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Premier Symposium Méditerranéen de Géoengineering «SMGE09» Alger 20 et 21 juin 2009
MECHANICAL CHARACTERISTICS OF LIME TREATED SOIL USED ON ROAD
CAPPING LAYERS IN PORTUGAL - TWO CASE STUDIES
CRUZ. Joana 1 FORTUNATO. Eduardo 2,1
VIANA DA FONSECA. António 1 & BARROS. Paulo 3
jfscruz@gmail.com
1 Faculdade de Engenharia da Universidade do Porto (FEUP), Portugal
2 Laboratório Nacional de Engenharia Civil (LNEC), Lisboa, Portugal
3 Brisa Engenharia e Gestão (BEG), Lisboa, Portugal
Résumé : Le traitement des sols à la chaux est une solution reconnu pour son énorme potentiel
dans la construction des routes. Néanmoins, il faut des études préliminaires pour déterminer la
formulation optimum du mélange et pour assurer un strict contrôle de qualité pendant son
exécution.
Cet article présente quelques résultats obtenus pendant la caractérisation mécanique de
couches de forme traités à la chaux exécutée pendant la construction de deux importantes
autoroutes au Portugal.
Les essais de charge performés et l’analyse postérieure des résultats a permis l’évaluation du
module de déformabilité de la couche de sol traité à la chaux. Les valeurs obtenues sont plus
élevés que ceux stipulés dans les spécifications techniques applicables.
Ainsi, l’optimisation de l’application du sol traité à la chaux peut être effectué, soit par la
formulation du mélange basé dans les résultats de contrôle de qualité obtenus in situ, soit par la
réduction de l’épaisseur du chaussé selon le module de déformabilité mesuré in situ dans le
niveau supérieur de la couche de forme.
Mots-Clefs : Chaux, traitement des sols, essais de charge, module de déformation
Abstract : The lime treated soils is a well recognized solution for road construction due to its
great potential. Nevertheless, it requires preliminary studies to determine the optimal mix
formulation and a strict quality control during its application.
This paper presents and analyses some results obtained during the mechanical characterization
of lime treated road capping layers, performed during the construction of two major highways in
Portugal.
The load tests performed and the back analysis of their results have allowed an evaluation of
the deformation modulus of the lime treated soil layer. The values obtained were significantly
higher than those required by the technical specifications applicable to these works.
Hence, an optimization of soil lime application might be performed, either by changing the mix
formulation based on in situ quality control results or by reducing the pavement thickness
according to the deformation modulus measured in situ at the top of the capping layer.
Key-Words: lime, soil treatment, load test, deformation modulus

Premier Symposium Méditerranéen de Géoengineering «SMGE09» Alger 20 et 21 juin 2009
1. Introduction
The lime treatment of soils is one of the oldest techniques used (more than 5000 years old).
Indeed, even before the Romans, 2000 years ago, other peoples were already acquainted with
that procedure. For instance, Shersi pyramids in Tibet were built with clay and lime compacted
mixtures. Also, throughout the years, in China and India, lime treatment was used in various
ways (Ancade, 1997).
Presently, the lime potential in reducing the water content and the plasticity of soils is well
recognized and, therefore, its application in soil mixtures, namely within the framework of
geotechnical works, is normally taken into account in technical specifications.
These mixtures have also been often used to improve the mechanical characteristics
(deformability and strength) of compacted soils, particularly soils that, due their significant
amount of fines, are usually discarded, both in fills and in the substructure of transportation
infra-structures, roads or railways. This aspect is very important, because the consequences of
unbalanced earth works (embankments and excavation/cuttings) are decisive, in terms of
economic and environmental costs.
