<![CDATA[ AbstractMarine environments are highly aggressive to reinforced concrete due to chloride ions that accelerate chemical degradation and initiate reinforcement corrosion, potentially causing early depassivation of steel. This study investigates the temporal evolution of chemical compounds in reinforced concrete and identifies early corrosion-related changes induced by artificial seawater exposure using Fourier Transform Infrared Spectroscopy (FTIR). Structural-grade reinforced concrete specimens were exposed to artificial seawater with a salinity of approximately 3.5% NaCl under partial immersion conditions, where half of each specimen was immersed while the remaining half was exposed to laboratory air. The exposure period lasted 30 days, with surface concrete powder samples collected at selected intervals. FTIR analysis was conducted to monitor changes in key functional groups, including –OH (Ca(OH)₂), CO₃²⁻ (CaCO₃), calcium silicate hydrate (C–S–H), and free silica. The results indicate progressive carbonation from the early stages of exposure, evidenced by a gradual reduction in –OH intensity and a corresponding increase in carbonate peaks, reflecting a decrease in concrete alkalinity. A notable increase in –OH intensity during the exposure period suggests enhanced moisture absorption, which may facilitate chloride ion diffusion. Although C–S–H phases persisted throughout the test duration, the appearance of free silica at later stages indicates the onset of hydration matrix degradation. These findings demonstrate that progressive carbonation combined with moisture absorption under partial immersion conditions can accelerate early reinforcement depassivation and potentially shorten the service life of reinforced concrete in artificial marine environments.Keywords:Reinforced concrete, corrosion, FTIR, carbonation, artificial seawater AbstrakLingkungan laut merupakan salah satu kondisi paling agresif terhadap beton bertulang karena keberadaan ion klorida yang dapat mempercepat degradasi kimia beton serta inisiasi korosi tulangan, sehingga berpotensi menyebabkan depasivasi lapisan pelindung baja tulangan pada tahap awal umur layan struktur. Penelitian ini bertujuan untuk menganalisis perubahan temporal senyawa kimia beton bertulang dan mengidentifikasi indikasi awal korosi akibat paparan air laut buatan menggunakan metode Fourier Transform Infrared Spectroscopy (FTIR). Spesimen beton bertulang bermutu struktural dipaparkan pada lingkungan air laut buatan dengan salinitas ±3,5% NaCl, di mana setengah panjang spesimen direndam dalam air laut buatan dan setengah lainnya terpapar udara. Pengamatan dilakukan selama 30 hari dengan pengambilan sampel serbuk permukaan beton pada hari ke-9, 13, 15, 17, 20, 21, 24, 27, dan 30. Analisis FTIR digunakan untuk memantau perubahan intensitas dan keberadaan gugus fungsional utama, meliputi –OH (Ca(OH)₂), CO₃²⁻ (CaCO₃), fase hidrasi silikat (C–S–H), dan silika bebas. Hasil penelitian menunjukkan terjadinya karbonasi progresif sejak tahap awal paparan, yang ditandai dengan penurunan bertahap intensitas puncak – OH (Ca(OH)₂) dan peningkatan puncak karbonat (CO₃²⁻, CaCO₃), sehingga mengindikasikan penurunan alkalinitas beton. Lonjakan signifikan intensitas –OH pada hari ke-17 menunjukkan penyerapan kelembapan yang tinggi, yang berpotensi mempercepat difusi ion klorida ke dalam beton. Fase C–S–H masih terdeteksi sepanjang periode pengujian, namun kemunculan silika bebas pada akhir paparan mengindikasikan awal degradasi matriks hidrasi. Temuan ini menegaskan bahwa kombinasi karbonasi progresif dan penyerapan kelembapan pada kondisi perendaman parsial dapat mempercepat indikasi depasivasi tulangan dan berpotensi menurunkan umur layan beton bertulang di lingkungan laut buatan.Kata Kunci: Beton bertulang, korosi, FTIR, karbonasi, air laut buatan]]>
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