Characteristics of Cinder Gravel as Road Pavement Construction Material in Meru County, Kenya
The availability of suitable road construction materials that meet the specification requirements is becoming scarce, therefore the use of marginal materials presents challenges during construction and performance when used in the construction of road projects. This study exploited the gap that existed by investigating the engineering properties of cinder gravel sourced from Meru County in Kenya. The objectives of the study were to evaluate the engineering characteristics of neat and blended cinder gravel for suitability as road pavement construction material of Low Volume Sealed Roads (LVSRs). The study evaluated the strength and grading properties of the material at different levels of compaction and investigated the relationship between the shear strength of cinder gravel and particle size using a shear box test. The methodology involved both fieldwork and laboratory tests of the material on grading, Atterberg’s limits, compaction tests, strength (CBR), repetitive sample compaction tests, and shear box tests. The study established that neat cinder gravel in its natural state was non-plastic and poorly graded due to deficiency in fine particles <0.075 mm (µm) and was blended with locally available fine material. The optimum blending ratio of 90% cinder + 10% weathered rock met the requirements for natural subbase and base materials for LVSRs. The study showed that the MDD of the blended material increased with the level of compaction, indicating better interlocking of the particles of the material. Similarly, the strength (unsoaked CBR) of blended cinder gravel increased with the level of compaction. There was a gradual increase in the Plasticity Index with the number of compaction cycles of the material due to the breakage of cinder gravels and the blending of material into finer particles with compaction. For the soaked specimen, the CBR decreased as the cycles of compaction increased because with the ingress of water, the finer particles of cinder gravel dispersed and lost the interlocking properties. The shear strength of cinder gravel decreased with compaction cycles due to the decrease in the angle of shearing resistance (φ). In conclusion, cinder gravel sourced from Meru County blended with fine material improved its engineering properties including cohesiveness
AASHTO T180-01 (2004) and T193-99 (2003), American Association of State Highway and Transportation Officials. 444 North Capitol St., N.W., Suite 249, Washington, DC 20001.
Alias, R., Kasa, A., & Taha, M. R. (2014). Particle size effect on shear strength of granular materials in direct shear test. International Journal of Civil and Environmental Engineering, 8(11), 1144-1147.
Berhanu, G. (2009). Stabilising cinder gravels for heavily trafficked base course. Zede Journal, 26, 23-29.
Charles, J. A., & Watts, S. K. (1980). The influence of confining pressure on the shear strength of compacted rockfill. Geotechnique, 30(4), 353-67.
Ermias, L. (2019). The Potential Use of Cinder as a Sub Base Material when Blended with Fine Grained Soil The Case of Durame Intercity Road Project. MSc Thesis, Addis Ababa University. http://10.6.20.92/xmlui/handle/123456789/20282.
Ethiopian Roads Authority (2018), Guideline for the Use of Cinder Gravels in Pavement Layers for Low Volume Roads. Final Draft.
Gareth, H. J., Otto, A., Greening, P. A. K., Endale, A. A., & Etefa, D. M. (2019). Engineering geology of cinder gravel in Ethiopia: prospecting, testing and application to low-volume roads. Bulletin of Engineering Geology and the Environment, 78(5), 3095-3110.
Geology Science (2021), Available at https://geologyscience.com/rocks/scoria/
Lupini, J. F., Skinner, A. E., & Vaughan, P. R. (2009). The drained residual strength of cohesive soils. In Selected papers on geotechnical engineering by PR Vaughan (pp. 88-120). Thomas Telford Publishing. https://doi.org/10.1680/geot.1922.214.171.124
Ministry of Transport and Communication Roads Department (1987). Kenyan Road Design Manual Part III Materials and Pavement Design for New Roads.
Nakao, T., & Fityus, S. (2008). Direct shear testing of a marginal material using a large shear box. Geotechnical Testing Journal, 31(5), 393-403.
Newill, D., Robinson, R., & Kassaye, A. (1987). Experimental use of cinder gravels on roads in Ethiopia. International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, 26(6), 327.
Pulfrey, W., & Walsh, J. (1969). Ministry of Natural Resources – Geological Survey of Kenya, The Geology and Mineral Resources of Kenya. Government Printer, Nairobi.
Smith, G. N., & Smith, I. G. N. (1988). Elements of Soil Mechanic. Napier University, Edinburg-Seven Edition.
Wang, J. J., Zhang, H. P., Tang, S. C., & Liang, Y. (2013). Effects of particle size distribution on shear strength of accumulation soil. Journal of Geotechnical and Geoenvironmental Engineering, 139(11), 1994-1997.
Copyright (c) 2023 Wilson Kipsang Kosgey, Simpson Nyambane Osano, PhD, Sixtus Kinyua Mwea, PhD
This work is licensed under a Creative Commons Attribution 4.0 International License.