Nevertheless, the lack of knowledge of the long term performances of these mixtures, together
with the specific equipment demands, the insufficient knowledge about the application
techniques and, sometimes, the lack of an adequate cost-benefit analysis, have placed major
obstacles to accepting the use of such treatment in Portugal. Therefore, its use has not been
systematically adopted. In fact, apart from the works indicated in this paper, regarding highways
A2 (subsection Almodôvar – São Bartolomeu de Messines) and A10 (subsection Arruda dos
Vinhos – IC11), which were carried out by the Brisa, SA in 2001 and 2005, respectively, the
lime treatment of soils has only been used in a very few works. Furthermore, special reference
is made to the works studied by Neves (1993), regarding the construction of the “North-South
Axle Road (subsection Telheiras - Sete Rios)” and the “Lisbon Inner Ring Road – CRIL”
(subsection Alto do Duque – Buraca), as well as to the earthworks included in the
modernization of the North Line (subsections Azambuja - Vale de Santarém and Entroncamento
Norte – Albergaria tunnel), which were performed in 2003 by the railway administration.
Nevertheless, this scenario has been significantly changing in construction pratice. In fact, the
technical and environmental requirements placed by the new transportation infra-structures, in
particular the high speed railway network and the new Lisbon airport, is most likely to promote
the use of the lime treatment of soils, as an alternative to their replacement.
2. Case Studies
This paper presents various studies related with the lime treatment of embankment and capping
layers of pavements. Those studies concern two major roads constructed in Portugal: highways
A2 and A10.
The 240 km long highway A2, constructed in 2002, is the main link between Lisbon and Algarve
project has taken into account the possibility of using lime treated soils on the pavement
capping layer. The insufficient amount of appropriate soils to be used in capping layer within an
acceptable distance was the main reason for adopting the lime treatment of soils.
Highway A10 is a multi-purpose road aimed for those traveling from the Central and the West
region of Lisbon towards the North of the country. It also serves those traveling from the West
central part and from the north of Portugal down to Algarve, thus avoiding passing through
Lisbon. The lay-out solution which was developed for the section of highway A10 led to a
significant volume of excavations and embankments. Furthermore, it required the use of borrow
materials with appropriate characteristics and in sufficient quantities, which were unavailable
within acceptable distances. These factors have led to the solution of treating soils for the
construction of embankments.
Quicklime was the binder used in both works. Table 1 indicates the lime properties. In
accordance with the specifications of the Portuguese Standard NP EN 459-1 (2002), this lime is
classified as CL90-Q.

Premier Symposium Méditerranéen de Géoengineering «SMGE09» Alger 20 et 21 juin 2009
Table 1. Lime characteristics
Properties
Values
CO 2 ≤ 3.5%
CaO ≥ 92%
SiO 2 ≤ 0.3%
S ≤ 0.3%
Retained on sieve #2.0 mm < 5%
Bulk density ≈ 1.0
3. Study of the Mechanical Caracteristics After Treatment
3.1. General aspects
The quality control during the execution of earthworks and the evaluation of the bearing
capacity of platforms, within the framework of transportation infra-structures, can be based on
the definition of minimum values of the deformation modulus measured at the top of the layers
by means of non-destructive load tests. Despite the possibility of the imposed load and the
associated response being rather different from those actually obtained during the passage of
vehicles, the in situ characterization resulting from that class of tests has been proving to be
very useful and reliable for assessing the different structural layers.
3.2. Numerical modeling of the load test
Based on the deflections obtained from falling weight deflectometer (FWD) load tests, it was
possible to determine the equivalent deformation modulus. Even more, it was possible to
determine the values of the deformation modulus of the different layers, by employing a
numerical model using the finite element method (FEM), by means of modeling in axysymmetric
conditions. Using the commercial software Plaxis ® , it was possible to model the load test on a
linear elastic stratified medium. In an iterative way, deformation modulus of the different layers
were changed as to converge the calculated deflection curves with those obtained in situ with
the FWD.
3.2.1 Highway A2
The upper part (25 to 30 cm) of the capping layer (40 to 45 cm) was lime treated. Thus, two
structures were considered for the load test modeling (Figure 1).
Figure 1. Structures considered for the load test modeling (A2).
