Comparison between Sediment Material and Natural Subgrade Material for Road Construction

Abstract

This paper presents the comparison between sediment and natural subgrade material for road construction to check its stability to improve soil properties. Two samples were investigated which are sediment and subgrade construction material which were taken from Wilayat A’seeb, Oman. Sediment was collected from Alkhoud dam, Muscat, and subgrade construction material was collected from Al Mubilah construction site, Muscat. Elemental analyses and mechanical tests were conducted to achieve the purpose of the study. According to the AASHTO classification, the result of the sediment samples shows that it was silty and clayey gravel A-2-4 and clayey sands or sandy clay mixtures according to USCS classification. Also, investigations on the subgrade construction material show that it was silty and clayey gravel and sand A-2-7 according to AASHTO classification and well-graded sands, gravelly sands according to USCS. The result of grain size distribution curves shows that subgrade soil is applicable to be used but sediment is not applicable as pavement construction and. The maximum dry density (MDD) and optimum moisture content (OMC) of the sediment sample are 1.422 g/cm3 and 20.3% respectively. Also, the maximum dry density (MDD) and optimum moisture content (OMC) of the subgrade construction material are 1.634 g/cm3 and 15.5 % respectively. As compared between the two materials, it found that the result of maximum CBR value of subgrade material was 16.13% and the maximum CBR value of sediment material was 16.07% and that means both materials are very close in strength and sediment has the power to be used in road construction with some improvement. According to the experimental results, it shows that the investigated sediment and natural subgrade soil are suitable to be used in the subgrade layer because it is corresponding to the range of Omani standards but it is not suitable to be used as subbase and base layers. Other standards might be compatible with the results to be effective use in subbase and base layers.