The Influence of Addition of Fly Ash from Astana Heat and Power Plants on the Properties of the Polystyrene Concrete oleh Rimma Niyazbekova, Gabit Mukhambetov, Rassul Tlegenov, Saule Aldabergenova, Lazzat Shansharova, Vasiliy Mikhalchenko, Michał Bembenek