THESIS ABSTRACT

Abstract

This study investigates the use of Pine Needle Fiber (PNF), a sustainable and low-cost material, to enhance the mechanical performance of concrete. While natural fibers such as jute, sisal, and coir have shown potential in improving tensile and flexural strength, research on PNF in concrete remains limited, with uncertainties regarding fiber length, dosage, and treatment methods. In particular, the performance of shorter fibers and the optimum dosage for maximizing mechanical properties have not been fully explored. Laboratory tests were conducted on concrete mixes containing PNF at dosages of 0.5–1.5% by weight of cement, with fibers treated using 4% NaOH for 24 hours followed by 10% sodium silicate for 2 hours. The design mix proportions were 1:2.21:3.33 (cement: fine aggregate: coarse aggregate) by weight, with a water–cement ratio of 0.39. Workability was evaluated using the slump test, and compressive, splitting tensile, and flexural strengths were measured at 7 and 28 days. Results showed that PNF reduced workability due to high water absorption, with compressive strength slightly decreasing with fiber addition, with minimal reduction at dosages of 0.5% and 1%. The optimum PNF content was found to be 1% by weight of cement, which provided the best performance, yielding 14.5% and 14.9% improvements in splitting tensile and flexural strengths, respectively. The 0.5% mix showed smaller gains, while the 1.5% mix suffered from fiber clumping, reducing performance. Cost analysis indicated that PNFRC is more economical than plain, synthetic, or steel fiber-reinforced concrete at comparable inclusion levels. PNFRC offers a sustainable and economical reinforcement, enhancing mechanical performance and promoting the use of natural waste. However, long-term durability and fiber–matrix interactions with environmental impacts need to be assessed.

Keywords

Concrete; Natural Fiber Reinforced Concrete; Pine Needle Fiber; Pine Needle Fiber Reinforced Concrete; Mechanical properties