Disclosed herein are foam glasses and compositions comprising such foam glasses, which can be used, for example, in structural applications. The foam glass can have one or more properties, such as a density ranging from about 20 Ib/ft3 to about 100 Ib/ft3, a compressive strength of at least about 650 psi, and an alumina content of at least about 5% by weight, relative to the total weight of the foam glass. Also disclosed are methods for preparing foam glasses.