The physical, mechanical and rheological properties of self-compacting concretes enable their application in the construction of bridges which are structures particularly vulnerable to the processes of carbonation and cyclic freezing and thawing. The technology of self-compacting concrete requires an increase in high powder content in the concrete mix, which is obtained by the application of mineral additives. The paper presents test results of the physical and mechanical properties of self-compacting concrete with cement with mineral additives and of the microstructure of its surface layer. The objective of the tests was to evaluate the influence of mineral additives (limestone powder, siliceous fly ash and blast-furnace slag) on the durability of the surface layer of self-compacting concrete subjected to accelerated carbonation and the freeze-thaw process in the presence of de-icing salts. The microstructure of the surface layer of the carbonated concrete was less compact, which was confirmed by the increased surface water absorption and water penetration in the layer in comparison with the non-carbonated concrete. Moreover, carbonated concrete exhibited more significant surface scaling when compared to non-carbonated concrete.

The article concerns the assessment of technical condition of the precast loggia wall in a large panel building after 25 years of use as well as the cause of its damage. As a result of the study, cracks and losses of the concrete cover were found. Corrosion products were visible on exposed reinforcing rods. The reinforcement distribution and concrete cover thickness in loggia wall were estimated using a rebar detector. The corrosion assessment of reinforcement was performed using a semi non-destructive galvanostatic pulse method that allows the location of areas of corrosion and estimate the reinforcement corrosion activity. The phase composition of the concrete cover was analyzed. The test results showed an insufficient thickness of the concrete cover as the main cause of loggia wall damage. The research indicated that manufacturing errors made in the prefabrication plants affect the technical condition of precast elements and may lead to the damage of the structure well before the expected of its service life. In the case of manufacturing errors causing the implementation of an element with a concrete cover that does not meet the standard requirements for thickness and tightness, it is recommended to use protective coatings to increase the element’s durability to the designed level.

The concrete cover has significant impact on the intensity of reinforcement corrosion process in reinforced concrete elements. Depending on the type of corrosion risk different types of cement are recommended for concrete. In conditions of chloride corrosion, due to, for example, the use of de-icing agents in winter, it is recommended to use concrete with cement containing granulated blast-furnace slag. The risk of chloride corrosion due to the use of de-icing agents is often additionally associated with the frost and repeated freezing and thawing actions of structural elements. The liquid freezing in the pores of concrete increases its volume, which causes the increase of internal stresses and leads to cracks in the concrete cover increasing the diffusion of chlorides. In order to reduce this phenomenon the introduction of air-entraining admixture is beneficial. The paper presents the experimental results that allow to determinate the effect of the air-entraining admixture addition on the intensity of reinforcement corrosion in concrete with blast-furnace slag cement. The tests were carried out on two groups of reinforced concrete specimens subjected to freezing and thawing cycles in 3% NaCl solution. One group of specimens was prepared with the airentraining admixture addition and the other without it. The electrochemical tests of the reinforcement corrosion activity, based on the measurements of the corrosion current density were curried. The phase composition by X-ray diffraction and microstructure of concrete under the scanning electron microscope (SEM) coupled with the X-ray microanalyser (EDS) were examined. The results allowed to comprehensively assess the effect of airentrained concrete with blast-furnace slag cement on the degree of reinforcement corrosion risk in concrete caused by the simultaneous action of chlorides and frost.

Heritage building structures in many situations contribute unique value to national cultural heritage. In engineering practice, monitoring of historic structures includes visual assessment. This article assesses the condition of the concrete in one of the most recognizable buildings in Łódź, the former German Reformed Gymnasium, located at Tadeusza Kościuszki Avenue. The paper reports a visual assessment of the structure and the degree of technical wear affecting selected structural components of the building. A historical analysis of the building’s state of preservation, characterization of the structural system, and an assessment of the condition of the floor-slab concrete were carried out. The state of preservation of the eastern and southern facades of the building was found to be satisfactory, while on the western side (with the courtyard) the facade is in a poor state of preservation. Tests were also conducted out on concrete samples taken from individual ceilings. The concrete cores were tested for compressive strength, water absorption, density, porosity, and carbonation depth. Corrosion processes including the degree of carbonization and the phase composition of the concrete were identified by X-ray diffraction. The results are indicative of the high quality of the concrete produced more than 100 years ago.

The composition of the binder in cement composites influences the partial or complete restoration of the material's properties during the self-healing process. The subject of the research was the influence of the binder composition on the ability to fill cracks in cement composites. The aim of the research was to assess the effectiveness of reducing scratches during autogenous self-healing of cement mortars with a binder containing metahalloysite and calcium sulphate-aluminate cement. The results of the conducted tests showed that the partial replacement of cement with a calcium-sulfate-aluminate binder and metahalloysite influenced the growth of cracks in the designed cement mortars

The paper describes a program of experimental and numerical tests aimed at determining the mechanical properties of beams made of laminated timber (BSH) and laminated veneer lumber (LVL) reinforced with pre-stressed bars made of basalt, glass, natural and steel fibers, basalt mats with roving and composite, polyethylene and natural yarn. The paper presents various types of reinforcements, the purpose of which was to obtain higher load-bearing capacity and stiffness in bending with shear than for unreinforced beams. The effectiveness of different reinforcement schemes was compared for seventeen beams subjected to experimental tests on a test stand, the modes of destruction were described, as well as mechanical properties, deformations and deflections for reinforced and unreinforced beams under multiply variable and long-term loading. Based on the experimental studies, a significant increase in the load-bearing capacity and stiffness of the reinforced beams subjected to simultaneous bending and shear was confirmed, and it was indicated that the reinforcements by pre-stressed bars (steel, with polymer reinforcement or natural fibers) and composite mats eliminated local defects and discontinuities in the wood, without affecting the quality and strength of the FRP-wood connection. The numerical results of the analysis of the beam models using the finite element method showed compliance with the experimental studies in terms of deflections, linear and angular strains for the reinforced and unreinforced beams