Electronic Theses and Dissertation

Keretakan pada beton dapat menurunkan kapasitas struktur balok terhadap lentur dan geser. Penelitian ini menganalisis pengaruh perbaikan balok beton bertulang pasca-retak menggunkan Bakteri Bacillus Sp. sebagai self-healing penghasil kalsit (CaCO₃) melalui metode injeksi yang mampu menutup retak mikro untuk memperbaiki balok yang telah mengalami retak. Pengujian dilakukan pada satu buah Balok BBMT–N (normal) dan satu buah Balok BBMT–N+BB yang telah mengalami kerusakan kemudian diperbaiki bakteri, dengan mengamati beban maksimum, lendutan, regangan baja dan beton, serta pola retak. Pengujian dilakukan secara eksperimental melalui metode pembebanan terpusat dua titik. Tahapan pembebanan dibagi menjadi dua fase utama: fase inisiasi kerusakan sebesar 75% dari beban ultimit untuk memicu retak awal, serta fase pembebanan akhir hingga balok mencapai kondisi runtuh pasca-injeksi bakteri. Respons struktural dipantau secara real-time menggunakan LVDT untuk lendutan dan strain gauge untuk mengukur regangan material baja serta beton. Hasil penelitian menunjukkan bahwa perbaikan menggunakan Bakteri Bacillus Sp. (BBMT-N+BB) memberikan peningkatan kapasitas beban balok sebesar 0,750 ton atau 3,27% dibandingkan balok normal (BBMT-N) pada mutu beton yang sama (f^' c 60,01 MPa). Lendutan pada beban yang sama lebih kecil setelah injeksi, menandakan peningkatan kekakuan akibat terbentuknya endapan kalsit (CaCO₃) pada celah retak. Pola retak juga menunjukkan bahwa sekitar 55% retak lama muncul kembali, sementara 45% retak baru muncul, yang membuktikan bahwa bakteri mampu menghambat perambatan retak secara efektif. Secara keseluruhan, penggunaan Bakteri Bacillus Sp. terbukti mampu meningkatkan kapasitas geser dan memperlambat perambatan retak, sehingga berpotensi menjadi metode perbaikan yang efektif untuk struktur beton bertulang.

Kata Kunci : kegagalan geser, self healing concrete, injeksi bakteri bacillus sp.

Cracks in concrete can reduce the capacity of the beam structure against bending and shear. This study analyzes the effect of post-crack reinforced concrete beam repair using Bacillus Sp. bacteria as a self-healing calcite (CaCO₃) producer through an injection method that is able to close micro cracks. to repair cracked beams. Tests were conducted on one BBMT-N (normal) beam and one BBMT-N+BB beam that had been damaged and then repaired by bacteria, by observing the maximum load, deflection, steel and concrete strain, and crack patterns. Tests were conducted experimentally using a two-point concentrated loading method. The loading stages were divided into two main phases: the damage initiation phase of 75% of the ultimate load to trigger initial cracks, and the final loading phase until the beam reached a collapsed condition after bacterial injection. Structural response was monitored in real-time using LVDT for deflection and strain gauge to measure the strain of steel and concrete materials. The results showed that repair using Bacillus Sp. bacteria. (BBMT-N+BB) provides an increase in the beam load capacity of 0.750 tons or 3.27% compared to the normal beam (BBMT-N) at the same concrete quality (f' c 60.01 MPa). The deflection at the same load is smaller after injection, indicating an increase in stiffness due to the formation of calcite (CaCO₃) deposits in the crack gap. The crack pattern also shows that approximately 55% of old cracks reappear, while 45% of new cracks appear, which proves that bacteria are able to inhibit crack propagation effectively. Overall, the use of Bacillus Sp. bacteria has been proven to increase shear capacity and slow crack propagation, thus potentially being an effective repair method for reinforced concrete structures. Keywords : shear failure, self healing concrete, bacillus sp. bakteria injection