Building a Concrete Driveway > Do it yourself > Driveway Specifications

Building a Concrete Driveway > Do it yourself > Driveway Specifications
While your removing your old driveway, dig down 8" deeper and remove the black soil.
Distribute 6" of crushed concrete, granite or gravel and machine pack the sub base to a
minimum 90% compaction of uniform density and thickness.

Once you;ve compacted your sub-base then distribute clean washed sand a minimum 2"
deep. Mist the sand with water as you machine vibra-plate the sand to a minimum 95%
compaction of soil uniform density and thickness.

Set your forms up for your new driveway 12 ft apart for a single car driveway and 24 ft
apart if you want a two car driveway. The Concrete needs to be 6" thick to meet national
building codes requiring that all steel reinforcement encased with concrete a minimum 3".
Where the driveway meets the street you'll need to make the radius a minimum 48". Dowel
#5 18" rebar rods into the street @ 24" on center with epoxy.

Measure 10' ft back from the street and install an expansion joint as per city municipality
building codes. This section of concrete drive needs to have #4 steel Rebar rods spaced
12" apart each way forming a grid that is placed on 3" chairs. Tie these grids into your
dowels that you have drilled into the street, (3" below elevation).

If your city has a sidewalk running through your driveway then you will need to match the
width (48" and form your sidewalk closest to your residence level while the form closest to
the street needs to have a 1/8" per ft fall.

Your curb and gutter needs to be formed up to continue across uninhibited. The depth of
the curb and gutter should be 12" deep by 16" wide with cont reinforcement.

At this point your ready to install your #3 steel rods in your driveway spaced 15" apart on
center each way and placed on 3" chairs to maintain the 3" encasement.

Now your ready to order concrete. Call a ready mix company (preferably Metro Concrete if
you live in Houston, they don't "cut" the Portland cement with fly ash like Houston Ready
Mix and many of the others do).

You'll need to order 1" gravel aggregate with 6 sacks of pure Portland per cubic yard with
a maximum 4" slump. Once the concrete arrives on site you will need to measure the
concrete temperature. It is well known that the chemical reaction of cement with water is
exothermic and liberates a considerable quantity of heat during the curing period. When
cement, water, stone and sand are mixed together, a chemical reaction starts. This is
between the cement paste and water. In this curing process, the volume of the structure,
and the inner pressure/strain exerted on the rebars will change in a fashion that depends
on the composition of the concrete mixture.

The curing process is affected by the water to cement ratio, the curing temperature,
humidity and the type of cement. Hydration is responsible for the hardening (strength) of
the concrete. For concrete, the gain in strength continues for a long time, and
theoretically for an indefinite period of time. However, the strength of the concrete
reaches a peak within 7days. During this process something else happens. Water in the
concrete mixture will evaporate, resulting in a decrease in the volume of the concrete.
The volume of concrete also decreases due to re-arrangement of finer particles within the
larger ones. The different proportions of cement, water, and sand will bring about
different temperature, pressure and strain variations within concrete structure. The result
of the volume change is strain, also known as shrinkage strain, and this is responsible for
some small cracks that may appear after the curing process. At times, the thermal
stresses induced during the curing process may cause cracks within the structure, thus
weakening it.

The maximum optimum temperature of the concrete cannot exceed 40.2 °C. The
temperature change measured within the concrete follows the same trend as the ambient
air and surface temperatures surrounding the structure but with a larger change in the
initial stage and tailing off to the ambient temperature with increasing time.

The barometric pressure variables and humidity content need to be taken into
consideration at the time of the pour as this will determine the amounts of air entrainment
and bi-calcium silicates admixtures required to optimize the mix.

Now that you've optimized your concrete mix you are ready to pour the cement. Screeding
the cement off must be done with an .o24 min aluminum 2x4 and NOT a wood 2x4.
(wooden 2x4 will flex and bow causing undesirable surface variations).

Float the surface with magnesium floats and texture with a horse hair broom resulting in a
fine textured finish that will be slip free

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