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Plasticity is the outstanding property of clay–water systems. It is the property a substance has when deformed continuously under a finite force. When the force is removed or reduced, the shape is maintained. Mineralogical composition, particle size distribution, organic substances and additives can affect the plasticity of clays. Several measuring techniques and devices were proposed to determine the optimal water content in a clay body required to allow this body to be plastically deformed by shaping. In this review, methods of evaluating the plasticity of clay–water systems are presented. Despite the advance in the theory of the plasticity and the methods of measurement, a common procedure for all types of materials does not exist. The most important methods are those that simulate the conditions of real processing.Research Highlights► Plasticity is related to deforming a substance continuously under a finite force. ► Composition, particle size, organic matter and additives may affect clay plasticity. ► Several techniques are used to determine the optimal water content of clays. ► Methods for evaluating the plasticity of water-clay systems were reviewed. ► A consolidated method for measuring clay plasticity still does not exist.
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Review Article
Measuring the plasticity of clays: A review
F.A. Andrade
, H.A. Al-Qureshi
, D. Hotza
Group of Ceramic and Glass Materials (CERMAT), Department of Mechanical Engineering (EMC), Federal University of Santa Catarina (UFSC), 88040-900 Florianópolis, SC, Brazil
Center of Mobility Engineering (CEM), Federal University of Santa Catarina (UFSC), 89219-905 Joinville, SC, Brazil
Department of Chemical Engineering (ENQ), Federal University of Santa Catarina (UFSC), 88040-900 Florianópolis, SC, Brazil
abstractarticle info
Article history:
Received 22 March 2010
Received in revised form 23 October 2010
Accepted 28 October 2010
Available online 3 November 2010
Atterberg limits
Pfefferkorn method
Plasticity is the outstanding property of claywater systems. It is the property a substance has when deformed
continuously under a nite force. When the force is removed or reduced, the shape is maintained.
Mineralogical composition, particle size distribution, organic substances and additives can affect the plasticity
of clays. Several measuring techniques and devices were proposed to determine the optimal water content in
a clay body required to allow this body to be plastically deformed by shaping. In this review, methods of
evaluating the plasticity of claywater systems are presented. Despite the advance in the theory of the
plasticity and the methods of measurement, a common procedure for all types of materials does not exist. The
most important methods are those that simulate the conditions of real processing.
© 2010 Elsevier B.V. All rights reserved.
1. Introduction
Plastic behavior involves many areas of science and engineering
and has applications in various materials, such as soils, clays, concrete,
plastics and metals. In the beginning, the concept of plasticity was
used to explain and to characterize the rheological behavior of
materials in the solid or liquid state.
Research on plasticity began with the studies of Coulomb in the
18th century (Smith, 2006) on the stability of piles and embankments.
In the last century, the work of Mohr served as a base of some
concepts currently used such as elastic and plastic deformation,
yielding (critical state), shear localization and post-failure behavior
(Ancey, 2007).
Plasticity in the processing of clay-based materials is a fundamental
property since it denes the technical parameters to convert a ceramic
mass into a given shape by application of pressure (Norton, 1938;
1974; Moore, 1963; 1965; Astbury et al., 1966; Singer and Singer,
1979). Plasticity, in this case, and particularly in clay mineral systems,
is dened as the property of a material which allows it to be
repeatedly deformed without rupture when acted upon by a force
sufcient to cause deformation and which allows it to retain its shape
after the applied force has been removed(Perkins, 1995). A clay
water system of high plasticity requires more force to deform it and
deforms to a greater extent without cracking than one of low plasticity
which deforms more easily and ruptures sooner (Brownell, 1977).
The plasticity of clays is related to the morphology of the plate-like
clay mineral particles that slide over the others when water is added,
which acts as a lubricant. As the water content of clay is increased,
plasticity increases up to a maximum, depending on the nature of the
clay. Clay workers are accustomed to speak of fator highly plastic
clay such as ball clay or lean, relatively non-plastic clay such as
kaolin, but it is very difcult to express these terms in measurable
quantities. In the industry, plasticity is also referred to as extrud-
ability,ductility,workabilityor consistency(Händle, 2007).
Reed (1995) uses the term consistencyreferring to states of
ceramic raw materials, namely dry powder,granules, plastic body, paste
and slip, which are dependent on the liquid content. Fig. 1 presents the
apparent shear resistance as a function of the water content for a typical
clayish material. When water is added to dry clay, the rst effect is an
increase in cohesion, which tends to reach a maximum when waterhas
nearly displaced all air from the pores between the particles. The
minimum amount of water necessary to make clay plastic is commonly
called the plastic limit(PL). Addition of water into the pores induces
the formation of a fairly high yield-strength body that, however, may
crack or rupture readily on deformation.
A plastic clay body can withstand the addition of considerable
amounts of water, passing through a stage in which it remains dry to
the ngers and is easily molded. As the water content increases, the
clay becomes a paste, in which the yield strength steadily diminishes.
