3187
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
1
The Use of Recycled Aggregates in Unbound Road Pavements
L'utilisation d'Agrégats Recyclés en Revêtements de Chaussée sans Liant
D. A. Cameron, M. M. Rahman and A. M. Azam
University of South Australia (UniSA), School of Natural and Built Environments, Adelaide, Australia
A. G. Gabr
Mansoura University, Public Works Department, Faculty of Engineering, Egypt
R. Andrews
ARRB Group (South Australia), Adelaide, Australia
P. W. Mitchell
Aurecon Australia Pty Ltd, Adelaide, Australia
ABSTRACT: This paper argues for the acceptability for use in unbound granular pavements of recycled concrete aggregates (RCA)
and recycled clay masonry (RCM) derived from demolition. Specifications from road authorities both within and outside Australia are
considered, and results of tests carried out on specimens of RCA and RCM are compared with these specifications. The tests included
conventional classification tests for soils and aggregates, Los Angeles abrasion value, Micro-Deval, falling head permeability, drying
shrinkage, undrained triaxial tests and repeated loading triaxial testing for resilient modulus and permanent strain rate. The influence
of matric suction on resilient modulus of the granular pavement materials is presented. Both RCA and RCA blended with RCM (20%
by mass maximum) were found to meet existing specifications and therefore can be incorporated in road pavements. RCA was found
to be suitable for use as a base course. In the case of RCA blended with RCM, as the proportion of RCM increases, the permanent
strain rate increases and resilient modulus decreases, thereby compromising use of the blends as base material. However, RCA with
up to 20% RCM is suitable for use as sub-base of a road pavement.
RÉSUMÉ : Ce document plaide pour l'acceptabilité, pour les revêtement de chaussée granulaires sans liant, des agrégats de bétons
recyclés (ABR) et de la maçonnerie recyclée d'argile (MRA) provenant de la démolition. Les spécifications des autorités routières
d'Australie et d'ailleurs sont considérées, et des résultats d'essais effectués sur des spécimens de ABR et de MRA sont comparés à ces
spécifications. Les essais comprennent des essais conventionnels de classification pour sols et agrégats (valeur d'abrasion Los
Angeles, Micro-Deval , perméabilité à charge variable, séchage et rétraction, essais triaxiaux non drainé et essais triaxiaux répétés
pour le module résilient et la vitesse de déformation constante. L'influence de la succion matricielle sur le module résilient des
matériaux granulaires de revêtement de chaussée est présentée. l'ABR et l'ABR mélangé avec le MRA (20% maximum en masse) se
sont avérés satisfaire les spécifications existantes et peuvent donc être incorporés en revêtement de chaussée. l'ABR s'est avéré
approprié pour l'usage comme couche de base. Dans le cas de l'ABR mélangé avec le MRA, à mesure que la proportion de MRA
augmente, le taux de déformation permanente augmente et le module résilient diminue, compromettant de ce fait l'utilisation des
mélanges en tant que matériau de couche de base. Cependant, l'ABR avec jusqu'à 20% RCM convient pour l'usage comme sous-
couche de chaussée routière.
KEYWORDS: recycled aggregate, C&D waste, resilient modulus, permanent strain, matric suction, prediction
1 INTRODUCTION
Recycling of construction and demolition wastes can produce
acceptable aggregates for civil engineering applications such as
unbound granular pavements. Australian practice is well behind
countries such as Japan, the United Kingdom, France, Germany
and the Netherlands, but the recycling aggregate industry, which
has emerged over the last decade, is growing. Quarry industries
seem to feel challenged by recycling but should realise that even
in Europe with its long history of recycling, recycled aggregate
supply is unlikely to exceed 10 to 15% of total demand
(Meininger and Stokowski 2011). Much of the research in
Australia to date has focussed on Recycled Concrete Aggregates
(RCA), Recycled Clay Masonry (RCM), recycled glass and
waste rock. Much can be learned from the European experience,
but this experience cannot be simply adopted as it is based on
the range of climates, pavement construction practices and
geology throughout Europe. Furthermore, the great majority of
pavements in Australia are thinly surfaced, resulting in higher
stresses being applied to the aggregates by passes of traffic.
Much of the work to date has been limited to the laboratory
(e.g. Nataatmadja and Tan 2001, Aatheesan et al. 2009, 2010,
Arulrajah et al. 2011, 2012a, 2012b and 2012c, Gabr et al. 2012,
Gabr and Cameron 2012a, Azam and Cameron 2012, Azam et
al. 2012, Jitsangiam et al. 2009, Leek and Siripun 2010). Gabr
2012 developed an empirical model for predicting permanent
strain from testing of South Australian RCA, which he
incorporated into Finite Element Analysis (FEA) to predict
pavement life, similar to the approach of Huvstig et al. 2008.
However the validation of this approach has not been made.
Nevertheless a few field trials of roads constructed with C&D
waste have been conducted (Ecocycle 1997 and Bowman &
Associates 2009a and 2009b). The combination of laboratory
and field data with FEA has much potential to improve
pavement design generally.
This paper summarizes the work undertaken at the
University of South Australia (UniSA) to evaluate aggregate
produced from two local producers of recycled C&D waste,
which consisted of either crushed concrete or RCA blended
with fired clay masonry (RCM). All products were nominally
20 mm sized maximum aggregate. Variations in moulding
moisture levels have been investigated, leading to some
interesting findings relating soil suction to resilient modulus.
The South Australian Department for Transport, Energy and
Infrastructure (DPTI, formerly DTEI) stipulates a range of
material properties (DPTI, 2011), but includes minimum
resilient modulus and maximum rate of permanent strain for
Class 1 bases, based on a simplified, single stress stage
Repeated Load Triaxial Test (RLTT). These performance based
specifications are unique in Australia if not worldwide. In parts
of Scandinavia, specifications require back-calculated resilient
Cameron D.A., Rahman H.H., Azam A.
Gabr A.G.
Andrews R.
Michell P.W.
