Structural behavior and failure modes of steel- and GFRP-reinforced geopolymer concrete slabs strengthened with FRCM: experimental and numerical study  : Structural performance and failure mode transition in hybrid geopolymer–FRP–FRCM slab systems

Huy-Cuong Nguyen; Thuy Chi Dang; Cong Hau Nguyen

Structural behavior and failure modes of steel- and GFRP-reinforced geopolymer concrete slabs strengthened with FRCM: experimental and numerical study

Structural performance and failure mode transition in hybrid geopolymer–FRP–FRCM slab systems

Authors

Huy-Cuong Nguyen University of Transport and Communications
Thuy Chi Dang University of Transport and Communications https://orcid.org/0009-0006-8829-0744
Cong Hau Nguyen University of Transport and Communications https://orcid.org/0009-0000-3020-1530

Abstract

This study presents an experimental–numerical investigation on one-way geopolymer concrete (GPC) slab strips internally reinforced with steel or GFRP bars and externally strengthened using a glass fabric-reinforced cementitious matrix (FRCM) system. Six full-scale specimens were tested under four-point bending to characterize cracking response, stiffness evolution, strengthening efficiency, and governing failure mechanisms. The steel-reinforced control slab exhibited a ductile flexure-controlled failure. With glass-FRCM strengthening, the ultimate load increased by approximately 31% for one layer and 59% for two layers, accompanied by improved crack distribution and enhanced post-cracking stiffness, while maintaining flexural dominance. In contrast, the GFRP-reinforced control slab failed in shear, highlighting the limited stress redistribution associated with the lower elastic modulus and linear-elastic behavior of GFRP bars. Glass-FRCM strengthening improved tensile stiffness and crack control; however, the strengthened GFRP slabs remained shear-governed, indicating that flexural strengthening alone may be insufficient to prevent premature diagonal cracking. Overall, the results demonstrate that strengthening effectiveness is strongly dependent on the internal reinforcement type, and that additional shear strengthening measures are required for GFRP-reinforced GPC slab systems.

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Published

23-03-2026

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Articles in Press

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Original Article

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