The present application is directed to a structural building unit formed from a set solid mixture consisting essentially of about 30% to about 75% by weight portland cement, about 1% to about 25% by weight percent ground expanded cellular polystyrene, about 1% to about 35% by weight ground cellulosic fiber, about 2% to about 15% by weight fly ash, about 1% to about 10% by weight silica fume, about 1% to about 15% by weight bentonite, about 25% to about 50% by weight water, about 0% to about 3% by weight air entrainer, about 0% to about 10% by weight paraffin wax emulsion and about 0% to about 15% by weight rubber emulsion.