## 1 Introduction  
Over the last century, the temperature of the Earth's surface has increased by around 1 \({}^{\circ}\)C, sea levels have risen by about 19 cm on average globally and the concentration of CO\({}_{2}\) in the atmosphere is now the highest in the last 800,000 years. All of this is mainly a consequence of industrial activity and the waste it produces. The cement industry is among the most highly polluting industries, being the source of approximately 8-9% of the world's CO\({}_{2}\) emissions [1]. Portland cement is the most widely used cementing material worldwide, but its production involves not only the landscape pollution produced by the extraction of raw material from quarries and during the chemical manufacturing process but also the large amounts of energy consumed by the furnaces used (temperatures above 1400 \({}^{\circ}\)C). For this reason, the need arises to develop alternative materials to Portland cement to help reduce the level of emissions as well as energy consumption [2; 3; 4; 5]. An alternative line of research to Portland cement is the use of different industrial wastes from other sectors such as thermal power plants (fly ash) [6; 7], the steel industry (blast furnace slag) [8; 9] or the ceramic industry [10; 11; 12]. These wastes, after an alkaline activation process, generate new, aluminosilicate-rich, alternative materials to Portland cement called geopolymers or alkaline-activated materials. Their mechanical and durable properties can be similar or even superior to those presented by Portland cement materials [6], depending on the optimization of their formulation and manufacturingprocedure. This alkaline activation reaction occurs between aluminosilicates (present in industrial wastes) and alkaline solutions (such as sodium silicate or NaOH). However, regarding the different aluminosilicates used for alkaline activation, it is necessary to search for other materials susceptible to activation for use as active pozzolans in cementitious systems [11; 13; 14]. In this sense, wastes from the ceramic sector become important. High production in the ceramic industry generates around 50,000 t of fired waste annually. A large part of this waste is indeed reused in the manufacturing process, defending the condition of zero discharge. This reuse process requires special facilities, involving high maintenance and management costs not normally offset by reducing the consumption of raw materials. Due to this, in many cases, this waste is deposited in controlled landfills. These cooked residues are chemically inert but generate considerable environmental impact and, therefore, their study is proposed for use as alternative pozzolanic materials in the manufacturing of cement [12]. The incorporation of these residues in the manufacturing of cement could offer numerous advantages such as the reduction of clinker content, with the consequent reduction of the negative effects generated by its production; the revaluation of these ceramic residues; and, on many occasions, the improvement of the properties of the cements obtained. Some of the most important characteristics of these geopolymers are high mechanical resistance and low heats of hydration. They possess high durability to aggressive physical and chemical agents, resistance to high temperatures [15], as well as resistance to freeze-thaw cycles [16; 17; 18], among other properties. However, alkaline-activated systems have some disadvantages and not all properties are good. In this sense, it is worth highlighting the use of alkaline activators, which are obtained after very expensive and environmentally harmful industrial processes. For instance, the preparation of 1 kg of sodium silicate emits 1.5 kg of CO\({}_{2}\) into the atmosphere. Therefore, the global and total replacement of Portland cement by any of the possible alkaline-activated cements is practically impossible.