2019-02-082019-02-081984-9FHWA-OKOklahoma Department of Transportation State Planning and Researchhttps://hdl.handle.net/11244/317182The improvement of U.S. 77 north of Ponca City, Oklahoma, into a four-lane divided highway involves the use of expansive clay as a subgrade material. To stabilize it, Portland cement, fly ash, lime and their conjunctive use were deemed necessary. Prior to field implementation, laboratory studies were conducted which showed that stabilization reduced the plasticity index substantially. The general amelioration of the shale subgrade is reflected in strength improvement after wet-dry cycles and the upgrading of the shear strength parameters of cohesion and angle of internal friction. The strength of short beams was correlated to unconfined compressive strength. The employment of the flexural and compressive moduli of elasticity is presented as an example of assessing pavement strength versus stresses induced by traffic. Data from X-ray diffractograms asvertain that the activity of the clay minerals in the raw shale is reduced as new crystals of hydrated and unhydrated calcium alumina and calcium silicates are formed. In addition, SEM observations depict these crystals and show that the void area is reduced thus rendering a more densified fabric.228 pages25,957,224 bytesapplication.pdfTechnical ReportCementDurabilityFly ashLimeSEMSHaleStabilizationX-ray diffraction