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Soft clay deposits are highly plastic, normally consolidated fine grained soils characterized by their low inherent shear strength. The mixing of soft clays with cement as a chemical stabilizer has become a well-known stabilization technique. The resulting strength of the clay–cement mix is controlled by different factors, but mainly the water to cement ratio, the cement content, and the curing conditions. It is crucial to develop a clear understanding of the changes in engineering behavior of the clay–cement mix that result from changes in controlling factors. A phase diagram was established to define the initial conditions of the mass–volume relationships of air, cement, clay, and water of a typical clay–cement mix. This phase diagram was then used to determine the total dry density, void ratio, and specific gravity of the clay–cement mix as a function of the cement content and water to cement ratio. The main objective of this work was to develop generalized trends for the geotechnical properties of clay–cement mixes. These trends were evaluated based on unconfined compressive strength as well as consistency tests carried out on soft clay samples before and after mixing with cement and at different curing times. A reduction in the plasticity index (PI) of 16 % and an increase in the unconfined shear strength of more than 200 kPa were obtained from the addition of 15 % cement. The reduction in the PI of the clay–cement mix was found to be an efficient tool to represent the improvement in the strength of the clay after mixing with cement.
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Geotechnical characterization of a clay–cement mix
Ramy Saadeldin Sumi Siddiqua
Received: 9 April 2013 / Accepted: 3 October 2013 / Published online: 16 November 2013
ÓSpringer-Verlag Berlin Heidelberg 2013
Abstract Soft clay deposits are highly plastic, normally
consolidated fine grained soils characterized by their low
inherent shear strength. The mixing of soft clays with
cement as a chemical stabilizer has become a well-known
stabilization technique. The resulting strength of the clay–
cement mix is controlled by different factors, but mainly
the water to cement ratio, the cement content, and the
curing conditions. It is crucial to develop a clear under-
standing of the changes in engineering behavior of the
clay–cement mix that result from changes in controlling
factors. A phase diagram was established to define the
initial conditions of the mass–volume relationships of air,
cement, clay, and water of a typical clay–cement mix. This
phase diagram was then used to determine the total dry
density, void ratio, and specific gravity of the clay–cement
mix as a function of the cement content and water to
cement ratio. The main objective of this work was to
develop generalized trends for the geotechnical properties
of clay–cement mixes. These trends were evaluated based
on unconfined compressive strength as well as consistency
tests carried out on soft clay samples before and after
mixing with cement and at different curing times. A
reduction in the plasticity index (PI) of 16 % and an
increase in the unconfined shear strength of more than
200 kPa were obtained from the addition of 15 % cement.
The reduction in the PI of the clay–cement mix was found
to be an efficient tool to represent the improvement in the
strength of the clay after mixing with cement.
Keywords Soft clay Clay–cement mix Curing
time Unconfined compressive strength
Volume–mass relationships Soil stabilization
The main engineering challenges presented by construction
on soft clay deposits are low shear strength (typically
\25 kPa) and bearing capacity. Foundation design on soft
clay has been a continuous source of concern for engineers
since the beginning of geotechnical engineering (Chen and
Morris 2000). These design concerns include the factor of
safety against shear failure and overall stability. The key
characteristics of the performance of natural clays include
time/rate dependency, strength/stiffness anisotropy, and
structure/destructuralization (Grimstad et al. 2010). The
engineering behavior of soft soils is controlled by the
parent material’s source, depositional processes, erosion,
re-deposition, consolidation, and fluctuations in ground-
water levels (Gue and Tan 2000). The physical and
mechanical properties of soft clays usually vary signifi-
cantly due to the variations in sedimentary processes
associated with different environmental conditions (Ho and
Chan 2011).
Cement stabilization of soft clay soils has become an
efficient ground improvement technique, and it has been
attempted with much success over the last few years.
Chemical stabilization of soft soils has been extensively
R. Saadeldin (&)
Environmental Systems Engineering, University of Regina,
Regina, SK, Canada
R. Saadeldin
AMEC Environment and Infrastructure, Regina, SK S4N 4Y1,
S. Siddiqua
School of Engineering, University of British Columbia,
Okanagan Campus, Kelowna, BC, Canada
Bull Eng Geol Environ (2013) 72:601–608
DOI 10.1007/s10064-013-0531-2
applied in both shallow and deep applications to improve
inherent soil properties such as shear strength and com-
pressibility indices (Bergado et al. 1996; Chen and Wang
2006). Mass stabilization with cement has been success-
fully used to treat soft clays, saving time in comparison
with other ground improvement techniques, such as pre-
loading (AASHTO and FHWA 2003). Cement stabilized
soils were found to be a reliable engineering alternative to
satisfy the entire requirements of sustainable infrastructure.
The increased bearing capacity of chemically stabilized
subgrades can result in a significant reduction of the
required base course layer thickness of highways (Aust-
roads 1998).
Field applications of cement stabilization of soils have
recently become more feasible due to the development of
commercial stabilization systems that are able to stabilize
soft soils up to a depth of about 5.0 m. Stabilizing the
upper 3.0–5.0 m of soil materials by mixing the soil with a
stabilizing agent (mass mixing) is an optimum foundation
improvement technique for highway construction. Cement
stabilization of soft clays is commonly accomplished
through the addition of dry or wet cement to the volume of
the soil. Stabilization of the soft clays occurs when both the
cement and water react to form cementitious calcium sili-
cate and aluminate hydrates while binding the soil particles
together (Ho and Chan 2011). The work described in the
present paper was intended to aid geotechnical engineers in
finding a quick estimation of engineering properties of a
clay–cement mix. Generalized volume–mass relationships
were established in order to understand the engineering
behavior of clay–cement mixes. The improvement in soft
clay strength was also measured for different cement
contents and at different curing times.
