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Mechanical and Physical Evaluations of Fine Sand-RAP Blends for Subgrade and Subbase Applications

Mohamed H. Zakaria, Mostafa El-Fewy, Sabry Fayed, Ali Basha

Abstract


Fine sand has a low load-bearing capacity and tends to deform easily, limiting its use in road construction. Recycled asphalt pavement (RAP) may offer a sustainable solution to improve these properties. Accordingly, the primary objective is to assess how varying RAP content affects the gradation, compaction, bearing capacity, and California Bearing Ratio (CBR) of sand-RAP blends. RAP contents ranged from 0% to 100% by weight. The results show that integrating RAP improves sand gradation, making it suitable for subgrade layers, with mixtures containing 40%-60% RAP meeting subbase requirements. CBR increases significantly with RAP, from 8.78% in fine sand to 41.67% at 100% RAP. Dry density also improves by 12%-16% with 40%-60% RAP, while optimum moisture content (OMC) decreases by over 30%. Bearing capacity increases significantly with RAP content. At 40%-60% RAP, increases range from 299.53% to 411.83% (Dr = 60%) and 243.69% to 318.43% (Dr = 90%). RAP inclusion enhances stiffness, peaking at 530% (Dr = 60%) and 326% (Dr= 90%) between 40%-60% RAP. Initial gains are steady at 10%-30% RAP, but diminishing returns occur beyond 50% RAP. Generally, notable performance is achieved at 40% RAP, while 50% RAP ensures optimal stiffness and structural integrity, with diminishing returns afterward.

 

Doi: 10.28991/CEJ-2025-011-05-017

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Keywords


Recycled Asphalt Pavement (RAP); Fine Sand-RAP Blends; California Bearing Ratio (CBR); Plate Bearing Tests; Sustainable Road Materials; Relative Density (Dr); Subbase; Subgrade.

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DOI: 10.28991/CEJ-2025-011-05-017

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Copyright (c) 2025 Mohamed Hamed Zakaria, Mostafa El-Fewy, Sabry Fayed, Ali Basha

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