Note: Descriptions are shown in the official language in which they were submitted.
CA 02584189 2007-04-05
SOIL STABILIZATION METHOD
Field of the Invention
The present invention relates to reconstructing and paving roads. More
specifically, the
present invention is method of using a soluble sodium silicate composition to
stabilize soil for a
road base or sub-base applicable to the construction of new roads and the
reconstruction or
reinforcement of existing roads.
Background of the Invention
Construction and maintenance of roads, especially secondary roads, requires a
solid,
stabilized base and sub-base on which to place the road surface. Preparation
for road paving
generally includes compaction of the base or sub-base, which may comprise
clay, gravel, crushed
stone, and the like, either taken from the native materials or transported to
the site. Frequently,
the base material includes crushed concrete and asphalt from the old road base
or surface.
Whether the material is primarily reclaimed from an old road surface material,
taken from a new
or old base on site, or is made from materials transported to the site,
maximizing the stability of
the material increases the longevity of the road surface and decreases the
frequency and cost of
repairs.
Soils too weak to bear the anticipated load can be stabilized by the addition
of materials
which impart mechanical strength, such as aggregate, and by the addition of
chemical stabilizers,
which decrease water absorption and increase the cohesion of the soil matrix
by forming a
cement-like compound to hold the matrix together. The appropriate type of
stabilization and
results to be expected depend upon the soil types encountered and methods of
application of the
2
CA 02584189 2007-04-05
stabilizer and construction of the road. A range of soil compositions can
serve as good road base
material, but high strength, resistance to shear, and resistance to erosion or
swelling by water are
required. Most native soils require some extent of stabilization to achieve
these goals and
provide a proper material for road construction.
Failure to provide an adequately stabilized base results in frequent and
expensive repairs.
Various techniques and compounds are known for stabilizing the soil or fill
beneath pavement or
other construction to provide a stable, high integrity base on which to place
the pavement or
other construction. Materials commonly used for this purpose include lime and
fly-ash mixtures,
calcium chloride, sodium silicates, mixtures of molasses and fuel oil, calcium
acrylate, lignin
sulfonate, and other materials.
Chlorides are the most commonly used product for soil stabilization. Calcium
chloride
assists in the compactive process, making it possible to obtain greater
densities and greater
strengths with normal compactive efforts. A major limitation of calcium
chloride is its narrow
application range. If the calcium chloride solution is applied at a less than
specific dilution ratio
the effectiveness of the compound is diminished, while application at a higher
than necessitated
dilution ratio causes beading on the application surface and thus prevents
treatment of the target
soil. Further, the widespread use of large quantities of chlorides has been
shown to be
environmentally harmful. Finally, chlorides are extremely corrosive on road
construction and
maintenance equipment.
Resins available under various commercial names are used as soil stabilizers
and
typically comprise lignin sulfonate, which is a by-product of the pulp milling
industry. Lignin
sulfonate is also referred to as "tree sap" by those skilled in the art of
road construction- They
3
CA 02584189 2011-10-04
provide cohesion to bind soil particles together, but are primarily used when
they can be
incorporated into the surface gravel.
Additives used for roadbed stabilization are disclosed by U. S. Patent No.
4,106,296
(epoxy resins), U.S. Patent No. 4,373,958 (lime kiln dust), U.S. Patent No.
5,577,338 (fly ash),
U.S. Patent No. 5,820,302 (silicate and cement), and U.S. Patent No. 6,689,204
(potassium
formate and cationic polymer). U.S. Patent No. 7,070,709, discloses various
prior art
compositions used for soil stabilization. Those products, however, have
numerous disadvantages
such as poor longevity, high cost, and environmental toxicity. The trade-offs
are either accepting
the environmental issues that come with products of longer useful life;
dealing with a shorter
lifespan for an environmentally friendly product; or paying significantly more
for
environmentally safe products with a favorable useful life.
A more acceptable method of roadbed stabilization is needed. It is an object
of this
invention to provide an improved composition and method of using the improved
composition
for soil stabilization that is both economical and environmentally sound.
Summar'of the Invention
The present invention is directed to a method of using a composition to
provide solid,
stabilized, and extremely hard bases and sub-bases for road construction. The
composition is
generally comprised of a soluble sodium silicate which, applied at the
disclosed application rate,
increases aggregate base strength for a given roadway at a faction of the cost
of existing
materials. The method of the invention addresses the application of the
disclosed composition to
-4-
CA 02584189 2007-04-05
maximize stabilization of roadbeds. The present invention addresses drawbacks
experienced
with the prior an because it provides an effective road stabilizer that is
both economical and
environmentally friendly.
Detailed Descries on of the Preferred Embodiments
The following descriptions of the present invention have been simplified to
illustrate
elements that are relevant for a clear understanding of the present invention.
The descriptions
eliminate, for purposes of clarity, elements found in typical soil stabilizers
and detailed
explanations of procedures used in road construction. Those of ordinary skill
in the art will
recognize that other elements of both the composition and method may be
desirable or necessary
to implement the present invention. Because such elements are well known in
the art and do not
facilitate a clearer understanding of present invention, a description of such
elements may not be
provided herein.
