New Concrete

Concrete flat workStill not decided on a driveway material: asphalt or concrete. Today, the concrete choice has expanded to include a multitude of decorative concrete options.

 

However plain gray concrete may look, it is still the most often installed in the Greater Chicago Area, but the decorative idea is catching on.

 

The concrete industry has rapidly developed many products that can be applied to existing plain gray concrete and final product will have entirely new look.

 

 

NEW Concrete Slab Construction

Properly Prepared Subgrade:

The subgrade should be compacted and have an even thickness. A standard is 4" thick – you want 4" thick continuously, not a 3½" to 4½" varying thickness.

The Correct Concrete Mix:

A 4000-psi, .50 water to cement ratio is best for concrete slab construction. This provides better wearability and a "denser" concrete than the typical 2500-psi mix.

 

In cold weather conditions, air entrainment is added to the concrete at the batch plant. This entrained air allows any moisture which does enter the concrete to expand in the microscopic air pockets during a freeze/thaw cycle instead of putting internal pressure on the concrete.

Correctly Placed Joints

Joints should be at least ¼ the concrete thickness – so a 1" deep joint should be used in a 4" thick slab. Joints should also be spaced 2-3 times in feet the thickness of the concrete: so a 4" thick slab should have joints no farther than 8’ – 12’. If joints are spaced too far apart, cracks will often occur where the joints should have been.

Proper Drainage

For best drainage, the concrete should slope ¼" per running foot away from the home. If proper drainage is prevented due to the area of concrete being locked between two structures, a drain may need to be installed which will collect the water at a low point in the concrete and feed it down the drain.  It is very important you direct water away from the slab.  Many slabs have to be replaced due to downspouts emptying directly onto or next to the drive or sidewalk.

Reinforcement

Reinforcement can be with either wire mesh, or steel bars placed in a grid pattern. In either effort need to be taken to keep the reinforcement in the center of the concrete. Note that reinforcement does not eliminate cracks – it simply holds them together.

Proper Finishing

After concrete is bull-floated, it should be left alone until all the bleed water on top of the concrete has evaporated. Starting the finishing operation too soon can trap surface water and create a weak surface.
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