Find the masonry: the walls of historical buildings will be reinforced with a special polymer

Russia has developed a technological solution for reinforcing brick walls of historic buildings using polymer compounds. The method allows to carry out work in hard-to-reach places, to dispense with high-temperature processes and not to use a massive plaster layer to hide reinforcement elements. In addition, the technology potentially makes it possible to create openings in brick walls without steel lintels and perform power belts without large-scale dismantling work. The author of the idea, a student at St. Petersburg State Agrarian University, was inspired by the architecture of the city on the Neva River and the desire to reduce the accident rate of houses with a history. For more information, see the "Izvestia" article.

A new method of strengthening historical buildings

Brick walls of historical buildings gradually lose their strength under the influence of moisture, temperature fluctuations and other factors. During restoration, it is important not only to preserve their appearance, but also to restore their bearing capacity. Traditional reinforcement methods often require the installation of additional metal or reinforced concrete elements, increase the thickness of the structure, or noticeably change the appearance of the wall.

Ilya Rusakov, a student of the "Construction" department at the Institute of Construction, Environmental Management and Landscape Architecture of St. Petersburg State University, proposed strengthening existing brickwork by saturating it with polymer-based repair compounds.

To do this, small holes are made in the wall, into which pipes are installed — short lengths of pipe. Through them, the polymer composition enters the masonry and saturates it under atmospheric pressure. This approach differs from the traditional method, in which the repair compound is injected into the wall under pressure, which can create additional stress on the already weakened structure.

— The idea of the project came from an interest in the architecture of St. Petersburg. When I started studying, I began to pay attention not only to the beauty of historical buildings, but also to their condition. Some facilities cannot be fully used or visited due to accidents, and I was wondering if it would be possible to suggest a way to strengthen the walls that would not seriously change their appearance. After the first year, I discussed this idea with my supervisor, and gradually it turned into a full—fledged research project," Ilya Rusakov said.

During the work, the existing methods of reinforcing brick walls were analyzed. For example, steel clips can increase the strength of masonry, but after their installation, a thicker plaster layer is required. Reinforced concrete jacket increases the weight of the structure and in some cases may require additional reinforcement of the foundation. The use of external polymer tapes can also affect the appearance of the historical wall.

Prospects for a new method

The developed solution allows reinforcement to be carried out in hard-to-reach places, dispense with high-temperature processes and does not require the installation of a massive plaster layer to hide reinforcement elements. In addition, the technology potentially allows you to create openings in brick walls without the use of steel lintels and perform power belts without large-scale dismantling work.

The method may be interesting for strengthening the surface of walls. ""It should be borne in mind that polymer compounds differ in characteristics from building mixes and stone," Evgeny Alexandrov, director of the NTI Center "Digital Materials Science: New Materials and Substances" at the Bauman Moscow State Technical University, told Izvestia.

— The service life of polymers usually does not exceed 50 years: their degradation or depolymerization gradually occurs. Ceramic materials can serve for centuries. The compressive strength of concrete and brick is significantly higher than that of polymers, while the latter have higher tensile strength. Therefore, it is better not to use polymer compounds to strengthen structural elements operating under compressive stress. They are more suitable for preventing masonry from spreading and peeling off the surface layers, that is, for transverse reinforcement," the scientist said.

It is also necessary to choose compositions with good adhesion to brick and building mixes, a close coefficient of linear thermal expansion, high moisture resistance, frost resistance and resistance to cyclic temperature influences, he added.

Significant changes have taken place in restoration over the past 40 years, but the main principle of scientific restoration remains unchanged: each object is individual, said Sergey Kartashov, a restorer and member of the Union of Moscow Architects. According to him, if we compare restoration with medicine, then in the latter there are proven principles for the treatment of various diseases that are often repeated. In restoration, specialists work with damages that are rarely the same and depend on the climate, location and operating conditions of the facility. Therefore, decisions must be made individually.

— The use of the same technology, such as injection, does not always give the expected result: the deformation may continue on a different, larger scale. In addition, the Venice Charter, the International Charter for the Conservation and Restoration of Monuments and Places of Interest, states that one of the most valuable elements of an architectural monument is the material from which it was created. Therefore, before replacing one material with another, you need to think carefully," he said.

New materials must undergo thorough testing so that specialists can assess how they will behave in the long term, including in 20 years, the expert concluded. According to him, all methods should be gentle and leave the opportunity for future generations to restore the monument if they find a more effective solution.