Chemical waterstop formulated from a unique mixture of bentonite and chemical additives (binders, polymers, and plasticizer materials) that are blended to a putty-like consistency for application by a hand-held, 30-ounce cartridge caulking gun to the construction joint of the previous concrete pour to seal through the joint, not across it. Installation is made exterior to the waterside of dowels or in the keyways to prevent water from reaching the reinforcing steel. At designed intervals, a cross-hatch pattern is made to help isolate the penetrating water to a fixed area of the wall, floor, or roof for rapid detection, isolation, or subsequent repair. It also reacts to form a premanent, high pressure seal that does not rely on adhesion to stop water in below-grade construction areas such as: exterior walls, floor slabs, covered roof or plaza decks, mechanical penetrations, footing/wall connections, wall/roof connections, and almost any construction joint along which water can enter and migrate. This expansion will move toward the water source, squeezing the water out of the joint, which is not characteristic of mechanical waterstops.