The clay becomes wet and sticky to the ngers and can no longer
maintain a molded shape. The water content which corresponds to
Applied Clay Science 51 (2011) 17
Corresponding author. Federal University of Santa Catarina (UFSC), 88040-970,
Florianópolis, SC, Brazil. Tel.: +55 48 3721 9448; Fax: +55 48 3721 9687.
E-mail address: (D. Hotza).
0169-1317/$ see front matter © 2010 Elsevier B.V. All rights reserved.
Contents lists available at ScienceDirect
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this state is called liquid limit(LL). With still higher water contents,
the system becomes a dispersion (slurry or slip). The difference in the
water amounts at these two limiting points, related to the dry mass of
the clay, is expressed as the plasticity index(PI), according to Fig. 1.
In traditional clay containing ceramic materials, the measurement
and control of the plasticity are needed to characterize the system and
to optimize the conditions of the processing (Ribeiro et al., 2005).
Factors inuencing plasticity may be related to the clay itself or to
the molding process (Henry, 1943; Carman, 1949; Marshall, 1955).
Clay-related factors are moisture content, mineralogical composition,
particle size distribution, type of exchangeable cations, presence of
salts and organic material (Talwalkar and Parmelee, 1927; Wilson,
1936; Whitaker, 1939; Lawrence, 1958; West and Lawrence, 1959;
Dumbleton and West, 1966; Barna, 1967; Onoda, 1996; Schmitz et al,
2004; Bergaya et al., 2006). Process-related factors are application of
pressure, temperature and characteristics of water and additives used
(Jefferson and Rogers, 1998; Malkawi et al., 1999; Ribeiro et al., 2004;
Uz et al., 2009; Zentar et al., 2009). A deeper discussion on the role of
clay composition and processing parameters on plasticity is beyond
the scope of this review.
In this review, techniques commonly used for assessing the
plasticity of clays are presented and discussed.
2. Measuring methods
There are several methods for measurement and characterization
of the plasticity of a clay body. The experimental determination, in
some cases, is operator dependent, which in turn may produce
different results when different methods are compared. Among these
methods, Atterberg, Pfefferkorn, stress/strain curves, indentation and
rheological measurements are the most used techniques (Table 1).
Atterberg and Pfefferkorn tests are widely used owing to the low
cost of the equipment employed (Moore, 1965; Van der Velden, 1979;
Bekker, 1981). The measurement is based on the moisture content at
which the material has some arbitrarily dened consistency. In these
tests, high moisture contents are associated with high plasticity and
vice versa.
Rheometry (McCabe, 1960; Alfani and Guerrini, 2005), indentation
methods (Doménech et al., 1994; Vaillant; 2008; Modesto and
Bernardini, 2008) and techniques which evaluate the relationship
between an applied force and the resulting deformation (Baran et al.,
2001; Ribeiro et al., 2005) are also used for measuring the plasticity of
clays. These methods are often more cost intensive due to the
equipment used. Nevertheless, they can supply important parameters
such as modulus of elasticity, yield strength, maximum deformation
and rupture strength.
2.1. The Atterberg method
Albert Atterberg (18461916), a Swedish chemist and agricultural
scientist, found that plasticity is a particular characteristic of clay. He
dened the consistency limits, called Atterberg limits (Atterberg,
1911). According to his ndings, there is a dened amount of water at
which the clay is easily moldable. With lower moisture content, the
body cracks when molded. The Atterberg plastic limit is the lowest
water content (expressed in mass percent of the clay dried at 120 °C)
at which the body can be rolled into threads without breaking
(Bergaya et al., 2006). The Atterberg liquid limit is the water content
at which the body begins to ow, using a specic apparatus (Fig. 2).
The difference between both values is called the plasticity (or plastic)
index (Fig. 3).
The liquid and plastic limits dene the transitions between liquid
and plastic behavior. Arthur Casagrande (19021981), an Austrian-
born American civil engineer, standardized the method to determine
such limits in soil consisting of clayish and non-clayish materials.
These limits can give signicant information about the behavior of
clay (Jefferson and Rogers, 1998). Casagrande (1958) studied dif-
ferent types of soil and evaluated plasticity by the Atterberg limits.
Although it is the most used method to evaluate plasticity, the
large number of variables involved hinders a detailed correlation of
the parameters with the behavior of the clay. To solve this, Gutiérrez
(2006) proposed a rigorous probabilistic approach according to a
regression analysis as a technique to express the linear behavior of the
Atterberg limits for a given soil.
Two methods for determining the liquid limit are standardized
(ASTM D4318, 2005): multipoint or one-point test. The correlation on
which the calculations of the one-point method are based may not be
valid for certain soils, such as organic soils or soils from a marine
environment. It is recommended to use the multipoint method in cases
where higher precision is required. Due to the fact that the one-point
method requires the operator to judge when the test specimen is
approximately at its liquid limit, it is particularly not recommended for
use by inexperienced operators. The method proposed by Atterberg
has some advantages such as low cost and sensitivity. In spite of this,
the method's lack of precision is a signicant drawback, mainly in one-
point method, which limits its use in controlling materials (Doménech
et al., 1994).
