| Cement Treated Bast (CTB)
is a compacted mixture of graded aggregate, cement, and
water, which is used as a base course for the
construction of highways, airport runways and taxiways.
The primary difference between CTB and soil cement is
that CTB usually utilizes a graded aggregate instead of
the native soils. It is primarily used to provide a
structurally sound base material over such things as an
expansive clay. It
has been laboratory proven to equal or exceed the modulus
of sub grade reaction (k) of a thicker coarse of crushed
stone sub-base and the flexural stress of a thicker
coarse of lime stabilized clay. Other benefits of CTB
over crushed stone sub-base include the ability to
distribute loads over a greater area and its resistance
to sub-grade failures associated with freeze/thaw cycles.
Close control and thorough
mixing of the material is required in order to meet
specifications while staying within budget, both of which
will be obtained through the use of continuous mixing
plant. This close control and thorough mixing will not
always be accomplished when mixing in place.
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Gears, Inc. and PEI
utilize an Aran portable continuous mixing plant whose
production is rated between 100 and 1,000 tons per hour
contingent upon the engineering properties of the
material being used, speed of excavation, and speed of
placement. The production of the
mixing plant is monitored by the use of instruments that
display the speeds of various feeds
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| to the mixer. Feed
rates for soil, cement, and water are variable and are
metered with a computerized system based on the weight
and density of the native soil. |
Since all of the
ingredient feeds are volumetric and the mix density is
generally specified in terms of weight, it is necessary
to calibrate each feed. The purpose of this calibration
is to establish an accurate relationship between
speed/gate setting and the resultant throughput in tons
per hour.
The aggregate is loaded in
the feed hopper by means of a front-end loader or
conveyor. A fixed or variable speed belt feeder draws
that material from the hopper at a uniform rate and
transfers it into the Aran twin shaft mixer.
The cement is metered from
the overhead storage silo by means of a cleated belt
feeder and enters the same zone as the native material.
Water is drawn from the
lower storage tank and metered by a variable speed,
positive displacement pump system. It is delivered to the
mixing chamber that minimizes the potential for escape of
dust during the mixing process.
For a list of Gears, Inc. & PEI
Cement
Treated Base Projects, up to 1998:
For a list of Gears, Inc. & PEI
Cement
Treated Base Projects, after 1998:
For contacts, phone
numbers and e-mail addresses, please click here:
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