Fixing a Concrete Driveway

A concrete driveway can crack after time due to weathering, excess water and just usage. Sometimes the concrete lifts along these cracks and you get protruding pieces that catch heels and, in wintry areas, make it difficult to shovel snow.

Installing a new concrete pad is very expensive. The present pad has to be taken up and a new one poured which could amount to $5,000 for a 400 square foot driveway. This is quite a price to pay when the rest of the driveway is in good shape. And if the pad isn’t in full view of the street a nice new driveway will only be seen by you and a few passersby.

Patching the driveway is a cheap alternative but the patches will, in time, fail. A few inches of concrete will not hold back the forces of nature. Even by getting the cement patch deep into the crack will not fix it permanently.

The best way to cure a bad crack is to take it out completely. Usually the offending line runs from one expansion joint to another. You can hire a concrete company to come out and cut out the small piece and pour a new slab. What they will do is cut out a rectangular (or square) piece surrounding the crack and pour a new section. You can do this yourself by renting a gas-powered cement saw.

To avoid movement from the new section it will have to be reinforced. Rent a heavy drill and drill holes large enough in diameter for reinforcing bars into the newly-cut edge of the old concrete. These should be around 6″ deep. Cut the reinforcing bars so that they fit into the holes and tie 2″ square wire mesh to this. Now you can pour concrete. If the patch is smaller than three-foot square you can get premixed concrete in a bag. This will take about 10 bags but you don’t have the mess of a cement mixer.

When you trowel out the cement it will form a durable patch that will last for years.

Fortifying Cement Driveways

We’ve all seen it happen either to of us or to a neighbor or friend. The beautiful driveway with exposed aggregate stone that concrete workers poured the year before has a tiny diagonal crack running through it. It probably happened over the winter when the freeze-thaw cycle was at its peak and in another year the crack will widen. Then comes the patching and after six or seven years the $6,000 driveway begins to look like a minefield.

This is a crying shame because I have a cement sidewalk beside my farmhouse that’s over 75 years old and not a crack. This is mostly due to the fact that it was poured in a very thick pad but also that the ground below was flat and had no water problems. This is because as cement cures it gets harder – even after years.

Because of its very nature concrete is prone to cracking and much of this comes from shrinking after it has dried. In fact concrete shrinks 1/16th of an inch for every 10 feet feet of length. This shrinking creates a force that will find the weakest part of the surface, sometimes the one where the most weight is applied like under a vehicle. To prevent this grooves called “control lines” are cut into the surface with a diamond saw 1/4″ deep at 15 feet intervals.

Basic Concrete Driveway Guidelines:

• Compacted base: If the ground shifts the pad will crack
• Heavy-duty steel reinforcing mesh: This should be placed in the wet cement. This not only make the pad resist cracks but will prevent any tiny cracks from getting bigger.
• Thick Pad: 5″ minimum
• Control lines: 1/4″ every 15 feet
• Cement mix: 4,000 pounds per square with a curing compound.

After the driveway has cured you can apply a siloxane water repellent. Siloxane seals the pores of the concrete an repels oil and water to prevent staining. Unlike many consumer products a siloxane-based sealer will allow the cement to breathe. This is important because moisture enters concrete through the ground and you want it to be able to find a way out. A silicone dealer will not let this happen and, in a freeze-thaw cycle, will expand and crack the cement.

There’s no reason a cement driveway should not last 30-50 years.