Polymer Paving Starter Guide
This manual is intended to serve as a guideline for those interested in planning, financing, managing or executing soil improvement and ground modification projects, such as building hard driving surfaces using copolymers as particle binders. One of the most common applications when using polymers to harden soil and rock mix, is to build hard driving surfaces. Every project where a structure of any kind must be built on the ground (soil) must follow certain rules, for example the expected loads must be supported without ground failure. While these rules are not inherently complicated, it is imperative that they are well understood before proceeding with a project.
Published on: Mar 4, 2016
Transcripts - Polymer Paving Starter Guide
Illustrated Technical Manual
This manual is intended to serve as a guideline for those interested in planning,
financing, managing or executing soil improvement and ground modification projects,
such as building hard driving surfaces using copolymers as particle binders. One of the
most common applications when using polymers to harden soil and rock mix, is to build
hard driving surfaces. Every project where a structure of any kind must be built on the
ground (soil) must follow certain rules, for example the expected loads must be
supported without ground failure. While these rules are not inherently complicated, it is
imperative that they are well understood before proceeding with a project.
Nothing is more important when engaging in building roads than a clear understanding
of soil improvement and ground modification techniques. Fortunately, this knowledge
is easy to acquire and the fundamentals are easy to understand. I hope you can use this
short introduction as a springboard to build your own library on the subject and continue
to learn in depth about the rules of working with soils. Having this knowledge, and with it
the ability to spot and avoid problems, will help you deliver many successful projects,
and give you much satisfaction in your professional career. It is very important that you
request on site help from someone experienced with polymer paving on your projects as
you start, or that you work with experienced geotechnical engineers. Skipping the proper
expertise is not the place to save money. The savings is inherent to the process and it
comes from the reduced logistics when possible, depending on the situation.
When a site is selected for raising a structure, such as a road or a building, special
consideration must be given to the ground's ability to support and respond to the load
that will be imposed upon it. This knowledge generally falls in the domain of
geotechnical engineers, and much of what you need to know to work with polymers is
basic soil behavior knowledge. Over time, a number of soil behaviors and responses
has been observed, which are now well understood by civil engineers. These soil
behaviors occur in response to man-made loads or to other natural / environmental
factors. Before raising any structure on soil / with soil / made of soil, we should gain a
basic understanding of how to best prepare a work site, select an aggregate, and
conduct a job by minimizing or counteracting possible negative soil behavior in
accordance with the load requirements and guidelines of each project.
Driving Surface - Assorted Size Particles
One of the quickest ways to raise the likelihood of success in any paving project, is to
ensure the particle mix has the proper gradation to interlock during compaction. The
ratio of the various sizes of soil particles determines the suitability and effectiveness of
the soil in a weight bearing application. The best soils for supporting weight are made of
a mixture of different size particles.
Sufficient Fine Particles and Mixing
If your soil has an adequate mix of particles of different sizes, then your next concern is
ensuring you have sufficient fine particles to cover all the spaces between the larger
rocks so that the mix of water and polymer, when thoroughly mixed, will not flush
through the rocks to the bottom, but rather remain suspended well mixed in the well-
graded aggregate with the help of these fine particles (allow water surface tension), and
provide lubrication to the compaction process, and then later harden into place in
between the rocks, locking all the individual rocks into place, for a solid and long lasting
hard driving surface.
Preparing a Road Base
Jusl like a building needs a proper foundation, a proper road requires a road base. At a
minimum, if working on top of excellent soil, the soil on which you build the road (the
subgrade, the lowest layer in the picture) needs to be well compacted. If certain soil
weaknesses are to be expected, a base layer should be added, preferably made of
larger rocks. If you separate the subgrade (native compacted soil) and base layer (large
rocks) with a layer of geofiber (thin, light color in the picture), it will prevent "pumping".
The water table will be able to raise and lower through the larger base rocks (the
thickest middle layer in the picture) without driving subgrade sediment into the road
structure. An additional low cost measure to compensate for a weak subgrade is to
encase the base layer (larger rocks) into a geocell grid (height of geocell you order must
match the estimated height of this layer). This additional support creates a matrix that
has been proven to provide excellent road performance even on some of the weakest
subgrades. Adding geosynthetics (geocell, geogrid, geofiber, gabion mesh, etc) to your
project ensures substantially superior performance and longevity at low cost.
