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WHAT IS ROAD BASE STABILIZATION?
Road Base Stabilization is the collective activities that improves the
strength and provides the volumetric stability of road base materials. The
stabilization of road base materials:
- improves the strength of the road base,
- helps the road last longer,
- reduces routine maintenance requirements,
- reduces the required thickness of required pavement overlays, and
- for unpaved roads, reduces aggregate material loss, especially the loss
of fine particles that help fill the space between the larger aggregate
and improve the compaction of the material.
What are the mechanisms of soil strength?
COHESION
Cohesion is classified as true and apparent cohesion. True cohesion
includes cementation, electrostatic and electromagnetic attractions and
adhesion. Apparent cohesion is caused by capillary stresses, or the surface
tension of moisture in soils. Apparent cohesion also
includes mechanical forces, or the interlocking of soil particles.
Cohesive soils contain enough clay or silt-sized particles to impart
significant strength. Non-cohesive soils include sands and gravels which are
rounded or angular (non-flaky) and do not exhibit plasticity or cohesion. The
non-cohesive soils attain strength from the friction
between the soil grains.
INTERNAL FRICTION
Internal friction is the resistance of movement between soil particles.
Internal friction is affected by:
• particle
size
• particle
size distribution
• density of
road aggregate material
• moisture
content
• mineral
composition
• others
Methods of increasing road base strength: Chemical and Physical
Chemical agents can be very effective by increasing the strength of soils
and aggregates by altering their cohesive qualities. A second way to increase
soil and aggregate strength is to mechanically manipulate them to alter the
internal friction. The best results are achieved by employing both methods.
Testing for strength
Compressive strength testing can be used in the laboratory to effectively
measure the effectiveness of soil stabilization and improvements in the
strength of soils and aggregate materials.
The laboratory test for compressive strength consists of importing a force on
a laboratory compacted stabilized soil or aggregate and measuring various
points at which strain and failure occur. The resulting data form a
stress-strain curve with percent axial strain on the X axis and stress (psi)
on the Y axis. The more force required to induce an equivalent strain, the
more stable the compacted material will be.
How PennzSuppress® D increases soil and
aggregate strength
PennzSuppress® D is formulated
with a very viscous petroleum resin, refined from a highly parafinnic-based
Pennsylvania-grade crude oil. This resin has adhesive qualities which improve
the internal friction of compacted soils and aggregates. The product also
contains a binder that can add cementitious qualities to soils and aggregates.
The adhesive and cementitious qualities discussed above increase the
effectiveness of mechanical treatments such as aggregate blending and
compaction. To see a complete discussion of field
methods used to stabilize road base materials, click
here.
Laboratory test results using PennzSuppress®
D to stabilize aggregate soil samples Pennzoil has begun a testing program to
better define the stabilization qualities of PennzSuppress®
D. Pennzoil has retained the services of Law Engineering, Inc., a major
international engineering and consulting company to provide engineering
consulting and laboratory testing services.
Laboratory reports for three distinctly different roadbase aggregate materials
are provided below. Don't forget to come back to this part of www.pennzsuppress.com
to see more geotechnical report information on the performance of
PennzSuppress®
D as a roadbase aggregate and soil stabilizer.
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