Development of eco-friendly FRP rebar building material with chopped pineapple fiber and Si₃N₄ bioceramic vinyl ester

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.