Indirect Tensile Strength Campuran AC-WC dengan Substitusi Aspal dan Serbuk Limbah Ban Karet

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ABSTRAK

Perkerasan lentur di daerah tropis menghadapi risiko kerusakan akibat air (moisture-induced damage) yang lazim dievaluasi melalui pengujian Indirect Tensile Strength (ITS) dan Tensile Strength Ratio (TSR). Substitusi sebagian aspal dengan serbuk limbah ban karet (crumb rubber) berpotensi memperbaiki kinerja campuran sekaligus mengurangi timbunan limbah ban bekas. Penelitian ini bertujuan mengevaluasi kinerja ITS campuran AC-WC yang menggunakan aspal Pen 60/70 yang disubstitusi dengan crumb rubber sebesar 0%, 3%, dan 6% terhadap berat aspal. Pengujian karakteristik aspal dan Marshall digunakan untuk memilih kadar rubber yang layak dan menetapkan Kadar Aspal Optimum (KAO); pengujian ITS kemudian dilakukan pada benda uji dengan KAO dalam kondisi terkondisi dan tidak terkondisi mengacu pada ASTM D4867. Kadar rubber 6% ditolak karena melanggar syarat daktilitas dan kelarutan aspal modifikasi. KAO diperoleh 6,375% (0% rubber) dan 6,500% (3% rubber). Nilai ITS tidak terkondisi hampir setara pada kedua campuran (1.083 vs 1.078 kPa), namun ITS terkondisi campuran 3% rubber (907 kPa) lebih rendah secara signifikan dibandingkan dengan kontrol (986 kPa), sehingga TSR menurun dari 91,01% menjadi 84,13%. Meskipun kedua nilai TSR memenuhi syarat Bina Marga 2024 (≥80%), penambahan crumb rubber pada kondisi produksi penelitian ini tidak meningkatkan ketahanan lembab campuran AC-WC

Kata kunci: AC-WC, crumb rubber, indirect tensile strength, substitusi aspal, tensile strength ratio

ABSTRACT

Flexible pavements in tropical climates face a significant risk of moisture-induced damage, commonly assessed through Indirect Tensile Strength (ITS) and Tensile Strength Ratio (TSR) tests. Partial substitution of bitumen with waste tyre crumb rubber offers a means to improve mixture performance while reducing the accumulation of used tyre waste. This study evaluates the ITS performance of AC-WC mixtures using Pen 60/70 bitumen substituted with crumb rubber at 0%, 3%, and 6% by weight of bitumen. Bitumen characterisation and Marshall testing were used to screen feasible rubber contents and to determine the Optimum Bitumen Content (OBC); ITS testing followed on OBC specimens under conditioned and unconditioned states in accordance with ASTM D4867. The 6% rubber content was rejected due to failure to meet modified-bitumen ductility and solubility requirements. OBC values were 6.375% (0% rubber) and 6.500% (3% rubber). Unconditioned ITS was practically identical for both mixtures (1,083 vs 1,078 kPa), while conditioned ITS at 3% rubber (907 kPa) was significantly lower than the control (986 kPa), reducing TSR from 91.01% to 84.13%. Although both TSR values satisfy the Bina Marga 2024 minimum requirement (≥80%), crumb rubber substitution under the mixing conditions used in this study did not enhance the moisture resistance of the AC-WC mixture.

Keywords: AC-WC, crumb rubber, indirect tensile strength, bitumen substitution, tensile strength ratio