Special care must be taken during the execution of the tests. The
specimens must be thoroughly mixed and be permitted to cure for a
sufcient period before testing. Erroneous results may be caused by
Fig. 1. States of consistency and plasticity limits of clays (adapted from Reed, 1995),
PL=plastic limit, LL = liquid limit, PI = plasticity index.
Table 1
Methods for evaluating the plasticity of clays.
Method Atterberg Pfefferkorn Penetrometer Capillary rheometer Brabender rheometer Tension versus
Measuring principle Molding Impact deformation Penetration Pressure Torque Pressure
Parameters measured
or calculated
PI (LL and PL) Water content
(mass percent)
Force Viscosity, pressure
extrusion, ow curve
Torque, shear stress, viscosity,
extrusion head pressure
Tension, deformation
Speed Low Low Average Average Average Average
Reproducibility Low Average Average/high High High High
Cost Low Low Average High High Average
Standard ASTM D4318 (2005) BS 1377 (1990)
2F.A. Andrade et al. / Applied Clay Science 51 (2011) 17
the loss of colloidal material when removing particles coarser than
0.42 mm (sieve #40) or by testing air-dried or oven-dried soils.
Inaccurate determination of the water content would greatly affect
the determined liquid and plastic limits if small, non-representative
quantities of material are available for the water content determina-
tions. Another source of errors can be the incorrect measure of the
nal thread diameter, or stopping the rolling process too soon.
2.2. The Pfefferkorn method
The Pfefferkorn method determines the amount of water required
to achieve a 30% contraction in relation to the initial height of a test
body under the action of a standard mass (Pfefferkorn, 1924). The
results are normally expressed as graphs showing height reduction as
a function of moisture content.
Measuring of plasticity according to Pfefferkorn is based on the
principle of impact deformation (Fig. 4). A dened sample with a
diameter of 33 mm and an initial height of 40 mm, produced either
manually or by extrusion, is deformed by a free falling plate with a
mass of 1.192 kg. The initial height is related to the impact defor-
mation height, the result of which is the ratio of deformation. As a
rule, this measurement is taken with bodies of varying moisture
content. The ratios of deformation or the impact deformation heights
, initial height; H
,nal height) are plotted against the moisture
content (Fig. 5). The steeper the curve, the shorterthe body, i.e. the
more intensely the body will react to variations of the moisture
content. The deformation heights for bodies to be extruded lie
between ~ 25 mm for soft extrusion and ~37 mm for stiff extrusion
(Händle, 2007).
The Pfefferkorn method is widely accepted in practice and was
originally developed for soft silicate ceramic materials. The method is
less suitable for stiffer bodies, as usually processed in the advanced
ceramics industry, as the low resolution at small deformation heights
reduces reproducibility.
The Pfefferkorn test is laborious and time consuming. It requires
changing the moisture content in order to reach 30% contraction. At
the end of the test, the sample has to be dried. The main problems
regarding plasticity determination using this method are related to
the determination of the moisture, and to the relation between
residual and sedimentary clays (Modesto and Bernardini, 2008).
Fig. 2. Casagrande apparatus for measuring the liquid limit (Timely Engineering Soil
Tests, 2010).
Fig. 3. Atterberg plastic index versus plastic limit of clay materials from Sassuolo, Italy
(Dondi, 1999).
Fig. 4. Pfefferkorn apparatus (Sassuolo Lab, 2010).
Fig. 5. Typical chart of Pfefferkorn for three clays.
3F.A. Andrade et al. / Applied Clay Science 51 (2011) 17
2.3. Penetration methods
The penetration (or indentation) method is based on the mea-
surement of the necessary force that a tool produces to make a mark
in the test body. This mark, according to the geometry of the used tool,
will serve to indicate the resistance of the mass to the penetration, and
thus providing information about its plasticity. The measuring
instruments of the penetration method devised for soil mechanics
may be also related to those used for hardness measurement
(Doménech et al., 1994; Händle, 2007).
In the fall cone test, a cone with an angle of 30° and total mass of
80 g is suspended above, but just in contact with, the clay sample. The
cone is permitted to fall freely within 5 s. The water content
corresponding to a cone penetration of 20 mm denes the liquid
limit. The plastic limit is determined by repeating the testing with a
cone of similar geometry, but with a mass of 240 g (Yu and Mitchell,
Some authors (Doménech et al., 1994; Feng, 2004) proposed the
use of a sample-holding mold of circular cross section, so that the edge
effects could be neglected. Doménech et al. (1994) used a cylindrical
plate of 50 mm diameter and 50 mm height, while Feng (2004) used a
smaller sample holder (20 mm diameter and 50 mm height). The
specimen ring facilitates the sample preparation and increases the
quality of the sample. For lower cone penetrations, when the clay
sample is relatively stiff, the traditional specimen cup apparently
reduces the measuring resolution of the plastic limit. As the fall cone is
recommended in several standards for determining the liquid limit, it
is advantageous to use it also for determining the plastic limit.
