Ananta, Exaudi (2025) Studi Efek Penambahan CaO sebagai Zat Aditif pada MgO-Al₂O₃ terhadap Sifat Mekanik dan Ketahanan Alkali pada Rotary kiln. Other thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Batu bata refraktori MgO.Al2O3 merupakan salah satu material yang banyak digunakan dalam industri suhu tinggi seperti rotary kiln, karena ketahanannya terhadap temperatur ekstrem dan lingkungan kimia agresif. Salah satu tantangan dalam pengembangan material ini adalah meningkatkan kekuatan mekanik dan ketahanan terhadap serangan alkali. Penambahan aditif seperti CaO dipercaya dapat mempengaruhi proses sintering dan pembentukan fasa, yang berperan dalam penguatan struktur mikro. Penelitian ini bertujuan untuk mengetahui pengaruh penambahan CaO terhadap sifat mekanik dan ketahanan alkali dari batu bata refraktori MgO.Al2O3. Proses fabrikasi dimulai dengan pencampuran bahan-bahan berupa MgO, Al₂O₃, bentonit, aquades, dan variasi CaO sebesar 0% dengan kode A1, 4% dengan kode B1, dan 8% dengan kode C1 menggunakan rasio distribusi partikel (PSD) berdasarkan Modified Andreassen Equation dengan nilai q = 0,25. Campuran yang telah homogen dipres menggunakan cetakan, dikeringkan selama 24 jam di suhu ruang, lalu dikeringkan kembali pada suhu 110°C selama 12 jam. Setelah proses pengeringan, sampel diproses sintering pada suhu 1300°C selama 2 jam untuk memfasilitasi pembentukan ikatan antarpartikel. Karakterisasi dilakukan melalui analisis X-ray Diffraction (XRD) untuk identifikasi fasa kristalin, Scanning Electron Microscopy dan EDX untuk pengamatan morfologi serta komposisi unsur, serta penghitungan porositas menggunakan aplikasi ImageJ. Pengujian meliputi uji kekuatan tekan dingin (Cold Crushing Strength/CCS), ketahanan abrasi, dan ketahanan alkali terhadap senyawa K₂CO₃. Hasil pengujian menunjukkan bahwa sampel dengan penambahan CaO sebesar 4% memiliki struktur mikro paling padat, nilai CCS tertinggi sebesar 19,94 MPa, nilai abrasion loss terendah sebesar 4,092 cm3/menit, serta perubahan volume lubang dan lebar retakan terendah setelah uji alkali. Sebaliknya, penambahan CaO sebesar 8% menghasilkan porositas tinggi dan penurunan ketahanan mekanik serta ketahanan kimia. Berdasarkan hasil tersebut, dapat disimpulkan bahwa penambahan CaO secara moderat, khususnya sebesar 4%,mampu meningkatkan performa batu bata magnesia spinel untuk aplikasi suhu tinggi yang melibatkan lingkungan abrasif dan lingkungan alkali.
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MgO-Al2O refractory bricks are among the materials widely used in high-temperature industries such as rotary kilns, due to their resistance to extreme temperatures and aggressive chemical environments. One of the main challenges in developing this material is enhancing its mechanical strength and resistance to alkali attack. The addition of additives such as CaO is believed to influence the sintering process and phase formation, which play a role in reinforcing the microstructure. This study aims to investigate the effect of CaO addition on the mechanical properties and alkali resistance of MgO–Al₂O₃-based refractory bricks. The fabrication process began by mixing MgO, Al₂O₃, bentonite, distilled water, and CaO in variations of 0% as code A1, 4% as code B1, and 8% as code C1, using a particle size distribution ratio (PSD) based on the Modified Andreassen Equation with a q value of 0.25. The homogeneous mixture was pressed using molds, dried at room temperature for 24 hours, and then dried again at 110°C for
12 hours. After drying, the samples were sintered at 1300°C for 2 hours to facilitate interparticle bonding. Characterization was performed using X-ray Diffraction (XRD) to identify crystalline phases, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) for morphological and elemental analysis, and porosity measurements using the ImageJ application. Tests included Cold Crushing Strength (CCS), abrasion resistance, and alkali resistance using K₂CO₃ exposure. The results showed that the sample with 4% CaO addition exhibited the densest microstructure, the highest CCS value of 19.94 MPa, the lowest abrasion loss value of 4,092 cm3/minute, and the lowest volume change and crack width after alkali testing. In contrast, the 8% CaO addition resulted in high porosity and a reduction in both mechanical and chemical resistance. Based on these findings, it can be concluded that moderate CaO addition, particularly at 4%, enhances the performance of magnesia spinel bricks for rotary kiln in abrasive environments and alkali-rich environments.
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