Falling weight deflectometer tests
In each FWD test point, three impacts were performed on a 30 cm diameter plate load,
corresponding to 20, 30 and 45 kN. The deflection transducers (geophones) were placed at the
following distances (in cm) from the load plate centre: 0 (Df1); 30 (Df2); 45 (Df3); 60 (Df4); 90
(Df5); 120 (Df6); 150 (Df7); 180 (Df8) e 210 (Df9).
Figure 2 presents the finite element mesh used for structure 1, taking into account the boundary
conditions and the different layers of the pavement substructure. All the finite element meshes
considered in the other cases presented in this paper are identical, except for the thicknesses of
the different layers.

Premier Symposium Méditerranéen de Géoengineering «SMGE09» Alger 20 et 21 juin 2009
Figure 2. Mesh used – structure 1 (A2).
Calculation of the deformation modulus based on the numerical analysis
First of all, it should be highlighted that a significant variability was obtained in the in situ
displacements measured by geophones on the different test points. The calculation of the
deformation modulus was done based on results obtained from the first height impact, i.e., for a
peak load of approximately 20 kN.
Initially, an attempt was made to find the deformation modulus of both the subgrade and the
bottom capping layer, in order to determine the outer part of the deflection basin (the most
distant from the load application place). For this purpose, the deformation modulus of the
treated soils was fixed on 200 MPa and the deformation modulus of the subgrade and of the
untreated soil (indicated as “soil”) varied as showed in Table 2.
Table 2. Hypotheses considered for the deformation modulus of the subgrade and untreated soil.
E treated
Deflections [μm]
E soil E
Hypothesis
subgrade
soil
Df1 Df2 Df3 Df4 Df5 Df6 Df7 Df8 Df9
[MPa] 0 30 45 60 90 120 150 180 210
1 50 80 434 218 144 99 55 35 25 19 16
2 60 80 423 210 140 98 55 36 26 20 16
3 80 100 372 170 111 77 44 29 21 16 13
4 80 120 348 149 94 64 35 23 17 13 10
200
5 60 140 346 143 85 55 29 19 14 11 9
6 80 160 317 122 72 47 26 17 13 10 8
7 100 170 300 111 66 43 24 16 12 9 7
8
120 170 292 107 64 43 25 17 12 9 7
The minimum and maximum deflection basins indicated in Figure 3, correspond to the minimum
and maximum displacements measured by geophones. Hence, the minimum basin corresponds
to the structure with the best mechanical characteristics and the maximum basin corresponds to
the structure with the worst mechanical characteristics.

Premier Symposium Méditerranéen de Géoengineering «SMGE09» Alger 20 et 21 juin 2009
Figure 3. Deflection basins obtained for the hypotheses considered for subgrade and soil deformation
modulus.
Based on this analysis, hypothesis 5 was chosen, because it was assumed to represent an
average curve. As consequence, a subgrade with a deformation modulus of about 140 MPa,
and a untreated soil with a modulus of 60 MPa, were considered.
A parametric study was then performed, in which the following calculation conditions were
considered:
- subgrade with a deformation modulus of 140 MPa;
- untreated soil with a deformation modulus of 60 MPa; and
- lime treated soil layer with a varying the deformation modulus on 120, 200, 400 and 600 MPa.
The calculations have taken into account this range of values for the different structures,
allowing to determine the deflections presented at the Table 3 and Table 4.
