density of the shredded polystyrene is preferably in the range of about 0 2 to 0 6 pounds per cubic foot more preferably about 0 3 to 0 5 pcf preferably the particle size at its maximum dimension is less than 1 4 inch portland cement can be used as the cementitious binder of the invention however it is generally preferred to employ a gypsum binder due to its advantageous fireproofing performance although the gypsum can be used in relatively low amounts e g as little as 60 by weight it is generally preferred to employ at least 75 by weight based on the total weight of the composition and more preferably at least about 85 by weight the fibrous component of the present compositions can be either organic or inorganic preferably the fibrous component is a mixture of a high wet bulking organic fiber preferably cellulose fiber as described in u s pat nos 3 719 513 and 3 839 059 and an inorganic fiber which provides reinforcement preferably glass fiber the total amount of the fibrous component in the composition is preferably in the range of about 4 to 20 by weight a particularly preferred composition comprises about 4 to 10 by weight of high wet bulking cellulosic fiber and about 0 1 to 2 by weight of glass fiber it has been found that these particularly preferred fiber loadings coupled with the preferred loading of about 1 to 5 by weight of shredded polystyrene particles provides an optimum composition for easy pumping without segregation and for placement in high yield i e placement over a relatively large area per weight of the dry composition at a given thickness of application.