Supervision of fabrication of precast steel fibre reinforced concrete (SFRC) segmental lining

Abstract

Precast reinforced concrete (RC) segments have been widely used to construct tunnels for mass rapid transit lines in Singapore. However, the reinforcement bar cages are labour intensive to fabricate and install in moulds. Then the cages must be adjusted in moulds to achieve minimum cover at critical locations such as bolt sockets and cover to external face. Supervision has to be tight to achieve good quality segments. However, with the use of steel fibre reinforced concrete (SFRC), steel reinforcement bars have been eliminated. Steel fibres are added during the batching of concrete. Concrete is then poured in moulds and compacted. Compaction is done by using external vibrators mounted on moulds. For downtown line stage 3 contract 933, SFRC segments were used as tunnel lining. C@nspecs Pte Ltd supervised the production of SFRC segments in the factory. This paper outlines the quality control tests done on the fresh and hardened concrete.