The increased strength of a clay–cement mix results from
the physicochemical reactions between soil and cement,
such as the interaction between the substances founded on
the soil and the products of the hydration of cement (Chen
and Wang 2006). The development of higher strength and
stiffness is achieved by: (1) reducing void space, (2)
bonding particles and aggregates together, (3) maintaining
flocculent structures, and (4) preventing soil swelling (Oh
2007). The most commonly used cement type is Portland
cement. Portland cement is composed primarily of calcium
aluminates and calcium silicates that hydrate after mixing
with water, creating the cementing compounds calcium
silicate hydrate and calcium aluminate hydrate. The hard-
ening process of the clay–cement mix occurs immediately
after mixing water with the cement. The hardening agent
provides the hydrated calcium silicates, hydrated calcium
aluminates, and calcium hydroxide, thereby forming
hardened cement structures (Saitoh et al. 1985).
The two major chemical reactions which govern the
behavior of clay–cement mixes are the primary hydration
reaction between cement and water and the secondary
pozzolanic reactions between the lime released by the
cement and clay minerals (Bergado et al. 1996). The
hydration reaction causes the formation of primary
cementitious products, leading to the initial gain in strength
of the clay–cement mix. However, the secondary pozzo-
lanic reaction occurs when a sufficient concentration of
hydroxide ions (OH
) is achieved in the pore water (Xiao
and Lee 2008). Pozzolanic reactions occur between the
silica and alumina found in the clay and the calcium ions of
the cement, which forms cementitious products, including
calcium aluminate hydrates, calcium silicate hydrates, and
calcium aluminum silicate hydrates (Solanki and Zaman
2012). The resulting cementitious material and the calcium
hydroxide are the main components that stabilize both
granular and fine-grained soils.
The improvement of cement-stabilized soil depends pre-
dominantly on the chemical components of the cementing
agent and soil properties (Kawasaki et al. 1981). Generally,
coarse-grained soils have been shown to gain a larger
increase in undrained shear strength than fine-grained soils
do when mixed with the same cement content (Taki and
Yang 1991). The hardening properties of cement-stabilized
clay mixtures are influenced by a number of factors, such as
the mixing mechanism, compaction, moisture content, and
temperature, as presented in Fig. 1(Kezdi 1979). The mixing
criteria for the cement and clay control the hardening char-
acteristics of cement-stabilized clay mixtures, and include
the mixing speed, temperature, and compaction specifica-
tion. The main factors that govern the strength development
of cement-stabilized soils are the cement content, water to
cement ratio, and the curing duration of the cemented soil.
Clay–cement mixes generally have a lower dry density than
that of untreated clay at the same degree of compaction.
However, the optimum moisture content of stabilized clay
increases with increasing cement content (Sherwood 1993).
The hydration process takes place immediately after the
cement comes into contact with water. Therefore, it is
important to compact the clay–cement mix as soon as the
cement comes into contact with water. Any delay in com-
paction may result in additional compaction effort.
The moisture content is important for hydration and
compaction processes of clay–cement mixes. Pozzolanic
reactions are highly affected by any changes in tempera-
ture. Lower temperatures may influence the pozzolanic
reactions between binders and soils and result in lower
shear strength. Therefore, in cold regions, it may be prac-
tical to limit the mixing of binder and soil to warm seasons,
however the curing process of the stabilized soil can take
602 R. Saadeldin, S. Siddiqua
place throughout the year (Maher et al. 2004). Al-Tabbaa
and Evans (1998) reported that cement stabilized soils may
not withstand freeze–thaw cycles in the field. Therefore, it
is important to insulate the stabilized soils against frost
action. Cement-stabilized clays are also influenced by
frequent dry–wet cycles, so adequate field protection is
typically necessary (Maher et al. 2004).
The compressive strength of a clay–cement mix gener-
ally increases with increasing cement content up to a certain
percentage, after which the rate of increase in strength
decreases (Uddin et al. 1997). The required cement content
depends mainly on the desired properties of the cement-
stabilized soil and soil type, and typically varies from 5 to
15 % of the weight of the soil (Jaritngam and Swasdi 2006).
An undrained shear strength parameter (c
) of cement-sta-
bilized soils was obtained for cement-stabilized soil samples
where the mass of dry cement to soil volume ranged from
200 to 450 kg/m
, according to Federal Highway Admin-
istration report no. FHWA-SA-98-086 (FHWA 1998). The
undrained shear strength of the cement-stabilized soils
typically ranged from 10 to 50 times the undrained shear
strength of the natural soils. The upper and lower limits of
the strength increase were obtained for higher cement
contents and/or cohesionless soils, as well as for lower
cement contents and/or cohesive soils, respectively.
The water to cement ratio is considered a significant
factor governing the engineering behavior and strength of
cement-stabilized clays (Miura et al. 2001). The uncon-
fined compressive strength of clay–cement mixes decreases
considerably as the initial water content of natural soil
increases. The water to cement ratio generally influences
the effect of the cementing agent, which controls the
strength of the clay–cement mix. A higher initial water
content requires more cement to achieve any significant
effect during the stabilization of the clay. As a general
trend, the unconfined compressive strength decreases sig-
nificantly with increasing water to cement ratio of a clay–
cement mix (Miura et al. 2001; Hassan 2009).
