Possible Recycling of End-of-Life Dolomite Refractories by the Production of Geopolymer-Based Composites: Experimental Investigation

Abstract

Production and characterization of geopolymers prepared by mixing metakaolin, end-of-life dolomite refractories, sodium silicate solution, and sodium hydroxide solution have been performed. The as-received refractory was crumbled in order to obtain products having, respectively, 250 μm, 1 mm, and 2.5 mm maximum particles size. Each batch of powder was added in different proportions to a blank geopolymeric matrix. It has been observed that the addition of waste refractory reduces workability of the reference refractory-free slurry. After hardening, only the set of samples prepared with powders with maximum size of 250 μm maintain integrity while the others resulted affected by the presence of fractures caused by volumetric instabilities; samples with composition R100 showed the highest compressive strength, whereas higher refractory addition lowers strength. Specific surface area appears independent by materials composition; conversely pore volume slightly increases with the addition of dolomite refractory powder. During the thermodilatometric tests all compositions display a shrinkage of about 0.1% between 170 and 400 °C; however, sintering starts at higher temperature (above 600 °C) and samples melt in the range between 650 and 750 °C as a function of their composition, thus showing that the resulting materials loose refractoriness with respect to both the reference geopolymer and the dolomite refractory. Graphical Abstract

Preparation and Properties of Geopolymer Matrix Composites Containing Waste Olivine Sands from a Metallurgical Process

“…In agreement with the approach followed in a previous research [22], geopolymeric monoliths have been produced using alkali-activated metakaolin (MK) which was mixed with different proportions of waste OS. Samples were prepared using either the as-received OS, or after a thermal treatment at 900 °C which was made to remove the residual organic compounds still present in the as-received waste olivine sands.…”

“…In addition, Table 2 also contains the Na 2 SiO 3 /NaOH ratio which is 3.4. The mix proportion design was built up on the base of previous research investigations [22,23].…”

Mechanical and antibacterial behavior of multilayered geopolymer coatings on Ti6Al4V alloys

“…Several formulations were tested in this work but, for the sake of brevity, only the best performing formulations for each type of geopolymer (acid/alkaline) will be reported. Compositions listed in Table 1, in fact, had both good mechanical properties and pore size distributions suitable for stimulating osteointegrative phenomena [4,[22][23][24].…”

Investigation of the Relationship Between Ferrochrome Ash Addition and Chemical Binders in Geopolymer Concrete

“…FCA has also been reported to be partially studied as a building material; however, most studies suggest its use as a binder material (with GGBS, FA, OPC, Lime, Red Mud). In several studies, authors have reported its use as a substitute for cement by Mishra et al 2020b, Kumar et al 2020, Acharya and Patro 2016a, Machiels et al 2017, Mishra et al 2022a, Mishra et al 2022c, Acharya and Patro 2016c, Saha et al 2021, Acharya and Patro 2016d, Sharma et al 2022, and as a precursor material in geopolymers and alkali-activated materials by Rangan 2014, Mishra et al 2022a, Phoongernkham et al 2014, York and Europe 2021, Furlani et al 2021, Acharya and Patro 2015, Acharya and Patro 2016c.…”