Abstract:

In this paper, the emergency treatment of No. 2 line of Nanjing Metro is described. In order to overcome the difficulties in the preparation of subzero temperature concrete used for tunnel construction under freezing conditions, the mechanical properties and workability of selfcompacting concrete at subzero temperature are studied and relevant concrete curing requirements during construction are established according to the study results. The research results show that varied minus temperature is more favorable to the concrete strength developing than constant minus temperature. At low temperature, the increase of the retarding agents in the admixture is favorable to the concrete’s workability. The optimum amount of antifreezing agent is 3%~4%, with the strength and durability of concrete being considered. The study provides reference for the preparation and quality control of concrete used for tunnel construction under freezing conditions in the future, which is helpful to the application of freezing method in tunnel construction.

Key words: concrete at subzero temperature, selfcompacting, freezing method, tunnel construction