FIELD: construction. SUBSTANCE: invention relates to technologies for processing acid ash from CHP into a filler for concrete for structural purposes. Method of obtaining an unburned fly ash aggregate based on acid ash, quicklime and alkaline hardening activator includes grinding, dosing, mixing of components and moistening of the mixture, granulation and compaction of granules in the sealant, in the process of which they are first dusted with the plasticizer C-3, and then portland cement M400D0, followed by hardening of the granules under normal conditions, Na2SO4 used as an alkaline activator, lime milk or a mixture of it with sodium sulfate used to moisten the mixture, while combining the mixing of the components of the mixture with hydromechanical activation at 1000 shaft speed per minute for a period of 3 minutes, hardened granules are dried at a temperature below 100 °C to a weight loss of about 5 %, and then modified by placing in an aqueous emulsion of polyvinyl acetate, in which they are simultaneously subjected to evacuation and vibration. EFFECT: technical result is the acceleration of hardening of unburned fly ash aggregate while simultaneously increasing the strength of the granules.