Stabilisasi Tanah Gambut Menggunakan Serbuk Cangkang Kerang Hijau Terhadap Nilai CBR Sebagai Subgrade Perkerasan Jalan

Nadhifah Alifia D.R, Ir. Latif Budi Suparma, M.Sc., Ph.D. ; Prof. Ir. Suryo Hapsoro Tri Utomo, Ph.D., IPU., ASEAN.Eng.

2026 | Tesis | S2 Mag. S. & T.Transportasi

Penelitian ini dilatarbelakangi oleh rendahnya daya dukung tanah gambut yang memiliki karakteristik kompresibel, kadar air tinggi, serta stabilitas yang buruk sebagai tanah dasar (subgrade) perkerasan jalan. Kondisi tersebut menuntut adanya upaya stabilisasi untuk meningkatkan kekuatan tanah. Salah satu alternatif yang digunakan adalah serbuk cangkang kerang hijau, yang mengandung kalsium karbonat (CaCO?) dan berpotensi dikalsinasi menjadi kalsium oksida (CaO), sehingga memiliki sifat menyerupai bahan pengikat seperti semen. Penelitian ini bertujuan untuk mengevaluasi pengaruh penambahan serbuk cangkang kerang hijau terhadap peningkatan nilai California Bearing Ratio (CBR) tanah gambut.

Metode penelitian dilakukan dengan variasi campuran serbuk cangkang kerang sebesar 0%, 10%, 20%, dan 30%, serta variasi waktu pemeraman selama 0, 3, dan 7 hari. Pengujian yang dilakukan meliputi sifat fisik tanah seperti kadar air, specific gravity, batas Atterberg, dan distribusi ukuran butiran, serta pengujian mekanik berupa CBR unsoaked dan CBR soaked. Selain itu, analisis kimia dilakukan menggunakan Fourier Transform Infrared (FTIR) dan Scanning Electron Microscope–Energy Dispersive X-Ray (SEM-EDX) untuk mengidentifikasi perubahan struktur dan reaksi kimia yang terjadi pada campuran tanah.

Hasil penelitian menunjukkan bahwa tanah awal tergolong tanah berbutir halus dengan daya dukung rendah, ditandai oleh kadar air sebesar 63,058%, specific gravity 1,70, Liquid Limit 53,292%, Plastic Limit 46,499%, Plasticity Index 6,793%, dan lolos saringan No. 200 sebesar 82,002%. Penambahan serbuk cangkang kerang terbukti meningkatkan kepadatan dan nilai CBR tanah. Variasi optimum diperoleh pada campuran 30% serbuk cangkang kerang dan 10?O dengan nilai Maximum Dry Density 1,525 gr/cm³, Optimum Moisture Content 20%, CBR unsoaked 35%, dan CBR soaked 55%. Analisis FTIR dan SEM-EDX menunjukkan adanya interaksi antara CaCO?, CaO, gugus hidroksil, dan mineral silikat yang berkontribusi dalam memperpadat struktur tanah, sehingga campuran ini berpotensi sebagai bahan stabilisasi tanah dasar dengan memperhatikan aspek pemeraman dan potensi swelling awal.

This study is motivated by the low bearing capacity of peat soil, which is characterized by high compressibility, high water content, and poor stability as a subgrade for road pavement. These conditions necessitate stabilization efforts to improve soil strength. One alternative material used is green mussel shell powder, which contains calcium carbonate (CaCO?) that can be calcined into calcium oxide (CaO), exhibiting properties similar to cementitious materials. This research aims to evaluate the effect of adding green mussel shell powder on the California Bearing Ratio (CBR) of peat soil.

The research method involved varying the percentage of green mussel shell powder at 0%, 10%, 20%, and 30%, along with curing periods of 0, 3, and 7 days. The tests conducted included physical properties such as water content, specific gravity, Atterberg limits, and grain size distribution, as well as mechanical properties through CBR unsoaked and CBR soaked tests. Additionally, chemical analyses were performed using Fourier Transform Infrared (FTIR) and Scanning Electron Microscope–Energy Dispersive X-Ray (SEM-EDX) to identify structural changes and chemical reactions occurring within the soil mixtures.

The results indicate that the original soil is classified as fine-grained soil with low bearing capacity, characterized by a water content of 63.058%, specific gravity of 1.70, Liquid Limit of 53.292%, Plastic Limit of 46.499%, Plasticity Index of 6.793%, and 82.002% passing sieve No. 200. The addition of green mussel shell powder significantly increased soil density and CBR values. The optimum mixture was achieved at 30% shell powder with 10?O, resulting in a Maximum Dry Density of 1.525 g/cm³, Optimum Moisture Content of 20%, CBR unsoaked of 35%, and CBR soaked of 55%. FTIR and SEM-EDX analyses revealed interactions among CaCO?, CaO, hydroxyl groups, and silicate minerals that contributed to a denser soil structure. This mixture shows strong potential as a subgrade stabilization material, with attention needed for curing control and initial swelling potential.

Kata Kunci : Stabilisasi, Tanah Gambut, Cangkang Kerang Hijau, Kalsinasi, CBR Soaked, CBR Unsoaked