Soil
stabilization can have a couple of slightly different definitions and goals. It
is a standard procedure in geotechnical engineering to determine the stability
of the soil before construction on a site. Soil stabilization may have to do
with erosion prevention since erosion removes soil. In geotechnical
engineering, soil stresses that influence how loads are transferred, are
determined.
The Civil Engineering Portal
has a good definition of soil stabilization:
“Soil stabilization is adding and mixing other materials
into the soil to change its properties. Soil stabilization is a way to improve
the soil’s shear strength parameters, which increases the soil’s ability to
support the weight. It is usually needed when the soil under a building’s
foundation is not strong enough to hold up the structure. Soil stabilization is
a way to stop structures from sinking into the ground. It does this by making
the soil less porous and easy to pack down. It also makes the soil more
resistant to shear.”
AMIX Systems has a good
explanation of soil solidification:
“Soil solidification represents a crucial ground
improvement method used in mining, tunneling, and construction projects to
enhance the stability and load-bearing capacity of weak soils. This technique
transforms problematic soil into a stronger, more stable material through the
addition of binding agents that chemically react with soil particles. As
projects increasingly encounter challenging ground conditions, the demand for
effective soil stabilization methods continues to grow.”
AMIX provides grout mixing systems for soil solidification.
According to building materials provider Holcim:
“…mixing cementitious materials into soil is one of the
most efficient, cost-effective, and widely used methods for stabilizing and
solidifying the ground in preparation for construction and redevelopment.
Moreover, it is quick, extremely durable, and environmentally responsible.”
While soil solidification is desirable for specific load-bearing sites on certain soils, it is undesirable for soil in general. It can also be used to contain and remediate soil contamination. Soil stabilization by adding carbon or clay also acts to reduce the mobility of soil contaminants. High-performance cements with longer setting and hardening time properties are utilized for soil cement stabilization and solidification. The slides below are from a 2024 Power Point presentation by Md Khairul Haque of Jatiya Kabi Kazi Nazrul Islam University.
Methods of Soil Stabilization and Solidification
There are different methods
of ‘ground improvement,’ with goals to increase soil strength, reduce
settlement potential, control permeability, and mitigate liquefaction risks.
Soil type, project requirements, site constraints, and economic considerations
are factors in choosing the method. According to AMIX Systems:
“Common ground stabilization approaches include
mechanical densification, preloading, reinforcement, and chemical treatment.
Each method offers distinct advantages for specific soil conditions and project
types. Mechanical densification, such as dynamic compaction, works well for
granular soils but may be less effective for cohesive materials. Preloading
requires significant time for consolidation to occur. Reinforcement techniques
like stone columns provide excellent load distribution but may require specialized
installation equipment.”
“Chemical treatment methods, including the process of
strengthening weak ground through binding agents, have gained popularity due to
their versatility and effectiveness across diverse soil types. These approaches
modify soil properties through chemical reactions rather than purely mechanical
means, often resulting in more permanent and predictable improvements.”
Civil Engineering Portal
lists ten types of soil stabilization: 1) mechanical; 2) chemical; 3) cement;
4) lime; 5) fly ash; 6) rice husk ash; 7) thermal; 8) bituminous; 9)
electrical; and 10) geotextile and fabrics. Mechanical soil stabilization
utilizes soil compaction with rollers, vibrators, and earth rammers. This
reduces soil porosity. Chemical stabilization typically utilizes a salt,
usually calcium chloride or sometimes sodium chloride. The result is lower
vapor pressure, higher surface tension, slower evaporation, and less frost
heaving. Cement stabilization involves mixing Portland cement and pulverized
soil with water, followed by packing to strengthen the mixture. Lime
stabilization is typically used to bind or improve the texture of clay soils,
making them less attractive to water and less likely to swell. It works best in
tropical regions as freezing causes it to degrade. Fly ash stabilization is
popular due to the low cost of fly ash. It is usually incorporated with other
cementitious binders. Rice husk ash is used similarly to fly ash. Both are
highly reactive. Thermal stabilization lowers water content and makes clay soil
more amenable to loads. Bituminous stabilization mostly utilizes asphalt and
tar. It reduces moisture-holding capacity. Electrical stabilization improves
the strength and drainage of clay soil. Geotextiles and porous fabrics made of
polyethylene, polyester, nylon, and polyvinyl chloride are used to build roads
without pavement on soft soils.
