Effect of Rice Hull Biochar as an Additive on the Shear Strength Parameters of Silty Sand

Ron Gabriel Navarro; Juliah Cristine Julio; Patrick Adrian Salazar; Andre Cruz; Bien Dave Papasin

doi:10.52751/cmujs.2026.v30.i1.evdz36f

Authors

Ron Gabriel O. Navarro University of the Philippines - Los Baños Author
Juliah Cristine I. Julio University of the Philippines - Los Baños Author
Patrick Adrian M. Salazar University of the Philippines - Los Baños Author
Andre C. Cruz University of the Philippines - Los Baños Author https://orcid.org/0009-0003-9635-8049
Bien Dave B. Papasin University of the Philippines - Los Baños Author

DOI:

https://doi.org/10.52751/cmujs.2026.v30.i1.evdz36f

Keywords:

silty sand, rice hull biochar, soil stabilization, shear strength

Abstract

Silty sand is a common soil type in the Philippines. While it exhibits moderate bearing capacity, its mechanical properties may not be adequate to support heavier structural loads without additional stabilization. This study investigates the use of rice hull biochar as a stabilizer for silty sand. Rice hull biochar is an emerging soil amendment derived from the pyrolysis of agricultural waste, which contains high amounts of silica and has been shown to influence the physical and mechanical behavior of soils. In this study, soil samples were amended with varying percentages of rice hull biochar (0%, 2%, 5%, 8%, 10%, and 12% by weight) combined with 5% cement. Shear strength was assessed under both drained and undrained conditions through direct shear tests and unconsolidated-undrained triaxial tests, respectively. The results revealed that the addition of biochar improved the cohesion and internal friction angle of the silty sand, contributing to overall enhancement in shear strength. Statistical analysis indicated that a 10% biochar concentration yielded significant improvements to the shear strength parameters compared to the control soil sample. These findings suggest that rice hull biochar, when used with partial cement, can effectively enhance the geotechnical properties of silty sand.

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References

Abbasi, N.; Mahdieh, M. Improvement of geotechnical properties of silty sand soils using natural pozzolan and lime. International Journal of Geo-Engineering. 2018. 9:4. https://doi.org/10.1186/s40703-018-0072-4

Budhu, M. Soil Mechanics and Foundations, 3rd ed.; John Wiley & Sons, Inc.: Hoboken, New Jersey, USA, 2011.

Bowles, J.E. Foundation Analysis and Design, 3rd ed.; McGraw-Hill International Edition: Singapore , 1997.

Han, J. Principles and Practices of Ground Improvement.; John Wiley & Sons, Inc.: Hoboken, New Jersey, USA, 2015

Singhal, S. Biochar as a cost-effective and eco-friendly substitute for binder in concrete: a review. European Journal of Environmental and Civil Engineering. 2022. 27(2):984–1009. https://doi.org/10.1080/19648189.2022.2068658

Barbhuiya, S.; Das, B.B.; Kanavaris, F. Biochar-concrete: a comprehensive review of properties, production and sustainability. Case Studies in Construction Materials. 2024. 20:e02859. https://doi.org/10.1016/j.cscm.2024.e02859

Castellini, M.; Giglio, L.; Niedda, M.; Palumbo, A.D.; Ventrella, D. Impact of biochar addition on the physical and hydraulic properties of a clay soil. Soil and Tillage Research. 2015. 154:1–13. https://doi.org/10.1016/j.still.2015.06.016

Blanco-Canqui H. Biochar and soil physical properties. Soil Science Society of America Journal. 2017. 81(4):687–711. https://doi.org/10.2136/sssaj2017.01.0017

Sadasivam, B.Y.; Reddy, K.R. Engineering properties of waste wood-derived biochars and biochar-amended soils. International Journal of Geotechnical Engineering. 2015. 9(5):521–535. https://doi.org/10.1179/1939787915Y.0000000004

Hussain, R.; Ghosh, K.K.; Garg, A.; Ravi, K. Effect of biochar produced from mesquite on the compaction characteristics and shear strength of a clayey sand. Geotechnical and Geological Engineering. 2020. 39:1117–1131. https://doi.org/10.1007/s10706-020-01549-2

Morales, L.F; Herrera, K.; Lopez, J.E.; Saldarriaga, J.F. Use of biochar from rice husk pyrolysis: assessment of reactivity in lime pastes. Heliyon. 2021. 7(11):e08423. https://doi.org/10.1016/j.heliyon.2021.e08423

Mahmoud, A.A.; El-Sayed, A.A.; Fathy, I.N.; Fawzy, S.; Alturki, M.; Elfakharany, M.E.; Abouelnour, M.A.; Mahmoud, K.A.; Dahish, H.A.; ElTalawy, S.M.; Nabil, I.M. Evaluation of rice husk biochar influence as a partial cement replacement material on the physical, mechanical, microstructural, and radiation shielding properties of ordinary concrete. Scientific Reports. 2025.15:27229. https://doi.org/10.1038/s41598-025-11987-8

PhilRice (Philippine Rice Research Institute). Rice husks as sustainable energy resource. 2016. Available online: https://www.philrice.gov.ph/ (accessed on 13 August 2025).

ASTM International. ASTM D6913/D6913M-17: Standard Test Methods for Particle-Size Distribution (Gradation) of Soils Using Sieve Analysis. ASTM International: West Conshohocken, Pennsylvania, USA, 2017.

ASTM International. ASTM D4318-17: Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils. ASTM International: West Conshohocken, Pennsylvania, USA, 2017.

ASTM International. ASTM D2487-17: Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System). ASTM International: West Conshohocken, Pennsylvania, USA, 2017.

ASTM International. ASTM D2850-23: Standard test method for unconsolidated-undrained triaxial compression test on cohesive soils. ASTM International: West Conshohocken, Pennsylvania, USA, 2023.

ASTM International. ASTM D3080/D3080M-22: Standard test method for direct shear test of soils under consolidated drained conditions. ASTM International: West Conshohocken, Pennsylvania, USA, 2023.