 In post-tension structures, grouts are used to protect the pre-stressing steel from corrosion. Basalt microfibers can be added to improve the physical properties of these grouts, including drying shrinkage, compressive strength, air permeability and chloride ion permeability. The best performance was achieved when 0.1% of basalt microfibers were added to the mix, resulting in a decrease of 15.98% in drying shrinkage and a decrease of 10.82% in chloride ion permeability compared to the control mix. This article was authored by Jose R. Zapata-Pedilla, Cesar A. Juarez-Alvarado, Alejandro Duran Herrera and others.