The invention relates to a gelled carbon-based composition forming an organic polymeric monolithic gel which is suitable for forming an aerogel by drying, to uses and to a process for preparing this carbon-based composition. The invention applies especially to the production of such gels having a very low density and a very low heat conductivity, a very high specific surface area and a satisfactory compression strength, for their use as thermal superinsulators or as carbon-based electrode precursors of supercondensers.A composition according to the invention comprises a resin at least partly derived from polyhydroxybenzenes H and from formaldehyde(s) F, said polyhydroxybenzenes comprising at least one unsubstituted polyhydroxybenzene R′ and at least one polyhydroxybenzene substituted with one or two alkyl groups.This composition is such that said polyhydroxybenzenes comprise several said unsubstituted polyhydroxybenzenes R and R′ and in that the composition comprises a water-soluble cationic polyelectrolyte P.