Optimal Design of Ferronickel Slag Alkali-Activated Material for High Thermal Load Applications Developed by Design of Experiment

Abstract

The development of an optimal low-calcium alkali-activated binder for high-temperature stability based on ferronickel slag, silica fume, potassium hydroxide, and potassium silicate was investigated based on Mixture Design of Experiment (Mixture DOE). Mass loss, shrinkage/expansion, and compressive and flexural strengths before and after exposure to a high thermal load (900 °C for two hours) were selected as performance markers. Chemical activator minimization was considered in the selection of the optimal mix to reduce CO2 emissions. Unheated 42-day compressive strength was found to be as high as 99.6 MPa whereas the 42-day residual compressive strength after exposure to the high temperature reached 35 MPa (results pertaining to different mixes). Similarly, the maximum unheated 42-day flexural strength achieved was 8.8 MPa, and the maximum residual flexural strength after extreme temperature exposure was 2.5 MPa. The binder showed comparable properties to other alkali-activated ones already studied and a superior thermal performance when compared to Ordinary Portland Cement. A quantitative X-ray diffraction analysis was performed on selected hardened mixes, and fayalite was found to be an important component in the optimal formulation. A life-cycle analysis was performed to study the CO2 savings, which corresponded to 55% for economic allocation.

Out-of-plane performance of structurally and energy retrofitted masonry walls: geopolymer versus cement-based textile-reinforced mortar combined with thermal insulation

“…Recent attempts to reduce the environmental impact of TRM systems focused on geopolymers as new binding materials for the textiles, which have potential to become an alternative to Ordinary Portland Cement (OPC) binders ( Arce et al , 2022a ; Askouni et al , 2021 ; Cholostiakow et al , 2023a ; Ghiassi et al , 2016 ; Gkournelos et al , 2022 ; Skyrianou et al , 2022 ; Tamburini et al , 2017 ; Wang et al , 2021 ; Zhang et al , 2019 ; Zhang et al , 2022 ). Geopolymers, which can be formed by mixing silicate dry products with an alkaline solution, exhibit excellent mechanical properties, high durability, and resistance to elevated temperatures, thus making them potential candidates as an alternative to cement-based materials, but also in a variety of uses as a fireproof adhesive for fibre-reinforced composites and laminates ( Arce et al , 2022b ; Chen et al , 2021 ; Giancaspro et al , 2009 ; Giancaspro et al , 2010 ; Katakalos & Papakonstantinou, 2009 ; Mobili et al , 2016 ; Papakonstantinou et al , 2001 ; Papakonstantinou & Balaguru, 2006 ; Papakonstantinou & Balaguru, 2007 ; Papakonstantinou & Katakalos, 2009 ; Zhang et al , 2018 ). Recent studies suggest that when geopolymer binders are used instead of OPC binders, the greenhouse gas emissions can be reduced by up to 64% and even lower production costs can be anticipated ( Komkova & Habert, 2023 ; McLellan et al , 2011 ).…”

Diagonal Compression Tests on Unfired and Fired Masonry Wallettes Retrofitted with Textile-Reinforced Alkali-Activated Mortar

“…Duxson et al [31] reported a reduction of 80% through the alkali activation of a fly ash (FA) and metakaolin (MK) blend. A study led by the first author [32] reported on the production of an AAM mortar based on the activation of ferronickel slag (FNS) for which a CO 2 reduction of 70% (compared to a counterpart OPC-based mortar) was achieved. The development of novel techniques, such as TRM based on AAM, is necessary for the construction sector to reduce the dependency on OPC and the sector's CO 2 emissions; the latter range from 5 to 8% [33] of the total global emissions due to the 1.6 billion tons of cement consumed every year [34].…”