DURA-MIX® CONCRETE
A durable, scale resistant
concrete driveway is easily built if the proper concrete mix
is used and correct procedures are followed during
construction. Each of the following recommendations is made
for a specific reason and each must be followed strictly in
order to achieve a quality concrete driveway that will serve
for many years. It is suggested construction of exterior
concrete slabs be done between May 1 and September .
WHAT IS DURA-MIX®?
DURA-MIX® in one word, identifies a product that the consumer can be
assured will meet all requirements of the National Building Code
Standards. The DURA-MIX® name has been registered as a
trademark by ARMCA. ® CAN ONLY be supplied by ARMCA
Members
Site Preparation:
All black dirt,
vegetation, wood, bricks, large rocks, etc. should be removed
and the site leveled off.
The driveway base should be uniform, preferably undisturbed
subgrade soil.
A granular base is usually not necessary, however, crushed fill
of 20mm maximum size base coarse material may be used to bring
the site to uniform bearing and final grade. Backfill
material should be well compacted.
The base should be dampened before the concrete is placed.
Forms should be constructed with
50mm normal thickness lumber and should be well anchored with
25mm X 50mm (1 X 2 inch) stakes, driven firmly into the ground
at 1 metre intervals.
(See Fig. 1). Forms should be oiled before placing the concrete
to facilitate form removal. Slab thickness should be a minimum
of 100mm where the driveway is to be used exclusively by
passenger cars. If larger vehicles, such as trucks with topsoil
or moving vans, will be using the driveway, a thickness of 150mm
is recommended.
Reinforcing steel is
recommended, but not required. Reinforcing steel does not
prevent crack formation, if properly placed it can reduce the
amount of control joints required in your concrete stab.
When Ordering
Concrete Specify DURA-MIX®:
DURA-MIX® assures that you will have
the following minimum standards:
- Minimum cement 300 kg/m3
- W/C Ratio .45
- Air Content 5-8%
- Slump 80 mm
* DURA-MIX® CAN ONLY be supplied by ARMCA Members.
IMPORTANT:
All Exterior Concrete MUST Include
Entrained Air.
Advantages of using air in the mix
are:
A) Resistant to scaling from salt or frost action is increased 10 to 20
times.
B) It is easier to handle and finish because bleed water is greatly
reduced.
Placing & Finishing:
Under no
circumstances should water be added to concrete in the mix
truck to increase the slump above 100mm.
By adding just 5
litres of water to one cubic metre of 30 MPa concrete you
will:
- Increase the
slump by about 25mm
- Increase the
shrinkage potential by 10%
- Reduce its
freeze-thaw resistance by 20%
If you
need workability in your mix ask your supplier to adjust the
mix at the plant.
Don't adjust the mix at the jobsite.
Discharge concrete from the chute as close as possible to its final
resting place.
DO NOT USE a garden rake to move the
concrete horizontally. Use a square mouth shovel for this
purpose to prevent segregation of the concrete.
Darby or bull-float immediately.
Following placement and leveling, allow any bleed water which
appears to evaporate before attempting to finish.
Failure to wait will result in a scaled surface after a few
seasons. Do not sprinkle on cement to absorb this
water. This waiting time may range from 15 minutes on hot days,
to several hours on cool, damp days.
Float surface prior to texturing and jointing.
Use an edging tool along forms.
Texture the driveway and garage slab surface with
a stiff broom to leave a non-slippery, slightly roughened
surface.
All control joints must be a minimum of 1/4 the
thickness of the concrete slab (see Fig.3). If the control
joints are sawed into the hardened concrete, it should be done
within 16 hours of concrete placement at intervals recommended
(see Fig. 3 & 4).
Curing
Concrete For Strength And Durability
Curing of concrete involves: TIME, TEMPERATURE and PROTECTION FROM MOISTURE LOSS.
TIME: Minimum 3 days at 10 degree
C or above.
TEMPERATURE: If ambient temperature drops
below 5 degrees C within 24 hours, concrete must be
protected for the first 3 days with insulating material,
such as insulated blankets or straw. Additionally, concrete
must be allowed to air-dry before winter; tarps must be
removed during the day, and re-applied at night.
Protection from moisture loss: Concrete
Hardening requires that moisture be present for cement
hydration; curing methods include:
1) curing compounds
2) continuous water spray
3) covering with wet burlap
4) ponding
5) covering with plastic sheets
When placing concrete after September 15, the use of
curing compounds is not recommended. Proper
cold-weather curing procedures should be followed. A
high-quality sealer should be applied in the spring. Your
driveway should be kept clear of ice, snow and freezable
materials.
Placement of concrete
pavements after September 30th is not recommended unless proper Cold Weather
Concrete procedures are followed. CSA A23.1
recommends: Concrete subject to freeze-thaw and de-icing
chemicals should be cured for 7 days at 10 degree C for minimum curing, or the time required to attain 70% of
specified 28 day concrete strength.
CAUTION: The use of DE-ICING CHEMICALS
AND SOME FERTILIZERS may be harmful to your concrete
surface.
