Lime-ash plugging mixtures (LAPM) with a density of 1450–1780 kg/m3 have been developed and studied as new and competitive plugging compositions. LAPM consisting of lime and acid fly ash were found to be expanded during setting. The composition of the products formed during LAPM hydration was determined by means of X-ray phase analysis. Kinetic curves of plugging material expansion have been obtained at the temperatures of 348–413 K. Rational temperature regimes of LAPM setting according to the criteria of strength and gas permeability of cement stone have been determined.