Studi Eksperimental Variasi Molaritas NaOH Pada Mortar Geopolimer Berbasis Abu Sekam Padi dan Abu Terbang
DOI:
https://doi.org/10.31851/deformasi.v11i1.21410Keywords:
Molaritas NaOH, Abu Sekam Padi, Abu Terbang, Mortar GeopolimerAbstract
Produksi semen Portland menyumbang sekitar 8-10% emisi CO₂ global, sehingga mendorong pengembangan material konstruksi alternatif yang lebih berkelanjutan, salah satunya mortar geopolimer. Penelitian ini bertujuan mengkaji pengaruh variasi molaritas natrium hidroksida (NaOH) terhadap sifat fisik dan mekanik mortar geopolimer berbasis abu sekam padi dan abu terbang. Lima variasi molaritas NaOH diterapkan, yaitu 8 M, 10 M, 12 M, 14 M, dan 16 M, dengan rasio natrium silikat (Na₂SiO₃) terhadap NaOH tetap sebesar 2,5:1 dan substitusi abu sekam padi sebesar 5% dari berat abu terbang. Benda uji berbentuk kubus berukuran 50×50×50 mm dirawat pada suhu 60°C selama 24 jam, lalu diuji kuat tekan pada umur 14, 21, dan 28 hari. Sebelum pengujian, karakterisasi bahan baku dilakukan menggunakan analisis X-ray fluorescence (XRF) yang mengonfirmasi bahwa abu sekam padi dan abu terbang memenuhi persyaratan material pozzolan SNI 2460:2014 dengan total SiO₂+Al₂O₃+Fe₂O₃ masing-masing sebesar 92,46% dan 84,76%. Hasil penelitian menunjukkan bahwa molaritas NaOH berpengaruh signifikan terhadap densitas dan kuat tekan mortar geopolimer. Molaritas optimal dicapai pada 14 M dengan densitas 2229,92 kg/m³ dan kuat tekan 39,19 MPa pada umur 28 hari, meningkat 69,7% dibandingkan molaritas 8 M (23,10 MPa). Peningkatan molaritas ke 16 M justru menurunkan kuat tekan menjadi 37,19 MPa, yang diduga akibat kelebihan ion OH⁻ yang menghambat proses geopolimerisasi (over-alkalisasi). Disimpulkan bahwa konsentrasi NaOH 14 M merupakan kondisi optimal dalam sistem mortar geopolimer abu sekam padi-abu terbang untuk menghasilkan sifat mekanik terbaik..
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