Frequently Asked Questions
Below are answers to some frequently asked
questions. If you have any other questions about our
company or services, please feel free to
contact us.
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Q: Why should I go with decorative
concrete over real stone?
A: On average, concrete tends to be half the
price of installing stone or brick. With
decorative concrete, you have a world full of
choices as to patterns and colors without the
headache of trying to find "the right stone" for
your look. Concrete also provides a much wider
range of options for use. Because it is
reinforced with steel, it can be used for
structural applications as well as decorative
ones. Large panels and spandrels that are
impractical or impossible to cut out of real
stone are no problem for concrete. Concrete also
resists the growth of many mosses and lichens (a
nasty fungus) that tend to thrive on many types
of real stone.
Q: How much concrete will I need?
Concrete calculator!
http://www.inlandcanada.com/ConcreteCalculator/ConcreteCalculator.aspx
Q: What is the difference between concrete
and cement?
A: In general terms concrete is a mixture of
aggregate, water and a cement binder. Cement is
an ingredient in concrete.
In construction, concrete is a composite
building material made from the combination of
aggregate and a cement binder.
Concrete does not solidify from drying after
mixing and placement; the water reacts with the
cement in a chemical process known as hydration.
This water is absorbed by cement, which hardens,
gluing the other components together and
eventually creating a stone-like material. When
used in the generic sense, this is the material
referred to by the term concrete. (http://en.wikipedia.org/wiki/Concrete#Cement)
In the most general sense of the word, cement is
a binder, a substance which sets and hardens
independently, and can bind other materials
together. Most important cements are hydraulic
cements, materials which set and harden after
combining with water, as a result of chemical
reactions with the mixing water and, after
hardening, retain strength and stability even
under water. (http://en.wikipedia.org/wiki/Cement)
Q: What kind of concrete will I need for my
job?
A: The Ready-mix concrete type you will probably
need is called … concrete. It is suitable for …
Please remember the appearance of concrete is
determined by the placing and finishing of the
concrete. Check our Request a Quote page so that
we may contact you for more information on
complete solutions for your placement and
finishing needs.
Q: Does Stamped Concrete Fade?
Cleaning and sealing stamped and colored
concrete should be done on a regular basis just
like any other home maintenance. The frequency
will depend on how exposed and how high a
traffic area to cars, foot traffic, water, and
any chemicals the concrete is. Just like waxing
a car, reseal your stamped concrete and the
color will be as vibrant as the day we installed
it.
Q: Why is rebar important in preparing and
placing concrete?
Concrete is a material that is very strong in
compression, but virtually without strength in
tension. To compensate for this imbalance in
concrete's behavior, rebar (reinforcement bar)
is cast into it to carry the tensile loads.
Q: What does it mean to "cure" concrete?
Curing is one of the most important steps in
concrete construction, because proper curing
greatly increases concrete strength and
durability. Concrete hardens as a result of
hydration: the chemical reaction between cement
and water. However, hydration occurs only if
water is available and if the concrete's
temperature stays within a suitable range.
During the curing period-from five to seven days
after placement for conventional concrete-the
concrete surface needs to be kept moist to
permit the hydration process. new concrete can
be wet with soaking hoses, sprinklers or covered
with wet burlap, or can be coated with
commercially available curing compounds, which
seal in moisture.
Q: Can it be too hot or too cold to place new
concrete?
Temperature extremes make it difficult to
properly cure concrete. On hot days, too much
water is lost by evaporation from newly placed
concrete. If the temperature drops too close to
freezing, hydration slows to nearly a
standstill. Under these conditions, concrete
ceases to gain strength and other desirable
properties. In general, the temperature of new
concrete should not be allowed to fall below 50
Fahrenheit (10 Celsius) during the curing
period.
Q: What is air-entrained concrete?
Air-entrained concrete contains billions of
microscopic air cells per cubic foot. These air
pockets relieve internal pressure on the
concrete by providing tiny chambers for water to
expand into when it freezes. Air-entrained
concrete is produced through the use of
air-entraining portland cement, or by the
introduction of air-entraining agents, under
careful engineering supervision as the concrete
is mixed on the job. The amount of entrained air
is usually between 4 percent and 7 percent of
the volume of the concrete, but may be varied as
required by special conditions.
Q: What are recommended mix proportions for
good concrete?
Good concrete can be obtained by using a wide
variety of mix proportions if proper mix design
procedures are used. A good general rule to use
is the rule of 6's:
● A minimum cement
content of 6 bags per cubic yard of concrete,
● A maximum water
content of 6 gallons per bag of cement,
● A curing period
(keeping concrete moist) a minimum of 6 days,
and
● An air content of
6 percent (if concrete will be subject to
freezing and thawing).
