Exploring the Potential of the Functionally Graded SCCC for Developing Sustainable Concrete Solutions

The feasibility of using layered- Functionally Graded Self Compacting Cement Composite (FGSCCC) for precast shield-tunnel segments, in harmony with present concrete industry sustainability trend, is presented herein. Limestone powder-type Self-Compacting Cement Composites (SCCC) either with silica fume (SiF) or with SiF and steel fibres (SF) were formulated for the watertight layer. While, SCCC with polypropylene fibres (PPF) or light weight aggregates and SF (LWA+SF) were used for the fire-resistant ones. Besides, a high strength SCCC (HS-SCCC) was considered for structural layers and monolithic samples. Layer composition influence and interlayer robustness on the structural element properties were evaluated. Experiments showed that the FGSCCCs are more effective than the HS-SCCC solutions in front of water, chloride, carbonation, fire or in terms of residual strength. Thanks to its precise spatial material arrangement, the effect of fire or the risk of steel reinforcement corrosion substantially decreases. The residual compressive strength, of FGSCCC specimens with LWA+SF layers, slightly decreases compared to that with PPF layers. Furthermore, they showed the increase of toughness of these specimens. Although none sharp failure at interface was observed, the results pointed out the necessity of considering other different effective parameters for validating the significance of casting process based on rheology.