Vaillant (2008) investigated the utilization of a modied Vicat
Apparatus (utilized in cement consistency analysis) to evaluate the
plasticity of clays. He adapted an aluminum cone in place of a rod,
reducing the weight to evaluate more accurately the liquid and plastic
Modesto and Bernardini (2008) presented a method based on an
indentation equipment. When penetration occurs, marks with cracks
or plastic ow mean a lack of plasticity (low water contents, Fig. 6a),
and when there are no cracks, a lack of consistency (high water
contents, Fig. 6b). These extreme points correspond to the Atterberg
plastic and the liquid limit. Adequate plasticity occurs when the marks
do not present either cracks or extreme moisture and the wall formed
is sufciently smooth.
Measurements of plasticity with the penetrometer are considered
to be more consistent, have better reproducibility, be easier to
determine and less operator dependent (Feng, 2004). Some authors
did not nd signicant differences between fall cone standard
methods for liquid limit determination (Jefferson and Rogers, 1998;
Vaz and Hopmans, 2001).
However, Benbow and Bridgwater (1993) reported some factors
that can limit the accuracy of the penetration test. If the depth of
penetration is too small, the accuracy is limited. If the sample is
predominantly viscous rather than plastic, the penetration will
depend on the time of penetration. Moreover, forces due to
deceleration of the cone are not taken into account.
2.4. Capillary rheometer
The plasticity of extrudable materials can also be measured by a
capillary rheometer. Various instruments are available, in the form of
either single-bore capillary or twin-bore capillary rheometers. Using a
pressure piston, the ceramic body is forced through a nozzle of a
Fig. 6. Clay indentation, showing (a) too low water content and (b) an excess of water (Modesto and Bernardini, 2008).
Fig. 7. Capillary rheometer (Alfani and Guerrini, 2005).
4F.A. Andrade et al. / Applied Clay Science 51 (2011) 17
dened geometry at different feed rates (Fig. 7). The resistance of the
ceramic body against the deformation in the nozzle causes a pressure
drop within the capillary, which corresponds to a certain shear stress
(σ). This pressure drop is the measured value, taken in the in-feed
zone of the nozzle (Händle, 2007).
This test could be also applied for determining the material's
apparent viscosity. To calculate the real viscosity of the materials as a
function of the ow rate, the MooneyRabinowitsch correction is
applied (Alfani and Guerrini, 2005) and a viscosity curve as a function
of the shear rate (γ) is derived
According to the Bagley correction, the measured pressure ΔP
can be calculated by:
ΔPtot =ΔPent +ΔP
where ΔP
represents the pressure drop in the s tatic zone, and (ΔP/L)
is the pressure drop along the die length. Eq. (2) shows that the pressure
decreases along the die as the capillary length increases. The evaluation
of (ΔP/L)
is essential to determine the ow of the material inside the
rheometer and to measure the viscosity. Typical capillary rheometer data
are in Fig. 8.
The main advantage in this method is the possibility to evaluate
more accurately the operational conditions on the extrusion process,
as different geometries of the die can be used.
2.5. Torque rheometer
The torque rheometer or Brabender plastograph (McCabe, 1960)
consists of a mixer with eccentric blades, inside which powdered clay
is mixed with rising quantities of water by a proportioning system
that allows keeping a steady liquid ow (Fig. 9). The torque reects
the change of consistency of dry powdered state to a plastic solid. The
data represent the work required by the motor to move the blades
inside the sample at a constant rotating speed and are recorded as
torque versus time or amount of water (Sanchez et al., 1998).
When water is added, a point (A) is reached at which the
material's consistency starts to increase (Fig. 10) and reaches a
maximum (τ
). Adding more liquid, the consistency decreases. At
point E, the solid is no longer plastic. In general, plasticity can be
dened by the maximum relative consistency (τ
) or the range of
plastic behavior (He-Hx) (Sanchez et al. 1998).
An advantage of this method is to perform an extrusion test, by
installing a barrel with an extrusion screw and several types of die in
the rheometer, monitoring the force by a pressure transducer. This
Fig. 8. Data obtained with a capillary rheometer (adapted from Alfani and Guerrini,
Fig. 9. Torque rheometer (C.W. Brabender Instruments, 2010).
Fig. 10. Torque rheometer test (adapted from Sanchez et al., 1998).
Fig. 11. Stressdeformation curve (adapted from Ribeiro et al., 2005).
5F.A. Andrade et al. / Applied Clay Science 51 (2011) 17
apparatus works with small quantities of material, which has to be
considered when passing into the industrial scale (Alfani and Guerrini,
2005). The test is very fast (b20 min), compared to traditional plas-
ticity measuring methods.
2.6. Stressstrain curves
As for other types of materials, a compression test can be used to
evaluate the plasticity of clays. The typical test curve gives information
about the modulus of elasticity, yield strength, maximum deformation
and rupture strength. As shown in Fig. 11, the material shows elastic
behavior up to point A, then plastic behavior until reaching point B
where cracks start to appear. Due to the small effective area, the
tension increases quickly until the test body breaks (Ribeiro et al.,
Some parameters obtained in the compression test are strongly
inuenced by the chemical composition and moisture of the clay.
Therefore, this method shows a great potential to be used in the
evaluation of the plasticity of clays used in extrusion. The high
precision and reproducibility of the test make it possible to evaluate
and to compare different claywater systems.
