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Go to Editorial ManagerPlastic concrete is widely used in hydraulic cut-off walls of earth and rockfill dams because of its low permeability, high deformability, and good workability. The addition of bentonite clay is also among the primary factors that can influence its performance as it greatly decreases the hydraulic conductivity. Mechanical performance and crack resistance are enhanced by the fiber reinforcement of polypropylene (PP) and steel fibers. This paper investigated the interaction of calcium bentonite dosage, fiber type and content, cement content, and water-to-binder ratio (W/(C +B)) on the flowability, compressive strength, and permeability of 29 plastic concrete mixtures to be used in cut-off wall construction. The experimental tests were performed in accordance with ASTM D6103 on flowability, ASTM C39 on compressive strength and BS EN 12390-8:2019 on permeability. The findings revealed that the best mixtures had a flowability of over 14 cm, compressive strength of 1.23 to 25.78 MPa and permeability coefficients of 10⁻⁹ to 10⁻⁷ cm/s. Adding more bentonite was a very effective way of decreasing permeability, but frequently had adverse effects on compressive strength and workability. Polypropylene fibers showed a more favorable contribution to crack resistance and workability compared to steel fiber. The findings indicate that close fine-tuning of the water to binder ratio (W/(C+B)) as well as dosages of superplasticizer is essential in attaining balanced performance. The study presents a guideline to enhance durable, non-pervious, plastic concrete that can be used in hydraulic works and prepares the groundwork in future investigations of long-term durability and chemical integrity.
This study investigates the influence of nano silica on the mechanical performance and interfacial behavior of fiber-reinforced cementitious composites (FRCCs) incorporating steel, glass, polypropylene, and raffia fibers. The objective is to evaluate the impact of nano-silica content (0%, 1.5%, 2.5%, and 3.5%) on workability, compressive strength, fiber–matrix bond strength, and tensile response under uniaxial loading. The addition of nano-silica reduced flowability due to its high surface area and water demand but enhanced compressive strength, reaching a maximum value of 77.14 MPa at 3.5 percent nano-silica. Field Emission Scanning Electron Microscopy (FESEM) confirmed matrix densification and refinement of the interfacial transition zone (ITZ) in nano silica modified mixtures, supporting the observed strength gains. Single-fiber pull-out tests revealed that nano silica significantly improved average and equivalent interfacial bond strengths. Steel fibers exhibited the most consistent bond improvement, while raffia fibers demonstrated the weakest performance. Longer fiber embedment enhanced bond strength and energy absorption for high-modulus fibers. Equivalent bond strength trends indicated a strong dependency on fiber type and embedment length. Direct tensile tests demonstrated that nano-silica significantly enhanced the tensile strength and ductility of composites. The most substantial improvement was observed in steel fiber-reinforced composites, with cracking strength increasing by 166.7% and ductility by 143.3% at 2.5% NS. Correction factors were proposed to align theoretical tensile predictions with experimental results. Overall, nano silica proved highly effective in improving FRCCs by densifying the matrix, strengthening the fiber matrix interface, and enhancing mechanical performance under tensile loading.