Chopped Continuous Basalt Roving in Concrete: From As-Supplied Fiber Properties to Actual Reinforcement Performance

Chopped basalt fiber used in concrete is commonly characterized by nominal cut length, filament diameter, tensile strength, and dosage. These parameters describe the supplied product but not necessarily the reinforcing system that exists after mixing and during service. This paper examines chopped continuous basalt roving as a hierarchical, sizing-bound multifilament material whose structure can evolve during concrete mixing. Particular attention is given to bundle opening, filament separation, aggregate-induced brittle fragmentation, dispersion, fiber-matrix load transfer, failure by rupture or pull-out, and chemical durability in alkaline cementitious environments. The review is combined with experimental observations and archival data obtained for continuous basalt fibers produced from different natural raw materials. The data demonstrate substantial variation in alkali resistance among fibers from different deposits and a pronounced effect of filament diameter. Earlier strength-retention experiments in cement-related alkaline environments also show that gravimetric chemical resistance and preservation of tensile strength are distinct characteristics. Published mechanical studies further demonstrate that increases in tensile or flexural strength do not by themselves establish structural post-cracking performance. The analysis leads to a central conclusion: basalt fiber is not a material with a single fixed reinforcement characteristic. The behavior of basalt-fiber-reinforced concrete depends on both the geological source of the raw material and the technology used to produce, size, chop, disperse, and incorporate the fiber into concrete. Consequently, fibers produced from different deposits - or by different processing routes from the same deposit - can produce different composite mechanical properties under otherwise identical concrete conditions.