Ahmad A. Attia

The integration of real-time monitoring capabilities into concrete materials offers significant potential for improving the safety and durability of building infrastructure. This study investigates the real-time electromechanical behavior of steel fiber-reinforced self-sensing concrete under compressive and splitting tensile loading. Eighteen cubes (150 × 150 × 150 mm) and eighteen cylinders (150 × 300 mm) containing 0.5%, 1.5%, and 3% steel fiber volume fractions were tested. Electrical resistance was continuously recorded at one-second intervals using an Arduino–ESP32-based system, enabling in situ tracking of damage evolution. The conductive steel fiber network functioned as an intrinsic sensing phase, where load-induced microstructural changes altered electrical pathways. Resistance variations consistently preceded visible cracking, with pronounced nonlinear increases observed at 65–80% of peak load, indicating micro-crack initiation. Distinct electromechanical stages were identified, including elastic stability, compaction-induced resistance reduction near yield, and rapid resistance growth during crack propagation. Higher fiber contents improved both mechanical performance and sensing sensitivity through enhanced crack-bridging and conductive network stability. Although curing age influenced baseline resistance, reliable real-time damage detection was achieved across all specimens. The findings demonstrate the feasibility of steel fiber-reinforced concrete as a cost-effective, distributed monitoring material for early damage detection in building structures.

Geopolymer concrete is concrete made from industrial materials, such as fly ash, GGBS, silica fume, and metakaolin, used as a cement alternative. In this study, geopolymer concrete will be based on fly ash as a binder material, alkaline activators of sodium hydroxide and sodium silicate, GPC beams of dimensions 800 mm × 250 mm × 100 mm, circular columns with diameter 350 mm and depth of 700 mm and GPC slabs of dimensions 500 mm × 500 mm × 100 mm are all cast with fly ash content of 350 kg/m³. The ratio of alkaline solution to fly ash was equal to 0.5 and was kept constant, and the Na₂SiO₃-to-NaOH ratio was 2.5 and the NaOH molarity was kept constant at 12 M. The beams reinforcement was changed to study the shear and flexural behaviour, and the slabs and columns reinforcement ratio was kept constant. The load capacity, stress–strain behaviour of the GPC and load-deflection behaviours of the members were also examined. The results showed that reinforced geopolymer members can be used as an alternative to reinforced concrete structural members, but they are more expensive than reinforced concrete. Further study is recommended to provide more practical design recommendations for incorporating geopolymer concrete into structural elements in order to accelerate the adoption of this concrete for large-scale field applications in the future.