Pengaruh Penggunaan Geopolimer Berbasis High Calcium Fly Ash Sebagai Bahan Stabilisasi Pada Tanah Lempung Di Wilayah Pantai Utara Lamongan

Tanah lempung menjadi permasalahan utama dalam Proyek Pembangunan Sarana Limbah di Wilayah Pantai Utara Lamongan karena memiliki kadar air tinggi, plastisitas yang tinggi, dan kekuatan mekanis yang rendah. Upaya stabilisasi dilakukan untuk memperbaiki karakteristik tanah sehingga dapat menopang konstruksi di atasnya. Stabilisasi dengan geopolimer sudah pernah dilakukan penelitian sebelumnya namun sedikit yang menggunakan fly ash sebagai bahan utama silika dan alumina. Disisi lain keberadaan fly ash digolongkan sebagai limbah nonB3 yang dapat dimanfaatkan sebagai substitusi bahan baku yang dilakukan pada pemadatan tanah seperti dicantumkan pada Peraturan Pemerintah 22 Tahun 2021 pasal 459 ayat 1 tentang pemanfaatan limbah nonB3. Penelitian tugas akhir terapan ini memfokuskan pada stabilisasi tanah menggunakan geopolimer berbasis high calcium fly ash dengan penambahan sebesar 3%, 5%, 7%, dan 10%. Kadar geopolimer yang digunakan mengacu penelitian sebelumnya dengan fly ash 70% dan alkali (NaOH dan Na2SiO3) 30%. Pengaruh penambahan geopolimer ditinjau terhadap sifat fisik, sifat mekanik dan sifat kimiawi serta mikropori dari kondisi tanah lempung inisial. Kondisi tanah inisial memiliki klasifikasi tanah lempung dengan plastisitas sedang. Parameter fisik dan mekanik yang didapatkan antara lain nilai berat volume 1.81 gr/cm3, kadar air 25.10%, angka pori 0.87, specify gravity 2.71, indeks plastisitas 28.50%, kadar air optimum 22.99%, berat kering maksimum 1.52 gr/cm3, nilai CBR 1.36, dan kuat tekan 0.29 kg/cm2. Hasil kimiawi tanah menunjukkan adanya mineral lempung magnetite dengan kondisi makro pori yang banyak. Penambahan geopolimer berbasis high calcium fly ash 3% memberikan hasil berat volume tanah meningkat sebesar 1.99 gr/cm3, kadar air tanah menurun 18.27, angka pori menurun menjadi 0.67, specify gravity menjadi 2.82 dan indeks plastisitas menurun hingga 17.63 %, kadar air optimum menurun 18.25 %, berat kering maksimum meningkat 1.67 gr/cm3, peningkatan nilai CBR hingga 5.58% dan kuat tekan tanah meningkat sebesar 1.89 kg/cm2 dari kondisi inisial. Penambahan geopolimer 5% menurun. Namun, penambahan geopolimer 7% menunjukkan nilai yang meningkat tetapi tidak melebihi 3%. Sedangkan penambahan geopolimer 10% menurun lagi. Hasil XRD menunjukkan mineral baru bernama berlinite dan hasil SEM menunjukkan kondisi mikropori tanah yang rapat setelah distabilisasi. Pola yang tidak beraturan seiring dengan penambahan geopolimer dikarenakan adanya perubahan molaritas akibat penambahan massa NaOH dan air. Perubahan yang paling signifikan terhadap sifat fisik dan mekanik tanah ditunjukkan pada penambahan geopolimer sebesar 3%. Sedangkan untuk penambahan geopolimer 5%, 7%, dan 10% menunjukkan inkonsisten dari setiap parameternya. Disisi lain hasil kimiawi dan mikro pori tanah mendukung terbentuknya gel pengikat antara partikel tanah lempung yang telah distabilisasi. ======================================================================================================= Clay soil is the main problem in the Waste Facility Development Project in the North Coast of Lamongan because it has high water content, high plasticity, and low mechanical strength. Stabilization efforts are carried out to improve the characteristics of the soil so that it can support the construction on it. Stabilization with geopolymers has been carried out in previous studies, but few have used fly ash as the main ingredient of silica and alumina. On the other hand, the existence of fly ash is classified as non-B3 waste that can be used as a substitute for raw materials carried out in soil compaction as stated in PP 22 of 2021 article 459 paragraph 1 regarding the use of non-B3 waste. This applied final project research focuses on soil stabilization using geopolymer based on high calcium fly ash with additions of 3%, 5%, 7%, and 10%. The geopolymer content used refers to previous studies with 70% fly ash and 30% alkali (NaOH and Na2SiO3). The effect of adding geopolymer in terms of physical properties, mechanical properties and chemical properties as well as micropores of the initial clay soil conditions. The initial soil condition was classified as clay with medium plasticity. The physical and mechanical parameters obtained include the volume weight value of 1.81 gr/cm3, moisture content 25.10%, pore number 0.87, specify gravity 2.71, plasticity index 28.50%, optimum moisture content 22.99%, maximum dry weight 1.52 gr/cm3, CBR value 1.36, and the compressive strength is 0.29 kg/cm2. Soil chemistry results showed the presence of magnetite clay minerals with many macro-pore conditions. The addition of geopolymer based on high calcium fly ash 3% resulted in an increase in soil volume weight of 1.99 gr/cm3, soil water content decreased by 18.27, pore number decreased to 0.67, specify gravity to 2.82 and plasticity index decreased to 17.63%, optimum water content decreased to 18.25. %, the maximum dry weight increased by 1.67 g/cm3, the CBR value increased to 5.58% and the compressive strength of the soil increased by 1.89 kg/cm2 from the initial conditions. The addition of 5% geopolymer decreased. However, the addition of 7% geopolymer showed a value that increased but did not exceed 3%. Meanwhile, the addition of 10% geopolymer decreased again. XRD results show a new mineral called berlinite and SEM results show tight soil micropores after stabilization. Irregular pattern along with the addition of geopolymer due to changes in molarity due to the addition of mass NaOH and water. The most significant changes to the physical and mechanical properties of the soil are shown in the addition of 3% geopolymer. Meanwhile, the addition of 5%, 7%, and 10% geopolymers shows the inconsistency of each parameter. On the other hand, the chemical results and soil micropores support the formation of binding gels between the stabilized clay particles