Fiber concrete

Classical concrete consists of three components: water, cement, filler (sand and crushed stone). Composite fiber-reinforced concrete is made from the same three components (they are called a concrete matrix) and a reinforcing additive - fibers. These are narrow short ribbons or fibers made of polymers, metals or composite materials. With the help of fiber, dispersed reinforcement of the concrete matrix is performed. Fibers or tapes are distributed over the entire volume of the monolith or product (in all planes), increasing the strength characteristics of the matrix. The introduction of micro-reinforcement into fiber-reinforced concrete takes place at the construction site or at the factory of concrete structures. From the point of view of strength, the latter option looks preferable, since factory technologies guarantee an even distribution of the fiber throughout the entire volume of the matrix.

Composite mortars have been used since ancient times. Chopped straw was added to the raw brick burned in the sun, and horsehair was added to the bonding solution. The first attempts to create fiber-reinforced concrete close to modern ones have been made since the beginning of the 20th century, when asbestos fibers were added to the classic solution. By the middle of the century, the industry abandoned toxic asbestos in favor of steel wire, fiberglass, and polymer threads. Successful experiments in this direction have given rise to fiber cement siding and cement boards. The era of steel fiber reinforced concrete began in the 70s, when the benefits of using a composite monolith in underground construction were proven. By adding specially bent wire to the solution, builders increased the moisture resistance, impact strength, and load-bearing capacity of the monolithic structure, since the volume of micro-reinforcement did not exceed 3%. This practice proved to be the best during the construction of the Channel Tunnel, the creators of which added up to a kilogram of polypropylene fibers up to 22 microns in diameter to a cubic meter of concrete.