Studi Eksperimental Stabilisasi Pasir Menggunakan Fly Ash: Korelasi Peningkatan Kuat Geser, Mikrostruktural, dan Sifat Ultrasonic

Abstract

Tanah pasir merupakan jenis tanah yang rentan terhadap permasalahan geoteknik seperti likuefaksi, erosi, dan kelongsoran akibat rendahnya kohesi dan kuat gesernya. Penelitian ini bertujuan menganalisis pengaruh variasi kadar fly ash tipe C, kepadatan relatif (DR), dan derajat kejenuhan (SR) terhadap kuat geser tanah pasir, mengkaji perubahan morfologi dan mineralogi, serta menentukan korelasi kuat geser tanah pasir berdasarkan kontribusi kadar fly ash, kepadatan relatif, derajat kejenuhan. Penelitian menggunakan pasir dan fly ash tipe C dengan variasi kadar fly ash (5%, 10%, 15%), kepadatan relatif (50%, 70, 90%), serta derajat kejenuhan (0%, 30%, 100%). Seluruh sampel mengalami curing selama 7 hari pada 3 tingkat derajat kejenuhan sebelum dilakukan pengujian Unconfined Compressive Strength (UCS), Ultrasonic Pulse Velocity (UPV), Scanning Electron Microscopy (SEM), dan X-Ray Diffraction (XRD). Hasil penelitian menunjukkan bahwa nilai UCS meningkat seiring bertambahnya kadar fly ash dan kepadatan relatif, serta berkurangnya derajat kejenuhan. Nilai UCS tertinggi sebesar 141,42 kPa dicapai pada kadar fly ash 15%, DR 90%, dan SR 0%. Peningkatan kekuatan paling signifikan terjadi pada penambahan fly ash 10-15% serta peningkatan kepadatan relatif 50-70%. Analisis SEM-XRD mengonfirmasi terbentuknya produk pozzolanik berupa calcium silicate hydrate (C-S-H) sebesar 19,30% yang berperan sebagai pengikat antarpartikel pasir. UCS dan UPV berkorelasi sangat kuat dengan y = 2,05 x + 670,46 dengan R² sebesar 0,98 sehingga berpotensi sebagai metode evaluasi non-destruktif kekuatan tanah. Persamaan regresi linear berganda terbaik yang diperoleh adalah UCS = 4,52 (FA) – 0,51 (SR) + 0,33 (DR) dengan R² sebesar 0,88 yang dapat digunakan sebagai alat prediksi kekuatan tanah pasir terstabilisasi.

Sandy soil is highly susceptible to geotechnical problems, including liquefaction, erosion, and slope failure, due to its low cohesion and shear strength. This study aimed to investigate the effects of Class C fly ash content, relative density (DR), and degree of saturation (SR) on the shear strength of sandy soil, examine the corresponding changes in its morphology and mineralogical characteristics, and develop a predictive correlation for the shear strength of fly ash-stabilized sandy soil based on the contributions of fly ash content, relative density, and degree of saturation. The study employed sandy soil stabilized with Class C fly ash at dosages of 5%, 10%, and 15%, with relative densities of 50%, 70%, and 90%, and degrees of saturation of 0%, 30%, and 100%. All specimens were cured for seven days under the designated saturation conditions before being tested using the Unconfined Compressive Strength (UCS), Ultrasonic Pulse Velocity (UPV), Scanning Electron Microscopy (SEM), and X-Ray Diffraction (XRD) methods. The results showed that the UCS increased with increasing fly ash content and relative density, while decreasing with increasing degree of saturation. The highest UCS value of 141.42 kPa was obtained at 15% fly ash, 90% relative density, and 0% degree of saturation. The most significant strength improvement occurred with fly ash contents ranging from 10% to 15% and an increase in relative density from 50% to 70%. SEM and XRD analyses confirmed the formation of the pozzolanic product calcium silicate hydrate (C-S-H), reaching 19.30%, which acted as a cementing agent between sand particles. A very strong correlation was observed between UCS and UPV, expressed by the equation y = 2.05x + 670.46 with an R² of 0.98, indicating the potential of UPV as a non-destructive technique for evaluating the strength of stabilized sandy soil. Furthermore, the best multiple linear regression equation obtained was UCS = 4.52(FA) - 0.51(SR) + 0.33(DR) with an R² of 0.88, demonstrating its applicability as a predictive model for estimating the strength of fly ash-stabilized sandy soil.