MAINTAINING YOUR CONCRETE SURFACE
To maintain a quality
and durable concrete surface for many years, the following
is highly recommended:
Concrete must be re-sealed
with a high quality sealer a minimum of every 3 years or
sooner if required.
The driveway, sidewalk, or
garage pad should be kept clear of ice, snow and freezable
materials in winter.
ARMCA RECOMMENDS THAT CONCRETE BE PLACED AND FINISHED BY A
CERTIFIED JOURNEYMAN FINISHER.
MAINTAINING YOUR CONCRETE
SIDEWALK AND/OR DRIVEWAY
In most cases concrete is a durable, long lasting product requiring little or
no maintenance. Concrete sidewalks and/or driveways
are often expected to be maintenance free, so
eyebrows are often raised when the subject of
maintaining concrete is brought up.
New concrete sidewalks and/or driveways should be
sealed with a concrete sealer before being
exposed to traffic.
Properly maintaining concrete can greatly extend its life and beauty: plain
concrete can look clean and bright-instead of oil stained
and grimy. Decorative Concrete can look the
same after years of enjoyment as it did when it was
brand new instead of faded, oil stained, and dirty.
Properly maintaining your concrete sidewalk and/or driveway protects
your investment - particularly if you have added the
beauty of pouring decorative concrete.
Maintaining concrete consists of 4 steps
1) Cleaning concrete on a regular basis
This should be done at least once per year to remove normal dirt
and grime build up and to remove rust or other stains. Methods
of cleaning concrete as well as cleaning products can vary widely. Some methods and products can be
detrimental to the concrete. For further information please
contact an experienced contractor, the Alberta Ready Mix
Concrete Association (ARMCA) or your local ARMCA member.
2) Repairing cracks in concrete
Repairing cracks in concrete maintains a structurally sound
surface and minimizes water intrusion through cracks, which can
cause problems with the subgrade.
3) Sealing joints in the concrete
Sealing joints minimizes or eliminates water intrusion through the joints, helps prevent dirt from collecting in the joints and helps prevent weeds sprouting up through the joints
4) Sealing the concrete surface
Sealing and periodic resealing of the concrete surface not only reduces moisture infiltration into the concrete but also helps reduce staining.
Some sealers offer other benefits, such as high resistance to abrasion, resistance to UV sunlight, resistance to dirt and grime, oil, grease, rust, acid, chlorine, fertilizer stains, sprinkler water residue and mildew, as well as stains from most other organic matter.
What your concrete is exposed to will affect your choice of a
sealer.
DECORATIVE CONCRETE
For decorative concrete, the same steps as above will apply, but we strongly suggest you visit the web site or contact the technical department of the decorative product manufacturer you have chosen.
For instance, if you used a concrete topping or dressing, or a certain brand of colored concrete, or a spray on
decorative finish - the technical departments of these companies will have real world experience with what works best for their products.
Concrete Sealers provide improved resistance to weather, water,
stains, and abrasives. Sealers also offer resistance to rain,
sun, freezing temperatures, petroleum, and deicing salts.
Concrete sealers make clean up easier.
All concrete sealers should be applied to concrete that is clean and dry. All stains, grease, oil, dust and dirt should be removed prior to application of the sealer.
Methods of cleaning concrete as well as cleaning products can
vary widely. Some methods and products can be detrimental to the
concrete. For further information please contact an experienced contractor, the Alberta Ready Mix Concrete Association (ARMCA) or your local ARMCA member.
Whichever brand sealer you use from your local hardware store or a pro contractor supply house-follow the specific instructions for the product you select in both preparation and application of the product. Also
consult the labels for specific safety instructions.
DEICERS
The use of inappropriate deicing chemicals such as agricultural or lawn fertilizers can result in severe damage to any concrete surface. Use only deicing chemicals intended for concrete sidewalks and driveways.
Concrete requires time to mature and produce a durable surface. Driveways placed during the fall often don't have a sufficient period of warm weather to fully mature. Avoid the use of deicing salts or chemicals on concrete placed after August 31.
Refer to ARMCA Concrete Tech-Tip #2 (Scaling Concrete Surfaces)
Hard Trowel Finish on Air-entrained Concrete
Some
specifications require concrete contractors to hard-trowel
air-entrained concrete. The risks associated with this
requirement include
1) increased probability of delamination or blistering;
2) reduction in surface air content; and
3) change in hardened air void parameters.
Under service
conditions, most interior slabs don't have a high moisture
content or a chance to freeze, so air-entrained concrete isn't
needed to ensure a durable floor surface. Unless the building is
enclosed and the roof is completed, it's impossible to protect
non-air-entrained concrete slabs from external moisture. Thus,
specifiers often require interior concrete to be air-entrained
if the slabs will be exposed to a cold, wet environment during
construction. In addition to requiring entrained air, designers
may also specify a lower water-cement ratio and a higher
compressive strengh that can increase the cost of the concrete.
Contact Next Level Concrete to discuss your next concrete design! |
