ARDEX E 90™ Mortar Admix is a synthetic additive for use with select ARDEX tile and stone mortars. ARDEX E 90 is diluted with water prior to mixing with mortars. The addition of ARDEX E 90 results in a mortar that, once set and hardened, has high bond strength, excellent elastic and water-repellent properties. ARDEX E 90 is ideal for internal and external tile and stone installations.