The stabilizer of thd present invention comprises a non-toxic, water soluble
chemical
composition used as a material stabilizer for road bases. The disclosed
stabilizer generally
comprises a soluble sodium silicate in a water base, otherwise known as
"waterglass." The
preferred embodiment of the stabilizer contemplates an aqueous solution
consisting of 28-30
percent silicon dioxide by weight and 8.5-9.5 percent sodium oxide by weight
with an overall
specific gravity ranging from 1.37 to 1.42 and an average viscosity of 150 at
20 C. The average
weight ratio of silicon dioxide to sodium oxide for the stabilizer should be
between 3.1 and 3.4.
A commercial version of the stabilizer is available from INEOS Silicas
Americas located in
Joliet, Illinois under the trade name Crystal 78.
5
CA 02584189 2007-04-05
Application of the stabilizer of the present invention is accomplished by the
use of
conventional spray equipment known in the an of road construction and
maintenance. It may be
gravity fed or pumped through hoses, spray nozzles, or fixed sprayers to
uniformly apply the
compound to the material to be treated. Motor-graders, asphalt grinders,
mixers, pug mills,
compactors, rollers, and other conventional road construction equipment may he
utilized to
blend, set grade, and compact the stabilized base.
Ili
A preferred embodiment of the present invention includes the application of
the stabilizer
at three steps of the road bed construction at specific application rates. In
the preferred
embodiment, it is recommended that the road bed be laid in sections of 1/4 to
1/2 mile in length.
Once the road bed has been leveled and the bed construction material has been
windrowed along
the road, the road bed is prepared by applying stabilizer to the road bed at a
rate of 20-25 gallons
per mile of 24'-30' width road surface with a depth of three inches to six
inches. The amount of
water in which the stabilizer is diluted will depend upon the type of
applicator used, size of the
water truck, and the weather conditions (temperature, humidity, wind). The
typical
recommended dilution is about 55 gallons of stabilizer per 5,000 gallons of
clean water. After
the initial application of the stabilizer, the road bed should be compacted by
any of the various
methods known in the art of road construction.
The second step of the preferred embodiment involves applying material from
the
windrow to the road bed in one to two-inch lifts. As the grader is laying
material from the
windrow across the road, the stabilizer is applied to the lift and then mixed
into the material
placed upon the road bed. The amount of stabilizer applied per lift will
depend upon the number
of lifts to be used in the road bed construction. A total of 220 gallons of
stabilizer should be
used for each mile of 24'-30' width of road surface assuming a total bed
thickness of three to six
6
CA 02584189 2007-04-05
inches. The amount of water used for the application of the 220 gallons of
stabilizer per mile
will depend upon the type of applicator used, size of the water truck, and the
weather conditions.
Each lift of mixed material and stabilizer should be well mixed and compacted
by any of the
methods known in the art prior to application of the next lift. This process
is repeated until all
lifts have been applied (windrow has been completely used) and well compacted.
The finish
grade and slope of the bed should then be prepared.
The third step of the preferred embodiment is finishing off the road bed
surface with
additional stabilizer. The stabilizer is applied to the finished bed at a rate
of 25-30 gallons per
mile of 24'-30' width road surface with a depth of three inches to six inches.
Compaction of the
road surface should continue until the surface is dry. As with the previous
steps, the amount of
water used to dilute the 25-30 gallons of stabilizer will depend upon the type
of applicator used,
the size of the water truck, and the weather conditions.
The preferred embodiment also contemplates keeping the working surfaces wet
while
compacting. The appropriate amount of moisture for working road compaction is
well known by
those in the art of road construction. It is recommended that compactors
constantly work the
road to maximize the hardening provided by the stabilizer. Roadways may be
further enhanced
by the application of a sealant to protect the new road bed from the elements.
The preferred
embodiment contemplates using a'surface treatment coating process such as the
application of a
bituminous chip seal, otta seal (oil/gravel mixture), cement, bituminous hot
mix, or any of the
other surface treatment processes known in the art.
As road widths vary, the present invention contemplates using the following
total
stabilizer amounts for all three steps per mile of three-inch to six-inch
depth road at the ratios
described herein:
7
it
CA 02584189 2007-04-05
Road Bed Surface Width (Peet) Amount of Stabilizer (Gallons)
24-30 275
31-37 330
38-44 385
45-51 440
For a seven-inch road depth, the present invention contemplates using the
following stabilizer amounts for all three steps per mile of road at the
ratios described herein:
Road S ace Width (Feet) Amount of Stabilizer (Gallons)
24-30 330
31-37 385
38-44 440
45-51 495
For an eight-inch road depth, the present invention contemplates using the
following
stabilizer amounts for all three steps per mile of road at the ratios
described herein:
Road Bed Surface Width (Feet) Am= of Stabilizer (Gallons)
24-30 385
31-37 440
38-44 495
45-51 550
While the present invention may be used for a wide variety of aggregate
mixtures
comprising clay material, caliche soils, and sandy loam with low sand content,
it is
recommended that the soil used in constructing the road bed consist of a good
binding material
8
i'.
