Using Recycled Aggregates from Construction and Demolition Waste in Unbound Layers of Pavements

Abstract

Pavements are an expensive part of transportation infrastructures, as their construction and maintenance require large amounts of resources and materials every year and all over the world. A sustainable solution for considering environmental concerns about roads and pavements, in general, is utilizing recycled materials for their construction. This has been shown to lower the carbon footprint of the construction sector and to result in natural resource conservation, in reduction of harmful emissions and in minimization of overall costs for pavement construction and maintenance. One of the main groups of recycled materials which has attracted much attention since the end of the last century is construction and demolition waste aggregates (CDW). This paper reviews the completed studies referring to the use of the construction and demolition waste aggregates in unbound layers of pavements and compare the in-hand results from various engineering assessments of these aggregates and mixes. A number of tests and evaluations are applied in order to enhance the required quality and durability of the pavements under given traffic volumes traffic loads and climate actions. Today, unbound recycled aggregates (RA) are mainly used in the lower layers, such as subgrade, capping, sub-base and base, but in rural roads they can be adopted also for bound layers, towards the surface of the structure and may be constituents of bound layers and of novel surfacing applications.

Sustainable Recycling of High-Strength Concrete as an Alternative to Natural Aggregates in Building Structures

“…The cement properties are presented in Table 2. Silica fume with the density of 2.40 g/cm 3 was used as a pozzolanic additive to the binder in the amount of 10% (w/w), in line with the requirements of the PN-EN 13263-1:2005 standard [29]. The w/c (water/cement) ratio in both cases amounted to 0.26.…”

“…The data has been taken from a paper previously published by one of the authors [31]. Natural quartz sand with the density of 0.65 g/cm 3 and fraction size of 0.0-2.0 mm were employed as natural fine aggregate (NFA). In NCA, natural basalt (fraction size 2.0-8.0 mm) was used as coarse aggregate; it was characterized by the following parameters: specific density-2.93 g/cm 3 , bulk density-2.92 g/cm 3 , absorptivity-0.31%, compressive strength-280 MPa, frost resistance-F 2 .…”

“…Along with the development of the construction industry, the amount of construction waste (i.e., concrete, masonry and ceramic rubble, plaster, wallpaper residues, adhesives, paints, door and window woodwork, and installation waste) systematically increases, and their storage is problematic [2]. Construction waste mainly originates from demolition and dismantling of unused concrete structures, road and railway construction, the destructive effects of natural disasters, as well as by-products from production plants [3]. According to the European statistics, in 2016 the construction wastes constituted over 36% of total wastes generated in the EU [4].…”

“…In order to reduce the mixing water, new generation polycarboxylic superplasticizer with the density of 1.08 g/cm 3 and pH 4.0 was used in the amount of 1.8% cement mass (w/w) [31]. Owing to the surface absorption phenomenon and the effect of spatial particle separation acting upon cement grains, the additive accelerates curing, as well as improves the early strength and the workability of fresh mixture [31].…”

Current Applications of Recycled Aggregates from Construction and Demolition: A Review

“…There is a huge market interest to reuse and recycle aggregates derived from CDW in construction materials and projects [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. Over the last decades, many studies have been performed to evaluate the feasibility of using CDW in projects, such as: Concrete, mortar, and ceramic materials [ 4 , 7 ]; Eco-friendly concrete blocks [ 8 , 10 ]; Geopolymers synthesis [ 11 , 13 ]; Geotechnical applications [ 14 ]; Use in sea-wall foundations [ 15 ]; Landfill cover layer [ 16 ]; Alternative pipe backfilling materials [ 17 ]; Asphalt and roads [ 18 , 19 , 20 ]. …”