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
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