The compressive strengths of cement-stabilized clays
have been found to increase significantly with increasing
curing time (Kawasaki et al. 1981; Uddin et al. 1997). The
increase in the compressive strength of the clay–cement
mix is rapid early in the curing period and then slows down
over time (Porbaha et al. 2000). White and Gnanendran
(2005) illustrated that during the preparation of the
cement–soil mix, up to a 40 % decrease in the resulting
unconfined compressive strength of the cement-stabilized
soil can be expected if any delay occurs between the
mixing and compaction processes. Saitoh et al. (1996)
reported that the compressive strength ratio ranged from
1.2 to 2.1 during days 7–28. Horpibulsk et al. (2011)
showed a generalized equation for the increase in the
unconfined compressive strength with the curing time:
q28 ¼0:039 þ0:283 lnðDÞ;ð1Þ
where Dis the curing time in days, q
is the strength at
time D, and q
is the strength at 28 days.
Volume–mass relationships
The generalized volume–mass relationships of a clay–
cement mix can be used beneficially in ground improve-
ment engineering practices. The moisture content is an
important property for hydration and compaction processes
of a clay–cement mix. In order to be fully hydrated, cement
requires around 20 % of its own weight in water from the
surrounding moisture (Sherwood 1993). This amount of
moisture will be consumed over time during the hydration
of cement. The relationships between the total dry density,
void ratio, and specific gravity were established for the
initial condition of a clay–cement mix based on the
assumption that there is no water loss during the mixing
period of the clay–cement slurry. The change in the initial
geotechnical properties of the clay–cement mix with time
is another essential factor that should be considered for
field applications. Figure 2shows the multi-phase diagram
for a generalized case of a saturated clay–cement slurry,
including water, clay, and cement. The volumes of these
phases are expressed as V
, and V
, respectively. The
total void ratio (e
) is defined as the ratio of the volume of
voids, V
, to the volume of soil solids, V
, as shown below:
For wet mixing processes, natural water content and the
amount of water added to the soil are taken into account in
Fig. 1 Factors affecting the properties of cement-stabilized soils
(after Kezdi 1979)
Geotechnical characterization of a clay–cement mix 603
the numerator of the clay water to cement ratio, which
governs the engineering parameters of the clay–cement
mix (Miura et al. 2001). Cement content is defined as the
mass of cement over the total mass of soil solids (W
Equation 2can be presented in terms of the cement content
and the clay water to cement ratio as
Gscm þ1CðÞ
where (w/c) is the clay water to cement ratio, Cis the
cement content, G
is the specific gravity of cement, and
is the specific gravity of clay.
Using the geotechnical definition of the total dry den-
sity, and under the same compaction energy, the dry den-
sity of a clay–cement mix can be established as follows:
ðw=cÞþ C
Gscm þð1CÞ
where c
is the total dry density and c
is the density of
The total specific gravity of the clay–cement mix can
also be determined as the average value of the combination
of the specific gravities of clay and cement, as shown
Gsct ¼1CðÞGsc þCGscm;ð5Þ
where G
is the total specific gravity of the clay–cement
The selection of the water to cement ratio and cement
content has a considerable effect on the resulting density
and the void ratio of the clay–cement mix, and therefore
influences the design of field applications. A parametric
study was conducted to show the effect of soil and cement
parameters on the resulting properties of the clay–cement
mix. The developed property trends can be useful for the
selection of the appropriate mixing criteria and to obtain
the optimized design parameters. The predicted relation-
ships for the clay–cement mix were plotted in Fig. 3in
accordance with the developed Eqs. 3and 4. The trends for
a water to cement ratio of 2 were verified against the
measured void ratio and dry density of a clay–cement mix.
Using the same water to cement ratio, increasing the
cement content of the clay–cement mix resulted in an
increased void ratio due to the increase in water volume,
which resulted in decreased total dry density. It was noted
that the compaction effort should be different at distinct
cement contents in order to achieve the same total dry
density of the resulting clay–cement mix. Higher com-
paction efforts should be applied with increasing cement
content. In addition, the water to cement ratio was found to
govern the resulting dry density of the clay–cement mix,
Fig. 2 Volume–mass phase
diagram for a clay–cement mix
Cement Content, C (%)
Total Dry Density, yd (kN/m3)
Total Void Ratio, et
Measured et at (w/c=2)
Measured yd at (w/c=2)
Total Void Ratio
Total Dry Density
Fig. 3 Total void ratio and dry density versus cement content for a
clay–cement mix
604 R. Saadeldin, S. Siddiqua
which influenced the overall effect of cement on the natural
Selection criteria for the optimum cement content
The liquid limit (W
), plastic limit (W
), and plasticity
index (PI) are representative geotechnical parameters for
clayey soils. The PI and W
are predominately used in
strength correlations and consolidation estimates (Bowles
1996). At higher plasticity indices, soils behave more
plastically, making them non-preferable for use in con-
struction. A simple method of predicting the improved
performance of clay is to measure the change in its plas-
ticity characteristics using the PI parameter (PI). Typically,
a reduction in the range of 12–15 % in PI serves as the
criterion for selecting cement content for the purpose of
soil stabilization (PCA 2003).
Figure 4shows the change in PI (DPI =PI
) at a curing time of 28 days with increasing
cement content. Three rates were observed for the change
in clay plasticity with the addition of cement (Saadeldin
and Siddiqua 2013). Initially, the PI showed a minor
decrease as the cement content increased to 5 %. As the
cement content rose from 5 to 15 %, the PI decreased
rapidly. Above 15 %, the rate of decrease of plasticity
decreased considerably with rising cement content. The
maximum reductions in the PI of about 16 and 19 % were
obtained at cement contents of 15 and 20 %, respectively.
A comparable trend was observed in previous testing data
on cement-stabilized clay presented by Kamruzzaman et al.
