Stabilization Techniques: Soil, Moisture
Content and Compaction
Road Bed Stabilization
Road beds are often constructed with
native site soils containing a wide gradation of materials which may
include a high content of soil fines (passing 200 mesh). Px-300
assists in binding fines together with larger materials into a dense,
well-compacted material that provides a high degree of stabilization
and higher tensile strength than untreated road beds. PX300
road beds also offer a high resistance to moisture penetration (2.9 x
10-8 cm/sec under ASTM D 5084). Benefits include
reduced maintenance costs and utilization of on-site materials,
eliminating the need to import off-site soil.
Three important determine a stabilization
Material Gradation refers to the distribution
(% by weight) of the different sizes of particles within a given soil
sample. A soil sample is well-graded if it contains a good, even
distribution of particle sizes. A soil sample composed of
predominantly one-sized particles is said to be poorly graded. A
well-graded soil contains smaller particles which tend to fill the
empty spaces between larger particles, leaving fewer voids after
below shows distribution guidelines for several different soil
Gradation (% passing)
| 85 %
| 62 %
| 48 %
Two conditions prevent a
successful stabilization: The presence of large rocks; and
types of contaminants.
Large rocks can cause structural breakdown in an
otherwise successful application and contaminants prevent the
successful curing of the PX-300 solution in the treated soil. When
either or both of these conditions are present, G.M. Boston Company
requires prior notice of the fact, so that soil remediation can be
PX300, enzymatic wetting agent and water are important components in any roadbed stabilization project. These three components combine to lubricate the soil particles, helping them to slide into the voids between larger particles and produce the greatest density. Soil fines and clay particles become "sticky" and cohesive, providing a necessary condition for stabilization. Engineers have determined that almost all soils have what they call an optimum moisture content which permits maximum density from a given amount of compaction. The illustration below shows the relationship between soil dry density and moisture content.
The presence of excess moisture in site
soil due to flooding or heavy rainfall will prevent an efficient cure
following the PX300 application. If present site soil moisture
plus the moisture accompanying a PX300 application will result in a
moisture level well above optimum, the project should be
deferred. Usually two days of dry, moderately warm weather will
bring the moisture level down to point that supports a successful
If flooding or heaving rainfall will
closely follow a PX-300 application, that could also impair or prevent
a successful PX-300 cure by diluting and washing away the uncured
PX-300. Accordingly, G.M. Boston Company strongly recommends a
curing/drying period of 36-72 hours following a PX-300 application to
ensure a successful project.
Without project conditions that comply
with the guidelines stated above, G.M. Boston Company cannot provide
assurance that a completed project will perform as expected by our
customers and by us.
Compactive effort is the process of physically increasing the weight
per unit volume of road bed soil. Compaction occurs in several
ways: a drum roller provides static weight or pressure, a
sheep foot roller provides a kneading action and a vibrating roller
provides a shaking pressure. All are acceptable compaction
methods and occasionally, are used together for optimal results.
Without a proper moisture level, compaction cannot occur
successfully. If too wet, the compacted soil will push out from
under the compaction equipment and, if too dry, the compacted soil will
not hold together because it will lack the cohesive, "sticky"
quality mentioned above in "Moisture Content." The
moisture density curve above has particular significance
Building the Road
Road Bed materials using PX-300 should have a gradation mix that
approaches the gradation specification values appearing in
"Material Gradation." Frequently, road beds have used
materials outside design standards; these projects require prior sample
testing to assess the likelihood of success. Where outside soil
will go on top of the existing road bed site soil, it is imperative to
do sample testing of the imported soil to determine that PX-300 can
achieve the customer's desired results before commencing the project
Generally, PX-300 is not recommended by compaction of lifts greater
than 6 inches. Type of material to be compacted plus the size and
type of compaction equipment will determine lift thickness.
Step 1: Blade or rip the existing base to a depth of 6 inches,
then windrow the loosened material. If the project requires
additional aggregate, the use the least-cost available material with
more fines. Check the overall gradation of the material to ensure
that it conforms to the tested, pre-project sample.
Step 2: For each acre of road base material, add 715 gallons of
PX300 to the amount of water necessary to obtain optimum
moisture. Spray both the bladed surface and the windrow to reach
optimum moisture. Blend the PX-300 material using a grader blade,
working the soil and aggregate back and forth to blend in the PX-300
and water. If the material is too wet, blade until it approaches
optimum moisture. If too dry, add more PX-300 solution to bring
the material up to optimum moisture. After thorough mixing spread
the material to grade.
Step 3: Extend and crown the road bed surface with a blade.
If the material dries out on a hot day, spray again with the PX-300 moisture.
Compact with a sheep foot a pneumatic roller. Use a vibratory
roller for the first pass only and do not use vibratory compaction
thereafter; additional vibratory compaction will cause cracking.
Compact in 6 inch lifts to ensure maximum compaction and, following the
final pass, do not disturb the finished surface by attempting to
"dress" minor imperfections. If possible, allow the
road bed to cure prior to use (and final testing). Allowing the
road base to dry (cure) will provide greater strength and decreased
If intending to apply an asphalt or chip seal wear surface, moisten the
road base surface with a diluted PX-300 application before applying the
new wear surface. That will ensure a better bonding of the two
us by phone or e-mail for information about quantities and
prices for your project.
Boston Company INTL, LLC 412
Beach, CA 92663 Tel:
(562) 592-0836 FAX:
(949) 722-6799 Craig Hoad - firstname.lastname@example.org Greg Boston - email@example.com