Q: Why does concrete crack?
Concrete, like all other materials, will
slightly change in volume when it dries out. In
typical concrete this change amounts to about
500 millionths. Translated into dimensions-this
is about 1/16 of an inch in 10 feet (.4 cm in 3
meters). The reason that contractors put joints
in concrete pavements and floors is to allow the
concrete to crack in a neat, straight line at
the joint when the volume of the concrete
changes due to shrinkage.
Q: Why test concrete?
Concrete is tested to ensure that the material
that was specified and bought is the same
material delivered to the job site. There are a
dozen different test methods for freshly mixed
concrete and at least another dozen tests for
hardened concrete, not including test methods
unique to organizations like the Army Corps of
Engineers, the Federal Highway Administration,
and state departments of transportation.
Q: What are the most common tests for fresh
concrete?
Slump, air content, unit weight and compressive
strength tests are the most common tests.
Slump is a measure of consistency, or relative
ability of the concrete to flow. If the concrete
can't flow because the consistency or slump is
too low, there are potential problems with
proper consolidation. If the concrete won't stop
flowing because the slump is too high, there are
potential problems with mortar loss through the
formwork, excessive formwork pressures,
finishing delays and segregation.
Air content measures the total air content in a
sample of fresh concrete, but does not indicate
what the final in-place air content will be,
because a certain amount of air is lost in
transportation, consolidating, placement and
finishing. Three field tests are widely
specified: the pressure meter and volumetric
method are ASTM standards and the Chace
Indicator is an AASHTO procedure.
Unit weight measures the weight of a known
volume of fresh concrete.
Compressive strength is tested by pouring
cylinders of fresh concrete and measuring the
force needed to break the concrete cylinders at
proscribed intervals as they harden. According
to Building Code Requirements for Reinforced
Concrete (ACI 318), as long as no single test is
more than 500 psi below the design strength and
the average of three consecutive tests equals or
exceed the design strength then the concrete is
acceptable. If the strength tests don't meet
these criteria, steps must be taken to raise the
average.
Q: How can you tell if you're getting the
amount of concrete you're paying for?
The real indicator is the yield, or the actual
volume produced based on the actual batch
quantities of cement, water and aggregates. The
unit weight test can be used to determine the
yield of a sample of the ready mixed concrete as
delivered. It's a simple calculation that
requires the unit weight of all materials
batched. The total weight information may be
shown on the delivery ticket or it can be
provided by the producer. Many concrete
producers actually over yield by about 1/2
percent to make sure they aren't short-changing
their customers. But other producers may not
even realize that a mix designed for one cubic
yard might only produce 26.5 cubic feet or 98
percent of what they designed.
Q: Why do concrete surfaces flake and spall?
Concrete surfaces can flake or spall for one or
more of the following reasons:
In areas of the country that are subjected to
freezing and thawing the concrete should be
air-entrained to resist flaking and scaling of
the surface. If air-entrained concrete is not
used, there will be subsequent damage to the
surface.
The water/cement ratio should be as low as
possible to improve durability of the surface.
Too much water in the mix will produce a weaker,
less durable concrete that will contribute to
early flaking and spalling of the surface.
The finishing operations should not begin until
the water sheen on the surface is gone and
excess bleed water on the surface has had a
chance to evaporate. If this excess water is
worked into the concrete because the finishing
operations are begun too soon, the concrete on
the surface will have too high a water content
and will be weaker and less durable.
Q: Will concrete harden under water?
Portland cement is a hydraulic cement which
means that it sets and hardens due to a chemical
reaction with water. Consequently, it will
harden under water.
Q: What does 28 -day strength mean?
Concrete hardens and gains strength as it
hydrates. The hydration process continues over a
long period of time. It happens rapidly at first
and slows down as time goes by. To measure the
ultimate strength of concrete would require a
wait of several years. This would be
impractical, so a time period of 28 days was
selected by specification writing authorities as
the age that all concrete should be tested. At
this age, a substantial percentage of the
hydration has taken place.
Q: What is 3,000 pound concrete?
It is concrete that is strong enough to carry a
compressive stress of 3,000 psi (20.7 MPa) at 28
days. Concrete may be specified at other
strengths as well. Conventional concrete has
strengths of 7,000 psi or less; concrete with
strengths between 7,000 and 14,500 psi is
considered high-strength concrete.
Q: How do you control the strength of
concrete?
