A Circular Economy Virtuous Example—Use of a Stabilized Waste Material Instead of Calcite to Produce Sustainable Composites

Abstract

This work reports and analyzes the mechanical properties of some composites obtained using stabilized waste with epoxy resins E-227. For comparison, correspondent composite samples were realized using calcite as a filler. The recovered stabilized waste was obtained by means of a new method to stabilize municipal solid waste incineration (MSWI) fly ash (FA), based on the use of bottom ash (BA). The aim of this paper is to show that the stabilization process, which can be considered a zero—waste treatment, produces inert materials, that can be reused as a filler. The production of new filler was made on a pilot plant, designed to verify the transferability of the proposed stabilization technology. Mechanical analysis revealed that flexural modulus raises by increasing the filler content around 30% wt, independently of filler type, stabilized sample or calcium carbonate. Mechanical properties are lower in the samples with the high amount of filler due to the crowding effect. The morphology of composite materials showed a non-homogeneous dispersion of particles in stabilized sample filler, characterized by large particle agglomerates. Finally, according to the ESCAPE simplified method, the obtained composites result more sustainable in comparison with the corresponding ones produced by using natural resources (like calcite). These findings open new possibilities for the reuse of the stabilized material, in frame of circular economy principles, with environmental and economic advantages.

Review of the Reuse Possibilities Concerning Ash Residues from Thermal Process in a Medium-Sized Urban System in Northern Italy

“…The flexural modulus determines how much a sample will bend when a given load is applied, calculated from the slope of the stress vs. The strain deflection curve, as reported by Assi [104]. As reported in Table 1 and as expected, increasing the filler amount in the PP matrix increased the flexural modulus [109].…”

“…The most promising results were obtained using these powders as a filler in plastic composites [103]. Several examples have already been proposed, while also discussing the mechanical performances of the obtained composites in comparison to the composites containing natural resources (calcite-CaCO 3 ) [104].…”

“…In order to promote the carbonation reaction that contributes to the stabilization of heavy metals, the material obtained after the mixing process was aged for 1 year, as discussed by [60]. As mentioned by Assi [104], a periodic leaching test was performed in order to control the stability of the sample. Figure 9 shows the scheme of the machine used to produce the samples that were fed by granules of PP and stabilized fly ashes with different percentages by mixing the two components before introducing them into the machine.…”

Stabilization of Municipal Solid Waste Fly Ash, Obtained by Co-Combustion with Sewage Sludge, Mixed with Bottom Ash Derived by the Same Plant

“…The obtained stabilized eco-material is a powder that is very similar to the inert material obtained by using similar treatments but using other by-products (such as silica fume) instead of BA for stabilization. This allows for us to suppose that the obtained eco-materials may be used in some applications, already explored for similar products, as a substitute of natural resources [10,33,35,36]. In particular, it was shown that the obtained eco-materials are biologically safe [37][38][39], opening the interesting opportunity of the investigation of their aquatic toxicity in the next future.…”

“…The obtained stabilized eco-material is a powder that is very similar to the inert material obtained by using similar treatments but using other by-products (such as silica fume) instead of BA for stabilization. This allows for us to suppose that the obtained eco-materials may be used in some applications, already explored for similar products, as a substitute of natural resources [10,33,35,36]. The obtained stabilized eco-material is a powder that is very similar to the inert material obtained by using similar treatments but using other by-products (such as silica fume) instead of BA for stabilization.…”