Mainstay ML-72F Sprayable Microsilica Mortar is a polymer modified mortar used on new or mildly deteriorated concrete structures in zoos, aquariums, and fish hatcheries. Mainstay ML-72F fills bugholes and irregularities on new concrete and repairs concrete surfaces roughened by the effects of mild corrosion. This low permeability mortar bonds tightly to concrete and provides a smooth finish suitable for the application of a protective coating.