(2000). The optimum cement content for cement stabil-
ization of the clay was found to be about 15 %, after which
the decrease in plasticity was relatively low. It was also
noted that the reduction in the PI at a cement content of
15 % fell within the range of 12–15 % reported by PCA
Normalized strength relationships
Unconfined compression tests were conducted on soft clay
samples to determine the physical and mechanical prop-
erties of soft clay before and after mixing them with
cement (Saadeldin et al. 2011). These tests, in accordance
with ASTM D2166 (2006), were implemented to measure
the undrained shear strength of clay–cement mixes. The
soft clay was composed of 4.9 % sand, 16.1 % silt, and
79 % clay. The natural soft clay has a liquid limit of 80 %,
a plastic limit of 30 %, and a field water content of 69 %.
According to the unified soil classification system (USCS),
the soil was classified as highly plastic clay (CH). The
geotechnical index properties of the soft clay are summa-
rized in Table 1. Portland cement was used as the chemical
stabilizer, and the clay–cement mix was investigated for
cement contents of 5, 10, and 15 %, as well as for a total
water to cement ratio of about 2 %. The cement slurry was
slowly added to the remolded clay and then mixed for a
period of 5 min until the mix was visually homogeneous,
as recommended by Den Haan (2000). Rafalko (2006)
illustrated that there was an increase in the unconfined
compressive strength of a cement-stabilized clay as the
mixing time was increased from 5 to 10 min, after which
the change was insignificant. As a general guideline, the
most reliable and repeatable indication of the homogeneity
of the clay–cement mix is the visual appearance (Euro-
SoilStab 2002). However, for comparable tests on a given
soil under different stabilizer and dosage conditions, it is
necessary to adopt the same mixing time, which can be a
period of 5 min, where possible (EuroSoilStab 2002).
Cement Content, C (%)
Change in Plasticity, PI (%)
This research, wi = 75%
Kamruzzaman et al. (2000), wi = 90%
PI = PIclay - PIclay-cement
Fig. 4 Change in plasticity of a clay–cement mix at different cement
Table 1 Geotechnical index properties of the soft clay
Property Value
Natural water content (%) 69
Moist unit weight (kN/m
) 15.8
Void ratio 1.81
Specific gravity 2.62
Liquid limit (%) 80
Plastic limit (%) 30
Sand (%) 4.9
Silt (%) 16.1
Clay (%) 79
Geotechnical characterization of a clay–cement mix 605
Cement content versus normalized unconfined strength
The effect of cement content on the normalized unconfined
compressive strength of the cement-clay mix is shown in
Fig. 5. As the cement content increased, the unconfined
compressive strength increased according to the general
relationship defined by Eq. 6below. Improvement in
unconfined compressive strength can be obtained as a ratio
of the cement content, and this increasing ratio varied with
curing time.
quclay ¼1þFC;ð6Þ
where Cis the cement content (%) and Frepresents an
increasing factor due to cementation, which varies with
curing time.
For the clay tested, Fwas found to be 0.6, 0.33, and 0.11
for curing times of 28, 7, and 3 days, respectively. For a
cement content of 15 % and a curing time of 28 days, the
unconfined compressive strength (q
) increased by about
10 times, from 24 kPa for natural soft clay to 242 kPa for
cement-stabilized clay—a result that is in agreement with
the findings reported by FHWA (1998).
Curing time versus normalized unconfined strength
The effect of the curing time on the normalized unconfined
compressive strength of cement-stabilized soft clay is
shown in Fig. 6. For the cement contents tested, the
unconfined compressive strength increased with the curing
time up to about 28 days, after which the increase in
compressive strength was less significant. Esrig (1999)
showed that most noticeable gain in the strength of the
clay–cement mix occurs within the first 28 days after
mixing, and the strength continues to increase at a slower
rate thereafter (Jacobson 2002). Xiao and Lee (2008)
showed that the increase in clay strength is dependent on
different factors, including the cement content, and in some
cases the increase in strength can still occur after 28 days.
For the cement contents tested, the unconfined compressive
strength (q
) ratio at 7–28 days ranged from 1.8 to 2.1,
which is in agreement with the ratio (1.2–2.1) reported by
Saitoh et al. (1996). A generalized equation was developed
for the normalized unconfined compressive strength of
clay–cement mixes applicable for different cement ratios,
particularly 5, 10, and 15 %, as shown in Eq. 7below. The
results of Eq. 7were found to be in close agreement with
the equation developed by Horpibulsk et al. (2011), as
presented in Eq. 1.
q28 ¼0:1þ0:25 lnðDÞ;ð7Þ
where Dis the curing time in days, q
, is the strength at
time D, and q
, is the strength at 28 days.
Soft clay soils consist of normally consolidated clays and
are generally identified by low shear strength. In the scope
of the tests carried out on soft clay samples, cement was
used as a soil stabilizer in order to improve the mechanical
properties of the natural soft clay. This paper was intended
to provide a quick estimation of the role of curing time and
cement content on the geotechnical properties of a clay–
cement mix.
