Application of porous luffa fiber as a natural internal curing material in high-strength mortar

This study explores the potential of renewable plant fibers as internal curing (IC) materials, analyzing their potential in high-strength mortar (HSM) applications. Experiments involving the incorporation of different volumetric ratios of luffa fiber into concrete assessed impacts on autogenous shrinkage (AS), mechanical properties, and microstructure. The research found that the addition of luffa fibers extended both the setting times of the mixture, and after final setting, continued the hydration reaction by releasing internally stored water. Compared to the control group, luffa fibers significantly reduced AS by up to 56.87 %, primarily due to their high-water absorption capacity (211 %), which mitigates the internal capillary pressures during the cement hydration process. Moreover, the inclusion of luffa fibers significantly affected the concrete's mechanical properties: a 1 % luffa addition enhanced the compressive strength at 28 days by 7.6 % over the control; concrete with 2 % luffa fiber exhibited the highest flexural strength at 28 days, showing a 9.4 % increase over the control. Microstructural analysis revealed that luffa fiber not only promoted continued hydration but also increased the content of hydration products and enhanced the compactness of the cementitious matrix. Overall, luffa fibers effectively reduce HSM’s AS and enhance its mechanical properties and microstructure, showing potential to improve concrete performance.