Utilization of recycled materials in unbound granular layers validated by experimental test sections

Abstract

The utilization of recycled materials has obvious environmental and economic
benefits that contribute for a more sustainable construction and rehabilitation of road
pavements. Despite the fact that many studies have already focused on the reusing and
recycling of materials, further research is always important to achieve a deeper knowledge on
these materials and technologies, and to increase the confidence of road owners and
construction companies for their use. This is the case of reclaimed asphalt, it is a material with
an enormous potential to be used in “unbound granular layers”, when it is not possible to
incorporate it in new asphalt mixtures. This paper concerns the structural evaluation of the
Construction and Demolition Recycled Materials (C&DRM) used in unbound granular layers
of bituminous pavements based on experimental test sections. An extensive study was
performed in experimental pavements, instrumented during the construction and submitted to
loading tests, where recycled materials were used in granular layers of sub-base and base.
This is part of the ongoing project SUPREMA – Sustainable Application of Construction and
Demolition Recycled Materials (C&DRM) in Road Infrastructures – by the National
Laboratory for Civil Engineering (LNEC, Portugal), in cooperation with the Technical
University of Lisbon (IST, Portugal) (2010-2013). The aggregates used in the experimental
sections were selected from C&DRM (crushed concrete and ceramic mixtures, reclaimed
asphalt material – crushed asphalt and milled material), and a natural material (limestone) as
the reference material. Four sections were instrumented with strain gauges and load cells,
placed in pavement layers and subgrade soil. The paper presents the results from in-situ
loading test series performed by the Falling Weight Deflectometer (FWD), for deflections
measurements of the instrumented pavements with different C&DRM and a natural material.
Analysis of results during load tests has demonstrated an acceptable performance of layers
with recycled materials.