Performance Evaluation of Innovative and Sustainable Pavement Solutions for Road Tunnels

This paper summarizes the studies which were carried out to support pavement design and construction operations in a major motorway tunnel. Candidate pavement cross sections subjected to analysis included a subgrade and foundation layer constituted by self-compacting cement-bound granular mixtures. The potential use of standard cement-stabilized foundations was also considered. The self-compacting mixtures were designed to incorporate significant amounts of recycled materials including Reclaimed Asphalt Pavement and mineral sludge retrieved from aggregate washing operations. Expected performance of the innovative pavement solutions and of a reference standard cross section were assessed by means of a mechanistic-empirical approach which in most part relied on the outcomes of laboratory and field tests. In particular, a full-scale test section was constructed with the use of self-compacting mixtures in the subgrade and foundation, overlaid by two asphalt layers. The subsequent investigation included Falling Weight Deflectometer measurements and laboratory tests carried out for the assessment of volumetric and mechanical properties of laid mixtures. Obtained results led to the identification of an optimal pavement cross section and highlighted the potential performance achieved by the proposed innovative solutions. The additional advantages related to the greater efficiency of construction operations in tunnels and to the lower consumption of virgin aggregates were also discussed.