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What is a concrete expansion joint? A concrete expansion joint – or control joint – is a gap which allows the concrete to expand and contract as/when the temperature changes. It forms a break between the concrete and other parts of a structure to allow movement without causing stress, which can lead to cracking.
Are expansion joints needed in concrete?
Expansion joints are virtually never needed with interior slabs, because the concrete doesn’t expand that much—it never gets that hot. Expansion joints in concrete pavement are also seldom needed, since the contraction joints open enough (from drying shrinkage) to account for temperature expansion.
What happens if you don’t put expansion joints in concrete?
If you have a concrete floor in your commercial building, you know expansion joints are necessary to allow for the natural expansion and contraction that occurs from temperature changes. Without these joints, large cracks can travel across your floor, creating costly damage.
How often should concrete have expansion joints?
Usually, expansion joints should be no farther apart than 2 to 3 times (in feet) the total width of the concrete (in inches).
What are concrete expansion joints made of?
Minimize Concrete Cracking and Damage with Expansion Joints. ASPHALT EXPANSION JOINT is composed of a blend of asphalts, vegetable fibers, and mineral fillers formed under heat and pressure between two asphalt-saturated liners. It is waterproof, permanent, flexible, and self-sealing.
Do house slabs have expansion joints?
Expansion joints separate the slab from structures such as foundation walls, footings, and structural support columns, and allow the slab to move unrestrained both horizontally and vertically.
Where are expansion joints required?
Expansion joints occur through all parts of a structure to provide complete separation – through floors, walls, ceilings, and roofs (interior & exterior).
How big of a slab can you pour without expansion joints?
Rule #1 – Keep joints as square as possible. Rule #2 – In order to prevent intermediate cracking, space joints (in feet) no more than 2 – 3 times the slab thickness (in inches).
What happens when expansion joints fail?
Metal expansion joints include bellows which work like a sealed spring to allow expansion, flexibility and movement. Without expansion joints, pipes and hoses could crack or break under various pressures, compromising your entire piping system.
How long do expansion joints last?
When expansion joints are designed, applied, and installed correctly, it is not unusual to achieve a service life of 15-20 years in most industrial applications.
Why do they cut lines in concrete?
To prevent sidewalks from cracking in random spots and breaking apart, builders make lines in sidewalks. The technical term for sidewalk lines is contraction joints. Contraction joints are placed in fresh concrete before the concrete dries and has a chance to create its own joints, which we call cracks.
How deep are concrete expansion joints?
Contraction/control joints must be established to a depth of ¼ the slab thickness (Figure 2). Proper joint spacing and depth are essential to effective control of random cracking.
What is the difference between expansion joints and control joints?
In building materials, a control joint is used to control cracking while an expansion joint is designed to handle structural movement. By contrast, an expansion joint (or movement joint) is sized and formed at a width prescribed by the building design team and sealed and bridged later by an expansion joint system.
Does concrete expand when wet?
Hardened concrete absorbs moisture and expands if it is laid into a humid environment or water, and the volume expansion deformation via the increase of moisture is called wet expansion deformation [[1], [2]].
How wide are expansion joints?
Expansion joints are created through the installation of a soft material, such as wood or foam, along the edges of concrete slabs. Joints should be at least 1/2-inch to 3/4-inch wide. Expansion joints should extend beyond the full depth of the concrete slab.
What is the best concrete expansion joint material?
Sikaflex can be used to seal horizontal expansion joints. It’s a great product because it remains permanently flexible, dries quickly, sticks to anything, is self-leveling, and highly resistant to weather conditions. You should apply Sikaflex when the temperature is between 40F-100F.
Does a garage slab need expansion joints?
Because concrete slabs will crack with expansion and contraction, these joints create a weakened line in the concrete that encourages cracks to follow the line within the joint. This helps by discouraging cracks from following a more resistant line across the surface of your garage floor.
Should I saw cut my concrete?
In addition to depth of contraction joints, saw cut timing is critical to minimize random cracking. In general, saw cut joints should be installed as soon as the concrete is sufficiently hard to resist tearing and raveling and before random cracking occurs.
Can we avoid expansion joint?
Expansion joint shall be so provided that the necessary movement occurs with a minimum resistant at joint. The structures adjacent to joint should be preferably supported on separate columns. Reinforcement shall not extend across the joint.
How do you find the expansion joints in a concrete slab?
Cut them to be the same height as the thickness of your concrete. So for a 4″ thick sidewalk you’ll cut 4″ expansion joints. As you pour each slab of concrete, stop and place your joint in between each slab. A joint trowel tool can be used to ensure there is a space between each slab.
How soon can you walk on concrete?
Please keep vehicles, children, pets, and yourself off of your newly poured concrete for the next 24 hours. After 24 hours, you can walk on your newly poured concrete, but avoid dragging your feet, ‘doing the twist’, or allowing your pets to walk on it as their claws can scuff the concrete.
Do driveways need control joints?
Control joints, or expansion joints as you call them, are better for driveways. Control joints are a deliberate plane of weakness placed in the slab, either cut with a concrete saw or formed with a jointer while the concrete is still wet. Control joints should transfer loads perpendicular to the surface of the slab.
