All industries produce wastes or byproducts, and if those are not properly managed, they will cause adverse effects on the environment. As the need for steel increases globally, waste from steel processing will also increase. Hazardous waste from steel processing is produced in the form of a coarse, dense aggregate, called steel slag. The aim of this paper is to present the possibility of using steel slag/blast furnace slag in the production of geopolymer concrete and to present the relevant results regarding the influence of this industrial byproduct on the mechanical properties of Geopolymer materials.

The presence of TiO2 nanoparticles in a cementitious matrix induces self-cleaning capacity in the presence of UV radiation by combining two mechanisms: surface hydrophilicity and degradation of the stain agent molecules. Experimental results indicate an increase in surface water absorption and, indirectly, in the degree of hydrophilicity, with the increase in the concentration of TiO2 nanoparticles in the matrix. Degradation of organic molecules, rhodamine B, is dependent on the duration of action and intensity of UV rays and the concentration of nanoparticles in the cementitious matrix. An addition of 3–6% TiO2 is effective and sufficient for a good self-cleaning capacity of cementitious surfaces.

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.

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.

Marble waste contains a high level of calcium, which is obtained from the cutting process in marble production. The properties of geopolymer binders are influenced not only by the amount of alkali activators, their ratio, the molarity used, and the Si and Al content of the mineral additives used in the mixture, but also by the duration of the heat treatment and the heat treatment temperature. This study aimed to produce alkali-activated geopolymer binders based on fly ash and marble dust. Alkali-activated geopolymer pastes were made both with heat treatment for 24h at 70°C and without heat treatment at (23±2) °C. Structural analysis by optical microscopy revealed, in the case of heat-treated samples, the formation of pores with an average size of 1÷1.5 mm, much larger than in the case of samples without heat treatment.