A change in the plasticity of the clay–cement mix was
observed as the cement content was increased for a curing
time of 28 days. Three rates were obtained for the decrease
in PI with increasing cement content. It was found that a
reduction of 12–15 % in the PI of the clay–cement mix is a
Cement Content, C (%)
Normalized Strength, qclay-cement/qclay
Curing time = 3 days
Curing time = 7 days
Curing time = 28 days
qclay-cement/q clay = 0.60 (C) + 1
R² = 0.98
qclay-cement/qclay = 0.33 (C) + 1
R² = 0.94
qclay-cement/qclay = 0.11 (C) + 1
R² = 0.96
Fig. 5 Unconfined compressive strength of a clay–cement mix at
different cement contents
011 23456789 2030
Curing Period, D (days)
Normalized Strength, qD/q28
C = 5 %
C = 10 %
C = 15 %
Horpibulsk et al., 2011
qD/q28 = 0.25 ln(D) + 0.1
R² = 0.95
Fig. 6 Unconfined compressive strength of a clay–cement mix at
different curing times
606 R. Saadeldin, S. Siddiqua
reasonable indication of the optimum cement content to
stabilize the tested clay soils.
Experiments suggested that the overall geotechnical
index properties of clay–cement mixes were controlled by
the water to cement ratio, as well as the cement content.
Therefore, a phase diagram was developed to present the
geotechnical index properties, such as dry density, specific
gravity, and void ratio of a typical clay–cement mix. This
phase diagram showed that increasing the cement content of
the clay–cement mix resulted in an increased void ratio and
decreased total dry density for the same water to cement
ratio. Therefore, higher compaction efforts may be needed to
achieve the same dry density with increased cement content.
The clay–cement mix had a greater strength than the
natural soft clay. The unconfined compressive strengths of
clay–cement mixes increased significantly with increasing
cement content and followed linear relationships at dif-
ferent curing times. The increase in unconfined compres-
sive strength was presented as a percentage of the cement
content, which varied from 11 to 60 % as the curing time
increased from 3 to 28 days. The normalized unconfined
compressive strength also increased linearly as curing time
increased up to 28 days.
Acknowledgments The authors would like to acknowledge the
contribution of Dr. Hani Lotfi and Dr. Manal A. Salem of Geotech-
nical Engineering, Cairo University, and thank them for their great
support during the course of obtaining some of the results presented in
this paper.
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... To combat with the persisting issues, improving the engineering properties of in-situ soil, aka 'soil stabilization', and using it for road construction is recommended by researchers [1][2][3]. Soil stabilization is performed by mixing additives including cement, lime and flyash with problematic in-situ soils [4][5][6][7][8] to produce improved construction material. Blending additives to such problematic soils is envisaged to reduce plasticity and swell/shrinkage behaviour, and improve their bearing capacity and durability [9,10]. ...
... The peak improvement with respect to untreated soil (S) was recorded as 155%, 134% and 121% for soil stabilized with cement, 3E1R1N and 2E2R1N, respectively. This could be attributed to the higher level of pH concentrations due to the presence of NaOH and the availability of constituents such as ESA and RHA, which supported the geopolymer reactions and the formation of C-S-H and C-A-S-H in the above systems as detailed in Eq. (2)- (5). When, ESA content further increased (4E0R1N), USC value started declining. ...
In line with sustainable development, the road sector has initiated the use of agro-wastes in road construction to preserve natural resources, which have been commonly used in conventional construction. In that sense, this study investigates the merits and demerits of incorporating eggshell ash (ESA) and rice husk ash (RHA) into geopolymer based lateritic soil stabilization for roadbase construction. Atterberg limits, modified Proctor compaction, unconfined compressive strength (UCS) tests were conducted on lateritic soil samples stabilized with cement or geopolymer that comprises of the combination of ESA, RHA and sodium hydroxide solution (NaOH). Results from the experimental study revealed that an increase in ESA substitution level reduced the plasticity index of lateritic soil. Maximum dry density was slightly reduced in all soil mixes stabilized with ESA, RHA and NaOH. With reference to cement stabilization, UCS showed a marginal reduction of 8.2 and 13.2% in geopolymer combinations of 3E1R1N (3% ESA + 1% RHA + 1% NaOH) and 2E2R1N (2% ESA + 2% RHA + 1% NaOH), respectively. Notably, out of all mixes, the mix combination of 3E1R1N and 2E2R1N produced the lowest cost to strength and embodied energy to strength ratio, and relatively lower CO2 emission to strength ratio. The authors believe that the proposed geopolymer stabilization method would be a competitive alternative to cement based lateritic soil stabilization for roadbase construction.
... Three mixtures were performed and tested, each with different proportions of its components, based on previously published works such as Arellano's patent [9], as well as the proposals of Saadeldin & Siddiqua [78] and Noor ul Amin [7]. The proportion of each ingredient was adjusted according to the results obtained from Formulations 1 and 2, keeping the use of cement to a minimum due to the environmental impact it entails. ...
Large quantities of carbon dioxide (CO 2) are emitted to the atmosphere during the traditional burning brick process, taking part in the construction industry affectations. This paper presents an alternative way that faces environmental issues by using low-Impact materials in construction; for this purpose, it is proposed the formulation of an admixture for the fabrication of unfired clay bricks. Three different clay-base formulations were developed to analyze their behavior underwater, plasticity, and drying time to determinate the best one to get an unfired brick. The sample with the better performance underwater was tested to water absorption and compressive strength tests. Results show that it is possible to obtain an unfired clay-based material utilizing low environmental impact admixtures to elaborate construction bricks. Finally, a Life Cycle Analysis assessment was conducted to determine CO 2 emissions when utilizing the propossed formulation.
... For storage of water, river flooding management, and meeting other basic demands, ancient civil engineering techniques used binders and natural resources. Roman concrete, a mixture of a natural pozzolan substance, aggregates, and a binder such as lime or gypsum, was widely used to build and study structures in ancient Rome (see [15]). Ringelberg et al. [16] find that during the Post Industrial Revolution, for the stabilization of soil, ordinary Portland cement was designed. ...
