The Krystol Waterstop system employs two cementitious products, Waterstop Grout and Waterstop Treatment, to create a physical barrier against water penetration. A triangular-shaped strip of grout is created along the edge of a concrete slab where a new wall is to be poured. It is covered with the waterstop treatment, and the concrete wall is poured. The system reacts with water and unhydrated cement to form microscopic crystals, sealing the spaces between concrete particles and permanently blocking water penetration. Kryton International, 800-267-8280,