Hybrid Glass and Sisal Fiber Cementitious Composites: Physical, Mechanical, Nondestructive, and Microstructural Analysis

Cementitious-based hybrid composites offer a promising route to sustainable, resilient, and high-performance construction materials. This study fabricated hybrid fiber cementitious composites (HFCCs) reinforced with sisal and glass fibers of varying lengths (6, 12, and 18 mm) and volume fractions (1%, 2%, and 3%). Their mechanical properties, water absorption, density, and apparent void volume were evaluated. Additionally, scanning electron microscopy was used to analyze the microscopic characteristics of the HFCCs. Furthermore, nondestructive testing was conducted, including ultrasonic pulse velocity to assess material quality and the rebound hammer test to measure surface hardness. Statistical and regression analyses were also conducted to evaluate the impact of fiber reinforcement on the properties of HFCCs. The results showed that fibers hybridization notably enhanced flexural strength and toughness, while compressive strength was only slightly affected. The composite with 12 mm fibers at 3% volume exhibited the highest flexural strength, with a 57.14% increase over the reference sample (cementitious matrix). The highest toughness of 3.1 kN-mm was achieved using 18 mm fibers at 2% volume, representing a 313% increase over the reference sample. These findings underscore the effectiveness of natural-synthetic fiber hybridization in improving the mechanical performance of cementitious composites.