Loading Methods Compared
Efficiently loading materials into a mixing drum to make
concrete is the key to a successful project. Every minute
spent loading increases the labor and reduces the effective
mixing time of the ready-mix. Cart-Away engineers have spent
enormous energy in developing a variety of ways to get the
sand, gravel, cement and water efficiently into your mixing
drum.
The following comparison will give you the pros
and cons of the different ways to fill a ready-mix drum.
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Before we begin to compare we must
know the basic statistics of the loading target on a
Cart-Away mixing drum:
 The
diameter of the loading opening is 23 inches
The
pour-in height of the loading opening is 66 inches
There
are four fins that reduce the opening to 18”.
These
spin, so caution must be taken as the drum is loaded. |
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1. The Shovel…
It
takes approximately 188 shovels full of pre-mixed sand and
gravel to create a yard.
After struggling with each
scoop of material you then will need to lift 5 to 7, 94
pound sacks of powdered cement the 66” up into the drum.
The advantage of this method is the low entry
cost to load, because a shovel requires an investment of
less than $50 dollars.
The disadvantages
of this method are obvious: |
This is the least efficient and the most inaccurate
measuring system for producing ready-mix.
Load time can be as high as 40 minutes per batch.
Shovel
volumes vary and can make each batch different.
Very high
probability of a workers comp. claim.
Few people
will want to mix this way for long.
Bagged
cement storage away from any moisture |
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2. Pre-mixed Concrete Bags…
 Every
home center stocks 80# bags of concrete in pallet
quantities.
It takes 42 of these bags to create a
yard of material. Like the shovelmethod previously
mentioned, this a completely manual loading method involving
lifting each bag up and into the drum opening.
The
standard mix design of these bags is not very high in cement
content, so it is recommended that you add at least one 80#
bag of powdered cement into each batch.
The advantage
of this method is the easy
availability of the bags in
every community, but it is not cheap when compared to using
the basic raw materials in ready-mix. A sack of concrete can
be as high as $3.50 per bag or $147. per yard before
delivery charges. The batching size is better controlled
with the bags than with the shovel method. |
The disadvantages of this method
are similar to the shovel:
Efficiency
is not good, but better than a shovel.
Load time can be as high as 30 minutes per batch.
High probability of injury from the four moving mix fins.
Very high probability of a workers comp. claim.
Few people will want to mix this way for long.
Bagged concrete storage away from any moisture
The higher cost of materials. |
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3. The Super Sack…
 This
device is a large woven polypropylene bag that holds about
3500 pounds of pre-mixed sand, gravel and cement.
These sacks are usually prepared with a specific mix design
at the factory. To load a
mixing drum with a super sack
will require some type of lifting device, usually a tractor
or forklift and a funnel to direct the material down into
the drum.
Loading is accomplished by pulling a string
to open a spout on the bottom of the bag and letting the
material flow into the drum.
The advantage of this
loading method is that it is extremely fast and the funnel
system is not very expensive.
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The Cart-Away C.U.B.E. has used this method successfully to
produce a specification mix in a mine.
The ability to
produce a specific mix design consistently is also an
advantage of this method.
The
disadvantages are:
Finding a local supplier for the pre-mixed super sacks.
Cost of transportation to the job site from a distant
supplier.
Building a useful funnel system that is not in the way of
emptying the drum.
The cost of the pre-packaged materials.
Storage of the sacks out of moisture and the space required
for a truckload price.
Tractor or Forklift for lifting the sacks. |
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4. CLS Loading Conveyor…
 Created
by Cart-Away in the early 90’s, this is small material
hopper feeding a inclined conveyor belt.
The CLS uses
an 8HP Honda engine to power the hydraulic functions on the
unit. There is a water hose hook-up and water meter for
adding in the water.
The sand and gravel are loaded
into the hopper using a tractor bucket.
The bucket of
the tractor is used to measure the quantity of raw material
that will go into the mixing drum.
Bags of powdered
cement are placed on a bag-breaker that is mounted over the
hopper allowing the cement to pour in on the top of the
aggregates.
The conveyor moves all of the sand,
gravel and cement up and into the mixing drum.
The
belt travels quickly and throws the material down deep into
the drum.
The water meter allow for a fairly
consistent mix as long as you remain consistent with the
tractor bucket volumes.
The advantage of a CLS is
that it can load less expensive individual raw materials
fairly quickly into the drum. |
A typical one-yard load can be put into the drum less than
10 minutes.
The advantages of
the CLS are the increased speed to load and the ability to
use less expensive materials for the mix.
The hopper
is also useful as a storage and measurement bin which helps
in creating a more consistent mix between batches.
The water meter also allows for consistent moisture
specifications.
The disadvantages to the CLS are:
Additional
investment in machinery for loading.
On-site batching requires an extra unit to transport.
Volumes of material can vary if not careful.
Some dust is created from the loading belts quick motion.
Daily clean-up is required.
Lifting 94# sacks of cement to the bag breaker knife at a
lift-over height of 44 inches.
Storage
of cement bags from moisture |
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5. The Concrete C.U.B.E.
 On-Site
Batching System. The C.U.B.E. is an all-in-one loading and
mixing system designed to
help people become independent
from the transit-mix companies.
The mixing drum is
mounted inside of a steel framework that supports a material
loading conveyor.
The conveyor is loaded over the top
of
the upper framework and the raw materials move into
the drum via a diverter.
The water is introduced into
the drum by a water metering system similar to the CLS.
Cement bags are emptied into a hydraulically operated
chute that moves the powder up and into the drum. The
lift-over height for each 94# bag of cement is about 32
inches. A typical 1 ½- yard load can be put into the drum in
about 10
minutes.
The advantages of the C.U.B.E.
are the complete packaging of all the material loading and
mixing functions. |
The C.U.B.E. reduces the number of pieces of equipment need
on site to make ready-mix.
The bag breaker chute has
a reduced lift-over height for less back strain and will
also load in 80# pre-mixed concrete bags.
The
C.U.B.E. can be ordered with gas, diesel and electric power
options and can load with super sacks of pre-mix with the
conveyor removed. Water is metered to create a consistent
mix batch.
The disadvantages to
the C.U.B.E. are:
Requires a trailer or truck to deliver.
Not as portable as a trailer mounted drum.
Volumes of material can vary if not careful.
Daily clean-up is required.
Lifting 94# sacks of cement to the bag breaker knife at a
lift-over height of 34 inches.
Storage of cement bags or concrete bags/sacks from moisture.
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6. CBL Automated Material Loader
 This
is the most efficient raw material loader available for
filling the mixing trailer. At 2 minutes per yard batching
time, the CBL can load several trailers in a fleet with
ease.
Each CBL comes equipped with a sand and gravel
hopper that can hold up to 12 yards of material.
A powdered cement silo will hold enough material to mix
well over 100 yards without refilling.
Using a silo
to store and distribute the cement powder saves material
costs, labor and storage hassles.
The CBL is
a dry batching system so the clean-up is easier than any of
the wet-auger loaders from the past. |
The CBL system is widely used in
applications where selling ready-mix to others is the
primary focus of the enterprise.
The disadvantages to the
CBL are:
May require special zoning for a silo installation.
Must be welded to metal plates on concrete footings.
Three-phase electrical service is required.
Daily clean-up is required.
Investment is larger than other loading systems.
Regular material calibrations are required.
Additional maintenance schedule.
Additional
Information:
Investment Comparison
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