# The Use of Volcanic Powder as a Cement Replacement for the Development of Sustainable Mortars
## 1 Introduction  
The great development of the construction industry in recent decades has entailed a worldwide rise in both the demand for raw materials and the production of a large quantity of construction and demolition wastes. This has produced inevitable environmental problems around the construction industry [1]. As a solution for reducing the effects of these issues, many countries have created sustainable development programs in which the use of recycled materials has a major importance [2]. Concrete is one of the most popular construction materials in the world. As a result, many studies have focused on reducing the environmental damages associated with its manufacturing. Several investigations have been based on one solution which is related to the study of the effects of substituting different concrete constituents with reused materials [3; 4; 5; 6; 7]. The high levels of CO\({}_{2}\) emissions generated by the cement industry, estimated to be 5% and 7% of the total worldwide emissions [8; 9; 10; 11] have motivated the cement industry to tackle the important challenges of reducing raw materials, energy demands, and CO\({}_{2}\) emissions. According to the study performed by [PERSON] and [PERSON] [12], within the service life of cement, the transport stage, followed by the production of fossil fuels and clinkering, were mostly responsible for the environmental impact of this industry. These processes combined were the origin of approximately 70% of equivalent CO\({}_{2}\), as well as 90% of equivalent CFC-11 (trichlorofluoromethane) gases of cement production. In light of this information, to substitute part of cement with a supplementary material derived from residues represents one of the most suitable ways to reduce the environmental negative effects of concrete [13; 14; 15; 16; 17]. This would entail a reduction of energy consumption, costs, and volume of wastes produced [18]. The research works conducted on the possibility of using volcanic powder (VP) in mortars, concretes, and cement-based materials in general, concluded that VP accomplishes the prescriptions of ASTM C618 standard regarding its use as a pozzolanic material [19]. However, the capacity of an ash or powder material for replacing Portland cement partly depends on its pozzolanic activity and, in turn, is related to the quantity of silica reactive and the amorphous phases present in the ash [20]. Generally, on the one hand, when the cement replacement percentage exceeds 10%, there are more significant losses in compressive strength, which is why the general recommendation is to use up to a maximum of 15% to 20% VP as a cement replacement, in order to limit losses in strength [21; 22]. According to [PERSON] et al. [23], this could be explained in relation to the presence in VP materials of diopside, deforsterite, and periclase that are related to phases based in magnesium, which entailed the appearance of M-S-H and other associated crystalline phases. Overall, they are considered as phases with lower strength as compared with C-S-H and C-A-S-H gels. Furthermore, high percentages of VP produce a greater porosity because of the presence of higher concentrations of CaO and Fe\({}_{2}\)O\({}_{3}\)[24], also resulting in a reduction in the strength. On the other hand, it has been indicated that using low contents of VP could be positive in terms of durability of concrete, since it produces materials more resistant to the attack of seawater [25], carbonation, and chloride ion penetration [26]. Regardingthe economic benefits of using VP in cement-based materials, they depend on the distance between the deposit of volcanic materials and the cement manufacturingfacility, the required grinding, and the reduction of the costs related to the transport of volcanic material to landfills [27].