Pengaruh Porositas Beton Agregat Batu Apung Terhadap Kuat Tekan dan Permeabilitas Menggunakan Analisa X-ray CT

Effects of Porosity on the Compressive Strength and Permeability of Pumice Aggregate Lightweight Concrete Using X-ray Micro-CT

Abstract

[IN] Beton ringan dengan agregat batu apung memiliki struktur internal berpori yang dapat memengaruhi kuat tekan dan permeabilitas. Penelitian ini bertujuan mengevaluasi hubungan antara distribusi porositas, kuat tekan, dan permeabilitas beton agregat batu apung melalui integrasi pengujian eksperimental dan analisis X-ray micro-computed tomography (micro-CT). Campuran beton dirancang dengan rasio air-semen (w/c) sebesar 0,35; 0,45; dan 0,60. Pengujian meliputi kuat tekan, penetrasi air bertekanan, serta karakterisasi porositas agregat dan mortar menggunakan X-ray micro-CT. Hasil penelitian menunjukkan bahwa sekitar 90% porositas terdeteksi berada di dalam agregat batu apung, dengan porositas total sebesar 17,68–18,62%. Peningkatan w/c dari 0,35 menjadi 0,60 menurunkan kuat tekan umur 28 hari sebesar 31,7%, dari 17,27 MPa menjadi 11,80 MPa, serta meningkatkan kedalaman penetrasi air dari 16,10 mm menjadi 19,88 mm. Estimasi koefisien permeabilitas menggunakan pendekatan Valenta dengan asumsi konektivitas pori menghasilkan rentang (1,18–1,30) × 10⁻¹² m/s hingga (1,90–2,09) × 10⁻¹² m/s. Pengamatan pola keruntuhan menunjukkan bahwa retak melintasi agregat batu apung, sedangkan evaluasi empiris berbasis porositas memperlihatkan keterbatasan penerapan model kuat tekan mortar pada beton ringan. Hasil penelitian menunjukkan bahwa dominasi volume pori agregat tidak secara langsung merepresentasikan kontribusinya terhadap kuat tekan maupun permeabilitas. Oleh karena itu, evaluasi kinerja beton agregat batu apung perlu mempertimbangkan distribusi porositas pada masing-masing fase material, karakteristik mekanis agregat, dan konektivitas jaringan pori.

[EN] Pumice aggregate lightweight concrete contains a highly porous internal structure that may influence its compressive strength and permeability. This study investigates the relationships among pore distribution, compressive strength, and permeability through an integrated experimental and X-ray micro-computed tomography (micro-CT) approach. Concrete mixtures with water-to-cement (w/c) ratios of 0.35, 0.45, and 0.60 were evaluated using compressive strength tests, pressurized water penetration tests, and X-ray micro-CT characterization of aggregate and mortar porosity. The results showed that approximately 90% of the detected pore volume was located within the pumice aggregates, while the total CT-detectable porosity ranged from 17.68% to 18.62%. Increasing the w/c ratio from 0.35 to 0.60 reduced the 28-day compressive strength by 31.7%, from 17.27 MPa to 11.80 MPa, and increased the water penetration depth from 16.10 mm to 19.88 mm. Permeability coefficients estimated using the Valenta approach with assumed pore connectivity ranged from (1.18–1.30) × 10⁻¹² m/s to (1.90–2.09) × 10⁻¹² m/s. Failure observations revealed cracks propagating through pumice aggregates, while porosity-based empirical analysis highlighted the limitations of applying mortar strength models to lightweight aggregate concrete. These findings indicate that the dominant pore volume within pumice aggregates does not directly represent their contribution to compressive strength or water permeability. Therefore, evaluating pumice aggregate concrete requires consideration of phase-specific pore distributions, aggregate mechanical characteristics, and pore network connectivity.