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| What
is "Ready Mix
Concrete"? |
Concrete
is a mixture of cement,
aggregates (fine and coarse) and
water. Often improperly
called "cement", which
is the binding component and
generally makes up only 12%-15%
of the mixture. |
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| What
is Cement? |
Portland
cements are hydraulic cements,
meaning they react and harden
chemically with the addition of
water. Cement contains
limestone, clay , cement rock
and iron ore blended and heated
to 2600-3000 F. The
resulting product
"clinker" is then
ground to the consistency of
powder. Gypsum is added to
control setting time. |
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| What
is Fine Aggregate? |
Normally
called sand, this component can
be natural sand or crushed
stone, and represents particles
smaller than 3/8".
Generally accounts for 30%-35%
of the mixture. |
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| What
is Coarse Aggregate? |
May
be either gravel or crushed
stone. Makes up 40%-45% of
the mixture, comprised of
particles greater than
1/4". |
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| What
are Chemical Admixtures? |
Materials
added to alter the properties of
concrete including:
- Air entrainment
- Set accelerators
- Set retarders
- Water reducers
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Air entraining
admixtures add microscopic air
bubbles to the concrete,
enhancing its resistance to
freeze/thaw cycles and makes the
concrete easier to finish.
Set accelerators speed the
set-time of the mixture,
enabling finishing operations to
begin sooner, useful during cold
weather pours.
Set retarders have the
opposite effect, slowing the set
and enabling delivery to distant
sites and finishing during hot
weather.
Water reducers are used to
reduce the amount of water
required to produce a given
slump. They also provide a
ball bearing effect, making the
concrete easier to finish, and
produce better cement
hydration. By reducing the
amount of water required, cement
amounts can be reduced because
concrete strength is directly
related to the water/cement
ratio.
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| What
are Mineral Admixtures? |
Mineral
admixtures include fly ash,
hydrated lime, silica fume and
ground blast furnace slag
(NewCem or
GranCem). Many
of these materials have
cement-like properties,
augmenting the strength and
density of the finished
concrete. They generally
improve the workability, density
and long-term strength of
concrete, at the expense of set
time and early strengths. |
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| What
are Synthetic Fibers? |
Most
often known by the brand name FiberMesh, these are thin
polypropylene fibers used as
secondary reinforcement.
They help control shrinkage
cracking and provide some impact
resistance. |
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| What
is Grout? |
Grout
is a mixture of cement, water
and (most generally) fine
aggregate. It is mixed to
a pourable consistency and used
to fill spaces within block
walls, or other cavities.
They generally contain large
amounts of cement. |
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| What
is Flowable Fill? |
Flowable
fill is a self-leveling,
self-compacting backfill
material. Can be produced
in structural and excavatable
(by hand or machine) forms, making
it ideal for use around utilities
that may need to be uncovered at
a later date. When
calculated against labor costs,
flowable fill provides an
economical alternative to
granular backfill. |
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| What
is Yield? |
Yield
is the volume of fresh concrete
produced from known quantities
of component materials,
generally expressed in cubic
yards or cubic meters. |
