Evolution of central temperature as a function of central density for 12 M_⊙ and 25 M_⊙ models with different ¹²C + ¹²C reaction rates (left panel). Kippenhahn diagrams for the centre of 25 M_⊙ models during the end of C-burning phase with Hin and HinRes ¹²C + ¹²C reaction rates (right panel). The grey shaded area shows the convective zones. The red dashed line show the limits of the C-burning zones (defined where ϵ_C ≥ 10² erg g⁻¹ s⁻¹).