Baran et al. (2001) applied the workability test for metals to
measure the yield stress (σ
) and the plastic tensile strain limit (ε
The product of the two characteristic values (σ
) was dened as
the workability. The variation of these three values as a function of the
moisture content of the green bodies is shown in Fig. 12. From the
maximum point of the σ
curve, called the workability curve,
the optimum moisture was determined (in this case, 22%).
Flores et al. (2010) modeling of plasticity of clays determined
several parameters such as the coefcient of friction and the effective
compressive stress (μand σin Eq. (3)), from the curves of the
compression test (Fig. 13). The developed mathematical model is a
potential and useful tool for the evaluation of clay-based materials
with optimized properties for a given application.
4μ2exp 2μrf
where his the nal height of clay body sample, r
is the nal sample
This method, where the clays are compressed until the cracks
appear (Fig. 14), seems to be more precise and independent of the
operator ability. It is faster to evaluate diverse types of clay bodies and
supplies parameters to specify the extrusion process (Andrade et al.,
2.7. Other methods
According to Linseis and Hofmann's method (Händle, 2007), the
materials to be extruded at different moisture contents are forced
through a nozzle of approximately 1 cm
cross section by means of a
piston extruder, and the shearing strength required for this process is
determined. The column is subsequently torn apart and the tear
resistance measured. The degree of plasticity is the ratio of tear
resistance to the shear strength. Highly plastic bodies are those which
offer little resistance to deformation, but nevertheless they still have a
high tear resistance.
In the Dietzel method (Händle, 2007), the same equipment is used
as in the Pfefferkorn method. Rather than using a high deformation
speed, the cylinder is compressed slowly, until cracks form. The
Fig. 12. Workability test (adapted from Baran et al., 2001).
Fig. 13. Experimental and theoretical data obtained in stressdeformation tests of clay
with different water contents (Flores et al., 2010).
Fig. 14. Compression test of clays (Flores et al., 2010).
6F.A. Andrade et al. / Applied Clay Science 51 (2011) 17
compression in percent of the original height is considered to be a
measure of plasticity.
Based on the Atterberg method, the plasticity number according to
Riecke (Händle, 2007) is considered to be the range between the roll-
out limit and the make-up requirement, which is dened to be the
moisture content at which the mass just stops sticking to a person's
3. Conclusions
The plasticity concept is employed in many areas of engineering
and science. Therefore, it is a hard task to choose a method that can be
used for any type of raw material or processing condition. The main
criteria that must be taken into account in the choice of the mea-
surement method are the required information, the type of proces-
sing, as well as verifying the inuence of one or more parameters on
the plastic behavior of the clay body.
In laboratory scales, for developing new formulations, more than
one method should be used. In the industry, where fast methods and
low cost are required, the automated methods will be preferred for
tests of raw materials or control process parameters.
The Brazilian agencies CNPq and Capes are acknowledged for
nancial support.
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7F.A. Andrade et al. / Applied Clay Science 51 (2011) 17
... The values of Young's modulus and yield strength of the bonds were varied according to the moisture content to mimic the mechanical behavior during compaction. Different relations have been proposed to correlate the values of Young's modulus with water content for clay materials [38][39][40]. The relationship proposed by Kodikara et al. [41] (Eq. ...
... These water molecules can then penetrate between the clay particles, effectively filling the interparticle voids. This is known as hydration or adsorption [38]. As the spaces are filled with water molecules, they act as a lubricant, lowering the friction between the clay particles. ...
... According to Prakash et al. [47], there are additional influences on induced yield stress on clays during compaction related to pore size, water pressure, and particle sizes. On average, it is estimated that yield strength on clays ranges from 400 to 600 kPa [38,46]. A series of simulations were run for each moisture content to find the yield strength that fit each moisture content the best. ...
... With a charge ranging from 0.3 to 0.8, the smectites subclass is among the expandable species. The crystalline structure might expand due to the water injected via the hydrated cations [26]. The swelling increased as a result of the high humidity. ...
... The amount of muscovite, albite, kaolinite, and illite in our soil will impact its shrinkage characteristics. These crystals have few water molecules between their layers due to their tiny interfoliar space [26]. As a result, they have negligible intercrystalline swelling when immersed in water [27]. ...
... The presence of kaolinite, muscovite, and illite, as well as the reduction in montmorillonite, will decrease the shrinking behavior. Indeed, these crystals have a weak intercrystalline swelling behavior and contain a minor amount of water [26]. The formation of carbonated calcium hemicarboaluminate leads to the enhancement of compressive strength (see Figure 10). ...
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Mastering construction times is of paramount importance in making vernacular earth construction techniques attractive to modern clients. The work presented here is a contribution towards the optimization of the construction time of cob buildings. Therefore, this paper follows the evolution of a cob’s mechanical properties during its drying process in the case of a double-walling CobBauge system. Laboratory tests and in situ measurements were performed, and further results were described. Volumetric water content sensors were immersed in the walls of a CobBauge prototype building during its construction. The evolution of the cob layer’s compressive strength and Clegg Impact Value (CIV) as a function of its water content has been experimentally studied and discussed. These studies showed that compressive strength and CIV are correlated with water content, and both properties decrease exponentially with time. In this study, a new tool to evaluate cob’s mechanical performances in situ has been proposed, Clegg Impact Soil Tester. This was linked to compressive strength, and a linear relationship between these two properties was found. Finally, appropriate values of compressive strength and CIV to satisfy before formwork stripping and re-lifting were proposed. For this study’s conditions, these values are reached after approximately 27 days.
