickness after 50% compression. The selection of proper concrete expansion joint on the nature of the concrete structure therefore it is a suggested to take advice from a professional structural engineer before selecting the concrete expansion joint for your building.