Ardex Setting MaterialsArdex E90 Mortar Admix is a synthetic additive for Use with select Ardex tile and stone mortars. Ardex E90 is diluted with water prior to mixing with mortars. The addition of Ardex E90 results in a mortar that, once set and hardened, has high bond strength and excellent elastic and water repellant properties. Ardex E90 is ideal for interior and exterior tile and stone installations.