... Fig. 5b shows a detail of the damaged sample after test. The plasticity of unfired clay is a direct function of the moisture content of the sample [76,8,64]. A second test with higher moisture content (20.00 ±0.26 %, after 24 h water-immersed as described in section 3.1), was conducted to verify the suitability of the sample to withstand mechanical loads. ...
... Fig. 5c shows the very large unit strain in such a sample. This behavior is due to the high plasticity of unfired samples due to the moisture content which is aligned with previously reported research [76,8,64]. ...
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.
... The flow behaviour of the extruded masses depends to a large extent on the time of measurement, the mixer, moisture content, particle size distribution, mineralogical composition, additives such as methylcellulose and the vacuum applied in the extruder. n ceramics the term "plasticit " is often used to describe the rheological beha iour Howe er the terms "extrudabilit " "ductilit " "consistenc " and "wor abilit " are also used as s non ms [23,75,[195][196][197]. In order to enable an adequate description of stiff masses, there are several test methods which are used depending on the type of material. ...
... With this method, it is possible to react quickly to possible changes due to changing raw materials, process conditions etc. In addition, the penetration method is a simpler measuring method compared to the capillary rheometer, which was used in this work and studied before [23,82,196]. The penetration method presented here also offers the possibility to quickly test the suitability of new material compositions for the plant scale. ...
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One of the main challenges in concrete construction at present is the reduction of CO2 emissions. To achieve this, both academia and industry are testing innovative methods, developing CO2-reduced materials, and implementing design principles. CO2-reduced materials are being developed and construction principles are being implemented. In addition to the development of new resource-saving construction materials, innovative manufacturing processes such as additive manufacturing are being tested to use the materials only where they are needed. One promising approach is the use of textile reinforced concrete, which uses woven glass, basalt, aramid or carbon fibres that have a much higher tensile strength than conventional structural steel. As a chemically inert material, carbon fibres offer the additional advantage of being insensitive to corrosion and are therefore particularly suitable for the realisation of durable, material-saving high-performance concrete elements. The extrusion process is an innovative method for implementing new construction concepts from carbon reinforced concrete. In this process, solid to viscous materials are transported through an extruder and pressed through a shaping mouthpiece. This enables the efficient production of precise linear components without the need for formwork. Initial approaches to integrating flexibly impregnated textiles in a laboratory extruder were already carried out in 2012 at the Institute of Building Materials Research at RWTH Aachen University (ibac). However, for the implementation of high-performance textile reinforced concrete components with subsequent longitudinal and transversal shaping with a laboratory extruder, scientifc fundamentals and methods are lacking. In this work, the state of the art of textile reinforced concrete, concrete extrusion and form optimised constructions is presented first. It is followed by four papers in which the scientific research and methods developed in the context of this work are presented. Chapter 2 presents the basic principles for the development of an innovative mouthpiece that allows the integration of arbitrarily stiff impregnated textiles in the concrete extrusion process. Chapter 3 describes the development of a test method used to accurately describe concrete mixtures prior to actual extrusion in order to predict defect-free extrusion in LabMorTex. In Chapter 4, the shaping behaviour of the (un)reinforced, microfiber- and textile reinforced concrete after extrusion is investigated. The aim of the investigations is to identify the technical limits of longitudinal and transverse shaping for the implementation of material-minimised structures. Chapter 5 describes the design and Chapter 6 the implementation of an innovative wall / slab element assembled from extruded textile reinforced components. In addition, the slab element is compared with an equivalent reinforced concrete system of the same dimensions and the same flexural strength in terms of sustainability and structural design. The aim of the study is to implement the findings obtained in Chapters 2–4 in an exemplary building component.Finally, chapter 6.3 presents and discusses the results of the durability study of the extruded concrete.
... The application of composites as suitable alternative to the commonly used agricultural binders such as cassava starch and wood based binders like paper, is gaining increased research interests today owing to the some inherent disadvantages of some other existing biological binders including nonavailability in commercial quantities, low shelf life and smokiness. Utilization of clay as binder in briquetting had been a recurring research activity over decades due to a relatively cheap cost and plastic characteristics with better mechanical properties lower combustion efficiency than other base materials (Gopakumar, 2002;Andrade et al., 2011;Shu et al., 2012;Obi et al., 2022). ...
