A mandrel or core mold is used in the manufacture of composite products. The current invention avoids the disadvantages of plaster mandrels by making mandrels or core molds composed of aggregate with a dual binder system. This system produces a mold with high green strength, high dry strength, and the ability to be disintegrated from a finished composite product. The cross-linked polyvinylpyrrolidone, poly-polyvinylpyrrolidone, of this invention provides many benefits and advantages.