Abstract: Improved lightweight insulating concretes containing expanded vermiculite or perlite aggregate and of the type which are mixed and pumped to roofs of buildings and the like are described. The improved concretes are mixtures in specified proportion of cementitious binder such as Portland cement, expanded vermiculite or perlite, air-entraining agent, polyelectrolytic sulfonate dispersing agent and preferably an inert densifying particulate, which, can be cast as thin cross-section, high strength layers requiring low amounts of "in-place" water, without sacrificing necessary properties such as yield, pumpability, etc. The improved concretes are preferably used as layers over plastic foam insulation boards in the formation of sloped or non-sloped insulated roof systems constructed at the job-site.