Construction and demolition waste (CDW) is the third-most abundant waste generated annually in the countries of the European Union. One of the alternatives to the use of these wastes is geopolymeric materials. Partial replacement of commonly used raw materials for the production of these materials can help reduce the number of landfills and the consumption of natural resources. In this study, the authors partially replaced metakaolin and fly ash with clay bricks and concrete debris. The research method in article is connected with analysis of microstructures and the mechanical and physical properties of the geopolymers. The results obtained show the possibility of manufacturing useful construction materials based on industrial byproducts (fly ash) and CDW. Compressive strength and flexural strength were, for samples containing metakaolin, 20.1 MPa and 5.3 MPa, respectively. Geopolymers containing fly ash displayed 19.7 MPa of compressive strength and 3.0 MPa of flexural strength. The results for both synthesized materials give them perspectives for future applications in the construction industry.

In recent years, new climate targets in EU have led to a growing demand for construction materials with a lower carbon footprint. This implies a demand for research on materials with comparable properties and reduced CO2 emission to replace those currently in use. Geopolymers belong to the group of alkali-activated aluminosilicates, whose advantages include high compressive strength and high corrosion resistance. Examples of aluminosilicate materials used to produce geopolymers are fly ash, metakaolin or volcanic tuff. Recently, there have also been papers discussing the use of diatomite as a replacement for metakaolin in geopolymer materials. The purpose of this work is to investigate the use of diatomite as a fly ash replacement in the production of foamed geopolymers. For this purpose, fly ash based geopolymer samples with different amounts of diatomite (5%, 10%, 50%) were foamed using hydrogen peroxide as a foaming agent. Then, to observe the microstructure of the produced samples, they were subjected to scanning microscope observations. Compressive strength tests according to EN 12390-3 standard were carried out to check the strength properties after 30 days of curing. In addition, the thermal conductivity coefficients of the samples were investigated to better determine their potential industrial application. The expected result is a change in strength and thermal properties with increasing diatomite content.

The main aim of this article, carried out in relation to ash-cement mortars, is to determine the effect of complex additives of polyfunctional modifiers, including, in addition to superplasticizers, air-entraining and water-retaining additives, at different values of water–cement ratios. With the use of experimental–statistical models, the complex effect on the adhesive strength of cement–ash mortars of water–cement and ash–cement ratios, as well as complex additives of polyfunctional modifiers, including air-entraining and water-retaining additives, is considered. The extreme nature of the water–cement and ash–cement ratios on the adhesive strength of ash–cement mortars are established. Their optimal values are in the ranges of 0.7–0.75 and 0.35–0.4, respectively. The addition of a naphthalene-formaldehyde superplasticizer makes it possible to increase the adhesive strength of mortars by up to 40%. A positive effect is achieved along with the addition of a superplasticizer by introducing optimal amounts of air-entraining and water-retaining additives into the mortar mixtures. Quantitative parameters of mortar compositions that positively affect adhesive strength are established. The influence on the adhesive strength of the fly ash was also investigated, as well as on the binder–sand ratio. In addition, a positive effect on the adhesive strength of modified cement–ash mortars was experimentally shown by increasing the specific surface area of fly ash by regrinding it and increasing the cement–sand ratio.