The process of recycling concrete rubble is accompanied by the formation of a large amount of fine fraction, which cannot be reused as aggregate. The results of research on the possibility of using recycled cement mortar (RCM), obtained during concrete recycling, as a cementitious supplementary material, are presented. The experimental research was carried out on the basis of two variables determining the recycling process: X 1 -temperature (range of variation 288-712 • C) and X 2 -time (range of variation 30-90 min) of thermal treatment of concrete rubble. The experiment included 10 series of new composites made with RCMs subjected to different variants of thermal treatment, and two additional control series. The best treatment parameters were determined based on the assessment of selected physical and mechanical properties of the new cement composites, as well as the analysis of characteristics and microstructure of RCM. The test results showed that proper thermal treatment of concrete rubble makes it possible to obtain a high-quality fine fraction, which has the properties of an active addition and can be used as a partial replacement for cement in mortars and concretes.

Waste mineral fibres are an alternative to current commercial reinforcements.• Mortars reinforced with mineral fibers waste minimize environmental impact.• There is a good connection between the cementitious matrix and the residues.• It is possible to replace large amount of the volume of sand used by mineral fiber waste.

No abstract

The objective of this study was to analyze the physico-mechanical properties of gypsum boards including plastic waste aggregates from cable recycling. The plastic cable waste is incorporated into the gypsum matrix without going through any type of selection and/or treatment, as it is obtained after the cable recycling process. In the experimental process, gypsum boards of different dimensions were manufactured and tested for their Young’s modulus, shock-impact resistance, flexural strength, thermal conductivity, and thermal comfort. The results obtained show a significant increase in the elasticity of the boards with plastic waste (limited cracking), compliance with the minimum value of flexural strength, and a slight improvement in the thermal conductivity coefficient (lower energy demand) and surface comfort (reduced condensation and greater adherence). Therefore, the analyzed material could provide a suitable alternative to currently marketed gypsum boards, contributing to sustainable construction not only in new constructions, but also in building renovations.

No abstract

No abstract

Experimental tests were carried out to assess the failure model of steel fiber reinforced concrete beams. Experimental research was focused on observing changes in the behavior of the tested elements depending on the amount of shear reinforcement and the fiber. Model two-span beams with a cross-section of 80x180 mm and a length of 2000 mm were tested. The beams had varied stirrup spacing. The following amounts of steel fibres in concrete were used: 78.5 kg/m3 (1.0%) i 118 kg/m3 (1.5%). Concrete beams without fibres were examined at the same time. The beams were loaded in a five-point bending test until they were destroyed. Shear or bending capacity of the element was observed. Fibre reinforced concrete beams were not destroyed rapidly, but they kept their shape consistent under load. Larger number of diagonal cracks with a smaller width were observed in fibre reinforced concrete beams. Failure of concrete beams without fibres was rapid, with a characteristic brittle cracking. Steel fibres revealed the ability to transfer significant shear stress after cracking in comparison to plain concrete.

Processing crushing concrete into coarse aggregate for the manufacturing of new concrete is one common means for achieving more environmentally friendly concrete. The use of recycled aggregate from construction and demolition waste as replacement of natural aggregate has increased in recent years in order to reduce the high consumption of natural resources by civil engineering. In the research work an experimental investigation was carried out to analyze the influence of steel fiber reinforcement on the load-strain behavior of beams made of recycled aggregate concrete. In addition, the selected properties of recycled aggregate were assessed and the strength properties of concretes were also determined. The concretes tested contained natural fine aggregate and 100 % recycled coarse aggregate. The flexural behavior was tested on model reinforced concrete beams. Apart from reinforcing steel bars, the steel fibers with 6 mm length and aspect ratio of 37,5 were used in a volume fraction of 0,52 %. The results showed that the addition of steel fiber and recycled aggregate increased the mechanical strength and modified the flexural behavior and fracture process relative to that of recycled aggregate concrete.