This paper presents a study of the electrical and mechanical behavior of several continuous carbon fibers epoxy composites for both strengthening and monitoring of structures. In these composites, the arrangement of fibers was deliberately diversified to test and understand the ability of the composites for self-sensing low strains. Composites with different arrangements of fibers and textile weaves, mainly unidirectional continuous carbon reinforced composites, were tested at the dynamometer. A two-probe method was considered to measure the relative electrical resistance of these composites during loading. The measured relative electrical resistance includes volume and contact electrical resistances. For all tested specimens, it increases with an increase in tensile strain, at low strain values. This is explained by the improved alignment of fibers and resulting reduction of the number of possible contacts between fibers during loading, increasing as a consequence the contact electrical resistance of the composite. Laboratory tests on strengthening of structural elements were also performed, making hand-made composites by the “wet process”, which is commonly used in civil engineering for the strengthening of all types of structures in-situ. Results show that the woven epoxy composite, used for strengthening of concrete elements is also able to sense low deformations, below 1%. Moreover, results clearly show that this textile sensor also improves the mechanical work of the strengthened structural elements, increasing their bearing capacity. Finally, the set of obtained results supports the concept of a textile fabric capable of both structural upgrade and self-monitoring of structures, especially large structures of difficult access and needing constant, sometimes very expensive, health monitoring.

The foaming of geopolymers lowers their density, thus opening up new environmental benefits, including acoustic and thermal insulation. At the same time, foaming disturbs the homogeneity of the material, which worsens the strength parameters, and particularly those related to tension, which can be improved by introducing reinforcement. This paper presents the results of research on foamed geopolymers reinforced with glass fiber meshes, a type of reinforcement that provides an adequate bond. The samples tested here were based on three types of coal fly ash, and were foamed with varying doses of hydrogen peroxide. Samples were cured at 40 °C and were tested after 28 days of maturing at ambient temperature. The strength parameters of the synthesized geopolymers were determined via laboratory testing, and were used to evaluate load-bearing capacity models of the tested samples reinforced with glass fiber mesh. The results showed the importance of the type of ash on the strength properties and efficiency of reinforcement. At the same time, a slight deterioration in the glass fibers was noticed; this was caused by the presence of sodium hydroxide solution, which was used as an activator.

The utilization of volcanic powders, specifically basalt powders (BPs), as filler materials in the synthesis of geopolymers has gained significant attention in recent years. This study aims to investigate the potential application of basalt powders (BPs) in the synthesis process of geopolymers to develop more environmentally friendly structural materials. A comparative analysis was conducted, beginning with reference samples—geopolymers formulated exclusively from metakaolin and alkali-activated materials incorporating various types of BPs supplemented with differing amounts of metakaolin. The synthesis process was characterized by evaluating parameters such as volume density, compressive strength, and flexural strength. The most advantageous results, in addition to those achieved with metakaolin (MK), were observed for samples with a material ratio of 1:2:10 (NaOH: Na₂SiO₃:BP + MK) and a curing temperature of 20 °C, irrespective of the type of BP and the quantity of MK included. Furthermore, the inclusion of basalt resulted in a significant cost reduction of up to 80%, enhancing competitiveness against traditional Portland cement.

This manuscript attempts to classify typical errors occurring during the design, production, and use of prefabricated and prestressed concrete girders and slabs manufactured in Poland for industrial buildings since the 1950s. Although the cases discussed concern Poland, most of them have a universal character, and as such are also found in other countries. The defects and errors are illustrated with examples and the causes of their occurrence are also discussed. A method of classifying flaws based on the period of their occurrence was proposed. Most of the examples discussed were encountered by the authors during their professional work. In most of the presented cases, repair was possible, enabling further safe operation. This paper shows how important it is to periodically check the technical condition of prestressed structures and how common and at the same time trivial mistakes may be made by designers and contractors of this type of structure, despite the experience of over 70 years of their mass use. The quality of modern prestressed structures is undoubtedly higher. Using the experience of previous generations, designers and contractors abandoned the less durable post-tensioned concrete lattice girders. Errors, if they appear, are most often at the stage of implementing new products or are the result of poor workmanship or disregard for unfavorable weather conditions.