Efendi, Nadia Aura Deka (2026) Pengaruh Substitusi Nanosilika Dan Limbah Plastik Pet Terhadap Beton Melalui Pengujian Slant shear Dan Shrinkage Sebagai Material Perbaikan Struktur Beton. Other thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Struktur beton rentan mengalami penurunan kinerja akibat penuaan, paparan lingkungan agresif, dan beban berlebih, sehingga memerlukan material perbaikan yang kuat, memiliki ikatan antarmuka baik, serta stabilitas dimensi memadai. Penelitian ini menganalisis pengaruh substitusi nanosilika dan penambahan (addition) serat limbah plastik PET pada beton sebagai material perbaikan struktur (dengan potensi aplikasi beton jacketing), ditinjau dari workability, kuat tekan, kekuatan ikatan (slant shear), susut, dan kelayakan biaya, melalui lima variasi campuran: OPC, nanosilika 3% (NS3P0), serat PET 1% (NS0P1), serat PP komersial (NS0C1), dan kombinasi nanosilika 3% dengan serat PET 1% (NS3P1), dengan target kuat tekan 35 MPa dan Superplasticizer 1,1%. Hasil pengujian slump menunjukkan seluruh variasi memenuhi syarat minimum ASTM C928, dengan nilai tertinggi pada OPC dan NS3P0 (150 mm). Pada pengujian kuat tekan, nanosilika terbukti dominan mempercepat perkembangan kekuatan awal, di mana NS3P0 menghasilkan nilai tertinggi sejak 3 jam (5,7 MPa) hingga 7 hari (36,2 MPa) dan menjadi satu-satunya variasi yang memenuhi kriteria kuat tekan 3 jam yang ditinjau untuk kategori R1 ASTM C928, sedangkan keempat variasi lainnya (OPC, NS0C1, NS0P1, dan NS3P1) belum memenuhi persyaratan kategori manapun (R1, R2, maupun R3) pada umur tersebut. Pada umur 28 hari, NS3P0 tetap tertinggi (42,2 MPa), diikuti NS3P1 (41,5 MPa) yang menunjukkan efek kombinasi yang menguntungkan dari nanosilika dan serat PET pada umur lanjut. Pengujian slant shear tanpa bonding agent menunjukkan dua dari empat variasi memenuhi kriteria apparent slant-shear bond strength (ASTM C882 yang diadaptasi), dengan nilai tertinggi pada NS3P0 (19 MPa), sedangkan penggunaan bonding agent berbasis PVA justru menurunkan bond strength akibat re-emulsifikasi lapisan selama curing perendaman air. Pengujian shrinkage menunjukkan nanosilika paling efektif menurunkan drying shrinkage melalui mekanisme pore refinement, dengan NS3P0 menghasilkan susut terendah (0,05 %), dan seluruh variasi memenuhi batas ASTM C928. Dari sisi biaya, seluruh variasi penelitian jauh lebih ekonomis dibandingkan material komersial di pasaran. Secara keseluruhan, kombinasi nanosilika dan serat PET terbukti menjanjikan sebagai material perbaikan struktur beton yang kuat, ekonomis, dan berkinerja baik.
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Concrete structures are prone to performance degradation due to aging, exposure to aggressive environments, and excessive loading, thus requiring repair materials with high strength, good interfacial bonding, and adequate dimensional stability. This study analyzes the effect of nanosilica substitution and recycled PET fiber addition on concrete as a structural repair material with potential for concrete jacketing applications, in terms of workability, compressive strength, bond strength (slant shear), shrinkage, and cost feasibility, through five mixture variations: OPC, 3% nanosilica (NS3P0), 1% PET fiber (NS0P1), commercial PP fiber (NS0C1), and a combination of 3% nanosilica with 1% PET fiber (NS3P1), with a target compressive strength of 35 MPa and a uniform Superplasticizer dosage of 1.1%. Slump test results showed that all variations met the minimum requirements of ASTM C928, with the highest values observed in OPC and NS3P0 (150 mm). In the compressive strength test, nanosilica was shown to be dominant in accelerating early strength development, with NS3P0 producing the highest values from 3 hours (5.7 MPa) up to 7 days (36.2 MPa), and being the only variation that met the investigated 3-hour compressive-strength criterion of ASTM C928 category R1, while the other four variations (OPC, NS0C1, NS0P1, and NS3P1) failed to meet any category requirements (R1, R2, or R3) at that age. At 28 days, NS3P0 remained the highest (42.2 MPa), followed by NS3P1 (41.5 MPa), indicating a favourable combined effect of nanosilica and PET fiber at later ages. The slant shear test without a bonding agent showed that two out of four variations met the adapted ASTM C882 apparent slant-shear bond-strength criterion, with the highest value recorded for NS3P0 (19 MPa), while the use of a PVA-based bonding agent instead reduced bond strength due to re-emulsification of the layer during water-immersion curing. The shrinkage test showed that nanosilica was most effective in reducing drying shrinkage through a pore refinement mechanism, with NS3P0 producing the lowest shrinkage (0.05 %), and all variations remaining within the ASTM C928 limit. In terms of cost, all research variations were significantly more economical than commercial materials available on the market. Overall, the combination of nanosilica and PET fiber proved promising as a strong, cost-effective, and well-performing structural concrete repair material.
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