Creating a Concrete Driveway | Best Pick Reports
Driveway replacement process.
The first step in replacing a concrete driveway is to break up the old
driveway and haul it away. Then, depending on the nature of the ground
under the driveway, the contractor may put down additional gravel or
fill to create a more solid base for the concrete. Without a good base,
the driveway is more likely to settle and/or crack. Next, the
contractor installs temporary forms to hold the wet concrete. Once the
forms are in place, the concrete arrives and is poured into them. The
concrete is smoothed, and contraction joints are cut. The concrete
hardens inside the forms. Once the concrete is hard, the forms are
removed.
Contraction joints. As
concrete sets and hardens, it has a tendency to shrink and therefore
crack. Contraction joints are shallow grooves cut into a concrete slab
soon after it is placed. This way, when the concrete hardens and
shrinks, any cracking that arises should tend to follow the contraction
joints, where the concrete is thinner and weaker. In temperate
climates, experts recommend cutting contraction joints approximately
every 15 feet.
Expansion joints. Expansion
joints are placed at intervals of about 75 feet, on very large slabs of
concrete. These joints extend through the entire thickness and width of
the slab, are filled with fiberboard, and are then sealed. Expansion
joints help prevent concrete cracking by giving room for thermal
expansion in hot weather. Like a contraction joint, an expansion joint
can prevent cracks from propagating across the joint. However, even
with proper joints, driveways often crack. Due to the variability of
materials and terrain, many established companies will not guarantee
their driveways against aesthetic cracking.
Concrete grade. Concrete
grade is defined by the strength of the concrete and is measured in
pounds per square inch (psi). In general, the higher the psi grade, the
more weight it can handle, the more durable it will be, and the better
it will hold up when pressure washed. Concrete used in driveways is
usually 3,000 or 4,000 psi. The 4,000-psi-grade concrete is slightly
more expensive than the 3,000-psi-grade concrete. However, this price
difference is small when compared to the total cost of driveway
replacement.
Setting or curing. Concrete
does not dry; it sets or cures through a chemical process called
hydration. During hydration, water molecules combine with the cement to
form very tiny crystals. These crystals interlock with one another, as
well as with the aggregate in the concrete, to give the concrete its
strength. If the concrete or the surface of the concrete dries before
hydration fully occurs, the concrete loses its strength and/or becomes
flaky. Therefore, it is very important to keep the surface of the
concrete wet after it is poured.
Driveway design. In
general, water should never puddle on the driveway. If the house is on
a hill, the driveway should channel the water down to the street or to
a storm drain. Residential driveways are usually four inches thick. In
general, thinner driveways are more apt to crack than thicker driveways.
Color variation.
Unfortunately, due to variation in the color of the raw materials that
make up concrete, colors will vary between batches of concrete. Color
variation is usually not a problem in a complete replacement job, since
all the concrete usually comes from the same batch. However, when
adding to or replacing a section of an existing driveway, you should
expect color variation.
Undermined driveways. Misplaced
gutters or missing downspouts often dump water alongside a driveway or
sidewalk. Over time, the flowing water may erode the ground next to the
driveway and then underneath it. As the earth beneath the driveway
washes away, the driveway loses its support and is likely to crack and
settle. Before replacing such a driveway, first fix the water flow
problem.
Pavers. Driveways made out
of pavers are becoming increasingly popular because
they offer a non-traditional variation to the standard concrete
driveway. Pavers are brick-like pieces of concrete that are molded at a
factory and shipped to the job site. Pavers can create many different
looks, including cobblestone, brick, and slate, which results in unique
driveways for homeowners. Pavers come in a variety of colors and
styles, but they are usually more expensive than standard concrete.
While many driveway contractors offer both concrete and paver
driveways, homeowners should be sure to select a company that is
experienced in the look that they desire.