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Cement asbestos slates, commonly known as Eternit® and still abundant in private and public buildings, were deactivated through a thermal process. The resulting deactivated cement asbestos powder (DCAP), a mixture of Ca-Mg-Al silicates and glass, was compounded with Pavatekno Gold 200 (PT) and Pavafloor H200/E (PF), two different epoxy resins (bisphenol A epichlorohydrin) for flooring applications. The addition of the DCAP filler to the PF samples causes a slight but acceptable decrease in the relevant mechanical properties (compressive, tensile, and flexural strengths) upon increasing DCAP content. The addition of the DCAP filler to pure epoxy (PT resin) causes a slight decrease in the tensile and flexural strengths with increasing DCAP content, while the compressive strength is almost unaffected, and the Shore hardness increases. The main mechanical properties of the PT samples are significantly better than those of the filler-bearing sample of normal production. Overall, these results suggest that DCAP can be advantageously used as filler in addition to, or in substitution for, commercial barite. In particular, the sample with 20 wt% of DCAP is the best performing in terms of compressive, tensile, and flexural strengths, whereas the sample with 30 wt% of DCAP shows the highest Shore hardness, which is an important property to be considered in flooring applications.

<p>Asbestos-containing material (ACM) still represents an emergency in Europe because of the related health problems. Based on dedicated legislation, ACM must be managed through several different operations such as: i) confinement, ii) encapsulation and iii) removal (with disposal in controlled landfills). A more attractive alternative to these non-ideal solutions, safer and sustainable, is the transformation of the ACM through thermal, thermo-chemical or thermo-mechanical methods into a non-hazardous secondary raw material. In this contribution, we explore the re-use of ACM thermally treated at 1100 °C in the production of sanitary ware ceramics.</p><p>Sanitary-ware vitreous bodies (VB) are generally obtained from mixtures of three fundamental raw materials: i) clay, mostly kaolinite, which provides plasticity to the ceramic mixture; ii) quartz, which acts as filler, forming the skeletal network of the ceramic body; iii) feldspar, a fluxing agent, which promotes the greification of the body and the dissolution of component like quartz upon firing (buller T 1200-1240 °C; Carty & Senapati, 1998).</p><p>The product of the thermally treated ACM, i.e. a mixture of non-hazardous Ca-Mg-rich silicates (akermanite, bredigite, merwinite and larnite) and glass, was added to a ceramic mixture as a partial substitute (5 wt%) of feldspar (mixture VBX), and characterized according to a standard protocol before and after firing in the industrial tunnel kiln (buller T 1230°C). The results pointed out a very good greification level of the VBX slip, as corroborated by very low water absorption. These results motivated us to better evaluate the greification behavior of the VBX slip at 6 different buller T by means of gradient kiln. From the mixture VBX, we prepared six samples which were heated at 1140, 1160, 1180, 1200, 1220, and 1240 °C, and characterized the mechanical, mineralogical and microstructural properties. For comparison, the same T steps and analyses were applied to six standard ceramic mixtures (i.e., vitreous China, VC).</p><p>XRPD indicates that VBX and VC have very similar mineralogical composition, with glass, quartz, feldspar and mullite as major constituents and minor Fe and Ti oxides. SEM observations suggest that VBX and VC have also similar microstructure, dominated by a glassy matrix embedding numerous 10-60 µm-sized particles of quartz, feldspar and mullite. Overall, thermally treated ACM seems a good candidate to substitute feldspar up to 5 wt% in the production of sanitary ware ceramics. This conclusion is further supported by the fact that VBX and VC display a very similar greification level at T>1200°C.</p><p>Carty, W. M., & Senapati, U. (1998). Porcelain—raw materials, processing, phase evolution, and mechanical behavior. <em>Journal of the American Ceramic Society</em>, <em>81</em>(1), 3-20.</p>

<p>Asbestos minerals, namely chrysotile and fibrous amphiboles, have long been used as components in construction materials, as for instance the cement-asbestos (CA) slates used in roofing, exploiting their capability to increase mechanical strength. As well known, asbestos minerals have been recognised toxic and banned almost worldwide. Current remediation approaches include confinement, encapsulation and removal (followed by disposal in controlled landfills). A more attractive solution, strongly recommended by the EC, is detoxification and reuse, in a perspective of circular economy.</p><p>In the present contribution we explored the possibility to reuse thermally treated and deactivated CA powder (a mixture of glass and Ca-Mg silicates typical of cement – details in Vergani et al. 2021) as filler in: i) flour-elastomers (FKM type, characterized by high resistance to oil and temperature) and bi-component epoxy resins (bisphenol-A, epichlorohydrine based resins) used in flooring. For each application, different formulations (different proportions of conventional raw materials and deactivated CA powder) have been prepared and tested according to conventional quality test protocols and SEM micro-textural observations.</p><p>As regard the reuse in epoxy resin, the inert CA powder was used either as unique inorganic filler (up to 30 wt%) or admixed to conventional ones (barite), in varying proportions (up to 10 wt%). Mechanical tests and SEM observations have shown encouraging results for all formulations, suggesting feasible reuse in this field.</p><p>The application of the inert CA powder as filler in fluor-elastomers in substitution of wollastonite (~22 wt%) or barite (~7 and ~14 wt%), has given some controversial results. Although rheological properties such as cure kinetics, viscosity and scorch temperature are comparable to the standard reference samples, some important physical-mechanical properties worsen because of compatibilization and dispersion problems. As demonstrate by SEM observations, the CA powder tends to agglomerate, and similarly to the coarser particles saved from ball-milling – the grain size distribution of the CA powder is tri-modal with peaks at ~35-40, ~4-5 and ~0.7-0.8 µm – separate from the elastomer, adding porosity with detrimental effects on breaking load, elongation at fracture and related M50 and M100 modules.</p><p>At the moment, in a perspective to keep the fine fraction low and to reduce the coarse particles, alternative milling procedures, including microwave and ultrasonic treatments and sieving, are evaluated.</p><p>Reference: Vergani et al. (2021) J. Mater. Cycles Waste. https://doi.org/10.1007/s10163-021-01320-6</p>