This study aims to examine the mechanical, thermal, and water absorption properties of Si3N4-reinforced vinyl ester rebars integrated with silane-treated chopped pineapple fiber for use in the construction sector. The development of FRP rebar building material using bio-extracted fiber and filler particle promotes innovation in infrastructural sector, and also for providing better bonding adhesion, strengthened composite rebar the silane treatment is utilized, which brings a novelty to this study. The materials used include unsaturated vinyl ester resin, methyl ethyl ketone peroxide (MEKP) catalyst, and chopped pineapple fiber. Si3N4 bioceramic was extracted from locally collected paddy straw. Silane treatment with 3-aminopropyltrimethoxysilane (APTMS) was applied to the fibers and bioceramic particles to enhance bonding with the matrix. Composite rebars were fabricated by mixing vinyl ester with varying volumes of silane-treated Si3N4 and pineapple fibers, followed by curing. Additionally, standard concrete beams were prepared using a hand-mix concrete process with M40 grade concrete, with a mix proportion of 1:15.58:2.76 and a water/cement ratio of 0.45, and were cured for 28 days. Mechanical testing revealed that specimen A3, containing 2 vol.% silane-treated Si3N4, exhibited superior properties with a tensile strength of 64 MPa, flexural strength of 107 MPa, and compression strength of 82 MPa. The silane treatment significantly improved interfacial bonding, enhancing load-bearing capacity and durability. Specimen A5, with 8 vol.% silane-treated Si3N4, showed the best thermal conductivity at 0.45 W/mK and the lowest water absorption rate at 0.00091%, indicating an optimal filler content for thermal conduction and impermeability. Silane treatment improved the dispersion and bonding of fillers and fibers, creating a uniform and effective composite structure. SEM analysis confirmed these findings by showing improved adhesion between fibers and matrix, uniform dispersion of filler particles, and potential issues like fiber pull-out and agglomeration. The study demonstrates that silane-treated bioceramic and fiber reinforcements significantly enhance the properties of vinyl ester composite rebars, making them suitable for advanced construction applications.