The easiest way to add strength is to add
cement. The factor that most predominantly
influences concrete strength is the ratio of
water to cement in the cement paste that binds
the aggregates together. The higher this ratio
is, the weaker the concrete will be and vice
versa. Every desirable physical property that
you can measure will be adversely effected by
adding more water.
Q: How do you remove stains from concrete?
Stains can be removed from concrete with dry or
mechanical methods, or by wet methods using
chemical or water.
Common dry methods include sandblasting, flame
cleaning and shotblasting, grinding, scabbing,
planing and scouring. Steel-wire brushes should
be used with care because they can leave metal
particles on the surface that later may rust and
stain the concrete.
Wet methods involve the application of water or
specific chemicals according to the nature of
the stain. The chemical treatment either
dissolves the staining substance so it can be
blotted up from the surface of the concrete or
bleaches the staining substance so it will not
show.
To remove blood stains, for example, wet the
stains with water and cover them with a layer of
sodium peroxide powder; let stand for a few
minutes, rinse with water and scrub vigorously.
Follow with the application of a 5 percent
solution of vinegar to neutralize any remaining
sodium peroxide.
Q: What are the decorative finishes that can
be applied to concrete surfaces?
Color may be added to concrete by adding
pigments-before or after concrete is place-and
using white cement rather than conventional gray
cement, by using chemical stains, or by exposing
colorful aggregates at the surface. Textured
finishes can vary from a smooth polish to the
roughness of gravel. Geometric patterns can be
scored, stamped, rolled, or inlaid into the
concrete to resemble stone, brick or tile
paving. Other interesting patterns are obtained
by using divider strips (commonly redwood) to
form panels of various sizes and shapes
rectangular, square, circular or diamond.
Special techniques are available to make
concrete slip-resistant and sparkling.
Q: How do you protect a concrete surface from
aggressive materials like acids?
Many materials have no effect on concrete.
However, there are some aggressive materials,
such as most acids, that can have a
deteriorating effect on concrete. The first line
of defense against chemical attack is to use
quality concrete with maximum chemical
resistance, followed by the application of
protective treatments to keep corrosive
substances from contacting the concrete.
Principles and practices that improve the
chemical resistance of concrete include using a
low water-cement ratio, selecting a suitable
cement type (such as sulfate-resistant cement to
prevent sulfate attack), using suitable
aggregates, water and air entrainment. A large
number of chemical formulations are available as
sealers and coatings to protect concrete from a
variety of environments; detailed
recommendations should be requested from
manufacturers, formulators or material
suppliers.
Q: Is there a universal international
specification for portland cement?
Each country has its own standard for portland
cement, so there is no universal international
standard. The United States uses the
specification prepared by the American Society
for Testing and Materials-ASTM C-150 Standard
Specification for Portland Cement. There are a
few other countries that also have adopted this
as their standard, however, there are countless
other specifications. Unfortunately, they do not
use the same criteria for measuring properties
and defining physical characteristics so they
are virtually "non-translatable." The European
Cement Association located in Brussels, Belgium,
publishes a book titled "Cement Standards of the
World."
Q: What is alkali-silica reactivity (ASR)?
Alkali-silica reactivity is an expansive
reaction between reactive forms of silica in
aggregates and potassium and sodium alkalis,
mostly from cement, but also from aggregates,
pozzolans, admixtures and mixing water. External
sources of alkali from soil, deicers and
industrial processes can also contribute to
reactivity. The reaction forms an alkali-silica
gel that swells as it draws water from the
surrounding cement paste, thereby inducing
pressure, expansion and cracking of the
aggregate and surrounding paste. This often
results in map-pattern cracks, sometimes
referred to as alligator pattern cracking. ASR
can be avoided through 1) proper aggregate
selection, 2) use of blended cements, 3) use of
proper pozzolanic materials and 4)
contaminant-free mixing water.
Q: Are there different types of portland
cement?
Though all portland cement is basically the
same, eight types of cement are manufactured to
meet different physical and chemical
requirements for specific applications:
● Type I is a
general purpose portland cement suitable for
most uses.
● Type II is used
for structures in water or soil containing
moderate amounts of sulfate, or when heat
build-up is a concern.
● Type III cement
provides high strength at an early state,
usually in a week or less.
● Type IV moderates
heat generated by hydration that is used for
massive concrete structures such as dams.
● Type V cement
resists chemical attack by soil and water high
in sulfates.
● Types IA, IIA and
IIIA are cements used to make air-entrained
concrete. ● They
have the same properties as types I, II, and
III, except that they have small quantities of
air-entrained materials combined with them.
White portland cement is made from raw materials
containing little or no iron or manganese, the
substances that give conventional cement its
gray color.
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