Sub grade soils and materials characterizations are the main parameter for flexiblernpavement both in the design and construction phases. Expansive soils in construction sites dornhave significant influence on planning, structural design, construction and maintenance costs,rnperformance and engineering life of roads and highways. They are susceptible to considerablernvolume changes in response to fluctuations in groundwater table and moisture content followingrnseasonal climatic variations. This property can cause severe damages to infrastructure unlessrnproper measures are taken in the design and construction phases. Identification of expansive soilsrnand characterization of their anticipated behavior is thus important for pavement structure &rndrainage design, and estimating the cost, mitigating their undesirable properties. Hence tornmitigate the possible damages, sub grade soils and materials characterization have beenrnconducted.rnThe sub grade soils and materials characterization is conducted at Aposto ~ Wondo ~rnNegele road upgrading project, contract 2: Irbamoda Wadera Road construction located in AdolarnRede woreda, Gujji Administrative zone of Oromia Region, The geographic locations for thernstudy area is bounded by UTM coordinates of 490698 E, 656488 N and 507644 E, 648577 N.rnThe main objectives of the study were: (1) to classify the sub grade soils in to homogenousrnclasses (2) to propose remedial measures for the unsuitable part of the sub grade soils and (3) tornpropose alternative pavement thickness design.rnTo achieve these objectives, a total of 112 sub grade soils samples have been taken atrn200m regular interval and tests are also conducted at project geotechnical laboratory for therndetermination of Atterberg limits, grading, MDD and OMC, CBR and swell values.rnInterpretations have been made with the data obtained from field works and laboratoryrninvestigations, supported by previous studies and researches. In addition, geological data havernalso been incorporated. From the laboratory investigation, it has been concluded that at least 82%rnof the sub grade soils are found to be suitable for bearing stratum and construction materials.rnMechanical stabilization methods have been proposed for the unsuitable section. After evaluatingrnthe pavement structure thickness conducted by the design review consultant, alternativernpavement design approaches have been forwarded. Based on the results and findings, certainrnrecommendations have also been given. These recommendations are removal and replacement,rnin situ treatement, rock fill with geo textiles and underground drains