Considering the number of variables you need to streamline in order to get your soil to
play nice, we firmly believe that it would be smart to avoid additional concerns or doubts
about the performance of your polymer. That is why PolymerPaving.com offers you the
most suitable polymer that you can possibly find, at a competitive price. When you use
the KompaFlex MX formula, you can rest assured you are already using a product that
will give you top notch repeatable performance time after time. Having the peace of
mind that comes with using the best product, frees you to focus on ground
improvement methods to bring your project to the desired performance standards. I
speak from experience when I tell you that if you get caught between trying to do ground
improvement while still having doubts about the performance of the binder, you will
never finish a project. So do yourself "a solid" and start with KompaFlex MX, and enjoy
the peace of mind that you already selected the best possible polymer, and the freedom
of focusing strictly on ground improvement, which is what we will discuss for the
remainder of this manual.
Polymer Mix-In Methods
The best way to achieve a perfect mixing of aggregate and polymer is by pre-mixing
(image 2). However, when the size of the job makes pre-mixing too slow, in order to
work faster you can also do the following 4 step procedure: apply aggregate (soil or rock
mix) and spread to 1 inch thick (2-3 cm); Use a spraybar to apply the proper amount of
liquid (water and polymer in the correct ratio) to reach optimum moisture (image 1).
Then immediately mix the liquid into the aggregate using a scarifier or power rake
(image 3). Repeat this process (add soil, spread, spray, scar/mix) until the desired road
surface thickness is achieved, then grade the surface to the correct angles, compact,
and allow it to cure. Follow-up with a sealing coat, regardless of the method used. After
8-24 hours, clean remaining debris (loose rock and dust) from the surface with a power
broom, and apply a second and final sealer coat to the surface.
Another fast method is to use a reclaimer connected to a water tank truck preloaded
with the water and polymer mix; this combination vehicle can wet and scar/mix the soil
at the same time while advancing without the need to stop, except to reload the tank.
Optimum Moisture Content is a humidity level that ensures all particles will receive
polymer treatment, and compaction is well lubricated. If you see liquid on the compactor
wheel or puddles, you have exceeded OMC. Never work below OMC. Exceeding it a
little is not critical, but exceeding it by a lot can reduce ability to achieve high
compaction. Try to make a ball in your hand with the mixed soil; if it crumbles in your
hand it is too dry. If you have liquid seeping through your fingers you are applying too
much liquid. When it holds shape without excess liquid showing, it is perfect for
"Poor" Soil Contingencies
A soil is considered "poor" if it has been determined or tested to have inadequate or
insufficient engineering characteristics to meet the minimum requirements of the
application. Another term commonly used is "marginal" and it applies when a soil comes
very close to meeting these requirements but doesn't quite make the cut. Here are
common methods for approaching these situations:
• Excavate the "poor" soil and replace it with good aggregate.
• Redesign the project to be able to work with the poor soil (for example reinforce with
geocell or a similar mechanical reinforcement).
• Modify the soil through soil remediation methods (mixing with other available soils / rocks,
mechanical or chemical, etc).
• Abandon the project - this approach is selected when you can pick a more suitable
alternative location, or when the cost of fixing the soil insufficiencies exceeds the
Soil Type Classification by Particle Size
A "sieve analysis" is a process where a given quantity of soil is passed through a certain
size of mesh to see how much passes and how much remains, determining whether a
soil has a "variety" or a "uniformity" of particle sizes. Generally speaking, soils with a
variety of particle sizes are called "well-graded" and are desirable for their ability to
be cohesive and to compact well. Soils with mostly uniform particle size do not have
good cohesion or compaction characteristics and should be avoided or modified.
Crushed rock (angular) is desirable in the mix. Round particles (river rock, beach sand)
are to be avoided; they may pass for "acceptable" when paving with asphalt because it
is a full ring aromatic, but round particles will not work when paving with polymer as your
binder because there isn't enough surface in contact with the particles surrounding it.
Soil is different from other engineering materials because it tends to fail in shear
rather than from direct tension or compression. With this fact in mind, imagine how much
stronger and resilient to shear forces the soil on the left is (compacted, mixed size [well
graded], interlocked, angular rocks) compared to the soil on the right (silt / clay).
Foundation: Bearing Capacity & Slope Stability
Nothing is more important or critical to success than a strong foundation, whether
you construct a road or a building. This becomes particularly important when the
foundation soil (subgrade) is poor or marginal. When the soil and the climate are
optimal, you can throw a road surface right on top of a good soil compaction without
problems. Many roads in Arizona and California are built just like that and they perform
to acceptable levels for the desired lifespan. These regions rarely see bad weather or
rain, or the deleterious effects of water penetration or frost heave. Building a road in
most other regions require a properly designed foundation to compensate for the natural
forces that work against you. For instance many tropical areas see non-stop rain for six
months out of the year. In such an instance, a large portion of your effort and budget
should be aimed at effective drainage and building the road above the water table.