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Topological indices are numerical descriptors that aid in the prediction of chemical molecules’ physiochemical properties and biological actions. It is often helpful to forecast numerous physiochemical attributes and biological actions of molecules in chemometrics, bioinformatics, and biomedicine. In this paper, we establish the M-polynomial and NM-polynomial of some very familiar biopolymers, which are xanthan gum, gellan gum, and polyacrylamide. The uses of these biopolymers can increasingly take the place of traditional admixtures for the application of soil stability and enhancement. We recover the important topological degree-based indices. Also, we give diverse graphs of topological indices and their relations with the parameters of structures.
... Stabilisation/solidification (S/S) is a process that is recognised as a leading remediation method of soil contaminated with heavy metals [1]- [4]. The relatively low cost of its application [5]- [7], time efficiency [8], [9], and most importantly, effective immobilisation of contaminants while increasing the strength characteristics of the subsoil contribute to this. Implementation of various types of binders into the soil in the presence of water causes the hydration process to begin. ...
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The effectiveness of various types of binders in stabilizing/solidifying (S/S) contaminated soils is strongly dependent on the type of soil and contaminants present. The literature abounds with studies of stabilisation/solidification of clayey soils, which provides a background for initial assumptions in design of the method application for contamination of this type of soil. However, studies on the stabilisation/solidification of loess silt contaminated with heavy metals are not available. Filling this deficiency is important in order to ensure the rapid adoption of the most effective remedies in case of contamination and their immediate implementation in the subsoil. This paper has enabled the determination of the most effective mixture among the examined for the remediation of loess silt contaminated with zinc in terms of compressive strength. Strengths were determined with the implementation of 30% Portland cement (2.63 MPa), 30% of fly ash-cement mixture (2.21 MPa), an incinerated sewage sludge ash-cement mixture (0.93 MPa) and mixtures in which cement was replaced by an MgO activator (0.18 MPa for fly ash and 0.63 MPa for incinerated sewage sludge ash). In addition, the determination of strength was carried out for samples containing a mixture of fly ash, activator and cement (0.26 MPa) and incinerated sewage sludge ash, activator and cement (0.26 MPa), with weight ratios of 5:4:1 respectively. In summary, fly ash and cement in a 2:1 ratio can be considered the most effective binding mix in terms of unconfined compressive strength increase.
... The strength (i.e. UCS) of the resulting clay-cement mixture is mainly determined by the cement content, water-cement ratio, and the curing conditions and follows linear relationships at various curing times [46][47][48][49][50] . Understanding chemical interaction between clay soils and water can be useful in making such systems suitable for engineering purposes such as materials science, petroleum engineering, geology, geophysics, sedimentology, and environmental science 51 . ...
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The study of the properties of engineered rocks is of great importance to researchers in engineering sciences such as petroleum, mining, and civil engineering owing to their wide application in these fields. In the present study, a physico-chemical and geomechanical investigation was carried out on the effects of different clay minerals on porous rocks. Various chemical products formed during chemical interactions between cement, clay minerals, and water can change the pore structure and thus the rock characteristics. The results of the current study showed that increasing the clay content could remarkably reduce the porosity and permeability of the rock by an average of 86% and 6.76%, respectively. In this regard, samples containing kaolinite were further influenced due to their new pore structure. Moreover, a power relationship was found between sonic velocity and porosity, which can be used to predict rock properties. Chemical analysis indicated an amplification in quantities of chemical products, particularly calcium silicate hydrate and portlandite, due to an increase in clay content. The impacts of porosity and cementation quality as two main factors on rock strength have also been studied. The outcomes revealed that a reduction in porosity could compensate for detrimental effects of poor bond quality and consequently improved UCS by up to 30% in samples containing kaolinite, while decreasing the degree of cementation prevailed over the porosity reduction in specimens including illite and resulted in a 14% decrease in UCS. The effects of porosity and bond quality on UCS would cancel each other out in samples containing bentonite. It is worth noting that when it comes to changes in geomechanical characteristics, the dominant factor (i.e., porosity reduction or cementation quality) determines the ultimate effect of clay minerals on the properties of engineered porous rocks.
This article presents an experimental study on the drainage-humidification pathways of a loamy soil treated with different cement dosages and compacted to the Normal Proctor Optimum at room temperature. The suctions used ranged from 0.05 MPa to 342.63 MPa and were applied to four studied formulations (natural soil, soil + 2% cement, soil + 4% cement, and soil + 6% cement). At the end of the drainage-humidification tests, the soil water retention curves of the treated soil at different cement dosages allowed us to determine the different state parameters of the treated soil: degree of saturation (Sr), dry unit weight (γd), void ratio (e), and water content (w). The range of suction imposition as well as the cement dosage significantly influence the hydraulic behavior of the studied material. Moreover, simulations were carried out using a hydraulic model from the literature; these simulations illustrate the effect of treatment on the soil hydraulic parameters studied, namely: shrinkage limit, shrinkage limit pressure, and desaturation pressure, to facilitate the interpretation of the experimental results obtained.
