Sika Sikaflex 1A Stone 10oz 91015. Sika Sikaflex 1a is a premium-grade, solvent-free, high-performance, moisture-cured, 1-component, polyurethane-based, non-sag elastomeric sealant. Sikaflex-1a can be used in green and damp concrete applications. Meets Federal SpecificationTT-S-00230C, Type II, Class A. Meets ASTM C-920, Type S, Grade NS, Class 35, use T, NT, O, M, G, I.