Too much organic matter in
the soil can result in acidity that is too high. Compaction increases soil
strength. Sulfides and sulfates in the soil can complicate and slow
stabilization. Moisture content and temperature affect reaction rates.
AMIX Systems specializes in
cementitious binding agents for soil stabilization and solidification:
“The primary mechanisms include hydration reactions,
cation exchange, pozzolanic reactions, and physical bonding. Hydration
reactions occur when cement-based binders react with water to form calcium
silicate hydrate gels that crystallize and harden over time. Cation exchange
happens when calcium ions from the binder replace weaker ions on clay particle
surfaces, reducing plasticity and water sensitivity. Pozzolanic reactions
involve the formation of additional cementitious compounds through interactions
between the binder and silica or alumina in the soil.”
“The effectiveness of these stabilization processes
depends on several factors: soil type and composition, moisture content, binder
type and dosage, mixing efficiency, and curing conditions. Clay soils typically
require different treatment approaches than sandy or silty materials due to
their different surface chemistry and particle interaction behaviors. The
moisture content must be carefully controlled to ensure optimal reactions
without diluting the binding agents excessively.”
Types of binding agents used
according to AMIX Systems are shown below:
They also point out that Portland cement is costly, and
that since fly ash and slag are waste products, they are cheap. Specialty
grouts are very effective, but they require precise mixing and application
techniques.
The most common application
techniques for soil stabilization include deep soil mixing, jet grouting,
permeation grouting, and shallow stabilization.
“Deep soil mixing involves mechanical mixing of binding
agents with in-situ soil using specialized equipment that can reach depths of
30 meters or more. This method creates columns or panels of treated soil that
provide structural support and containment. The equipment typically includes a
drilling rig with mixing tools that simultaneously inject and blend the binding
agent with the soil. This technique works well for large-scale projects
requiring significant depth of treatment.”
“Jet grouting uses high-pressure injection of grout to
simultaneously erode and mix the soil with binding agents. This creates
cylindrical columns of treated material that can form barriers, support
structures, or underpinning elements. The process involves drilling to the
desired depth, then injecting grout at pressures ranging from 300 to 600 bar,
effectively cutting through and mixing with the surrounding soil. This method
proves particularly useful in areas with limited access or when working around existing
structures.”
Some of the important
equipment for soil solidification via grouts is listed below.
According to Holcim, adding
cementitious materials is the main method of soil stabilization:
“Soil cement stabilization is typically the method of
choice when it comes to assuring the load-bearing capacity and quality of soil
in preparation for road construction and civil engineering projects. This
requires precise planning based on laboratory analysis to determine the optimal
treatment approach. Solutions could involve the application of Portland
limestone cement (PLC) or cement kiln dust (CKD) as a standalone treatment, or
it may require the use of a custom blend of PLC and CKD or a blend of PLC and a
supplementary cementitious material (SCM), such as slag or fly ash. It may also
call for a ternary combination of various SCMs blended in proportions required
to complete the job successfully.”
Soil Solidification Benefits
The benefits of soil
solidification for construction are numerous. By increasing bearing capacity,
it enables unsuitable ground for building to be made suitable. It creates a
more uniform foundation material and prevents differential settling. It is much
cheaper and less disruptive than having to excavate and remove soil and then
bring in expensive fill materials. By solidifying the existing soil, it is
economically advantageous. It also enables the use of shallower foundations,
which also lowers cost. Environmental advantages include minimum soil
disturbance, less trucking of material into and off the site.
