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Mineral wastes coming from demolition activities, including rock and soil from excavations, and extractive industry, represent the first and the second source of waste production at EU level (35.9% and 26.6% respectively). Although some of these waste products can cause environmental and economic problems if not adequately managed and disposed, they represent an alternative resource for civil, building, infrastructure and environmental applications. This study introduces the state of the art of the research and applications of products arising from mineral waste, with a focus on new potential application of fine fractions for artificial substrate production. The agronomic characteristics of the produced mixes were tested to evaluate their use and the environmental criticalities for land rehabilitation. The results showed that, when mixed with organic materials, the overall quality and fertility of the mineral waste fine fraction was improved, and that this mixture was not phytotoxic. This indicates that when properly managed and treated the mineral waste fine fraction could be effectively employed for land rehabilitation. In general, both coarse and fine mineral waste fractions are valuable alternative construction materials for buildings infrastructures and environmental applications. Sustainable and circular management of mineral waste contributes to guarantee raw materials supply, contemporary reducing environmental (including CO2 production) impacts associated to waste management and landfilling. The potential decrement of environmental impacts and CO2 production will contribute to enhance the NET-zero greenhouse gas emissions EU strategy. Statement of Novelty The present research outlines the possible reuses of different mineral wastes coming from demolition activities and rocks and soils from excavation works as a replacement for natural aggregates, in line with the circular economy paradigm. These materials represent the first source of wastes (in mass) in Europe and innovative processes for their efficient reutilization are needed. This research addressed the main problems connected with their management, focusing on some experimental processes, such as the production of artificial substrates, as a sustainable alternative to contrast the land consumption. However, the updating of the current legislation and the inclusion of these new products for public works (Green Procurement) is regarded fundamental to the effective application of novel technologies.

Recent works have demonstrated that construction and demolition waste (CDW) aggregates for subbase road pavement applications can be stabilized via the alkali activation of their fine fract...

The paper presents the results of a laboratory investigation seeking to quantify the effects of fine quantity and type on the workability and resilient response of aggregate-fine soil mixtures for ...

This study investigates the effects of curing temperature on alkali-activated fine particles of undivided construction and demolition waste (CDW) aggregates. Previous investigations demonstrated that such activated fines can stabilize the whole mixture thereby improving its mechanical properties. To comprehensively investigate the behaviour of the activated fine, its strength and leaching properties under different curing temperatures were compared to those of the four alkali-activated powders of CDW aggregate constituents (concrete, reclaimed asphalt, bricks and tiles, and natural aggregate). Flexural and compressive strength tests at 28 days of curing were performed on different pastes prepared with different liquid to solid (l/s) mass ratios (0.4, 0.5, and 0.6), and cured at 5, 20, 40, and 80 °C. All components showed satisfactory strength properties for l/s = 0.4, which was found to be optimal. A significant enhancement of the mechanical properties was observed for specimens treated at 80 °C. However, non-negligible strength values were obtained at other temperatures. In particular, the undivided fractions showed satisfactory results and a low variability in properties when cured at average roadside temperatures from − 5 to 40 °C. Following leaching tests, the environmental compatibility of alkali-activated materials was deemed satisfactory with the concentration of pollutants considerably below the threshold of the European Council Decision 2003/33/EC for non-hazardous waste.

Pervious concrete (PC) pavements are water control systems for infiltrating storm water, reducing runoffs, contrasting heat-island effects and noise diffusion in urban environments. Their poor strength and stiffness, which stem from their porosity, limit their application for use in sidewalks and residential streets. To overcome this limitation, the research aimed at developing an alkali-activated blast furnace slag binder (AA-BFS) which, when added to the concrete mixture, would enable it to attain the characteristics required for application in trafficked road pavements. A Portland cement (CEM-I) and a blast furnace cement (CEM-III/C) were included for comparison purposes. Standard and high-performance pervious concrete (HPPC) mortars were tested with the same mix ratio of binder, sand, and admixtures. The effects of a latex polymer admixture were also analysed. After 2, 7, and 28 days of curing, AA-BFS mortars exhibited the greatest flexural and compressive strengths. As expected, CEM-III/C needed more time to achieve strengths comparable to those recorded for CEM-I. The addition of latex failed to result in any discernible benefits in terms of the stress-strain behaviour of mortars. The results confirm that AA-BFS is a sustainable option for HPPC production.

