1373
Laboratory characterization and model calibration of a cemented aggregate for
application in transportation infrastructures
Caractérisation en laboratoire et calibration d'un modèle d'agrégat cimenté pour une utilisation
dans les infrastructures de transport
Viana da Fonseca A., Rios S., Domingues A.M., Silva A.
University of Porto, Dep. of Civil Engineering – FEUP, Porto
Fortunato E.
National Laboratory for Civil Engineering - LNEC, Lisbon
ABSTRACT: Research on increasingly stiffer and more resistant artificially stabilized geomaterials, such as soil-cement mixtures has
frequently revealed interesting properties. The knowledge of such materials behaviour is as important as they are increasingly used in
several layers of transportation infrastructures, as well as in transition zones between embankments and rigid structures. Most of these
last situations involve zones close to sensitive prefabricated structures, where compaction of soils or aggregates demand for moderate
energies, being necessary to increase the content of the hydraulic binders to increase their stiffness and strength. The present work
reports some of the most notorious results obtained in some laboratory studies aiming to characterize different mixtures of cement and
limestone aggregate. Seismic wave measurements, indirect tensile strength tests and triaxial compression tests were performed. The
results indicated some relevant differences on dynamic and static stiffness properties and shear strength Mohr-Coulomb parameters,
directly associated to the variation of porosity/cement ratio. Based on the triaxial test results, a calibration of the geo-mechanical
parameters of the Hardening Soil Model available on commercial software was made.
RÉSUMÉ: La recherche sur des géomatériaux de plus en plus rigides et plus résistants artificiellement stabilisés, comme les mélanges
sol-ciment, a souvent révélée des propriétés intéressantes. La connaissance du comportement de ces matériaux est importante car ils
sont de plus en plus utilisés en plusieurs couches dans les infrastructures de transport, ainsi que dans les zones de transition entre
remblais et structures rigides. Dans la plupart de ces dernières situations, on trouve des zones sensibles proches de structures
préfabriquées, où le compactage des sols ou d'agrégats doit être réalisé à énergie modérée. En conséquence, il est nécessaire
d'augmenter la teneur en liants hydrauliques pour augmenter leur rigidité et résistance. Ce travail présente des résultats remarquables
obtenus dans certaines études en laboratoire visant caractériser différents mélanges de ciment et de granulats calcaires. Des mesures
d'ondes sismiques, des essais de résistance à la traction indirecte et des essais de compression triaxiale ont été réalisés. Les résultats
ont montré des différences intéressantes sur les propriétés de rigidité statique et dynamique aussi bien que sur les paramètres de
résistance au cisaillement de Mohr-Coulomb, directement liées à la variation du ratio porosité/ciment. Sur la base des résultats
d’essais triaxiaux, une calibration des paramètres géo-mécaniques du Hardening Soil Model, disponible sur logiciels commerciaux, a
été réalisée.
KEYWORDS: Aggregate-cement mixtures, Hardening Soil Model, Parametric calibration, Porosity cement ratio.
1 INTRODUCTION
The research on increasingly stiffer and more resistant
artificially stabilized geomaterials, such as aggregate-cement
mixtures, has frequently revealed interesting properties. The
knowledge of such materials behaviour is as important as they
are regularly used in several layers of transportation
infrastructures, as well as in transition zones between
embankments and rigid structures. Most of these last situations
involve zones close to sensitive prefabricated structures, where
compaction of soils or aggregates demand for moderate
energies, being necessary to increase the content of the
hydraulic binders to increase their stiffness and strength.
Despite the widespread use of Portland cement in the
improvement of soils and aggregates, there seems to be no
dosage methodologies based on rational criteria.
However, the relationship between the porosity of the
mixture (
n
) and the volumetric cement content (ie, the ratio
between the cement volume and the total volume - C
iv
) adjusted
by an exponent x, (x Є [0, 1]) has become a good parameter to
evaluate the strength and stiffness of artificially cemented soils.
This parameter, designated as adjusted porosity/cement ratio
(
n
/
C
iv
x
) has been related with the compressive strength
determined in uniaxial compression tests (Consoli et al., 2007)
and with the parameters of strength and deformability obtained
in triaxial compression tests (Consoli et al., 2009). More
recently, the ratio was applied to the stress–dilatancy relation of
an artificially cemented sand (Rios et al., 2012) and even more
recently in stress–strain and strength-dilatancy relationships on
a cemented aggregate (Viana da Fonseca et al. 2012).
The present paper reports some of the most notorious results
obtained with the scope of optimization of mixtures of
aggregates and Portland cement. A laboratory program was
developed to define the geomechanical characteristics of those
mixtures, which includes indirect tensile strength tests, seismic
wave measurements and triaxial compression tests. Based on
the results obtained, the relationships between the mechanical
properties and the
n
/
C
iv
x
parameter were evaluated. A
constitutive law was calibrated, taking into account the
behaviour of these mixtures - in laboratory tests, and then
evaluated in numerical modelling of triaxial compression tests.
2 LABORATORY TESTS
2.1
Tested materials
The aggregate tested is a well graded material which grain size
is shown in Figure 1. This material has a plasticity index of 10%
and a liquid limit of 22%. The Los Angeles Abrasion Index is
30%. The maximum dry unit weight obtained by the Modified
Proctor test is 21.4 kN/m
3
and the corresponding optimum
water content is 6.6%. This aggregate was mixed with different
percentages of cement, namely 2%, 3%, 4% and 5%. Portland
cement of very high initial strength (CEM I 52.5 R) was used as
