EFEKTIVITAS CAMPURAN PALM OIL FUEL ASH-MgO (POFA-MgO) SEBAGAI BAHAN STABILISASI TANAH LEMPUNG EKSPANSIF DITINJAU PADA NILAI CBR

Abstract

Tanah lempung ekspansif memiliki potensi kembang-susut yang tinggi dan daya dukung yang rendah sehingga berpotensi menurunkan kinerja lapisan tanah dasar jalan. Penelitian ini bertujuan menganalisis pengaruh campuran Palm Oil Fuel Ash (POFA) dan Magnesium Oksida (MgO) terhadap sifat tanah lempung ekspansif, mengevaluasi perubahan indeks plastisitas dan nilai California Bearing Ratio (CBR), serta menentukan kadar optimum campuran yang efektif sebagai material subgrade. Penelitian dilakukan pada tanah lempung ekspansif sedang dan tinggi dengan penambahan POFA sebesar 15% dan variasi MgO sebesar 0,25%, 0,50%, dan 0,75%. Pengujian meliputi batas Atterberg, swelling, CBR rendaman, dan Scanning Electron Microscopy (SEM). Hasil penelitian menunjukkan bahwa campuran POFA–MgO mampu menurunkan indeks plastisitas dan potensi pengembangan tanah serta meningkatkan nilai CBR rendaman. Komposisi optimum diperoleh dengan kadar POFA tetap 15% dengan penambahan 0,25% MgO dengan nilai swelling terendah sebesar 1,41% pada tanah ekspansif sedang dan 1,97% pada tanah ekspansif tinggi, serta nilai CBR rendaman masing-masing sebesar 13,80% dan 15,21%. Hasil tersebut menunjukkan bahwa campuran POFA–MgO berpotensi menjadi alternatif bahan stabilisasi yang efektif dan berkelanjutan untuk meningkatkan kinerja tanah lempung ekspansif.

Expansive clay has a high potential for expansion and contraction and low bearing capacity, which may compromise the performance of the road sub-base layer. This study aims to analyse the effect of mixtures of Palm Oil Fuel Ash (POFA) and Magnesium Oxide (MgO) on the properties of expansive clay, to evaluate changes in the plasticity index and California Bearing Ratio (CBR) values, and to determine the optimum mixture content that is effective as a subgrade material. The study was conducted on medium- and high-expansive clay soils with a 15% addition of POFA and MgO variations of 0.25%, 0.50% and 0.75%. Tests included Atterberg limits, swelling, saturated CBR, and Scanning Electron Microscopy (SEM). The results showed that the POFA–MgO mixture was able to reduce the plasticity index and swelling potential of the soil, whilst increasing the saturated CBR value. The optimum composition was obtained with a fixed POFA content of 15% and the addition of 0.25% MgO, yielding the lowest swelling values of 1.41% for moderately expansive soil and 1.97% for highly expansive soil, as well as saturated CBR values of 13.80% and 15.21%, respectively. These results indicate that the POFA–MgO mixture has the potential to serve as an effective and sustainable alternative stabilisation material for improving the performance of expansive clay soils.