Soil Solidification Challenges
The first challenge is to
accurately characterize the soil. This is typically done by geotechnical
engineers and geologists. Once the soil is adequately characterized, the
binding agents and dosages can be determined. The geochemistry of the soil is
also important. The presence of organic matter, sulfides and sulfates, extreme
pH, and contaminants can affect binding reactions, triggering the
need for additives or alternative approaches. Quality control and monitoring of
the soil at the site need to be ongoing. This includes periodic sampling,
laboratory testing, field penetration tests, and other verification methods.
Environmental challenges include dust management and runoff management.
Documentation of the material used is required for regulatory purposes. Below
are AMIX’s recommended strategies for overcoming these challenges.
The Future of Soil Solidification Technology
AMIX Systems provides a good
analysis of emerging technology in soil solidification, noting that binding
agents, like specialty grouts, and grout mixing capabilities in different
environments is a major focus:
Innovative binding agents represent one of the most active
areas of development. Research into geopolymers, bio-based stabilizers, and
nano-modified materials promises to deliver improved performance with reduced
environmental impact. These next-generation materials may offer faster strength
development, greater durability in aggressive environments, or specialized
properties like self-healing capabilities.
“Advanced mixing and application technologies are also
transforming the industry. Computer-controlled batching systems provide
unprecedented precision in mixture proportioning, while automated quality
control systems offer real-time monitoring of treatment effectiveness.
Specialized equipment for challenging environments, such as underwater or
contaminated sites, continues to expand the applicability of these techniques.”
“Sustainability considerations increasingly drive
innovation in this field. The industry is moving toward lower-carbon binding
agents, energy-efficient equipment, and processes that minimize waste
generation. The incorporation of recycled materials and industrial byproducts
as supplementary binding agents supports circular economy principles while
often enhancing treatment performance.”
They recommend a process of four steps: 1) Geotechnical
site investigation, soil boring, and laboratory testing to determine optimal
approach, 2) Select the proper equipment and sizes for the job, 3) Quality
control and monitoring programs including pre-construction testing, production
monitoring, and post-treatment verification, and 4) partner with experienced
equipment providers for both equipment and technical support.
Soil Nailing
Another specialty method of
soil stabilization is soil nailing. In the 2010s, a colleague of mine in the
oil and gas industry was working for Geostabilization International (GSI) and
gave a talk at a conference we both attended on soil nailing for stabilizing
vulnerable slopes along oil & gas lease roads in hilly areas. GSI describes
soil nailing as follows:
“An engineered method used to stabilize existing slopes
or excavation utilizing “top down” construction sequencing. This passive
reinforcement system remediates unstable natural slopes or construct new or
existing over-steepened slopes using closely spaced steel inclusions. The
practice involves drilling solid or hollow bars to depths specified by a
geotechnical engineer. GeoStabilization’s innovative ™ Nail Launcher Soil
utilizes compressed air to blast up to 20-foot-long nails into the slope at
speeds reaching 250-mph.”
“Soil nails are reinforced bars installed in soil mass.
Soil nails can be installed in a variety of methods including drilled, driven,
or launched nails and can be installed in a wide range of soil conditions
accommodating changes in ground conditions. Soil nails perform well under
seismic loading due to coupling with the ground. Each installed nail is a soil
probe which can aid in design refinement during construction. Soil nails are
part of a soil-structure system, consisting of the following elements: earth
materials, tendons, grout, facing, connections, and drainage.”
Self-drilling soil nails are used to stabilize active
landslides or collapsing soil. Open-hole soil nails use the nail itself to
drill the hole and grout as the drilling fluid. The result is an effective
grout column where the grout mixes well with the surrounding material. Launched
soil nails utilize highly compressed air to force the nails into
place. The nails are usually fully grouted and installed at a slight
downward inclination, with regularly spaced points across the slope. Steel-reinforced
rigid shotcrete or flexible wire mesh can add strength and erosion control. An
advantage of soil nailing is its low cost compared to other soil stabilization
methods.
