Abstract: Shaped articles for construction and insulation which are water repellent are prepared by dry blending expanded perlite particles and fibers, applying to the resulting mixture a solution of a reactive synthetic organic binder in a low boiling organic solvent. The binder is capable of being cured at ambient temperatures and of reacting with hydroxyl groups present in the perlite and fibers to provide the articles with water repellent properties. The mixture containing binder is formed into the desired shape, e.g. panels, solvent is removed and the binder is cured at substantially ambient or slightly higher temperatures.