start of every successful concrete project involves careful planning
and follow-up, whether you handle the project yourself or hire
a concrete contractor.
Involving a professional concrete contractor may be wise if the
project is very large or complicated. Hiring a contractor also
relieves the home or property owner of a lot of the planning,
preparation and direct project management. However, if a contractor
is used, be sure to request and receive lien waivers, from all
contractors and sub-contractors involved, upon payment and completion
of the project. If the contractor fails to pay the suppliers for
materials or services on your project, they are still entitled
to file a lien against your property for the price of their product
or service to ensure payment.
If you choose to handle your project yourself
we offer the following suggestions:
is an excellent construction material for many applications.
The expected use of the concrete will help determine the required
thickness and any special properties. The load carrying capacity
of a slab is primarily dependent on thickness. A four-inch-thick
slab will handle common weight loads such as foot traffic, light
storage, cars, pickups, light tractors and animals. Whereas a
six-inch-think slab will handle most medium-duty weight loads,
such as motor homes, straight trucks and larger equipment. Reinforcement
materials such as wire mesh, fibers or rebar add strength and
durability to the slab and reduce cracking and shifting. Unusually
heavy vehicles or high-traffic projects may require special design
tools commonly required are:
strike-off board (screed)
by removing all organic matter, such as grass, weeds, wood and
any pockets of soft or water-soaked soil.
In some cases, the slab can be placed directly on undisturbed
soil. If any of the sub-grade or base has been disturbed, fill
may be added to raise the final height of the slab and create
uniform depth or thickness of concrete. Any fill should be placed
on undisturbed soil and compacted in layers six inches thick or
less. For soils with questionable drainage, such as clays or soft
black dirt, use a fill base of four to eight inches of compacted
sand or fine gravel to help disburse water and reduce settlement.
Never place concrete on muddy or frozen ground.
Use 2x4s or 2x6s to form the parameter of the slab. The
tops of the forms need to be set to the desired final height of
the slab. Lumber should be straight and staked at two-foot intervals
to minimize form bowing. After forming is completed, check the
slab thickness. Using a stringline or straightedge across the
top of the forms, measure the depth to the base or sub-grade.
Pay careful attention to the depth or slab thickness. Variances
as small as one inch can result in up to 25% more concrete being
required, based on a four-inch-thick slab.
Check the weather forecast before ordering concrete. Ideal
temperatures for placing concrete are between 50°F and 90°F.
Warmer temperatures will make the concrete dry quicker, leaving
less time to complete the job. Lower temperatures will lengthen
the amount of time for the concrete to dry. Newly placed concrete
should not be subjected to temperatures below 40°F for at
least a week.
Concrete is ordered by the cubic yard.
It is calculated by multiplying
the surface area by the thickness in feet to determine the total
volume in cubic feet. Divide this value by 27 to obtain the volume
in cubic yards. It is often wise to increase the calculated volume
by five or ten percent to help account for slight deviations in
slab thickness, spillage, etc.
Sufficient manpower and tools should be
ready before the concrete arrives. Ideally, concrete should
be in place less than 90 minutes after batching at the ready-mix
plant. Place concrete as close to its final position as possible,
not in large piles. Screed the concrete using a sawing action
pulling a straight board along the top of the forms. One of the
most common mistakes at the job site is adding too much water
to the concrete mix. This is done to change the consistency of
the concrete, but should be done sparingly. Too much water can
reduce strength and durability, leading to the formation of shrinkage
the concrete is in place, the surface needs to be finished.
Finishing involves settling the aggregate and removing surface
imperfections. Start by using a bull float, this helps to push
the aggregates below the surface allowing for subsequent finishing
activities. A wooden or metal hand float or trowel is used to
remove slight surface imperfections. An edger, which is like a
short steel trowel with a rounded side, is used adjacent to the
forms and along the parameter of the slab. When correctly used,
an edger produces a more attractive rounded edge and can reduce
chipping or breaking along the edge. Steel troweling follows floating
and edging when a smooth, dense surface is desired. Timing is
important in this operation because if delayed too long, the surface
becomes too hard to trowel. All outdoor slabs subject to weather
conditions should be broomed. Brooming the surface after floating
or troweling is the last step in finishing that produces an abrasive,
shrinks slightly as it dries.
Once fully dried, seasonal changes in temperature cause the concrete
to expand and contract, which can lead to cracking. Control joints
are cuts in the surface of the slab approximately one-quarter
of its thickness, purposely placed to position cracks in predetermined
locations. Jointing tools can be used if done during finishing
and saws with concrete or masonry blades enable you to cut control
joints after the concrete has dried. A good rule of thumb for
control joints is to double the thickness as feet. For example
a four-inch-thick slab should have control joints placed every
the concrete has set for 12 or more hours, careful consideration
should be given allowing it to cure.
Fresh concrete should not be subjected to temperatures below 40°F
for at least a week. When pouring concrete in cold weather, some
type of insulation should be used to keep the concrete surface
from freezing (e.g., insulation blankets or straw). Inversely,
concrete should not be allowed to dry too quickly in very warm
weather. When pouring concrete that is in direct sunlight with
temperatures in excess of 90°F, it is recommended to keep
the surface damp with a light water mist, dampened straw or flooding
to enhance curing by supplying additional water.
To Care For Your Concrete Driveway
residential driveways enhance the appearance of the home and
will provide many years of service with minimum maintenance.
In order to maintain a durable driveway that will be relatively
free of surface blemishes throughout its service life, the homeowner
should carry out the following recommendations.
drive on new concrete for at least seven days.
allow drain water to undermine the slab and cause settlement
allow snow and ice to accumulate on the slab during the first
winter. Keep it cleaned off.
from the use of de-icing chemicals (salt or calcium chloride)
for snow and ice removal the first winter. Sand can be used
Never use de-icers containing fertilizer ingredients such as
ammonium sulfate and ammonium nitrate. Concrete should also
be protected from exposure to liquid fertilizer systems used
for lawn treatment.
Scaling is one of the most insidious attacks on concrete and
can happen even with quality concrete, yet there are methods
of reducing and even preventing this yearly problem.
Concrete Will Reduce Or Stop Scaling
Scaling of sidewalks, driveways and other exterior flatwork
can be minimized. It is especially important that exposed concrete
be sealed in climates that experience severe cold weather. A
concrete sealer applied after 30 days will help to prevent water
from entering the concrete during autumn rains and the intrusion
of de-icing salts tracked onto driveways during winter months.
of the most economical and easiest methods of sealing is to
apply boiled linseed oil thinned with mineral spirits, mixed
approximately 1:1. The mixture is usually applied in two applications
by roller, spraying or a squeegee. Resealing with this boiled
linseed oil mixture should be done at least every two years.
concrete sealing should be done after approximately 30 days
of air drying, when the surface is dry and preferably when the
air temperature is above 70°F.
It should be noted that some temporary discoloration of the
surface may be expected when sealing with a boiled linseed oil
City Ready Mix has sealers available.