Abstract
Sustainable building material design relies mostly on energy saving processes, decrease of raw materials consumption, and increase of waste and by-products recycling. Natural and lightweight artificial aggregates production implies relevant environmental impact. This paper addresses both the issues of residues recycling and energy optimization. Particularly, three coal combustion wastes (Weathered Fly Ash, WFA; Wastewater Treatment Sludge, WTS; Desulfurization Device Sludge, DDS) supplied by the Italian electric utility company (ENEL) have been employed in the manufacture of cold bonded artificial aggregates. Previously, the residues have been characterized in terms of chemical and mineralogical compositions, water content, particle size distribution, and heavy metal release behavior. These wastes have been used in the mix design of binding systems with the only addition of lime. Finally, the artificial aggregates have been submitted to physical, mechanical, and leaching testing, revealing that they are potentially suitable for many civil engineering applications.
Highlights
This paper focuses on the possibility of employing coal combustion wastes in a cold bonding pelletization process in order to produce sustainable artificial aggregates, developing, a possible alternative in the above described action line 2
In the case of Weathered Fly Ash (WFA), the high water content is related to the storage method
The complete set of above results confirm that binder mixtures containing two wastes, such as weathered coal fly ash and chemical gypsum, and calcium hydroxide can give hydrated system based on ettringite and calcium silicate hydrate
Summary
Many authors have already discussed the environmental impact of building material industry [1,2,3]. Research attention on alkali activated binders is relevantly increased, frequently presented as a green alternative to traditional cements, both for low process and curing temperatures and for the possibility of employing wastes/by-products/sludge as raw aluminosilicate powdered precursor [14,15,16,17,18,19] This new class of materials has been widely tested for several civil and environmental engineering applications, but there is still a lack of data on the behavior of these materials under service life conditions [20,21,22,23,24,25,26]. The cold bonding pelletization is usually carried out at room temperature
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