Cementitious materials in the fresh state are commonly regarded as viscoplastic. That is, below a given yield stress, they exhibit solid-like behavior, whereas above this threshold, they behave as fluids. In this context, the shear strength of such materials has traditionally been analyzed from a rheological standpoint, considering them as fluids and using time as the primary state variable. From a structural perspective, however, relatively few studies have treated the material as a solid. With the advent of 3D printing technology, this trend has persisted. Within this framework, the present research aims to evaluate the shear strength of a structural mortar for 3D printing in its solid-like regime, by applying the Mohr–Coulomb failure criterion. Furthermore, in a novel approach, the degree of hydration of Portland cement is proposed as a state variable to replace time, enabling a more comprehensive and objective description of the material’s mechanical evolution. Thus, addressing this gap in the state of the art, a chemo-mechanical coupling is developed. To obtain the necessary data, direct shear, uniaxial compression, and isothermal calorimetry tests are performed. The results indicate that the friction angle remains constant, at approximately 33°, and that cohesion, the parameter governing strength gain, exhibits the same linear rate of increase with hydration in both mechanical tests, indicating an intrinsic relationship within the material.

Objective: The aim of this research is to assess the feasibility of incorporating processed COVID-19 masks into Compressed Earth Blocks (CEBs), with the goal of providing a sustainable disposal solution for these materials. Theoretical Framework: This section presents the concepts of soil-cement mixtures and polypropylene reinforcement, providing a solid foundation for understanding the context of the research. Method: The experimental methodology involved processing polypropylene masks and manufacturing CEBs. The compressive strength of the CEBs produced with and without masks was tested. Results and Discussion: The masks were processed using thermal and mechanical energy, resulting in fragments that were compatible with granular particles. Furthermore, the compressive strength of the CEBs was not significantly affected. Research Implications: The practical implications of this research are related to the environmentally correct disposal of these masks, contributing to various Sustainable Development Goals. Originality/Value: The use of processed COVID-19 masks in compressed earth blocks is novel and promising. From a technical perspective, it is noteworthy that there was no loss of compressive strength. From an environmental perspective, the processed masks were incorporated into a construction material widely used in various types of construction.