Starting from the context of the principles of Sustainable Development and Circular Economy concepts, the paper presents a synthesis of research in the field of the development of materials of interest, such as cementitious composites or alkali-activated geopolymers. Based on the reviewed literature, the influence of compositional or technological factors on the physical-mechanical performance, self-healing capacity and biocidal capacity obtained was analyzed. The inclusion of TiO₂ nanoparticles in the matrix increase the performances of cementitious composites, producing a self-cleaning capacity and an anti-microbial biocidal mechanism. As an alternative, the self-cleaning capacity can be achieved through geopolymerization, which provides a similar biocidal mechanism. The results of the research carried out indicate the real and growing interest for the development of these materials but also the existence of some elements still controversial or insufficiently analyzed, therefore concluding the need for further research in these areas. The scientific contribution of this study consists of bringing together two apparently distinct research directions in order to identify convergent points, to create a favorable framework for the development of an area of research little addressed so far, namely, the development of innovative building materials by combining improved performance with the possibility of reducing environmental impact, awareness and implementation of the concept of a Circular Economy.

The use of waste from industrial activities is of particular importance for environmental protection. Fly ash has a high potential in the production of construction materials. In the present study, the use of fly ash in the production of geopolymer paste and the effect of Fe₂O₃, MgO and molarity of NaOH solution on the mechanical strength of geopolymer paste are presented. Samples resulting from the heat treatment of the geopolymer paste were subjected to mechanical tests and SEM, EDS and XRD analyses. Samples were obtained using 6 molar and 8 molar NaOH solution with and without the addition of Fe₂O₃ and MgO. Samples obtained using a 6 molar NaOH solution where Fe₂O₃ and MgO were added had higher mechanical strengths compared to the other samples.

The durability of steel reinforcement in geopolymer composites is significantly influenced by the chemical characteristics of the alkaline medium in which they are embedded. This research offers detailed insights into the corrosion kinetics and mechanisms of geopolymers derived from various fly ash and alkaline activator formulations, considering their inherent microstructural and chemical heterogeneity. This study investigates the effect of the molarity of sodium hydroxide (NaOH) solution and the ratio of sodium silicate to sodium hydroxide (Na₂SiO₃/NaOH) on the corrosion behavior of steel reinforcement in geopolymer matrix under the action of chloride ions. Corrosion of steel reinforcement embedded in geopolymer binder prepared by alkaline activation of fly ash with alkaline activator prepared with different Na₂SiO₃/NaOH ratios (1:1, 1:2, 2:1) and different molar concentrations of NaOH solution (6 M, 8 M and 10 M) was analyzed in terms of process kinetics using Open Circuit Potential (OCP) and Linear Polarization (LP) and mechanism by Electrochemical Impedance Spectroscopy (EIS). The study demonstrates that a Na₂SiO₃:NaOH ratio of 1:2 and an 8 M NaOH solution yield the most favorable combination of physical and mechanical properties and corrosion resistance, confirmed by the highest apparent density, lowest water absorption, and significantly reduced corrosion current densities (as low as 0.72 μA/cm²), as well as highlighting porosity and pH as key factors influencing steel protection in geopolymer matrices.

The long-term durability and structural integrity of modern buildings, which are inherently reliant on reinforced concrete, are governed by the rate of corrosion of embedded steel reinforcement. Corrosion kinetics, therefore, is not merely an academic exercise, but rather a critical foundation for predicting and extending a structure’s life span, mitigating safety risks, and ensuring the sustainability of the built environment against a host of environmental and chemical degradation factors. The present study conducts a comparative analysis of the short-term corrosion initiation behavior of steel reinforcement embedded in three distinct types of geopolymer binders, a cementitious paste, and a cementitious composite with natural aggregates. Electrochemical techniques, such as Open Circuit Potential (OCP) and linear polarization tests were used to characterize the behavior of the steel reinforcement embedded in the 4 types of samples. Additionally, these samples containing the reinforcement were further characterized using advanced microstructural techniques, specifically porosimetry, Nuclear Magnetic Resonance (NMR), and Scanning Electron Microscopy (SEM).

Thermoelectric generators can operate at small temperature differences providing enough electricity for low-power electronics, sensors in distribution networks, and biomedical devices. The article presents the obtaining of a thermoelectric generator and its electrical characteristics using usual substances. Experimental research was carried out using a mixture consisting of several substances (copper sulfate, calcium hydroxide, silicon dioxide, and sodium silicate) in different proportions. The mixture was inserted between two plates, one graphite (hot plate) and the other aluminum (cold plate), thus obtaining a thermoelectric generator. Electrical voltage, output current, and electrical power were measured at different temperatures.

The aim of this paper was to examine the effects of adding TiO₂ nanoparticles to cementitious compositions and partially substituting natural aggregates with recycled aggregates consisting of glass, brick, slag, or textolite, and to examine the material’s ability to resist corrosion under the action of chloride ions existent in the environment that attack the steel reinforcement. The results show that the changes in the cementitious composite when it comes to the composition and microstructure influence the formation of the oxide passivating layer of the reinforcement. The addition of TiO₂ nanoparticles and recycled aggregates impacts the kinetics and corrosion mechanism of the reinforcement. An addition of 3% TiO₂ was found to be optimal for reinforcement protection. Electrochemical impedance spectroscopy confirmed the results obtained by open-circuit potential and linear polarization tests. The classification of favorable conditions indicates that compositions with recycled aggregates and 3% TiO₂ are the most effective, with compositions in which the natural aggregates were partially substituted with slag being the most effective.