When you work in muddy or volcanic silt (such as in most of Southeastern Europe) you
need to explain to your beneficiaries the importance of building roads the same way they
build their railroads (with a solid crushed rock base that allows for water drainage and
frost heave), if they want them to last as long. You should seek additional reading on
"shallow foundation design" to understand bearing capacity failure. You can imagine
the risk of slope stability failure when you think that every few square feet of your
compacted pavement surface weighs tons by itself, and there are enormous natural
shear pressures acting on a slope, especially when the pavement structure is imbibed
with water molecules in between the soil particles (a very important phenomenon that is
worth exploring in detail, to have it well understood), and subjected to additional traffic
weight. That is why we strongly recommend the use of geosynthetic materials for
reinforcement, not as a luxury, but as a way to raise project longevity and to prevent
catastrophic failure due to unforseen events (bad winter, floods, earthquakes,
liquefaction, etc). No other materials offer a better price to performance ratio for
enhancing the desirable characteristics of a road and/or road base (and also for other
soil projects - embankments, overpasses, etc).
Soil Densification and Consolidation
Soil densification is a process by which the air pockets are removed from soil through
compaction. Soil consolidation is a process by which water is removed from soil. There
is sufficient technology available today to literally be able to say that "no soil is
unsuitable" if you have the budget, the equipment, and use the right methods to fix it, or
to compensate for the respective defficiencies.
Types of Compactors
There are various types of compactors available, each designed for specific tasks, and
some are more suitable than others for specific jobs. It is important to know what kind of
compactor to use depending on your soil type and the desired end result which you are
trying to achieve. Different soil types will present diverse characteristics that will affect
the soil improvement decisions you make.
Smooth Drum Rollers: a static load roller used for compaction of soils and asphalts, they
provide even weight distribution over the width of the roller and a smooth finished
surface. Also good for "proof rolling" during base preparation (to identify soft spots that
Pneumatic (rubber tire) rolles: these are engineered to apply very high static loads to a
wide variety of soils, pavements, bases and subgrades. They are even better suited at
finding soft spots, particularly because individual tires have the ability to move up and
down a small distance independently.
Combination rollers: easily identifiable as having both a steel drum and a set of
pneumatic roller wheels, with the ability to use either.
Vibratory rollers: they look similar to static rollers, with the ability to provide impact and
vibration to the soil beneath. If you have granular soils (poor cohesion aggregate) a
vibratory roller will help overcome the frictional resistance and achieve better
Sheepsfoot / Padfoot / Wedgefoot rollers can apply very high static loads by
concentrating extreme weight on a small contact surface. These are ideal for breaking
hard dry boulders inherent in clay, silt and other cohesive soils, and in this way allowing
high and uniform compaction.
Weight and Number of Passes
Although mathematically you should get the same result by adding the weight between
the number of passes, field experience shows that if you don't get the desired
compaction after 5-7 passes, you should perhaps switch to a heavier compactor. One
exception to this rule may be saturated sands, which have shown to improve up to 15-20
passes. However, since one of the "commandments" of working with polymer is to never
use sands or other round particles, this detail is irrelevant in our context.
Requesting a Laboratory Test
So you are interested in polymer paving, perhaps because it is eco-friendly, or because
it is affordable or maybe because it is easy to complete and maintain. Perhaps it is for a
combination of reasons, or perhaps someone asked you to look into it. Many of the
variables you need to determine, including the suitability of a soil, can be easily and
inexpensively resolved by sending a soil sample and a small fee to our laboratory, where
we can test your soil for you and provide you with a report of your general situation. This
way you have a much better idea which approach / method / procedures we would
recommend as the most suitable for your particular project.
Building an eco-friendly road with in-situ soil and polymer binder is really a process of
self-development, of becoming really good at soil improvement and ground modification
procedures. Clean, affordable, long-lasting roads are just a result of accumulating that
knowledge and experience. I hope this brief guide served to introduce you to (or to
remind you of) some of the basics of sound soil engineering. Success in polymer paving
only requires a dilligence in following these proven and time tested principles. Soil
improvement methods are generally applicable in almost any other type of construction,
not only road building. We look forward to working with you.
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