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 of recycled materials, further research is always important to achieve a deeper knowledge on materials and technologies and to increase the confidence of road owners and construction companies for the use of these materials. This is the case of reclaimed asphalt, it is also 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 recycled materials 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 Portuguese National Laboratory for Civil Engineering (LNEC), in cooperation with the Technical University of Lisbon (IST) (2010-2014). The aggregates used in the experimental sections were selected from construction and demolition materials (crushed concrete and ceramic mixtures), reclaimed asphalt material (crushed asphalt and milled material) and natural 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 recycled and natural materials. Analysis of results during load tests has demonstrated an acceptable performance of layers with recycled materials.