# An Investigation on the Synthesis of Alkali Activated Materials from Thermally Modified Clays
## 1 Introduction  
In the coming decades, global tensions and conflicts over natural resources, social inequality, forced migration, and global economic instability will be exacerbated by rampant climate changes if profound actions are not immediately taken to modify our current development models. Global warming is among the most pressing environmental problems that should be prioritized when tackling climate change, and anthropologic greenhouse gas (GHG) emissions must be drastically reduced. GHGs are mostly driven by CO\({}_{2}\) emissions, which account for approximately 80% of the total GHG [1]. Carbon capture and storage technologies are expected to deliver massive CO\({}_{2}\) uptakes [2, 3], but these technologies still require massive capital investments and elevated operating costs that throttle their economic feasibility and prevent their worldwide spread with meaningful global impacts. Therefore, redefining our current industrial and manufacturing technologies has become urgent to reduce GHG emissions, limit the rate of climate change progression, and meet theUN Sustainable Development Goals. The importance of the built environment in this matter can be gleaned from the numbers: the construction and operation of buildings consumes approximately 36% of all energy produced worldwide, and accounts for about 39% of global CO\({}_{2}\) emissions [4]. The world's growing population will drive further urbanization needs and concomitant increases in the consumption of building materials. Steel and cement are the most significant building materials and their manufacturing jointly accounts for 12-15% of the global annual CO\({}_{2}\) emissions [5]. Cement production alone represents 20% of industrial CO\({}_{2}\) emissions [2] and global consumption patterns forecast a significant soar in cement demand until 2050 [6]. Therefore, the development of low carbon binders able of replace ordinary Portland cement (OPC) is crucial to address the growing housing needs and decouple social development and well-being from climate change. Emergent binders with environmentally favorable profiles that are being intensely investigated include, among others, belite-rich Portland and belite ye'elimite-ferrite cements [7; 8; 9; 10; 11], magnesium-based cements [7], carbonation-hardening cements [7; 12], calcined clay limestone cements [13; 14; 15; 16], geopolymers, and alkali-activated materials [17; 18; 19]. Alkali-activated materials (AAMs) are one of most promising candidates to replace OPC-based products. Initial research on AAMs have been driven by the economic benefits delivered by using industrial by-products as alternative feedstock raw materials, but AAMs have proven to offer excellent technical and environmental performances if some conditions and predicates are safeguarded in the mixture design stage (i.e., thoughtful definition of precursors and alkaline solutions) [17; 19; 20; 21; 22; 23; 24]. AAMs have also shown enhanced resistance to chemical attack and harsh environments, which can reduce the maintenance costs and recurrent environmental impacts, further increasing the body of arguments supporting AAMs as alternative green binders suitable for the construction sector. In addition, as AAMs are the product of the reaction between an alkali metal source and amorphous or semi-vitreous aluminosilicate precursors, virtually any powdered material with sufficient alumina and silica in a reactive form--meaning sufficiently soluble in alkaline environments--can be used as a precursor, if adequate synthesis conditions are provided. This allows for resilient industrial manufacturing processes and extreme design versatility that allows for the use of locally available resources to address the specific needs and opportunities of regional markets while by-passing the external constraints of global value chains.