This study aims to perform experiments to determine both initial shear modulus and unconfined compressive strength of Bangkok soft clay improved by the ordinary Portland cement (OPC) and fly ash (FA). The role of cement is for stabilizing Bangkok soft clay, whereas the cement replacement by FA is for sustainable purpose because FA is a waste by-product from the Mae Moh power plant in Thailand. The Bangkok soft clay is mixed with OPC of 20% by weight as well as FA replacement of 0–30% by weight. After curing for 7, 14, 28 and 90 days, the initial shear modulus is determined from shear wave velocity measured by a self-developed non-destructive bender element, which is appropriate for cyclically and continuously curing time modelling. For comparisons and result validation, the strength development of tested clay samples is also determined by the destructive unconfined compressive strength (UCS) tests. From the study, the initial shear modulus reveals the optimum FA replacement of 20% at 90 days, whereas the unconfined compressive strength reveals that of 15% at 90 days. Moreover, both the initial shear modulus and the unconfined compressive strength increases with the curing time. The relationship between the normalized unconfined compressive strength and the curing time is found as naturally logarithmic with the increase rate at 0.3433, and the early-age normalized unconfined compressive strength is found as 0.09. By comparison with a study, the limitation of the bender element tests is found, as only the small strain quantity in terms of G0 or E can be determined in spite of being beneficial for constitutive modelling in various computations (e.g., the finite element method, FEM, dynamic analysis of soil property, etc.). The relationship between normalized shear modulus and unconfined compressive strength in this study agrees with other studies, but some discrepancy exists due to different compositions, clay type, cement content, and stabilizers. Thus, further studies on this discrepancy are recommended.
In this study, the installation parameters of the deep mixing (DM) column were optimized to manufacture a homogeneously mixed column and to reduce variability in the strength of the column. DM columns, 30 cm in diameter and 70 cm in length, were manufactured on clayey soils of different consistencies using a DM machine and slurry batch plant in the laboratory. The strength of DM columns and soil improvement ratio were investigated using installation parameters such as the cement dosage, the rotational speed of the mixing blades, the nozzle diameter, and the liquidity index of the soil. The design of experiments was conducted using the Taguchi method with a 4-parameter and 3-level L9 orthogonal array table. According to the observations during the installation of columns, the mixing time required to obtain a homogeneous soil-slurry mixture depended on the liquidity index of the fresh soilcrete. In addition, an interface layer, which is stiffer than the unimproved clay, was observed between the column and the unimproved soil. The thickness of the interface layer is 3–8% of the column diameter. Statistical evaluation was performed with S/N (signal-to-noise) and variance (ANOVA) analyses using the 28-day core strength of the columns. Optimum installation parameters were determined as cement dosage of 325 kg/m3, the rotation speed of the mixing blade is 80 rpm, nozzle diameter is 3 mm, and liquidity index of the soil is 1. The coefficient of variance for strength values decreased from 0.29 to 0.1 when the column was constructed with optimum installation parameters.
Soft clay presents many problems in the construction of infrastructures, which can be well solved by using effective solidification materials and technologies. The carbonated reactive magnesia (CRM) comes to the fore for its superiority in energy-saving and high solidification efficiency. Nevertheless, research on the applicability of CRM in soft clay solidifying is limited. In the current study, two major factors, including initial moisture content (w0) and reactive MgO content (Cm), were examined by measuring the unconfined compressive strength (UCS), mass and volume variations, and moisture content variation of CRM-treated soft clay. The intrinsic mechanisms were discussed based on the mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and X-ray diffraction (XRD) tests. The findings reveal that carbonated specimens with low Cm (≤ 25%) or w0 (≤ 25%) suffer from severe volumetric expansion and cracks, which cause serious reductions in UCS, and the strength of these specimens can be even much lower than that of the uncarbonated ones. Specimens with high Cm and w0 acquire satisfactory strength by carbonation, and the highest UCS can exceed 4 MPa, indicating that the CRM is capable of solidifying soft clay. Water and MgO are both vital for the crystallization of hydrated magnesium carbonates (HMCs), and Cm is also beneficial for restricting volumetric expansion and reducing macropores; while proper w0 is required for the formation and evolution of HMCs, especially the nesquehonite.
Conference Paper
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Cement stabilization has been widely used for improving the strength and stiffness of soft clayey soils. Cement treated soil specimens used to investigate the stress-strain behaviour in the laboratory study are usually cured for 7 days. This paper examines the effects of curing time on the strength and stress strain behaviour of cement treated marine clay under triaxial loading condition. Laboratory-prepared cement treated Singapore marine clay with different mix proportion S-C-W (soil solid-cement solid-water) and curing time (7 days to 180 days) was investigated through conducting unconfined compressive strength test and triaxial test. The results show that the curing time has a significant effect on the unconfined compressive strength u q , isotropic compression behaviour and stress strain behaviour. Although the primary yield loci of the cement treated soil specimens with the same mix proportion expand with curing time, they are very narrowly banded and have nearly the same shape after being normalized by isotropic compression primary stress ' py p . The isotropic compression primary yield stress ' py p was shown to be linearly related to unconfined compressive strength u q for specimens with different curing time and mix proportion. The effect of curing time on the hardening behaviour will diminish with consolidation stress higher than isotropic compression primary yield stress but its damping rate is dependent on the cement content.
