Onyango, Julius2026-08-132026-08-132025-11Onyango, J. (2025). Strength properties of concrete incorporating pine needle and sisal fibre composites.Kyambogo University(Un Published workhttps://hdl.handle.net/20.500.12504/3042xiv, 128 p. : col.The constitution industry’s reliance on traditional materials has significant unprecedented material, economic, and environmental challenges. The urgent need for sustainable and environmentally friendly building materials has become increasingly important towards abating environmental degradation, Concrete, a widely used construction material, can benefit from the incorporation of natural fibres, which can improve on its mechanical properties whilst reducing its environmental-related footprint. The mine objective of this study was to develop an optimum cost-effective, environmental sustainable pine needle and sisal fibre reinforced concrete composite with enhanced strength properties. More specifically, this study evaluated the physical and mechanical properties, and examined the durability and economic viability including the environmental benefits of pine needle and sisal fibre content on concrete strength and determine the optimal fibre content for achieving desired mechanical properties, and examined the durability and economic viability including the environmental benefits pine needle and sisal fibres reinforced concrete composites. The methodological scope of this study involved an experimental approach, where the strength properties of concrete were evaluated under various fibre dosages(for single fibre type: 0.1%, 0.2%, 0.5%, 1%, 1.5% and 2% and for hybrid (0.1%+0. 1%, 0.2%+0.2%, 1%+0.5%, 0.5%+1% sisal and pine needle fibre respectively. Sigma plot and ANOVA were used in data analysis, presentation and determination of the statistical significance of the perceived variance. The optimal fibre content for compressive strength was found to be 0.1%, while 0.2% by weight was optimal for split tensile strength. The results showed that addition of pine needle and sisal fibres led to reduction in compressive strength by 19.1% and a reduction in flexural strength by 2.5% compared to plain concrete. However, a notable incre­ment of 21.7% was recorded for the split tensile strength. Despite reductions in some strength properties, the design concrete strength class of 20 N/mm2 was still achieved. A cost-benefit analysis revealed that using fibres resulted in a cost savings of Ugandan shillings 55,000 in 0.36m3.The carbon dioxide emissions analysis showed that whereas using steel reinforcement would result in 34.4 kilogram s of C02 emission, the use of fibres would result in emissions of only 5.28 kilograms of C02 emission, this study demonstrated an innovative approach into sustainable material development.enConcreteMechanical propertiesStrengthFiber-reinforced concreteAdditivesThesis