Precast segments with sulphoaluminate cement and GFRP reinforcement

During tunnel excavation by means of a tunnel boring machine (TBM), the lining consists of precast structural elements, placed by the TBM during the excavation process and used as support elements during the advancing phase. The use of concrete based on sulphoaluminate binders allows the production of the elements to be speeded up, a reduction in the number of segments stacked waiting for the required strengths to be achieved and provides a more eco-sustainable process avoiding the use of steam curing. In order to verify the feasibility of the proposed solution, two full-scale tests (bending test and TBM jacks thrust test) on metro tunnel precast segments were carried out. The internal reinforcement consisted of a next-gen Glass Fibre Reinforced Polymer (GFRP) cage. The use of GFRP reinforcement, to replace traditional steel, in tunnel segments provides several advantages mainly related to durability aspects or when the use of a provisional lining is foreseen.