Assessment of durability and compatibility of injection compositions and composite materials in the restoration and strengthening of historical foundations in aggressive soil and atmospheric environments

Abstract

The article examines the durability and compatibility of injection compositions and composite materials used in the restoration and strengthening of historical foundations operating under conditions of sulfate–chloride attack, capillary rise, and cyclic freeze–thaw. Using masonry models made of authentic 19th-century brick and restored lime mortar, three injection systems are compared: lime–pozzolanic, microcement with polymer additives, and a low-viscosity epoxy composition; in addition, the performance of external reinforcement with carbon fiber strips and glass fiber meshes is evaluated. It is shown that differences in porosity, water absorption, elastic modulus, and the nature of failure at the “old material – new material” interface form fundamentally different degradation scenarios. Microcement demonstrates a high initial strength level but sensitivity to sulfate attack and a noticeable reduction in adhesion after freeze–thaw cycles, indicating a risk of damage accumulation in the contact zone. The epoxy composition is characterized by the best chemical resistance and frost resistance; however, it forms an almost impermeable matrix and, with high adhesion, initiates failure within the brick, increasing the likelihood of iatrogenic damage. The lime–pozzolanic system is inferior in strength but provides more favorable deformational and physicochemical compatibility with historical masonry, reducing stress concentration and ensuring stability under salt loading due to “reserve” porosity. The material of the article makes it possible to substantiate the choice of repair solutions based on the criterion of the composite action of the strengthened system rather than on maximum strength indicators.