Table 3. Deflections obtained with PLAXIS ® for different hypotheses (structure 1)
Deflections [μm]
E soil E subgrade
soil
Df1 Df2 Df3 Df4 Df5 Df6 Df7 Df8 Df9
[MPa] 0 30 45 60 90 120 150 180 210
120 458 149 81 51 28 19 14 11 9
200 346 143 85 55 29 19 14 11 9
60 140
400 247 131 87 59 31 20 14 11 9
600
206 123 86 61 33 20 14 11 9
E treated
Table 4. Deflections obtained with PLAXIS ® for different hypotheses (structure 2)
Deflections [μm]
E soil E subgrade
soil
Df1 Df2 Df3 Df4 Df5 Df6 Df7 Df8 Df9
[MPa] 0 30 45 60 90 120 150 180 210
120 452 149 84 53 28 19 14 11 9
200 332 138 86 57 30 20 14 11 9
60 140
400 229 122 85 60 33 21 14 11 9
600
188 112 83 61 35 21 15 11 9
E treated

Premier Symposium Méditerranéen de Géoengineering «SMGE09» Alger 20 et 21 juin 2009
From the analysis of the deflections obtained on structures 1 and 2, it was possible to observe,
as expected, that the deflections on structure 1 are higher, when the treated soil layer is thinner.
Nevertheless, the difference is not significant, and, therefore, the interpretation was done using
only structure 1, i.e., the most unfavorable one.
Figure 4 depicts the deflection basin of structure 1, taking into account the various hypotheses
considered. Furthermore, the normalised deflections for 20 kN load of FWD tests performed in
situ on the treated soil (mixture with 4% of lime) are also represented (Pk26525 and Pk26550).
Figure 4. Deflections obtained with PLAXIS ® for different hypotheses (structure 1) and normalized
deflections for 20 kN load (layer with 4% lime)
The comparison of the different deflection basins – measured in situ and obtained with
PLAXIS® – allowed to conclude that the best fit corresponds to deformation modulus values of
lime treated soils of about 200 to 400 MPa.
The equivalent deformation modulus calculated using the maximum deflection obtained at the
Pk26550 test (375 μm) is 170 MPa. This value is higher than the one specified in the design.
3.2.2 Highway A10
The design of this highway specifies that the pavement substructure should present
characteristics that will ensure that the deformation modulus at the top of the capping layer
would be higher than 120 MPa at long term.
In a first stage, a test section was constructed in order to confirm if the substructure deformation
characteristics required in the design could be achieved, and also to assess the effectiveness of
the equipment used and to verify the homogeneity of the work performed. In a second stage,
two evaluation campaigns were performed on previously completed work sections.
As a result, and in accordance with the layout presented in Figure 5, the pavement structure is
expected to be as follows:
- the bottom capping layer of lime treated soils (LT1) with a 40 cm thickness;
- the top capping layer consist of two layers: a 20 cm layer of lime treated soils (LT2) overlaid by
a 20 cm layer of a well graded crushed aggregate (ABGC).

Premier Symposium Méditerranéen de Géoengineering «SMGE09» Alger 20 et 21 juin 2009
The subgrade was considered to be divided into two separate layers, a top layer with a 60 cm
thickness and a bottom layer (SubR) more rigid and semi-infinite in depth as often adopted for
modeling purposes.
Figure 5. Pavement structure (A10).
Falling weight deflectometer tests
The load tests using the falling weight deflectometer (FWD) were performed on a well identified
section, on the top of the capping layer. The configuration adopted for the FWD as follows:
- 20 kN load applied on a 45 cm diameter plate;
- deflection transducers placed at the following distances (in cm) from the load plate center: 0
(Df1); 30 (Df2); 45 (Df3); 60 (Df4); 90 (Df5); 120 (Df6); 150 (Df7); 180 (Df8) and 210 (Df9).
Calculation of the deformation modulus based on a numerical analysis
The deformation of the different substructure layers were estimated using the results of the
FWD load tests, the thickness of the layers and the characteristics of the materials.
Nevertheless, a great variability in results was observed on campaigns performed both on the
test section and during the construction of the highway.
The values of the deformation modulus (E) considered are indicated in Table 5, while the
corresponding deflections obtained through numerical modeling are indicated in Table 6.
Table 5. Hypotheses considered in the numerical modeling.
E [MPa]
Hypotheses
LT1 Top of
ABGC and the Subgrade
LT2 Subgrade
1 280 550 55 810
2 220 350 50 750
3 300 600 100 800
4 600 600 100 800
5 300 400 100 800
6 150 300 100 800
7 300 600 200 800

Premier Symposium Méditerranéen de Géoengineering «SMGE09» Alger 20 et 21 juin 2009
Table 6. Deflections obtained with PLAXIS ® .
