Basalt glasses and fibers with zirconia content in the range from 0 to 7 wt% were obtained using ZrSiO4 as
a zirconium source. Weight loss and tensile strength loss of fibers after refluxing in alkali solution were
determined. Basalt fiber with 5.7 wt% ZrO2 had the best alkali resistance properties. Alkali treatment
results in formation of protective surface layer on fibers. Morphology and chemical composition of surface
layer were investigated. It was shown that alkali resistance of zirconia doped basalt fibers is caused
by insoluble compounds of Zr4+, Fe3+ and Mg2+ in corrosion layer. Mechanical properties of initial and
leached fibers were evaluated by a Weibull distribution. The properties of basalt fibers with ZrSiO4 were
compared with AR-glass fibers. The performance of concrete with obtained fibers was investigated.