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The global population growth and the demand for agricultural food products have generated a significant volume of agro-industrial by-products which, inadequately managed, affect the quality of the environment. The construction industry, a large consumer of raw materials and energy, constitutes an important source of waste and greenhouse gas emissions. In this context, the circular economy provides the right framework for the valorization of such natural materials, allowing us to obtain innovative sustainable building materials. The paper presents experimental research that led to the development of twelve plasters incorporating rice husks that were characterized by means of thickness (2.71–6.26 mm, when applied on concrete, and 4.20–10.29 mm, when applied on plasterboards), adhesion to the concrete surface (0.18–0.65 N/mm2), thermal conductivity (0.072–0.083 W/m·K), and impact on indoor air quality, in terms of total volatile organic compounds (TVOCs) emissions (3272–9470 µg/m3). The determined levels of the emissions suggest the possibility that by extending the monitoring for at least seven days after application, the information is more relevant. The findings confirmed that using the rice husks for the obtaining of such plasters represents a possible direction of valorization in construction; additional research is necessary for a more precise delineation of the characteristics of these products.

Geopolymer materials obtained through the alkaline activation of fly ash represent a promising alternative for reducing the environmental impact of the construction sector, which is currently dominated by cement use. This study aimed to develop self-cleaning geopolymer composites by incorporating TiO2 nanoparticles. Specimens containing 1%, 3%, and 4% TiO2 were prepared using alkaline solutions based on Na2SiO3 and NaOH (6 M or 8 M), at mass ratios of 1:1 and 2:1. The results indicate that the three analyzed factors—the NaOH solution concentration, the activator ratio, and the nanoparticle dosage—significantly influence density, mechanical strength, and water absorption. Increasing the NaOH concentration to 8 M led to slight densification, improved flexural and compressive strength, and reduced water absorption. Modifying the Na2SiO3:NaOH ratio produced similar densification effects but resulted in reductions in mechanical strengths. The addition of 1–3% TiO2 increased density and mechanical performance while reducing water absorption, whereas 4% TiO2 content had the opposite effect. Self-cleaning capacity was confirmed by up to ~90% degradation of Rhodamine B after five UV–artificial rain–drying cycles, compared to only 27.3% degradation for the control samples.

Currently, the need to ensure adequate quality of air inside the living space but also the thermal efficiency of buildings is pressing. This paper presents the capacity of sheep wool heat-insulating mattresses to simultaneously provide these needs, cumulatively analyzing efficiency indicators for thermal insulation and indicators of improving air quality. Thus, the values obtained for the coefficient of thermal conductivity, and its resistance to heat transfer, demonstrate the suitability of their use for thermal insulation. The results of the permeability to water vapor characteristics on the sorption/desorption of water, air, demonstrate the ability to control the humidity of the indoor air and the results on the reduction of the concentration of formaldehyde, demonstrating their contribution to the growth of the quality of the air, and to reduce the risk of disease in the population.

Soil contamination by heavy metals poses serious risks to human health and the environment. This study investigates the removal of Pb, Cu, Zn, Cd, and Cr from heavily contaminated slightly acidic to neutral soil (pH 6.5) using organic washing agents (humus, malic acid, and gluconic acid) at concentrations of 1% and 3% and a solid-to-liquid ratio (S/L) of 1:8. The results reveal that metal mobilization depends strongly on the type and concentration of the extraction agent, the target metal, and soil properties. Cd was highly mobilized, reaching more than 90% with 3% gluconic acid, whereas Cu and Pb remained largely immobile (<3%), and Cr (40–78%) and Zn (8–26%) showed intermediate extraction. This study establishes a clear hierarchy of metal mobility (Cd > Cr > Zn > Cu ≈ Pb) and demonstrates that metal speciation, soil chemistry, pH, and S/L ratio critically govern extraction efficiency. These findings provide mechanistic insights into metal–ligand interactions and practical guidance for optimizing soil remediation strategies using organic acids.

