Inorganic polymer/organic polymer composites and methods for their preparation are described herein. The inorganic polymer/organic polymer composites comprise a first layer comprising an inorganic polymer and a second layer adhered to the first layer comprising an organic polymer. The inorganic polymer is formed by reacting, in the presence of water, a reactive powder, an activator, and optionally a retardant. The reactive powder comprises 85% by weight or greater fly ash and less than 10% by weight portland cement. Also described herein are building materials including the composites.