International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 12 Issue: 11 | Nov 2025
p-ISSN: 2395-0072
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Comparative Analysis of Mechanical and Physical Properties of Cement Mortar Reinforced with Synthetic (Polypropylene) and Natural (Pine Needle) Fibers Aqeel Haider1, Fahad Yaqoob1, Khawaja Haseeb Maqbool1 1School of Mechanics and Transportation Engineering, Northwestern Polytechnical University, Xi’an 710129, China
---------------------------------------------------------------------------***--------------------------------------------------------------------------efficiency depends on geometry (length, diameter, aspect Abstract This study investigates the mechanical and physical properties of cement mortar reinforced with synthetic polypropylene (PP) and natural pine needle (PN) fibers at 1– 5% by cement weight. Fresh and hardened properties including workability, flexural strength, compressive strength, ultrasonic pulse velocity, density, and water absorption were evaluated. Results identified 2% PP as an optimal dosage, giving a 7% increase in flexural strength while maintaining acceptable compressive strength and internal quality. PN fibers showed potential as a wastederived, sustainable alternative but exhibited lower mechanical performance and higher water absorption than PP at comparable contents. For both fiber types, increasing dosage reduced workability and compressive strength and increased water absorption while reducing density in a dosedependent manner. A strong correlation between fiber content, decreased pulse velocity, and reduced compressive strength indicated increased porosity. Overall, PP fibers provided superior reinforcement with a better balance of properties, while PN fibers require further treatment to improve compatibility with the cement matrix. Keywords: Fiber-reinforced mortar, polypropylene fibers, pine needle fibers, mechanical properties, sustainable construction materials
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Introduction
Cement-based materials form the backbone of modern construction but remain intrinsically brittle and weak in tension. Under load, shrinkage, or environmental actions, this leads to crack initiation and sudden failure, limiting service life and reliability. Incorporating discrete fibers is a well-established strategy to mitigate these drawbacks: properly designed fiber reinforcement bridges cracks, increases energy absorption, and converts a brittle matrix into a more ductile composite [1,2].
ratio), mechanical properties (modulus, strength), and the quality of the fiber–matrix interface, which together control stress transfer and crack-bridging capacity [3].
Synthetic fiber systems have been extensively characterized. Nataraja et al. [5] linked fiber type to composite stress– strain response under different loading conditions. Long et al. [6] showed that the matrix-to-fiber modulus ratio governs whether stiffness or ductility is improved, with high-modulus carbon fibers primarily enhancing stiffness and low-modulus polypropylene fibers improving toughness and energy dissipation. Nayak [7] reported clear mechanical benefits from polypropylene fibers, accompanied by a reduction in workability at higher dosages. At the high-performance end, Engineered Cementitious Composites (ECC) achieve strain-hardening and tensile strains of 3–5% using carefully tailored PVA or polyethylene fibers [9]. Hybrid concepts, such as combining polypropylene fibers with nano-silica, have demonstrated improved fiber– matrix bond and more stable crack patterns [10], illustrating how microstructural tailoring can further enhance performance. In parallel, environmental and resource considerations have renewed interest in natural and waste-derived fibers as partial substitutes for petroleum-based synthetics. Among these, pine needles are an abundant forest residue that can acidify soil and hinder vegetation if left on the forest floor. Utilizing pine needles as cementitious reinforcement offers the dual benefit of waste valorization and reduced dependence on conventional synthetic fibers [14].
A wide range of fibers has been used in cementitious systems, including synthetic polymers (e.g. polypropylene, polyvinyl alcohol), steel, and glass or carbon fibers. Their
Polypropylene fibers in cement-based materials have been studied in depth [12], and natural fibers have been explored in various polymer and cementitious composites [13]. However, direct, side-by-side comparisons of conventional synthetic fibers and natural waste fibers within the same mortar system, test matrix, and curing conditions remain limited. This lack of controlled comparative data makes it difficult to judge whether natural waste fibers can
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