Fixing Cracks In The Concrete

Cracks in the Concrete

Cracks in concrete can appear in driveways, patios, sidewalks, and even around the foundation of your home.

Most concrete will crack, because concrete shrinks as it dries and cures. In fact, concrete slabs shrink about 1/16th inch for every ten or so feet. This type of stress is a lot like holding up a magazine, grabbing each end, then pulling it apart.

But there are many other reasons concrete cracks. Root growth, standing water, and the freeze/thaw cycle (not an exhaustive list)

Standing water is a particularly hard on concrete. When water isn't draining properly, the water works down between a weakened section and creates a crack. It is easy to fix the crack, but it will happen again unless the underlying drainage problem is fixed.

Here are some tips to fix cracks:

For small concrete cracks, 1/8" (3mm) or less:

• Buy a concrete patching compound from the local hardware store.
• Use a screwdriver to chip away any flakes or loose concrete, then use a wire brush to remove any dirt and debris.
• Rinse the cracked area using a hose.
• Mix the concrete patching compound.
• Use a putty knife to put the compound into the crack, then smooth out the surface before the compound hardens.
• Work fast -- most compounds set up quickly
• Keep the feet and the cars off the repair until it is thoroughly dry.

For large cement cracks, ¼" (6mm) or more:

While the beginning steps are the same for repairing larger cracks as for small cracks, Bigger concrete cracks require the use of caulking or sand packing.

For caulk, pick up some siliconized latex caulk and a caulking gun from the hardware store.

For sand packing, buy some sand and concrete patching compound from the hardware store.

Before you start:

• Use a screwdriver to chip away any flakes or loose concrete, then use a wire brush to remove any dirt and debris.
• Rinse the cracked area using a hose.
• Mix the concrete patching compound.

Then:

• (Caulking) Using the caulking gun, force the caulk deep into the crack, across the length of the crack.
• The caulk will expand to fill the crack, and will self-level.

• (Sand packing) Pour in a layer of sand, then apply the patching compound with a trowel.
  
• Work quickly -- it dries fast.
• Feather the new surface into the existing edges gives it a finished look.

You may have seen the lines concrete masons put into slabs after they are poured. This groove reduces the thickness at that point, making easier for that particular spot to crack -- but the crack is controlled. In fact, it is called a control joint. It is the same idea as folding a piece of paper to create a crease before tearing it.

The Portland Cement Association suggests a control joint should be at least 1/4 of the slab thickness. For a typical 4-inch slab, you should have a 1-inch control joint.

Other options, like reinforcing steel or wire mesh hold the concrete together in the event it does crack (except on Michigan roads... nothing holds them together... stinkin' potholes).