Concrete Expansion Joints

Basic Information About Concrete Expansion Joints

Concrete is truly a special building material, being one of the two materials without which we wouldn’t have most of the present day infrastructure but despite concrete’s strength and durability it is very vulnerable to damage caused when it contracts due to various reasons. In order to get past the problem three types of concrete joints have been invented in order to deal with this: contraction or control joints, construction joints and concrete expansion joints.

The role of contraction joints is to regulate the cracking of the concrete that will surely take place; these are also called control joints as they are meant to control the crack locations.
The location of construction joints will usually predetermined in order to limit the amount of work that can be done at one time with the least impairment to the overall finishes structure.
Expansion joints are designed to prevent any distorting that concrete slabs might incur due to the transmission of compressive forces which can develop via expansion, applied loads or a differential movement.

While the first two types of joints are usually to be found during the building of a structure the latter one, expansion joints are part of everyday life because they keep together the concrete slabs that make up the pavement, driveways, sidewalks or the floors in parking garages.

Expansion joints are needed because slabs of concrete need a space of half an inch to three quarters of an inch between them in order to take account the expansion of concrete. That space can’t be left empty as waiter can then easily infiltrate under the slabs, steadily eroding the soil underneath and thus leading to the eventual cracking of the slab above. This is why using some time of filler for that gap is crucial, in this case using something that can deform as well like rubber or caulking.

Now due to the type of materials that make up an expansion joint, repairing them from time to time also becomes something that has to be done as rubber will deteriorate, caulking will get worn away as a result of weathering and wood will rot sooner or later; if the expansion gaps aren’t filled with some sort of flexible material then they become vulnerable.

When repairing of the expansion joints becomes apparent there are several materials to choose from depending on the requirements of each location. Woods like cedar and redwood work very well, but using hardwoods is not considered to be a great idea as these don’t deform as much. On the synthetic side of things there are many more options available ranging from polyurethane and silicone to tri-polymer, polysulfide or acrylic sealants in tubes or tubs; worth to mention is the fact that before any repairing can occur the gap must be thoroughly cleaned and a new backer rod must be installed for leveling.

The entire process of repairing concrete expansion joints is a very difficult and messy one and ideally should be done by a professional in concrete repair.

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