Hypotheses
Deflections [μm]
Df 1 Df 2 Df 3 Df 4 Df 5 Df 6 Df 7 Df 8 Df 9
1 118 66 44 35 24 16 10 6 3
2 156 88 57 44 27 17 10 6 3
3 101 53 34 26 17 11 7 5 3
4 76 49 33 26 17 11 7 5 3
5 90 60 40 30 18 11 7 4 3
6 177 83 45 32 18 10 6 4 3
7 92 45 26 19 12 8 6 4 3
Figure 6 shows the deflection basins obtained taking into account the various hypotheses. The
same figure also shows the deflections of three FWD tests (20 kN load) performed in situ during
one of the campaigns (Pk3+750, Pk3+875, Pk3+975).
Figure 6. Deflection basins obtained through numerical modeling and in situ test campaign.
From the analysis of results, it is possible to conclude that the layers of lime treated soil can
present values of the deformation modulus ranging from 300 to 600 MPa. The equivalent
deformation modulus calculated using the maximum deflection obtained at the Pk3+750 test
(210 μm) is 200 MPa. This value is higher than the one specified in the design (120 MPa).
4. CONCLUSIONS
The use of lime treated soils during the construction of the substructure of road pavements is an
ancient technique, yet not common in transportation infrastructure construction practice in
Portugal. Nevertheless, during the construction of the two highways that technical solution was
applied. The falling weight deflectometer equipment was used to perform in situ tests.
The use of numerical analysis of obtained results allowed to estimate the values of the
deformation modulus of the lime treated capping layer. It was observed that the values of the
deformation modulus obtained are higher than the pre-established ones.

Premier Symposium Méditerranéen de Géoengineering «SMGE09» Alger 20 et 21 juin 2009
Within certain limits, higher lime percentages are expected to provide layers with better
performance, yet leading to expensive structures. Consequently, the lime content must be
determined in order to reach the pre-established deformation modulus value. Only this
procedure enables to reach a technical and economical solution that can be compared with
traditional ones.
The quality control during the construction of stabilized layers by performance based tests
should be a current practice leading to a consistent evaluation of the adequate lime dosages to
be used.
5. ACKNOWLEDGEMENTS
This work is integrated within the framework of a research work for obtaining the MSc degree in
Civil Engineering and it was performed under a protocol for co-operation established between
the Instituto da Construção of Faculdade de Engenharia da Universidade do Porto (IC-FEUP)
and the company LUSICAL Companhia Lusitana de Cal, SA - Société Balthazard & Cotte,
member of the Lhoist Group with the purpose of conducting the studies intitled “Estudos de
solos portugueses tratados com cal com vista à sua aplicação nas infra-estruturas de
transporte”. Therefore, acknowledgements are due to Mr Paulo Correia and Mr Mário Marques,
for their kind support.
Furthermore, thanks are also due to the company Brisa for providing all the necessary
elements, which were essential for carrying out the study and the comparison of results
obtained in the numerical simulation with those observed in situ.
6. REFERENCES
Ancade (1997). Asociación Nacional de Fabricantes de Cales y Derivados de España - Manual de
estabilización de suelos con cal. Madrid, España.
CAeMD (2005). Publicações e Projectos de Engenharia, Lda - A10 - Auto Estrada
Bucelas/Carregado/A13. Sublanço Arruda dos Vinhos/IC11. Nota Técnica: Avaliação das
características de deformabilidade do leito de pavimento. Portugal.
Neves, J. M. C. (1993). Estabilização de Solos com Cal - Estudos e Aplicações Rodoviárias. MSc thesis.
Universidade Nova de Lisboa, Portugal.
NP EN 459-1 (2002) Cal de Construção: Definições, especificações e critérios de conformidade.
Portuguese Standard. Instituto Português da Qualidade.