Use of Unbound Materials for Sustainable Road Infrastructures

Abstract

The growing environmental sensitivity and the reduction of natural resources create, in Italy and other developed countries, an increasing interest in the search for alternative materials to be used in road construction works. In recent years, the problems related to environmental sustainability have made it increasingly difficult to remove natural aggregates from quarries and, at the same time, the regulations for the management of waste dumps are more and more restrictive. For this reason, the use of recycled aggregates is experiencing a continuous increase in the civil construction sector. This paper deals with the study of construction and demolition waste (CDW) in the field of road construction, in particular for the construction of embankment, road subgrades, foundation layers and unbound bases for flexible superstructures. Three different particle size fractions were used to prepare the mixtures: the first having a coarse size and designation 0–63 mm, the second intermediate size with aggregates of 0–31.5 mm grain size and the third with the finest aggregates having a grain size of 0–4 mm. The study was carried out by analyzing three granulometric fractions, verifying the best application for each of them. Subsequently, the mix-design was investigated, operating in compliance with the requirements imposed by UNI 11531-1, EN ISO 14688, EN 13242 and EN 13285. For the unbound layers of subgrade, foundation and base, which require greater resistance to fragmentation, the use of CDW alone has shown some limitations. Therefore, in the experimentation, it was decided to mix the CDW with a granulated slag coming from the steel production in the electric arc furnaces (EAF) and with an additional CDW (0–31.5 mm) coming from the recovery of concrete with slag. EAF granulated slag was used in small quantities, due to its relatively high cost. Four eco-friendly and recycled mixtures were studied, with low economic impact and high environmental sustainability, suitable for the construction of unbound layers of road superstructures.

Performance Characterization of Hot Mix Asphalt with High RAP Content and Basalt Fiber

“…The application of reclaimed asphalt pavement (RAP) in asphalt mixtures has been vigorously encouraged and promoted over the past decades due to the desirable environmental benefit, along with the cost reduction [1][2][3][4]. The use of RAP has been promoted from low-value use (as unbound layer materials [5], etc.) to high-value use (as surface materials, etc.…”

Analysis of the Physicochemical and Mineralogical Properties of the Materials Used in the Preparation of Recoblocks

“…China reported 600 million tons of construction waste in 2017, representing 30% to 40% of the total amount of urban garbage [ 2 ]. The European Union estimated that 820 million tons of construction and demolition waste were generated, corresponding to 25–30% of all waste produced in Europe [ 3 , 4 ]. In America, Canada produced more than 9 million tons in 2015 [ 5 ].…”

“…The Mexico City Norm [16] indicates multiple uses that have already been tested in different locations in Mexico City [17]. The recycled aggregates easily comply with the standards to be used as road sub-bases [4,18], as construction materials in new buildings and structures or as concrete filler for reconstruction of hydraulic structures [19]. Such use of concrete waste will reduce the volume of extracted natural resources, decrease the load on landfills, and minimize the logistics costs for the transportation of waste and natural resources [8,20,21].…”

Study on Migratory Behavior of Aggregate in Asphalt Mixture Based on the Intelligent Acquisition System of Aggregate Attitude Data

“…Referring to Section 2.1, the same specifications of asphalt mixture specimens containing IAA were prepared to ensure that the test operation is consistent and the data are comparable [21].…”