The technology of crack repair by polymer composition

Introduction. During the inspection of buildings and structures and development of design documentation for restoration works it was found that there is a need to provide recommendations or to develop solutions for repair work. These repair works either are not regulated by standards or may be technically or economically inefficient. Problem Statement. The most common defect of the tension zone in reinforced concrete beams, floor slabs or roof slabs are cracks. Injection technology is normally used to repair it. However, in case of large number of small cracks, this technology is time consuming. Purpose. Development of a new technology for repairing the tension zone of reinforced concrete beams, floor slabs or roof slabs with a large number of small cracks. This will ensure maximum filling of cracks with polymer compositions with their subsequent bonding. Materials and methods. A number of factors that may affect the technology of filling cracks with polymer compositions have been identified from the analysis of scientific and technical literature. A special device ‘tray’ was produced for experimental research. It was attached to the lower zone by a system of ties or props. A repair mix to fill the cracks was fed into the tray under pressure. By means of changing the experiment conditions the strengthening level of previously destroyed samples were set. Results. As a result, it was found that the maximum filling of cracks with the polymer composition is achieved within the 5-10 minutes of repair mix supply at a pressure in the system in the range of 0.5-0.6 atmospheres (atm). The maximum strengthening of the repaired structures under the re-applied destructive force was achieved at the conditions of repair work with a structural temperature of 20 ± 2 оС and dry state of the structure. Conclusions. The technology of repair with polymer compositions of the cracks located on the lower surface of horizontal reinforced concrete structures has been developed. It was established that in the presence of small cracks on the structure (the width is up to 0.2 mm) the developed technology is most effective, in case of widths from 0.3 to 0.8 mm it is advisable to use injection technology whereas for widths larger than 0.8 mm the hybrid technology should be applied.