Clay had been used as binders in briquetting research activities, however their performance characterization in terms of quality and combustion have not been clearly evaluated or reported. This study therefore provide a qualitative evaluation of briquettes produced using sawdust of Gmelina arborea and montmorillonite clay. Sun-dried sawdust (~9% moisture contents) obtained from sawmills in Ishiagu, Ebonyi State were mixed with processed clay samples collected from earthen pot mould sites characterized, then used in briquette production using five mixing ratios of 90:10, 80:20, 70:30, 60:40, & 50:50 (weight/weight)% and standard test procedures for characterization. Data were analyzed using SPSS at p< 0.05 significance levels. The quality characteristics of clay briquettes compared favourably with other binder types with an increase in performance as binder concentration increases. The briquettes combustion performance in air and stove are significantly affected by the agglomerated non-combustible clay particle impregnating the biomass matrix. Best combustion performance occurred at 10% binder concentration with no significant value-addition to ignition time, flame combustion and heating values. Above 10% binder addition, briquettes failed self-ignition, flame combustion, and retarded char combustion tests. This implied clay is a poor performing binder and the associated briquette are combustibly poor.
... Clay is famous for its plasticity property, where clay deforms its shape under limited force and retains its shape after the applied force is removed [22]. Essentially, the intensity of this property is based on the clay family. ...
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Natural clay mineral and its modifier called modified clay have been used in many environmental applications for a number of years. However, they are not capable enough to achieve a higher conversion rate and so-called ecological sustainability. This can be due to a lack of understanding of the selectivity of the clay and its modifier or a lack of compatibility between clay and pollutants. Recently, the development and implementation of green principles into practice have become an emerging field that brings together green chemistry and engineering practices to achieve a pollutant-free environment (air, water, and soil). This review summarizes the role of clay/modified clay in pollution control and discusses the role of green chemistry in creating global sustainability. In this context, this review sheds light on the complete classification of the clay family to identify its properties and to critically examine the applicability of clay and modified clay for air, water, and soil pollution control over the past decade. This is the unique point of this review, showing how the properties of clay/modified clay can be useful for removing any type of pollutant without focusing on a single type of pollutant or clay. Furthermore, the importance of green materials in clay research, as well as the future area of application, was discussed. Overall, this review places value on multidisciplinary researchers to determine the role of the green pathway in the application of clay and modified clay in achieving environmental sustainability.
... Moreover, the plasticity index decreased with increases in the treatment temperature until 600°C; at 900°C, the sample became non-plastic. The plasticity of a clay is due to its capacity to incorporate water (Andrade et al., 2011), so when the sample was treated thermally, the plasticity index reduction and the density increase could be related. At 900°C, some illite peaks in the XRD patterns (Fig. 3) disappeared as a consequence of dehydroxylation, which could result in structure collapse, thus accounting for a density decrease and the complete loss of plasticity. ...
... The mineral composition of clay might play an important role in the puri ication process which may pose a problem when not properly selected. To achieve the desired low rate, the plasticity of clay [27,28] and the size of the burnout material (Hagan, et al. 2009) will in luence the quality of burnout material added to achieve the low rate. ...
In this study, ceramic pot filters are made from clay and burn-out materials (sawdust) that give pore sizes capable of capturing contaminants. Manufacturing specifications were selected to achieve some results. Clay and sawdust are mixed in a 50% volume ratio each and sawdust was subjected to hot water extraction to give a treated sample. Filters produced comprised of untreated, treated, and a mixture of treated and untreated sawdust samples, some of which were dipped in a solution of silver nanoparticles while others were not dipped (treated undipped, treated dipped, mixed dipped, mixed undipped, untreated undipped, untreated dipped). The effectiveness of the produced filters for the removal of contaminants such as dissolved solids, turbidity, and metals was tested using water collected from the Ikeji Arakeji River in Osun, Nigeria. The results showed the filter with treated sawdust undipped in a solution of silver nano gave the best result in the removal of the contaminants. Also, the filter with the mixtures of treated and untreated sawdust gave a better result compared to the standard. While the standard gave a better result than the untreated undipped ceramic filter pot. In conclusion, with proper cleaning and maintenance of the filters, they can effectively provide treated water suitable for drinking to rural people affected by polluted water sources.
... Water moisture is essential for the plasticity of soil, enabling it to be molded into various forms [24]. Its significance lies in achieving optimal soil compaction. ...
The significance of knowing the engineering properties of cement stabilized compressed earth brick (CSCEB) becomes useful within the context of manufacturing, construction, and the associated business domains, mostly at the local level. Chemical and mechanical stabilization techniques play a vital role in the production of soil bricks with adequate engineering properties. Cement, one of the most used chemical stabilizers, is the only easy approach of locally in the context of many developing countries. The study of soil bricks with such stabilizers will eventually benefit local-level manufacturers. This experimental study aims to assess the certain structural and durability properties of two categories of CSCEB samples: one with zero percent sand and another with forty percent sand content, mixed with clay soil constituting a total of eight sample types. The proportion of ordinary portland cement varied from five to twenty percent in intervals of five for both sample categories. The CSCEBs were evaluated through structural properties, including dry compressive strength, wet compressive strength, and three-point bending tests. To understand the durability property, a moisture absorption test was performed. The results showed that an increase in cement content led to higher dry and wet compressive strength and bending strength for both sample types. Additionally, increasing the cement content resulted in decreased water absorption for both samples. These findings complied with national and international specifications at a certain stage. The sample containing sand demonstrated superior engineering properties compared to the sample without sand.
