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Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
1
Characterization of recycled materials for sustainable construction
Caractérisation des matériaux recyclés pour la Construction durable
T. B. Edil
University of Wisconsin-Madison, USA
ABSTRACT: Recyclable materials and industrial byproducts provide an environmentally and economical alternative to natural
earthen materials when used safely and wisely in geotechnical construction. In particular, the construction of various elements of
transportation systems requires large quantities of materials and locally available recyclable materials can be used extensively
enhancing sustainability of construction. This paper addresses the rapid characterization required for this new class of materials such
as recycled asphalt pavement, concrete aggregate, and coal combustion residues (fly ash, bottom ash). Recycled materials and
industrial byproducts require an assessment of their environmental suitability in terms of potential impacts on surface and ground
water quality for their acceptance. Finally, their field behavior need to be evaluated and their contribution to sustainability to be
assessed.
RÉSUMÉ : Les matériaux recyclables et les sous-produits industriels fournissent ambiant et l'alternative économique aux matériaux
de terre naturels une fois utilisés sans risque et sagement dans la construction géotechnique. En particulier, la construction de divers
éléments des systèmes de transport exige de grandes quantités de matériaux et localement des matériaux recyclables disponibles
peuvent être employés intensivement augmentant la durabilité de la construction. Ce document adresse la caractérisation rapide
exigée pour cette nouvelle classe des matériaux tels que le trottoir réutilisé d'asphalte, l'agrégat concret, et les résidus de combustion
de charbon (cendres volantes, cendre inférieure). Étant les matériaux réutilisés ou les sous-produits industriels, leur acceptation exige
une évaluation de l'aptitude environnementale en termes d'impacts potentiels sur la qualité extérieure et d'eaux souterraines. En
conclusion, leur besoin de comportement de champ d'être évalué et leur contribution à la durabilité à évaluer.
KEYWORDS: recycled materials, sustainable construction, recycled asphalt pavement, recycled concrete aggregate, coal ash.
1 INTRODUCTION
Development and growth need to be sustainable, in other words,
integrate environmental, economic, and social dimensions
towards global stewardship and responsible management of
resources. Strategies need to evolve for sustainable
development..Large quantities of natural and processed
materials are used in construction activities such as buildings,
transportation facilities, infrastructure, and environmental
applications. These materials use natural resources and
consume large quantities of energy to extract or process with
associated green house gas emissions. Transportation facilities,
such as highways, in particular use large quantities of materials
in initial reconstruction and also during periodic rehabilitation.
Recycling industrial byproducts and construction materials in
highway construction can generate “green highways” where use
of virgin materials and large amounts of energy and generation
of green house gas emissions are minimized.
The necessary steps for characterization of widely used
recycled materials (i.e., recycled asphalt pavement and recycled
concrete aggregate) and industrial byproducts (i.e., coal
combustion products such as bottom ash and fly ash) in
highway construction are presented and discussed. The
approaches for determining their physical characteristics,
geomechanical behavior (i.e., resilient modulus), durability (i.e.,
freeze-thaw cycling, temperature effects, wet-dry cycling),
constructability (i.e., compaction), material control, and their
environmental suitability (i.e., leaching characteristics) for
alternative beneficial uses are presented. Life cycle assessment
(LCA) of the environmental benefits and the life cycle cost
analysis (LCCA) for use of these materials are also discussed.
2 CHARACTERIZATION
We have been characterizing natural earthen materials
systematically for nearly a century. Widespread use of these
recycled materials is relatively new and time window to
characterize them is short because of economical and
environmental drivers. Testing methods developed for soils and
construction specifications for natural aggregates and soils can
be adapted to this new class of recycled materials and the
existing pavement design procedures can be followed.
Material control in terms of variability of composition, grain
size characteristics, inclusion of impurities are issues that need
to be assessed for recycled materials, as they are products of
anthropogenic processes rather than geological processes.
There may be differences arising from basic material
characteristics that may impact constructability in terms of
compaction control. Modern pavement design requires resilient
or elastic modulus as the primary geomechanical property. On
the basis of this property layer thicknesses in a pavement and
service life of a pavement can be determined. Durability under
climatic effects, i.e., freeze
-
thaw and wet
-
dry cycles, is a critical
quality for pavement materials because the pavements are
surficial and directly influenced by the climate. Some of these
materials have sensitivity to temperature in ways we are
unaccustomed dealing with soils. Finally, while we do not
question the environmental suitability of traditional materials
like crushed aggregate, concrete and asphalt used in highway
construction, use of recycled materials and industrial
byproducts requires evaluation of environmental suitability, i.e.,
the leaching characteristics.
3 MATERIALS,
APPLICATIONS
&
CRITICAL
CHARACTERISTICS
The outstanding characteristics of a range of recycled materials
widely used in highway construction are described along with
typical applications.
Edil T.B.