CA 02584189 2007-04-05
with aggregate large enough to provide a driving surface. Examples of
aggregate gradation that
provide exceptional results are provided below:
Esample Example l3
Sieve Size % Passing Sieve Size % Passing
1" 100 1" 100
3/4" 100 3/4" 100
3/8" 65-95 3/8" 50-85
#4 40-85 #4 35-80
#10 20-70 #10 20-70
#40 10-45 #40 10-40
#200 10-15 #200 10-15
Example C Exa rile D
Sieve Size % Passing Sieve Size Pas in
1" 100 3/4" 100
3/4" 95-100 #4 38-75
3/8" 65-95 #8 22-62
#4 40-75 #30 12-37
#10 25-70 #200 8-15
#40 10-45
#200 10-15
The material passing through the #200 sieve should be binding-type material
consisting of more
clay than silt (an average of 8-15 percent silt).
9
CA 02584189 2007-04-05
Another preferred embodiment of the present invention is the use of the
disclosed
stabilizer with full-depth reclamation. Full-depth reclamation is an in-place
recycling alternative
to road reconstruction. A reclaiming machine is used to cum an old asphalt
pavement into a road
base by uniformly pulverizing the full thickness of the old pavement and
blending it with a
portion of underlying material. The process for full depth reclamation
involves three steps: the
pulverization of the original surface and the blending of additives and
imported materials,
grading and compacting the new surface, and the application of a wearing
surface. The process
allows for correcting drainage and cross slope problems, as well as widening
the roadway.
The process usually adds bituminous emulsion, chemical or mechanical
stabilization
agents to enhance the strength of the new base that is sealed with an asphalt
friction course or a
sealing treatment, depending on expected loads. Prior art additives used in
full-depth
reclamation commonly include bituminous emulsions, but they are often used in
combination
with chemical additives like lime, portland cement, and fly ash to add
strength, as well as
mechanical additives like crushed stone, RAP, and sand to correct deficiencies
in the existing
materials. Use of the stabilizer of the present invention provides the same
benefits as with new
road construction and eliminates the same disadvantages of existing
stabilizers.
The steps in the preferred embodiment of full-depth reclamation are similar to
those used
in new road bed construction, but includes the initial steps of scarifying
(ripping) and pulverizing
existing pavement. The depth of pulverization is usually six to ten inches,
which on secondary
roads will typically include all of the surface and base, plus some part of
the subgrade. To
achieve the proper gradation after pulverization, more than one pass of the
equipment may be
necessary. For particle distribution, the final pulverized material should be
100% smaller than
two inches with 55% passing a No. 4 sieve. The material may be pulverized in
place, or may be
CA 02584189 2007-04-05
removed and windrowed along the side of the road bed for application. If the
material is
windrowed. the same steps may be used as disclosed above for new road bed
construction.
For in-place pulverization, once the existing pavement has been sufficiently
pulverized,
the material must be shaped and graded to the desired cross-section and grade.
The final base
elevation requirements may necessitate a small amount of material removal or
addition. For in-
place pulverization, once the material is properly graded, the stabilizer of
the present invention is
applied to the road bed at a rate of 240-245 gallons per mile of 24'-30' width
road surface with a
depth of three inches to six inches. As with new roadbed construction, it is
recommended that
the road bed be laid in sections of 1/4 to 1/2 mile in length. The amount of
water in which the
stabilizer is diluted will depend upon the type of applicator used, size of
the water truck, and the
weather conditions (temperature, humidity, wind). The typical recommended
dilution is about
55 gallons of stabilizer per 5,000 gallons of clean water. The stabilizer and
pulverized pavement
should then be well mixed and compacted by any of the methods known in the art
prior to
application of the next lift. The finish grade and slope of the bed should
then be prepared.
As with new road bed construction, the preferred embodiment includes finishing
off the
~~II
road bed surface with additional stabilizer. The stabilizer is applied to the
finished bed at a rate
of 25-30 gallons per mile of 24'-30' width road surface with a depth of three
inches to six inches.
Compaction of the road surface should continue until the surface is dry. As
with the previous
steps, the amount of water used to dilute the 25-30 gallons of stabilizer will
depend upon the type
of applicator used, the size of the water truck, and the weather conditions.
The preferred
embodiment contemplates using a surface treatment coating process such as the
application of a
bituminous chip seal, otta seal (oillgravel mixture), cement, bituminous hot
mix, or any of the
other surface treatment processes known in the art.
11
CA 02584189 2007-04-05
The present invention may be embodied in other specific forms without
departing from
the spirit of any of the essential attributes thereof; therefore, the
illustrated embodiment should
be considered in all respects as illustrative and not restrictive, reference
being made to the
appended claims rather than to the foregoing description to indicate the scope
of the invention.
ICI
12
