The aim of this research is to find an optimum combination of silicate admixtures and epoxy dispersion additives which would positively influence the durability and mechanical properties of concretes made of concrete recyclate. The durability of concrete is dependent on its cover layer permeability and also on the overall permeability of concrete recyclate. The cover layer permeability was evaluated by means of three methods, namely the air permeability method TPT and two methods of measuring water permeability, GWT and ISAT. Fine silicate admixtures and dispersion additives influence the air and water permeability of concrete made of concrete recyclate in different ways. The dose of 10% of microsilica or 30% of slag or fly ash decreases the air permeability of concrete. Water permeability, on the other hand, is decreased by adding a dose of 12% of pure epoxy dispersion. As regards improving the mechanical properties of concrete made of concrete recyclate, it seems to be promising to use a combination of 30% of slag admixture or 10% of microsilica admixture with 12% of epoxy dispersion additive. However, the price of admixtures and additives is relatively high. That is why additive enhanced concretes made of concrete recyclate are intended for special purposes.

The aim of this paper is to evaluate the suitability of the Torrent method of determining air permeability of concrete for an approximate assessment of damage to the surface layer of concrete caused by microcracks. The combined measurement of deformation and air permeability by means of Torrent method and of the width of microcracks on the tested concrete cubes during loading in the splitting tensile test contributed to the clarification of certain facts. The use of Torrent method seems to be more suitable in reinforced concretes where it is possible to anticipate a slower opening of cracks during the increase of load. In spite of that, the testing of these concretes is limited by the maximum dimensions of cracks, i.e. 0.075–0.1 mm in the width and 60 mm in the length. Exceeding these limit dimensions causes a massive decrease in vacuum and subsequent separation of the adhering bell of the Torrent tester.

The paper deals with the possibilities of use of glass recyclate from photovoltaic panels for concrete masonry units. It compares different recipes and its physical and mechanical properties with the focus on the compressive strength, density. It then compares the values of these recipes with the values of commonly used composite materials for masonry units without recyclates. Recycling of materials from photovoltaic panels is a highly discussed topic nowadays. The paper presents possibility for secondary use of glass from these panels in building industry, namely the substitution of aggregate in concrete with glass recyclate.

Today, concrete comprises more than 65% of the total volume of building constructions. As it undergoes degradation and buildings require refurbishment, the volume of concrete increases at disposal sites. Due to a lack of non-renewable resources and due to high prices of energies, the reuse of concrete seems to be more than desirable. It is common knowledge that in concretes made from recycled concrete, the strengths of the original concretes can hardly be achieved. The addition of dispersion additives and mineral admixtures into the freshly mixed concrete can contribute to improving the mechanical properties of concretes made from recycled concrete. Potential composite action of the recyclate, mineral admixtures and dispersion additives in increasing the compressive strength of concretes made from recycled concrete remains to be a question.

The mechanical and deformation characteristics of mass concrete are considerably improved by adding long structural fibres. This addition, however, does not always extend the durability of concrete. One of the key factors in the evaluation of durability of fibre concretes is the assessment of permeability of their surface layer using one of the non-destructive methods. In this research, three of these methods were used: two permeation methods with a gaseous medium, TORRENT and CO2 permeability method, and the British ISAT with a liquid medium, on the grounds of their simplicity of application and their possible combinability. The test results show that both TORRENT and ISAT methods can be used to assess the durability of both concrete and fibre concrete with dense aggregate. In the case of concrete containing concrete recyclate, however, the TORRENT method was not effective. Also the method of determining the permeability for CO2 was not suitable for the concrete with concrete recyclate. Even for other concretes this method was too complicated and too dependent on the marginal conditions of the measurement.