Alkali activated materials as a sustainable material solution for waste remediation, smart construction, and energy storage applications

Abstract

Alkali activated materials (AAM) are a class of amorphous aluminosilicate solids that have attracted interest because of their facile production and unusual properties. They cure at room temperature without energy-intensive processing and can be produced from industrial byproducts, making them an environmentally friendly alternative to ceramics and cement products. AAM have been heavily studied as a green alternative to Portland cement but, to date, have seen little commercialization in North America. Two key obstacles to their industrial production are (1) the competition for raw materials with cement production and (2) the lack of high-value applications to facilitate the scale up of AAM production. This thesis addresses these challenges by proposing a new methodology to utilize bauxite residue as a raw material for high-strength AAM and identifying new applications that serve as a stepping stone to scale up AAM production. Bauxite residue is a large volume by-product of the aluminum industry that is particularly significant to the province of Quebec. In this thesis, the first obstacle to AAM production is addressed by developing a new methodology to utilize bauxite residue as a raw material for high-strength AAM. While the use of bauxite residue as a raw material is not new, the proposed methodology triples the content of bauxite residue in the AAM, up to 77%, can valorize bauxite residue in its raw state without additional modification, and achieve compressive strength over 32 MPa, exceeding the ASTM standards for load-bearing structural materials. The second obstacle to AAM production is addressed through the identification of new highvalue applications for AAM from an investigation of their unique electrical and electromechanical properties. AAM were discovered to possess a unique self-sensing property that can be leveraged to produce smart construction materials. Unlike cement, AAM exhibit self-sensing as an intrinsic material property without the need for costly self-sensing additives. This makes AAM an unparalleled solution for the field of smart construction materials. AAM with self-sensing piezoresistivity above 50% and compressive strength above 50 MPa were produced, demonstrating the possibility to tune the composition of AAM to achieve both high self-sensing and mechanical performance. An investigation of the electrical properties of AAM revealed an unprecedented dielectric behavior. AAM have not been previously considered as an alternative to dielectric ceramics, but the results demonstrate that they are among the most polarizable materials ever reported with dielectric constants as high as 109 . This presents a novel opportunity to utilize AAM as a powerful low-cost alternative for supercapacitors. These two applications provide a new avenue to scale up AAM production and take advantage of this environmentally friendly class of materials.

Date	1 Feb 2023
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Claudiane Ouellet-Plamondon (Supervisor)