This paper presents a procedure to optimize the construction of mass concrete structures using genetic algorithms. The optimization criterion is construction cost and the decision variables are material types, placing temperature, the height of lifts and time intervals between lifts. The constraint imposed on the decision variables is cracking. Transient hydration, thermal and stress fields were calculated using a coupled thermo-chemo-mechanical model. To show the potential of the proposed methodology, the construction phase of a small hydropower plant dam was optimized. The results indicated that the procedure can be successfully used in the design of massive concrete structures.