Seungwook Seok

This study investigates the axial–flexural behavior of steel fiber–reinforced concrete (SFRC) columns under combined constant axial load and monotonic lateral loading. Nine column specimens with different axial load ratios (0.0, 0.10, and 0.20) and steel fiber contents (0.0%, 0.5%, and 1.0%) were tested under monotonic loading to evaluate their failure modes, load–deflection behavior, ductility, and energy absorption capacity. In addition, a sectional P–M interaction analysis was performed to examine the influence of steel fiber inclusion on flexural strength under different axial compression levels. The interaction diagrams indicated that steel fibers expanded the flexural strength envelope, with a more pronounced enhancement in the low-axial-load region. The test results revealed that increasing the axial load ratio enhanced the specimens’ peak load capacity but reduced their ductility, leading to a brittle failure mode. Conversely, the incorporation of steel fiber improved the crack distribution, delayed crack propagation, and enhanced both ductility and energy absorption, particularly under moderate axial load conditions. The failure modes were characterized generally by flexural cracking and localized crushing in the compression zone, with the specimens that contained steel fiber exhibiting a more gradual post-peak load response than the specimens without steel fiber. The energy absorption capacity, quantified as the area under the load–deflection curve, was maximized when the axial load ratio of 0.10 was used in tandem with steel fiber reinforcement, indicating an optimal balance between strength and ductility. Overall, steel fiber inclusion improved deformation capacity and energy absorption under monotonic loading, particularly at low-to-moderate axial load ratios.

Immediate action is required to achieve carbon neutrality within the cement industry. The integration of biochar into cement as a component of reinforced concrete has potential to mitigate carbon emissions in the construction sector by enabling carbon sequestration. In pursuit of eco-friendly practices and improved physical properties of cement composites, this study investigated the properties of wood-based, micron-sized biochar as a non-carbonate raw material, including its chemical composition, morphology, and wettability. The characterization of lignocellulosic micro-biochar and its mechanical impact on cement composites was a focus of this study. Cement was partially replaced with varying weight percentages of micro-biochar (1, 3, and 5 wt%), and the effects were evaluated through compressive strength tests after 7 and 28 d. The results demonstrated that the micro-biochar could sustain strength even when substituted for cement. Notably, after 28 d, the compressive strength of the sample with only cement was 29.6 MPa, while the sample with 3 wt% biochar substitution showed 30.9 MPa, indicating a 4.4% increase. This research contributes to sustainable construction practices by offering a green solution for reducing carbon emissions in the industry.