Crystalline waterproofing (Xypex, Penetron, Kryton): catalytic chemicals react with moisture and cement byproducts to form insoluble crystals within concrete pores and micro-cracks. Self-healing: reactivates when new moisture enters, sealing cracks up to 0.4mm (0.016 in). Dosage: 0.8-1.0% by weight of cement. Added to mix at batch plant or jobsite. Applications: foundation walls, water tanks, tunnels, parking structures, elevator pits — any below-grade or water-retaining structure. Advantages: integral (no membrane to damage), self-healing, permanent, withstands hydrostatic pressure (tested to 200+ psi). ACI 212.3R. Cost: $3-$8/cy of concrete. NSF/ANSI 61 certified for potable water contact. CSI 03 05 13.