When should you use expansion joints in concrete?

Need of Expansion Joint in Concrete

These joints need to be carefully designed, located, and installed. If a slab is positioned continuously on surfaces exceeding one face, an expansion joint will be necessary to reduce stresses. Concrete sealer may be used for the filling of gaps produced by cracks.

Click to see full answer

Furthermore, how often do you need an expansion joint in concrete?

Usually, 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.

Furthermore, what material is used for expansion joints in concrete? 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.

Also to know is, are concrete expansion joints necessary?

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.

Should expansion joints be filled?

Just remember that expansion joints should always be sealed and filled with a flexible joint sealer and never be epoxied or coated over. Contraction joints can be filled in the same manner after a coating or sealer is applied.

25 Related Question Answers Found

What is the difference between expansion joints and control joints?

A control joint is used to reduce the occurrence of shrinkage in concrete, and it is usually a continuous, vertical joint filled with mortar. An expansion joint is a continuous or horizontal joint.

How do you fix an expansion joint?

How to Replace Concrete Expansion Joints

Sweep away any dirt and debris from the area.
Dig out and remove all the old material that's in the joints with a putty knife.
With a wet-dry vacuum, clean out the joints between the slabs very well.
Apply a bonding adhesive, usually epoxy, into the joints with a brush.
Insert foam backer rod.
Cover and seal the joint.

Where do concrete control joints go?

Space joints (in feet) no more than 2-3 times the slab thickness (in inches). A 4" slab should have joints 8-12 feet apart. Cut joints deep enough. Cut joints 25% of the depth of the slab.

Does concrete shrink or expand when it dries?

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. However, concrete does indeed expand when it gets hot or when the moisture content changes.

How do you control joints in a concrete slab?

How to Make Concrete Control Joints

Step 1 - Pouring. Concrete control joints, also known as expansion joints, are something best added when you're pouring the concrete or before it cures.
Step 2 - Setting in Place. When you pour a concrete path or driveway you'll see slits between areas of concrete.
Step 3 - Trowel.
Step 4 - Cement Saw.

How do you attach concrete to concrete?

A bonding agent (bonding adhesive) needs to be painted onto the existing concrete first to ensure that the fresh concrete will successfully adhere. This is also true of floor repairs, if concrete is used to fill gaps caused by damage. The new won't adhere to the old without the help of a bonding adhesive.

Why do they cut lines in concrete?

If you're using concrete to make a sidewalk, the shrinking concrete will cause cracks to appear as it dries. To prevent sidewalks from cracking in random spots and breaking apart, builders make lines in sidewalks. Of course, they don't just call them lines. The technical term for sidewalk lines is contraction joints.

How far apart should expansion joints be in concrete driveway?

Placing concrete expansion joints is a necessary step when installing concrete slabs because they allow room for movement. The suggested distance between expansion joints is 10 feet. They should be placed at least this close together to ensure that the concrete slabs do not crack or break.

How often should you cut concrete?

One of the first places to start is knowing how much space you need between your cuts. While experience will help you get a better idea of what works for your concrete and climate, there is a rule of thumb to start with. Cuts should be approx. 2-3 times the thickness of your slab in feet.

Does concrete expand and contract?

When free to deform, concrete will expand or contract due to fluctuations in temperature. The size of the concrete structure whether it is a bridge, a highway, or a building does not make it immune to the effects of temperature. Concrete expands slightly as temperature rises and contracts as temperature falls.

Why do we need expansion joints?

Importance of Expansion Joints in an Architectural Structure. An expansion joint is an assembly that is designed to absorb safely expansion and contraction of different construction materials caused by heat. These joints also absorb vibration and permit movement due to earthquakes and ground settlement.

Are control joints necessary?

This means that any cracks that occur before the concrete is sawed will render the sawed joint ineffective. Timing is very important. 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 do you use to fill gaps in concrete?

Once a year, go around your home and fill these gaps and joints with urethane caulk (or polyurethane caulk) to prevent problems. The expansion joint caulk is available at contractor supply stores, well-stocked home centers and hardware stores. For gaps and joints more than 1/4 in.

How wide should an expansion joint be?

Expansion joints should be wide enough to prevent portions of the building on either side of the joint from corning in contact, when the structure is subjected to the maximum expected temperature rise. Joints vary in width from 1 to 6 in.

Do you need to put expansion joints in concrete?

Expansion joints are put in place before the concrete is poured. Expansion joints are used to allow the slab to move and not put stress on whatever it abuts. With a little planning prior to pouring, utilizing control joints and expansion joints will help minimize cracking and extend the life of the concrete.

Where are expansion joints used?

Expansion Joints are the Gaps put in structures to accommodate the relative movement caused as a result of Expansion, Contraction or caused by Tremors which could damage the entire structure. They are commonly used in Large Structures, where a wobble can bring the whole and nearby structures Crumbling.

Where are expansion joints required?

Pavement expansion joints are only needed when: The pavement is divided into long panels (60 ft (18 m) or more) without contraction joints in-between. The pavement is constructed while ambient temperatures are below 40F (4C). The contraction joints are allowed to be infiltrated by large incompressible materials.