While design and application are just as crucial, proper expansion joint installation is vital to their service life. A properly designed and installed part typically lasts 15 to 20 years in most industrial applications. Over so many years, you can expect to perform maintenance and care to preserve their integrity.
Having the right amount of expansion joints between concrete slabs is essential, but large openings exposed to the elements can cause many different problems over the lifetime of the concrete. For this reason, it's important to fill or seal your expansion joints.
Tips for placing concrete expansion joints
Place joints around 30 times the slab thickness apart. So, for a slab which is 100mm thick, the joints should be placed around 3,000mm (3 metres) apart. Make sure joints are cut deep enough: they need to be at least a quarter of the thickness of the slab.
In most situations, this won't be a sudden event requiring your immediate attention. Instead, expansion joints crack slowly and steadily. It's much the same way that concrete expansion and contraction itself is a slow and steady process.
To replace old or damaged expansion joints, remove the old material, clean the joints, apply bonding adhesive, insert foam backer rod and seal them with self-leveling urethane sealant. It's essential to block off the area until the sealant dries to ensure the new expansion joints function correctly.
If your joints crack once or twice after a period of immobility, it is generally normal and harmless. Repeated joint cracking that occurs every time you move a joint or that causes pain may indicate a more serious problem that you should talk to your healthcare provider about.
Generally speaking, expansion joints should be no farther apart than 2 to 3 times (in feet) the total width of the concrete (in inches). So for a 4‑inch thick concrete slab, expansion joints should be no more than 8 to 12 feet apart.
As per IS- 456:2000, in the case of buildings, structures exceeding 45 m in length are designed with one or more expansion joints. As per IS 3414 which is a specific code for joints, it is mentioned as 30 m. It is clear from the above table that the maximum spacing for the expansion joint is 140 m.
A.: When it first dries, concrete shrinks and undergoes structural alterations that make some of the shrinkage irreversible. Thus, even if it is later resaturated, the initial drying shrinkage isn't fully recovered.
In building construction, expansion joints are strategically placed gaps that allow concrete slabs to expand and contract without damaging the structure. They act as a buffer zone, absorbing thermal movement and preventing the formation of cracks and fissures.
Because expansion joints are open gaps leading straight to the soil and sub-material under the concrete, they should always be caulked to prevent water from eroding away the base that the concrete is sitting on.
Caulking intentional expansion joints and unwanted cracks is a great way to prevent damage to your concrete. By keeping up with this maintenance practice, you will help prevent water from entering the slab and causing freeze-thaw damage, as well as eroding the sub-material and causing your slab to settle.
Expansion joint thickness can vary from . 010 inches to . 125 inches thick depending upon the design requirements for your application.
Leaking Water. Water leaking through an expansion joint cover can often be attributed to poor blockout conditions and water actually leaking through the adjacent concrete.
Avoiding Over-Expansion and Compression
Adhering to the specified limits of movement (expansion, compression, lateral, and angular) is vital. Over-expansion or over-compression can stress the joint, leading to cracks and tears.
Cold joints have a negative effect on the structure; they can reduce the load-bearing capacity by creating weak points in areas subject to shear or tensile forces. They are also possible entry points for water or other contaminants, which could cause a concrete crack or deterioration.
A practical limit between expansion joints for TFR is in the range of 100' to 200', when these roofs are attached to light gage cold- formed purlins. Standing seam roofs are limited by the range of the sliding clips. Depending on the manufacturer, it is in the range of 150' to 200'.
JOINT SPACING
When spacing out joint cuts, the general rule of thumb is that each joint should be around 2-3 times the thickness of the slab, but in feet.
These joints are cut into the concrete while it is still fairly fresh. Most of the time, it will be cut within about six to 18 hours of a concrete pour. While expansion joints are cut all the way through, control joints only go about a quarter of the way through a slab.
Ideally, for most concrete work, if you want to avoid unwanted cracks, then you should wait at least 6 to 18 hours before you start cutting concrete. It is not advised to cut concrete beyond 24 hours after a pour.
Most experts theorize that cracking or popping in the back, called crepitus, comes from one of three causes: ligament or tendon repositioning, vertebrae rubbing against each other, or cavitations (gas bubbles) in your spinal joint fluid.
Synovial fluid, also known as joint fluid, is a thick liquid located between your joints. The fluid cushions and protects the ends of bones and reduces friction during movement. Normally, there is only a small amount of synovial fluid between the joints.