New Research Incorporates Recycled Glass and Construction
Waste into a Geopolymer-Based Soil Solidifier
New research shows very good
results incorporating recycled glass and siding waste into a geopolymer-based
soil solidifying cementitious material. The use of waste materials for binding
instead of expensive Portland cement makes the process cost-effective. Japanese
scientists at the Shibaura Institute of Technology (SIT) utilized a
high-performance geopolymer-based soil solidifier developed from Siding Cut
Powder (SCP), a construction waste byproduct, and earth silica (ES), sourced
from recycled glass. The result is a solidified soil with adequate strength for
construction. Thermal treatment of SCP at 110 °C and 200 °C was a critical
step. This increases reactivity. The researchers also demonstrated that
incorporating calcium hydroxide effectively mitigated the potential for arsenic
leaching from the glass by reacting it to form more stable calcium arsenate
compounds.
According to Wikipedia:
“A geopolymer is an inorganic, often ceramic-like material,
that forms a stable, covalently bonded, non-crystalline to semi-crystalline
network through the reaction of aluminosilicate materials with an alkaline or
acidic solution. Many geopolymers may also be classified as alkali-activated
cements or acid-activated binders. They are mainly produced by a chemical
reaction between a chemically reactive aluminosilicate powder e.g. metakaolin
or other clay-derived powders, natural pozzolan, or suitable glasses, and an
aqueous solution (alkaline or acidic) that causes this powder to react and
re-form into a solid monolith. The most common pathway to produce geopolymers
is by the reaction of metakaolin with sodium silicate, which is an alkaline
solution, but other processes are also possible.”
The geopolymer has “proven
durability under sulfate attack, chloride ingress, and freeze-thaw cycles.”
Its main advantage is the replacement of Portland cement, resulting in
significantly lower cost and significantly lower pollution and greenhouse gas
emissions. It represents another sustainable construction method that will
likely catch on. Key findings and future research directions of ES and
SCP-based geopolymers, from the paper published in Cleaner Engineering and
Technology, are shown below.
References:
Geopolymer
technology turns recycled glass and construction waste into a durable and green
construction material. Science X staff. TechXplore. May 29, 2025. Geopolymer technology turns recycled
glass and construction waste into a durable and green construction material
Development
of environmentally sustainable geopolymer-based soil solidifiers using waste
siding and glass powders. Shinya Inazumi, Ryo Hashimoto, Yoji Hontani, Atsuya
Yoshimoto, Ken-ichi Shishido, and Kuo Chieh Chao. Cleaner Engineering and
Technology. Volume 26, May 2025, 100976. Development of environmentally
sustainable geopolymer-based soil solidifiers using waste siding and glass
powders - ScienceDirect
Revolutionary
Soil Solidification for Stability. AMIX Systems. Revolutionary Soil Solidification for
Stability - AMIX Systems
Soil
Cement Stabilization and Solidification: Custom Solutions for High Performance
and Sustainability. Holcim. Soil Cement Stabilization and
Solidification | Holcim US
What
is Soil Stabilization, and what are the Methods of Soil Stabilization? Civil
Engineering Portal. What is Soil Stabilization, and what
are the Methods of Soil Stabilization? - Civil Engineering Portal
Community
Guide to Solidification and Stabilization. US EPA. April 2021. Community Guide to Solidification and Stabilization
Soil
Sol-idification, Soil Acidi-fication, Soil Alkalizat-ion and Soil Pol-lution
Presented By Md Khairul Haque. Jatiya Kabi Kazi Nazrul Islam University. March
2024. (PDF) Soil Sol-idification, Soil
Acidi-fication, Soil Alkalizat-ion and Soil Pol-lution Presented By
What
is Soil Nailing? Geostabilization International. Soil Nailing - Geostabilization
International
Geopolymer.
Wikipedia. Geopolymer -
Wikipedia
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