Making a decision to perform an overhaul of a damaged reinforced concrete structure should be preceded by an analysis of the real durability of that structure after the repair in connection with the anticipated service life. One of the basic problems is the avoidance of further corrosion of concrete and steel after the repair, which depends on the degree of concrete contamination with harmful chemical factors. It is particularly important to determine the content of chloride and sulfate ions which cause corrosion. Concrete pH is equally significant because it conditions effective passivation of the reinforcement. The paper presents the basic issues related to the main chemical threats, including the main sources of their origin as well as their limit values. It emphasizes the importance of conducting the chemical tests of concrete, which should be treated as one of the methods of determining structure suitability for an overhaul, especially in the context of subsequent durability. This seems obvious to an experienced specialist, but in practice, such studies are often ignored. Those considerations are backed up with selected examples of reinforced concrete industrial structures exposed to aggressive chemicals during their operation. The text shows the correlation between their technical condition and chemical test results as well as the influence of those results on making decisions concerning effective overhauls.

In typical technical applications, steel components are usually connected by welding or with mechanical connectors. An alternative solution, typical in the aviation and automotive industry, but not widespread in engineering structures, is to join thin sheet metal using adhesives. The article presents an experimental study of adhesive joints used in overlap connections subjected to static tension. A methacrylate adhesive, selected experimentally from a range of adhesives, which combines the optimum strength and strain properties, was tested. The laboratory tests were carried out on double-lap specimens made of high-strength Domex 700 steel. On the basis of the experimental results, the behavior of the specimens and their failure mechanism, depending on the anchorage lengths used (200, 300 and 400 mm), are described. The tests confirmed the effectiveness of the selected methacrylate adhesive in a practical application. It was shown that with the appropriate anchorage length (adequate to the type of steel components and the joint geometry) between 300 and 400 mm, the capacity of the adhesive joint is higher than the capacity of a single steel component. Two types of specimen behavior were recognized: Quasi-brittle, which occurs at the anchorage length of 200 mm, and ductile, observed for 300 mm and 400 mm anchoring. In addition, thanks to the optical measurement method used, a detailed strain distribution on the specimen surface was determined. The data will be used for subsequent validation of an analytical and numerical model.

In recent years, the autoclaved aerated concrete has become as one of the most popular material used in erecting of small housings as well as multi-apartment residential buildings. Recommended construction technology involves the use of the ACC blocks arranged on thin bed joints, with the head joints left unfilled. Practice has shown that this type of construction is characterised by low crack resistance, which was also confirmed during experimental investigation [1]. One of the solutions to this problem, proposed by the staff of the Silesian University of Technology, was the superficial strengthening of such type of masonry walls. Strengthening materials tested so far (glass and carbon fibre mesh used in FRP system solutions) gave very promising results but a relatively high cost of the material itself constituted the main drawback. This prompted a further search for new and relatively inexpensive materials that would allow improving the use of the existing structures made of AAC blocks. The goal of the laboratory test results presented in this paper was to determine the influence of wall surface strengthening made of not expensive GRFP mesh (dedicated as reinforcement of thin external plastering in thermal insulation systems) on the behaviour and mechanical properties of masonry wallettes made of AAC blocks with thin joints. Three series of masonry specimens were tested: not strengthened wallettes (as reference members), walls with superficial strengthening only on one side and walls with both sides strengthened. A total of 18 specimens subjected to diagonally compressive loading were tested (6 in each series). The results turned out to be highly promising. Increasing of shear capacity of both types of superficially strengthened masonry in comparison with reference members was observed. The tests also allowed determining a positive effect of external reinforcement on the type of cracking and failure mode of such walls.