Polyurethane foam is an outstanding material for various applications. It is manufactured by propelling liquid isocyanate-polyol mixture to form foams in the presence of a blowing agent. This paper comprises an experimental study on acoustic properties improvement of rigid polyurethane closed-cell foam, by incorporating various quantities of textile waste into the matrix. In order to obtain a homogenous, easy to handle material, an optimal percent of 10-50% textile waste was used. The sound absorption coefficient of the composite materials was measured using an impedance tube. The composite materials obtained have better sound absorption properties compared to rigid polyurethane foam. The noise reduction coefficient (NRC) of the composite material with 40% textile waste and 60% rigid polyurethane foam is twice as high as the 100% rigid polyurethane material

Industrial activities in the Baia Mare, Romania area have generated strong pollution, and the impact on soil quality in the neighboring areas of the city remains unclear. The aim of the research is to investigate samples of soil from Baia Mare in order to determine the quality of the soil and also the ecological risk of the soil. This study presents among the first studies using the ecological risk assessment methodology on the soil from the Baia Mare area and aims to serve as scientific support for future studies and research. Evaluation of the soil quality state was performed by determining the physical-chemical characteristics of the soil (pH, texture, structure, and concentration of metals). Evaluation of the anthropic activity from the studied areas was conducted by determining the pollution indices: C_f; C_d, PLI, Er, and PERI. The results of this study indicate that the surface soils have very high concentrations of metals (Cd: 3.5–14.4 mg kg⁻¹; Cu: 9.4–361.5 mg kg⁻¹; Pb: 29.7–1973 mg kg⁻¹), with exceedances of the limit values established in the Romanian legislation. Results regarding the degree of contamination, the PLI pollution load index (1.3–14.9), and the PERI potential ecological risk index (733.9–4686) indicate that soils in the studied area have a very high degree of pollution.

Worldwide, it is now known that industrial by-products rich in silicon (Si) and aluminum (Al) can be transformed by alkaline activation into so-called “green concrete”, an efficient and sustainable material in the field of construction; the geopolymer material. In this work, geopolymer materials produced using fly ash and marble dust or blast furnace slag were studied to assess the influence of these substitutions on the performances of the final product. Geopolymer materials have been characterized by physico-mechanical methods, FTIR spectroscopy and microscopically. The analysis of the results indicates the reduction of the mechanical strength performance by substituting the fly ash as the raw material.

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 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 aim of this study is to analyze the effect of the addition of TiO₂ nanoparticles (NTs) on the physical and mechanical properties, as well as the microstructural changes, of cementitious composites containing partially substituted natural aggregates (NAs) with aggregates derived from the following four recycled materials: glass (RGA), brick (RGB), blast-furnace slag (GBA), and recycled textolite waste with WEEE (waste from electrical and electronic equipment) as the primary source (RTA), in line with sustainable construction practices. The research methodology included the following phases: selection and characterization of raw materials, formulation design, experimental preparation and testing of specimens using standardized methods specific to cementitious composite mortars (including determination of apparent density in the hardened state, mechanical strength in compression, flexure, and abrasion, and water absorption by capillarity), and structural analysis using specialized techniques (scanning electron microscopy (SEM) images and energy dispersive X-ray spectroscopy (EDS)). The analysis and interpretation of the results focused primarily on identifying the effects of NT addition on the composites. Results show a decrease in density resulting from replacing NAs with recycled aggregates, particularly in the case of RGB and RTA. Conversely, the introduction of TiO₂ nanoparticles resulted in a slight increase in density, ranging from 0.2% for RTA to 7.4% for samples containing NAs. Additionally, the introduction of TiO₂ contributes to improved compressive strength, especially in samples containing RTA, while flexural strength benefits from a 3–4% TiO₂ addition in all composites. The compressive strength ranged from 35.19 to 70.13 N/mm², while the flexural strength ranged from 8.4 to 10.47 N/mm². The abrasion loss varied between 2.4% and 5.71%, and the water absorption coefficient varied between 0.03 and 0.37 kg/m²m^0.5, the variations being influenced by both the nature of the aggregates and the amount of NTs added. Scanning electron microscopy (SEM) images and energy dispersive X-ray spectroscopy (EDS) analysis showed that TiO₂ nanoparticles are uniformly distributed in the cementitious composites, mainly forming CSH gel. TiO₂ nanoparticles act as nucleating agents during early hydration, as confirmed by EDS spectra after curing.