Development of Inorganic Polymers for Near-zero Energy Dwellings

Alkali activation has been emerging as a sustainable technology to produce innovative construction materials. Alkali-activated materials have been extensively investigated, but different levels of scientific understanding and industrial implementation can be found among several subgroups of such materials. The most widely examined alkali-activated materials are commonly known as geopolymers. The scientific knowledge of their reaction mechanisms and structures is mature, and their market implementation fairly consolidated. Conversely, inorganic polymers (IP) is a different subgroup of alkali-activated materials since their chemistry does not exactly correspond to the definition of geopolymers. These systems are challenging but unlikely geopolymers can admit a wide range of precursors offering an opportunity to valorize low-value raw materials that include several wastes and industrial by-products. The diversity of precursors that can be used in IP production hinders the definition of production guideposts, and dedicated research is needed to define ad hoc mix designs according to the precursors' characteristics and envisioned applications. This doctoral research was focused on the multiscale development of inorganic polymers and the conceptual design of sustainable and multifunctional materials for near-zero energy-consuming buildings. Vitrified residues produced during the thermochemical conversion of refused derived fuel were taken as a representative case study of a broad group of currently underutilized industrial by-products, namely calcium-iron-rich slags. The aim of this work was to understand the fundamental processing parameters affecting the reaction mechanism involved in the formation of calcium-iron-rich IPs and their correlation with the chemical and physico-mechanical properties of the developed materials. The major technological constraints related to the use of such slags as IP precursors were examined, and the most suitable production conditions to obtain IP products with enhanced properties identified. A broad range of IP materials with engineered properties was developed and optimized. The efforts made in developing predictive models, in optimizing mixture proportions and in minimizing the shrinkage of IP binders and mortars are described. Optimized products characterized by a high dosage of residues in their composition, increased volumetric stability, excellent mechanical properties, and good residual properties after exposure to high temperatures were developed. The functionalization of IP mortars was addressed, and the effects of incorporating phase change materials in the mix design investigated. Lightweight IPs were developed using different processing routes, and their mechanical and thermal properties examined. Different IP products were used to develop multi-layer sandwich panels that were both thermal insulating and reactive to temperature fluctuations. The problematics related to their upscaling were analyzed, and the production processes optimized. Semi-industrial sandwich panels were produced to demonstrate the feasibility of the solutions proposed. The topic analyzed in this doctoral research and the insights provided are a significant contribution to the implementation of alkali-activation technology as a viable upcycling solution for industrial by-products, and particularly interesting to the construction sector in which current efforts to achieve lower environmental impacts are considerable. The use of calcium-iron-rich slags, like the ones produced in thermochemical conversion processes, in such production schemes is a plausible large-scale upcycling route that can absorb significant volumes of those residues and, by doing so, contribute to increasing the sustainability of industrial sectors in which such residues are produced.

Jaar van publicatie:2020

Toegankelijkheid:Embargoed