Conference Paper
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Soft clay deposits are typically identified as highly plastic and normally consolidated fine grained soils. The main engineering concerns regarding the construction on soft clay soil are its low inherent shear strength and high compressibility. Mixing of soft clay with cement as a chemical stabilizer has become a well known technology. Cement stabilization has been used all over the world to enhance the shear strength and deformation characteristics of the soft clay deposits. The improvement trends were evaluated based on unconfined compression and consistency tests carried out on soft clay samples before and after mixing with cement and at different curing times. The results of unconfined compression tests of cement stabilized soft clay were analyzed to provide general relationships between the cement content, curing time, and the expected unconfined compressive strength. The plasticity index of the clay cement mix was found to noticeably decrease with the increase of cement content. The rate of increase of the unconfined compressive strength and the decrease of plasticity index was found to vary with curing time. The maximum unconfined compressive strength of the clay-cement mix occurred at a curing time of 28 days. A reduction in the plasticity index of 16% and an increase of the unconfined shear strength of more than 200 kPa were obtained with the addition of cement content of 15 %. The reduction in plasticity index of the clay-cement mix was found to be an efficient tool to represent the improvement of the clay strength after mixing with cement. RÉSUMÉ Dépôts d'argile molle sont généralement identifiées comme hautement plastique et normalement consolidé sols à grains fins. Les principales préoccupations de l'ingénierie de la construction sur le sol d'argile molle sont sa faible résistance au cisaillement inhérente et forte compressibilité. Mélange d'argile molle avec du ciment comme stabilisateur chimique est devenue une technologie bien connue. Stabilisation au ciment a été utilisé partout dans le monde pour améliorer la résistance au cisaillement et les caractéristiques de déformation des dépôts d'argile molle. Les tendances d'amélioration ont été évaluées en fonction de compression non confiné et des tests de cohérence effectués sur des échantillons d'argile molle avant et après mélange avec du ciment et à différents moments de durcissement. Les résultats des essais de compression simple de ciment stabilisé argile molle ont été analysés pour fournir des relations générales entre la teneur en ciment, le temps de séchage, et la résistance en compression simple attendu. L'indice de plasticité du mélange de ciment d'argile a été trouvée pour diminuer sensiblement avec l'augmentation de la teneur en ciment.
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This paper presents the physical characteristics, index properties, unconfined compressive strength and compressibility characteristics of cement-treated soft Bangkok clay. The cement-treated samples have reduced water contents and the reduction ceased after 30% cement content. The changes in the liquid limit were insignificant while the plastic limit significantly increased. The unconfined compressive strength increased from 15 kPa to 35 kPa with cement content of 10% to 20% for curing time of 28 days. The undrained behavior of cement-treated clays corresponded to 3 zones, namely: Zone I (untreated), Zone II (treated), and Zone III (softening part). Phase transformation was manifested by the abrupt change in the curvature of the stress paths. Higher cement content as much as 10% to 25% was found effective in reducing the compressibility of the clay. For cement-treated clays, the coefficient of consolidation increased by 12 to 19 times with the highest increase at 15% cement content. The reduction of compression index, Cc, reached optimum also at 15% cement content.
In the last forty years, at least fifty books have been written on the subject of soil mechanics, most of them textbooks. Only a few touch on practical applications. Soil Engineering: Testing, Design, and Remediation supplies the information needed to fill the gap between textbook learning and practical know-how. When engineers deal with major projects, such as the Teton Dam or the Leaning Tower of Pisa, they need high-tech solutions. More often than not, however, they deal with the foundations for warehouses, schools, medium-rise buildings, and residential structures, projects that need low-tech solutions. Ninety percent of the time consulting engineers don't require mathematical treatment or computer analysis, they require experience. Soil engineering problems cannot be resolved with tetbook information alone. This book provides the practical meaning of the different aspects of soil mechanics, the use of unconfined compression test data, the meaning of consolidated tests, the practical value of lateral pressure, and more. In addition to the technical aspects of foundation investigation, in the real world the shadow of litigation looms over every consultant's head. The author covers legal issues in detail. After several years in foundation investigation most consultants realize that soil engineering is a combination of art and science. Soil Engineering: Testing, Design and Remediation demystifies this connection and supplies real-world examples of practical applications. This hands-on, ready reference will be essential tool for any consultant working in the field.
For ground improved by the deep mixing method to function effectively, it is necessary that the treated ground retains a required strength and that this strength is determined on the basis of a logical theory. This paper introduces a logical method for determining the required strength and practical work such as mix proportion test and test construction to achieve it.
Soft clays are defined as cohesive soil whose water content is higher than its liquid limits. Thus, soil-cement mixing is adopted to improve the ground conditions by enhancing the strength and deformation characteristics of the soft clays. For the above mentioned reasons, a series of laboratory tests were carried out to study some fundamental mechanical properties of cement stabilized soft clay. The test specimens were prepared by varying the portion of ordinary Portland cement to the soft clay sample retrieved from the test site of RECESS (Research Centre for Soft Soil). Comparisons were made for both homogeneous and columnar system specimens by relating the effects of cement stabilized clay of for 0, 5 and 10 % cement and curing for 3, 28 and 56 days. The mechanical properties examined included one-dimensional compressibility and undrained shear strength. For the mechanical properties, both homogeneous and columnar system specimens were prepared to examine the effect of different cement contents and curing periods on the stabilized soil. The one-dimensional compressibility test was conducted using an oedometer, while a direct shear box was used for measuring the undrained shear strength. The higher the value of cement content, the greater is the enhancement of the yield stress and the decrease of compression index. The value of cement content in a specimen is a more active parameter than the curing period.
A deep mixing method using cement slurry as a hardening agent, a new method of soil stabilization, is explained. This report describes the features of the method, the deep mixing machine which is of great importance for this stabilization method, the physical and mechanical properties of the improved soil for which cement slurry had been used, and two cases of application employing the method.
In this series of articles, the aim is to present the latest advancements in research, development, and practical issues related to deep mixing technology. The first article examined the basic concepts, definitions, classifications, and historical developments. This article emphasizes various functions of the technology.
The deep mixnig method (DM method) for strengthening thick deposits of weak sedimentary soil by mixing, in situ with a strengthening agent is now widely used in Japan. The authors have studied the mechanism which produces this strengthening. The result of their study indicate that adsorption and the pozzolanic reaction in the soil as well as the reaction of the strengthening agent itself, contribute greatly to the increase in strength of the various soils. This provides a uniform basis for explaining the complicated soil strengthening process and explains why the same treatment used in different soils produces a wide variation in results.