Durability of Sustainable Ceramics Produced by Alkaline Activation of Clay Brick Residue

Abstract

Alkali-activated materials (AAMs) were produced using residues from the red ceramic industry as a precursor, and sodium hydroxide (NaOH), potassium hydroxide (KOH), and sodium silicate (Na2SiO3) as alkaline activators. The effect of activators and curing conditions on physical-mechanical properties and durability were evaluated. The processing parameters (amount of water and consistency index) and the activation conditions (the activator contents and curing temperature) were defined based on an experimental design getting the flexural rupture module as the response. The durability behavior was evaluated by natural aging, accelerated aging (simulated rain test), exposure to the marine environment (salt fog), and acidic environments (HCl and H2SO4). The results showed that the NaOH- and KOH-activated samples exhibited inferior mechanical behavior than those activated with Na2SiO3. In the durability studies, due to leaching, there was a decrease in mechanical strength when samples are subjected to aggressive exposure conditions. However, the strength values are still higher than the minimum indicated for traditional ceramic applications.

New Urea Controlled-Release Fertilizers Based on Bentonite and Carnauba Wax

“…The chemical analysis measured from the Bent-Na and Bent-R samples is summarized in Table 3. As expected, both clays presented SiO 2 and Al 2 O 3 as major constituents, corresponding to more than 60% of their chemical composition [19][20][21][22]. The detected SiO 2 comes from the tetrahedral layer of the smectite clay mineral and quartz, while the Al 2 O 3 is present in the octahedral layer of the clay mineral.…”

Valorizing (cleaned) sulfidic mine waste as a resource for construction materials

“…With respect to the end life (landfilling) or second life (e.g., tennis courts, landscaping, road construction or in AAMs (Costa et al, 2021)) of the ceramics, the ceramic samples that did not exceed the non-hazardous waste threshold values of metal(loid)s leaching (EN 12457-2 test) do not necessarily pose a threat to the environment after use. Additionally, the possible use of ceramics in alkaline environments (e.g., recycling ceramics in AAMs or cements or landfilling with lime) or adding a high lime containing body to ceramics could be further investigated given the low levels of metal(loid)sfrom all tested ceramics at pH > 12 (Figure 6).…”