Alkali resistance, microstructural and mechanical performance of zirconia-coated basalt fibers

•Sol-gel approach was developed to apply zirconia coatings on basalt fibers.•The alkali resistance of uncoated and coated basalt fibers was studied.•Scheme of etching was proposed.•Dense ZrO2 coating slows down the corrosion of basalt fiber in alkali solution.•The coated fiber is affected by the cement matrix only slightly.

Sol–gel approach was developed to apply zirconia coatings on basalt fibers. Dense or porous ZrO2 coatings were obtained, depending on the process parameters. The alkali resistance of uncoated and ZrO2-coated basalt fibers in alkali solution was studied. The morphology, elemental and phase composition of etched fibers as a function of etching time were studied by means of a set of analytical methods. A scheme of etching of as-received and coated basalt fiber was proposed. Zirconia coating slows down the corrosion of basalt fiber in alkali solution. The denser zirconia coating slows down the corrosion to a higher extent than the porous coating. The uncoated and coated basalt fibers were tested in mini composites with cement matrix. It was shown that the surface of the coated fiber is affected by the alkaline medium of the cement matrix to a smaller extent than the surface of as-received basalt fiber.