The Spanish National Accreditation Body ENAC and the Spanish Innovation Certification Agency ACIE have issued a Technological Innovation certificate to the Sando-FCC temporary joint venture for its development of a type of heavy-duty cement designed especially for ring segments. Sando-FCC is concluding the construction of the biggest high-speed train tunnel in Andalusia, the Sorbas-Barranco de los Gafarillos Tunnel.

The geological characteristics of the terrain where the tunnel is located make construction a complex challenge. Workers must mine through several fault zones and anhydrites, a singular combination that forced Sando and FCC to get straight to work on finding a special solution to get the project done right.

The resulting achievement in technological innovation involved a preliminary study of different concrete compositions, followed by research into and creation of a formula harder than 100 MPa (megapascals). The new formula employs unusual additives, such as silica smoke and latest-generation polycarboxyl-based additives.

The Sorbas Tunnel is part of Adif’s high-speed line between Almería and Murcia. Its construction required the use of a TBM. Ring segments were cast on site.

The Innovation certificate refers not only to the cement’s composition, but also to the system of work applied in this unusual job. The new concrete formula actually created conditions favouring organizational improvements, because the building procedure that goes with it makes stripping formwork faster, so the infrastructure can be built in less time.

The new concrete substantially improves the technology used to bore tunnels through unstable terrain, both because it is so safe and because it shortens the construction period.