In the initial part of the Ecosister project, geopolymer binders with solid or liquid activator were studied. Binders with a solid activator were proposed in Ecosister for non-structural uses, such as thermal-insulating plasters.

In the present project, a structural use of geopolymer binders with liquid activator is proposed, specifically geopolymer concrete (GPC) for the construction of precast segments for the structural rehabilitation of the lining of existing reinforced concrete or masonry tunnels.

In civil engineering, structural applications of geopolymers are practically non-existent for several reasons:

• lack of specific standards

• higher cost compared to ordinary Portland concrete (OPC)

• limited availability of the raw materials used to produce the geopolymer binder

However, geopolymer concrete is superior to OPC in some specific applications where high mechanical strength is required together with fire and chemical resistance.

One such application is the use of GPC in the manufacture of precast segments for the reinforcement of existing tunnels. In Europe, the renewal and reinforcement of hundreds of existing tunnels is a critical issue.

Typically, a tunnel is reinforced by removing the inner layer of the old lining and creating a new layer of OPC. In-situ works take a long time. Reinforcement with prefabricated, ready-to-install GPC segments is a novel idea that can:

• save time

• reduce costs

• lower environmental impact

The project starts with the selection of the geopolymer binder (TRL3), followed by the development of the high-performance geopolymer concrete to produce a real reinforcement prototype (TRL7).

The project is divided into 10 work packages (WP), carried out by:

• UNIPR: structural, chemical parts, and LCA

• CNR: chemical parts