This paper studies the sustainable integration of vernacular construction techniques and natural materials in the context of sustainable development, using Danube Delta UNESCO World Heritage site as case study. Through a comprehensive literature review, this research examines the potential of clay-based composites reinforced with plant fibres such as reed, bulrush, and hemp as environmentally responsible building materials. The methodology, based on a narrative literature review, combines bibliometric analysis with a case study approach to evaluate scientific interest in vernacular construction and to identify locally available natural resources. Results reveal increasing academic attention to sustainable vernacular architecture, highlighting clay-based composite’s favourable hygrothermal properties and the remarkable thermal insulation capabilities of vegetable fibres. The case study shows that most Danube Delta’s natural construction materials—particularly the world’s largest continuous reed vegetation—remain underutilized. The research concludes that revitalizing traditional construction methods, by integrating modern technological innovations, presents significant potential for sustainable rural development, preserving cultural heritage, enhancing regional identity, and reducing environmental impact in construction while supporting local economic growth through culturally authentic tourism.

Sustainable investments in construction are essential for the development of communities and for reducing environmental impacts. This study analyzes two scenarios: rehabilitation of an existing building and construction of a new NZEB-compliant building, based on a life cycle cost–benefit analysis. The results show that both scenarios generate negative Net Present Values (NPVs) due to the social nature of the project, but the new NZEB building presents superior performance (NPV: USD –2.61 million vs. USD –3.05 million for rehabilitation) and lower operational costs (USD 1.49 million vs. USD 1.92 million over 30 years). Key financial indicators (IRR, CBR), sensitivity analysis, and discount rate variation support the conclusion that the NZEB scenario ensures greater economic resilience. This study highlights the relevance of extended LCCBA in guiding sustainable investment decisions in social infrastructure.

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).

Soil contamination by heavy metals is a significant sustainability and ecological issue, impacting on the health of ecosystems and groundwater. This study assessed the efficacy of malic acid as a biodegradable and environmentally benign agent for the remediation of soils contaminated with cadmium, chromium, copper, and zinc. Two soils with contrasting textures were treated with a 10% malic acid solution at solid/liquid ratios of 1:5 and 1:10 for contact times of 2, 4, 6, and 8 h. The extraction efficiency varied depending on metal type, soil texture, and washing conditions. Cadmium removal ranged from 26% to 55%, zinc removal ranged from 10% to 25%, while copper showed variable extraction (5–45%) depending on initial soil concentration. Chromium exhibited the highest removal efficiency (30–90%), quantified as total chromium; however, the absence of speciation analysis (Cr(III)/Cr(VI)) represents a key limitation and may affect the interpretation of the removal performance. FTIR and UV–Vis analyses confirmed the formation of metal–carboxylate complexes and changes in soil functional groups during the washing process. In addition, significant mobilization of nitrogen and potassium was observed, whereas phosphorus remained relatively stable. The results highlight the influence of soil texture and multi-metal interactions on malic acid washing efficiency and provide a laboratory-scale environmental assessment of malic acid as a sustainable remediation alternative for soil remediation, while emphasizing the need for further evaluation regarding chromium speciation and post-treatment soil quality and sustainability impacts.

The urgent need for sustainable construction that corresponds to the three pillars of sustainable development is obvious and continuously requires innovative solutions. Cementitious composites with TiO2 nanoparticles (NT) addition show potential due to their improved durability, physico–mechanical characteristics, and self-cleaning capacity. This study aimed to evaluate the influence of NT on cementitious composites by comparing those with 2%–5% nanoparticles with a similar control sample without nanoparticles, as well as an analysis of cost growth. The experimental results showed an increase in bulk density of the material (4.7%–7.4%), reduction in large pore sizes by min. 12.5%, together with an increase in cumulative volume and cumulative specific surface area of small pore sizes, indicating densification of the material, also supported by SEM, EDS, and XRD analyses indicating acceleration of cement hydration processes with formation of specific products. The changes at microstructural level support the experimental results obtained at macrostructural level, i.e., modest but existent increases in flexural strength (0.6%–7.9%) and compressive strength (0.2%–2.6%) or more significant improvements in abrasion resistance (8.2%–58%) and reduction in water absorption coefficient (37.5%–81.3%). Following the cost–benefit analysis, it was concluded that, for the example case considered of a pedestrian pavement with a surface area of 100 m2, using 100 mm thick slabs, if these slabs were to be made with two layers, the lower layer made of cementitious composite as a reference and the upper layer with a thickness of 10 mm made of cementitious composite with 3% NT or 4% NT, the increase in cost would be acceptable, representing less than 15% compared to the cost for the exclusive use of cementitious composite without NT.

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.