The alkaline-activation of aluminosilicate compounds present in fine particles of unselected construction and demolition waste (UCDW) aggregates is investigated here. The aim is to stabilize UCDW aggregates by adding an alkali-activating solution (AAS) composed of sodium hydroxide and sodium silicate and then assess their potential employment in stabilized base/subbase road pavement layers. Contrary to the practice in other studies, no industrial–waste by-products (i.e., fly ash, slag precursor) or other components containing silica-aluminates were added to the material. Workability, strength, and stiffness values were evaluated at laboratory temperature (around 25 °C) for 7, 28 and 60 days. The resulting mixtures were compared with those containing pure water and a diluted AAS (50% of pure AAS and 50% of water). The resilient modulus of UCDW aggregates compacted with pure AAS was considerably higher than those containing both diluted AAS and water only. Similar conclusions were drawn for the unconfined compressive strength and indirect tensile strength parameters, which for UCDW with pure AAS were comparable to those for ordinary cement-stabilized granular materials. These results demonstrate the potential offered by the alkali-activation of aluminosilicate compounds present in fine particles of UCDW. The microstructural observation, carried out by Field Emission Scanning Electron Microscopy, coupled with an elemental analysis performed by Energy Dispersive Spectroscopy, supported the successful alkali-activation of UCDW fines.

This study investigates the potential of fine particles of recycled construction and demolition waste (CDW) aggregate to undergo alkali-activation when mixed with an appropriate alkaline solution. The fine is a natural by-product of the milling process and includes particles from four main material sources (i.e., recycled concrete, recycled asphalt, crushed bricks and tiles, and natural aggregate and excavated soil) and other occasional elements which are too small for identification. The fine was obtained by sifting the material through a 125 μm sieve. Since the reactivity of unselected material depends on its constituents, these were also individually investigated. Firstly, the four constituents of CDW recycled aggregates were separated, then milled to a size smaller than 125 μm, before being tested to measure their reactivity to an alkaline solution. A preliminary chemical and mineralogical characterization of the five powders was carried out to identify the main crystalline phases and ascertain the presence of aluminosilicates needed for the alkali-activation process. Particles of each powder were afterwards mixed with three concentrations of the same alkaline solution with a liquid/solid mass ratio of 0.4, cast in prismatic moulds, and cured at room temperature. Mechanical tests after 3, 7, and 28 days of curing demonstrated that powders react positively in a basic environment, showing an increase in strength without any thermal treatment. Hardened pastes of undivided fine aggregate and recycled asphalt exhibited the best results in terms of flexural and compressive strength with the more concentrated solution. A Field Emission Scanning Electron Microscopy analysis was also carried out to observe the microstructure and to support an interpretation of the mechanical strength data. Results demonstrated the feasibility of using a solution to activate unselected CDW fine particles to stabilize CDW aggregates. In full scale applications, CDW aggregates can be stabilized without the addition of any binder.

Although previous studies attested to the feasibility of using recycled aggregates from unseparated construction and demolition waste (UCDW aggregates) in unbound layers of road pavements, the degradation caused by compaction and freezing action under simulative conditions has not been investigated yet. To investigate the effects of these two sources of degradation on resilient modulus (RM), three UCDW aggregates were collected from different plants in the Turin area and compared with a natural (NAT) aggregate. Partially-saturated specimens of UCDW aggregates at the optimal moisture content (wopt) and at wopt±2% were prepared at the gyratory shear compactor with 30 and 100 gyrations, and by subjecting specimens to 0, 4 and 8 two-day freeze–thaw cycles from −18 °C to +20 °C. Brittle and weak components of UCDW aggregates (crushed concrete, bricks) generate fine particles in the first part of the compaction process (in the first 30 gyrations). Freeze–thaw action led to a clear increase in the resilient modulus of UCDW specimens compacted at wopt and wopt+2%. A similar trend in RM was observed in the case of NAT aggregate in similar moisture conditions, while both UCDW and NAT exhibited a slight decrease for some samples prepared at wopt−2%. Under more severe but non–simulative testing conditions such as those currently used to select conventional granular materials, UCDW aggregate exhibits lower performances than NAT aggregate. Conversely, when evaluated in more simulative test conditions, the behaviour of UCDW aggregate is comparable to that of NAT one.

This work is aimed at investigating the use of green infrastructure technologies for the infiltration of stormwater runoff from urban road pavements into soil, and as a means to support the evapotranspiration and harvesting processes. Porous concrete pavements and vegetated biofilters were considered to assess pollutant removal and hydraulic performances. The investigations were at bench-scale for single materials, and at column and box scale for composite structures. The pollutant reduction was determined on the basis of suspended solids, heavy metals and hydrocarbon concentration, with promising results that were found to be dependent on filter material characteristics, layer distribution, and permeability.

High volumes of construction and demolition waste (CDW) are continuously produced worldwide. The European Commission aims to increase the recycling of nonhazardous CDW to a minimum of 70% i...