REPAIR MORTARS REINFORCED WITH DISCRETE FIBERS

Articulation of issue. Modern repair mortars for the restoration and strengthening of structures must demonstrate enhanced crack resistance, adhesion to the substrate and durability. One of the effective approaches is the use of discrete reinforcement, which involves introducing short fibers of various origins into the binding matrix, thereby providing micro-reinforcement throughout the entire volume. In addition to mineral binders, modern repair mortars contain surfactants and plasticizers that regulate hydration, structure formation, and the properties of the artificial stone. Plasticizers reduce water demand and increase structural density. Particular attention is given to systems based on aluminate, sulfate and sulfoaluminate binders, as they provide rapid strength development and the formation of a stable crystalline structure. The purpose of this article is to justify the selection of compositions for repair mortars reinforced with discrete fibers to enhance adhesion, reduce shrinkage deformations and prevent crack formation during curing. Conclusions. Studies have been conducted on the influence of the content of various types of fibers (polypropylene, steel, basalt) on the physical and mechanical characteristics and rheological behavior of the mortars. It has been shown that the introduction of 0.5–1.0 % short polypropylene fibers reduces the risk of shrinkage cracks and increases crack resistance, while steel and basalt fibers increase tensile strength in bending by up to 20–30 %. A set of experimental and statistical models of nano-modified compositions based on alumina cement and gypsum has been obtained, enabling the determination of the influence of input factors on the development of key physical and mechanical properties. The studies has established the proportion of the basic components of the composite based on 70 % alumina cement, 30 % gypsum, and the plasticizer Sika VG as follows: Sika VG = 0,10÷0,40; Alumina cement = 69,72÷69,93; Gypsum = 29,88÷29,97. According to the manufacturing technology, the number of components has been reduced to a minimum, resulting in a binder ‒ filler ‒ plasticizer system. In economic terms, depending on the customer's requirements, the consumption of alumina cement and gypsum binder can be adjusted by approximately 10 %.