Unique antibacterial properties of silver have been known since the time of Egyptian pharaohs. With the discovery of antibiotics at the beginning of the twentieth century, silver is mostly pushed out from conventional medicine. However, with the excessive use of antibiotics, antibiotic-resistant super bacteria have appeared. Therefore, there is an increased interest in studying the antibacterial effects of colloidal silver. In this paper, the influence of various concentrations of silver nitrate on formation of colloidal silver particles in the solution was investigated. Colloidal silver was prepared by a chemical precipitation method using sodium borohydride as a reducing agent. As influence factors, color of the solution, Tyndall effect, UV/Vis absorption, and nanoparticle size estimated by PWHM (Peak Width at Half Maximum) and Mie methods were used. By increasing the silver concentration, color of the solution ranged from light yellow to dark yellow. All solutions showed Tyndall's effect equally. By the UV/Vis analysis it was found that the solutions absorbed radiation in the wavelength range 390-402 nm, and the intensity increased with increasing silver nitrate concentrations. By the PWHM and Mie methods silver nanoparticle sizes were estimated in the range 12-20 nm.

This study investigates the effects of incorporating recycled concrete powder (RCP) as a supplementary cementitious material in Portland cement composites at replacement levels of 5–30% by weight. A comprehensive characterization using isothermal calorimetry, electrical conductivity measurements, thermogravimetric analysis, FT-IR spectroscopy, and scanning electron microscopy revealed that RCP modified the hydration behavior and microstructural development. The results showed a linear 16.5% reduction in the total heat of hydration (from 145.38 to 121.44 J/g) at 30% RCP content, accompanied by a 26.5% decrease in peak electrical conductivity (19.16 to 14.08 mS/cm) and delayed reaction kinetics. Thermal analysis demonstrated an increased stability of hydration products, with portlandite decomposition temperatures rising by up to 10.8 °C. Microstructural observations confirmed the formation of denser but more amorphous C–S–H phases alongside increased interfacial porosity at higher RCP contents. The study provides quantitative evidence of RCP’s dual functionality as both an inert filler and a nucleation agent, identifying an optimal 20–25% replacement range that balances performance and sustainability. These findings advance the understanding of construction waste utilization in cementitious materials and provide practical solutions for developing more sustainable building composites while addressing circular economy objectives in the construction sector.

This review synthesizes recent advances in the characterization of eco-friendly cement composites, focusing on hydration kinetics, microstructural evolution, and mechanical durability. Advanced techniques—from isothermal calorimetry to nanoindentation—enable decoding of reaction pathways, mix optimization, and long-term performance prediction. The analysis covers supplementary cementitious materials (fly ash, slag, silica fume), geopolymers, bio-based additives (SNSs, biochar, CNCs, lignosulfonates), and microbially induced calcite precipitation (MICP). For each category, key mechanisms are identified, property effects quantified, and microstructural correlations established. SCMs achieve pore refinement and enhanced durability through long-term pozzolanic reactions. Geopolymers exhibit exceptional thermal stability (800–1000 °C) and acid resistance. Fly ash-based geopolymers exhibit chloride diffusion coefficients 1–2 orders of magnitude lower than ordinary Portland cement (OPC), though slag-based systems show more moderate improvements due to their different pore structure and higher calcium content. Bio-based additives enable accelerated hydration (SNSs), internal curing and CO₂ sequestration (biochar), pore refinement (CNCs), workability enhancement (lignosulfonates), and autonomous crack healing (MICP). Multi-scale characterization is essential for establishing robust structure–property relationships. The review concludes that properly optimized eco-friendly cement composites offer viable pathways toward sustainable construction with reduced carbon footprint, enhanced durability, and extended service life. This review is novel in its systematic comparison of hydration kinetics, microstructural evolution, and mechanical performance across three distinct classes of eco-friendly additives (SCMs, geopolymers, and bio-based materials), with particular emphasis on the complementarity of advanced characterization techniques—an aspect that has received limited attention in previous reviews.

Study was conducted on the electrochemical method of preparing colloidal silver at low DC voltage. A natural stabilizer was used as a carob bean gum from the carob bean. Using a UV-Vis spectrophotometer and a transmission electron microscope (TEM), colloidal silver (silver nanoparticles) was characterized. It is possible to produce colloidal silver of satisfactory quality by means of this electrochemical method. Silver nanoparticles have exhibited surface plasmon resonance as determined by UV-vis analysis. Based on the TEM analysis, the silver nanoparticles appear to be spherical except in sample E1, where they appear rod-shaped and micrometer-sized. Other three samples had particle sizes ranging from 23–52 nm. In a qualitative analysis of colloidal silver solutions, two types of antibacterial activity were observed. At all dilutions, some colloidal solutions showed better antibacterial activity against gram-positive bacteria (S. aureus, S. pyogenes, E. faecalis) while others displayed better antibacterial activity against gram-negative bacteria (S. enteridis, P. aeruginosa, E. coli).

This article discusses construction waste and its management in the territory of Croatia. In order to better understand the concept of waste, the first part of this paper discusses its origin, characteristics, and categorisation. In addition, it mentions special categories of waste defined within Croatian borders. All members of the European Union are encouraged to adopt a circular economy approach to manage these various types of waste. Furthermore, the article emphasises the necessity to construct legal landfills in addition to building management centres, recycling yards, and transfer stations, in order to reduce the formation of wild landfills, which result from irresponsible waste disposal. The second part of the article provides a detailed description of construction and demolition waste. In addition to the types of occurrences and the associated degree of hazard, a categorisation system is used. This system includes records and key numbers, and allows finding the appropriate species in the database with the corresponding key number. Modern technology has made it possible to recycle all types of waste, including construction waste, into secondary raw materials. Proper management is essential to achieve this goal. The first step involves prevention, diversion or conversion of waste into a resource. When these options are not possible, one of the recovery processes should be employed. Managing Construction Waste also provides a comprehensive explanation of recycling, which is given significant attention. The article concludes with an overview of the Republic of Croatia’s system for managing construction waste, which lags behind more developed countries, as well as offers examples of best practices and possible improvements.