A very unique, high-performance, rapid drying and rapid hardening, microfiber-reinforced, polymer-modified tile and stone mortar for interior installations. ARDEX S 28 is highly flexible with virtually no shrinkage and an extended open time, making it perfect for large and super format tile and stone installations. ARDEX Self Drying Technology; Rapid Drying, Rapid Hardening and NO Shrinkage! Walk on and grout in just 4 hours Extended open time of 45 minutes Perfect for large and super-format tile and stone installations Excellent for use with ARDEX FLEXBONE® Uncoupling Membranes and other approved uncoupling membranes! Semi-pourable consistency; easily enables full tile coverage Thin to medium bed installation up to 5/8" (15 mm) Pot life: 75 minutes Adjustment time: 20 to 25 minutes 40 lb (18 kg) bag; Gray Outstanding coverage: 103 sq. ft. (9.5 m²) / 40 lb. bag