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In the forming of ceramic materials the plasticity concept is commonly used. This term is related to a particular mechanical behavior when clay is mixed with water. A plastic ceramic material shows a permanent strain without rupture when a compressive load produces a shear stress that exceeds the material's yield strength. For a plastic ceramic body it observes a measurable elastic behavior before the yield strength and when the applied load is removed. In this work, a mathematical model was developed from applied concepts of the plasticity theory by using the stress/strain diagram under compression.
1. History and Classification.- 1.1. Early History.- 1.2. Industrial Revolution.- 1.3. Scientific Revolution.- 1.4. Classification of Structural Clay Products.- References.- 2. Mineralogical Composition of Structural Clay Products.- 2.1. Structure of Disilicate Minerals.- 2.2. Classification of Disilicate Minerals.- 2.3. Essential Minerals.- 2.4. Nonessential Minerals.- 2.5. Typical Compositions.- References.- 3. Raw Materials and Processing.- 3.1. Mining.- 3.1.1. Exploration for Raw Materials.- 3.1.2. Testing and Evaluation of Deposits.- 3.1.3. Mining Procedures.- 3 1 4 Mining Pollution Controls.- 3.2. Raw Material Processing.- 3.3. Particle-Size Distribution.- 3.4. Dust Pollution Controls.- 3.5. Blending and Additives.- References.- 4. Forming of Structural Clay Products.- 4.1. Structure and Properties of Water.- 4.2. Clay-Water Interaction.- 4.3. Plasticity of Clays.- 4.4. Plastic Forming Methods.- 4.4.1. Plasticity in Forming.- 4.4.2. Soft-Mud Process.- 4.4.3. Stiff-Mud Process.- 4.4.4. Plastic Pressing.- 4.4.5. Cutting of Extruded Columns.- 4.4.6. Automatic Hacking of Bricks.- 4.4.7. Dry-Press Forming.- References.- 5. Drying Process.- 5.1. Fundamentals of Drying Clay Bodies.- 5.2. Shrinkage, Stresses, and Strength.- 5.3. Practical Drying Schedules.- 5.4. Types of Dryers and Energy Sources.- 5.4.1. Periodic and Continuous Dryers.- 5.4.2. Energy Sources.- 5.5. Heat Balance in Dryers.- 5.6. Scum Development.- References.- 6. Firing Process.- 6.1. High-Temperature Reactions in Disilicate Minerals.- 6.2. Reactions in Typical Clay Bodies.- 6.3 Influences of Kiln Atmospheres.- 6.3.1. Kiln Atmospheres.- 6.3.2. Oxidation-Reduction.- 6.3.3. Oxidation of Carbon and Pyrite.- 6.3.4. Color Development and Control.- 6.4. Types of Kilns.- 6 5 Kiln Firing.- 6.6. Burner System.- 6.7. Cooling Stresses.- References.- 7. Decoration, Panels, and Packaging.- 7.1. Sanded Surfaces.- 7.2. Texturing of Extruded Bricks.- 7.3. Coating Decorations.- 7.3.1 Engobes and Slurries.- 7.3.2. Glazes.- 7.4. Panelling.- 7.5. Packaging.- References.- 8. Jointing of Vitrified Clay Sewer Pipe.- 8.1. Factory Installed Jointing Units.- 8.2. Requirements for Good Joints.- 8.3. Types of Compression Joints.- 8.3.1. Polyvinyl Chloride Joints.- 8.3.2. Polyester Joints.- 8.3.3. Polyurethane Joints.- 8.3.4. Jointing of Plain-End Pipes.- 8.4. Specifications and Tests for Vitrified Clay Pipe Joints.- References.- 9. Quality Control.- 9.1. Philosophy.- 9.2. Nature of the Quality-Control Program.- 9.3. Procedure.- 9.4. Statistical Approach.- References.- 10. Plant Layout and Design.- 10.1. Predesign Planning.- 10.2. Factors Affecting Plant Design.- 10 3 Planning for Starting the Plant.- References.- 11. Serviceability and Durability.- 11.1. Serviceability of Structural Clay Products.- 11.2. Durability of Bricks and Roofing Tiles.- 11.3. Durability of Sewer Pipes.- 11.4. Moisture Expansion.- 11.5. Bonding of Mortar to Bricks and Tiles.- 11 6 Efflorescence and Staining of Brickwork.- 11.7. Cleaning Brickwork.- References.- 12. Future Trends.- 12.1. Production.- 12.2. Technical Changes.- 12.3. Research of the Future.- 12 4 Summary.- References.
Cone tip resistance is the most widely measured quantity in the cone penetration test. A brief review is made of presently available theories for the analysis of cone resistance. The theories are presented in farms that enable direct comparisons among them. The simplifying assumptions made in the analysis using various theories are emphasized. In the light of experimental evidence and the fundamental principles of mechanics, the limitations and advantages of each theory are: assessed. Comparison with limited experimental data indicates that cavity expansion theories give the closest overall agreement between predicted and measured penetration resistance.