One-component heat-curing epoxy resin composition comprising a) at least one epoxy resin A having an average of more than one epoxy group per molecule; b) dicyandiamide B; c) at least one accelerator C, where the accelerator C is a compound obtainable by reaction of: - 1 part by weight of an amine/epoxy adduct (a) with - 0.1 to 0.8, preferably 0.2 to 0.6, part by weight of a compound (b) selected from the group consisting of phenolic resins and polyhydric phenol compounds; wherein the amine/epoxy adduct (a) is obtainable by a reaction of: - an amino compound of the formula in which R3 and R4 are each independently an alkyl group having 1 to 5 carbon atoms, especially 1 to 2 carbon atoms, more preferably 2 carbon atoms, and R5 is an alkylene group having 1 to 5 carbon atoms, especially 3 carbon atoms; or - preferably an amino compound mixture containing the amino compound and 1-amino-4-ethylpiperazine in a weight ratio of: of 70/30 to 99/1, especially 80/20 to 97/3; with at least one epoxy resin having an average of more than one epoxy group per molecule, in such a ratio that the amount of epoxy groups in the epoxy resin is 0.8 to 2.5, especially 1.0 to 1.6, equivalents per equivalent of the amino groups in the amino compound(s) or +; d) at least one toughness improver D; wherein the ratio of the proportion of dicyandiamide B in grams per mole of epoxy groups in the epoxy resin A is 3-40 g/mol of epoxy groups, and wherein the ratio of the proportion of accelerator C in grams per mole of epoxy groups in the epoxy resin A is 5-35 g/mol of epoxy groups. a) at least one epoxy resin A having an average of more than one epoxy group per molecule; b) dicyandiamide B; c) at least one accelerator C, where the accelerator C is a compound obtainable by reaction of: - 1 part by weight of an amine/epoxy adduct (a) with - 0.1 to 0.8, preferably 0.2 to 0.6, part by weight of a compound (b) selected from the group consisting of phenolic resins and polyhydric phenol compounds; wherein the amine/epoxy adduct (a) is obtainable by a reaction of: - an amino compound of the formula in which R3 and R4 are each independently an alkyl group having 1 to 5 carbon atoms, especially 1 to 2 carbon atoms, more preferably 2 carbon atoms, and R5 is an alkylene group having 1 to 5 carbon atoms, especially 3 carbon atoms; or - preferably an amino compound mixture containing the amino compound and 1-amino-4-ethylpiperazine in a weight ratio of: of 70/30 to 99/1, especially 80/20 to 97/3; with at least one epoxy resin having an average of more than one epoxy group per molecule, in such a ratio that the amount of epoxy groups in the epoxy resin is 0.8 to 2.5, especially 1.0 to 1.6, equivalents per equivalent of the amino groups in the amino compound(s) or +; - 1 part by weight of an amine/epoxy adduct (a) with - 0.1 to 0.8, preferably 0.2 to 0.6, part by weight of a compound (b) selected from the group consisting of phenolic resins and polyhydric phenol compounds; wherein the amine/epoxy adduct (a) is obtainable by a reaction of: - an amino compound of the formula in which R3 and R4 are each independently an alkyl group having 1 to 5 carbon atoms, especially 1 to 2 carbon atoms, more preferably 2 carbon atoms, and R5 is an alkylene group having 1 to 5 carbon atoms, especially 3 carbon atoms; or - preferably an amino compound mixture containing the amino compound and 1-amino-4-ethylpiperazine in a weight ratio of: of 70/30 to 99/1, especially 80/20 to 97/3; with at least one epoxy resin having an average of more than one epoxy group per molecule, in such a ratio that the amount of epoxy groups in the epoxy resin is 0.8 to 2.5, especially 1.0 to 1.6, equivalents per equivalent of the amino groups in the amino compound(s) or +; - an amino compound of the formula in which R3 and R4 are each independently an alkyl group having 1 to 5 carbon atoms, especially 1 to 2 carbon atoms, more preferably 2 carbon atoms, and R5 is an alkylene group having 1 to 5 carbon atoms, especially 3 carbon atoms; or - preferably an amino compound mixture containing the amino compound and 1-amino-4-ethylpiperazine in a weight ratio of: of 70/30 to 99/1, especially 80/20 to 97/3; with at least one epoxy resin having an average of more than one epoxy group per molecule, in such a ratio that the amount of epoxy groups in the epoxy resin is 0.8 to 2.5, especially 1.0 to 1.6, equivalents per equivalent of the amino groups in the amino compound(s) or +; d) at least one toughness improver D;