A study was conducted to stabilize low stiffness road surface material with high carbon fly ash. The non-cementitious Maryland fly ash was activated with another recycled material, lime kiln dust (LKD). California bearing ratio (CBR) and resilient modulus tests were conducted to determine the strength and stiffness, respectively, of the stabilized materials. Addition of LKD and curing of specimens generally increased CBR and summary resilient modulus (SMR) and lowered plastic strains, whereas fly ash addition alone decreased the strength and stiffness due to the non-cementitious nature of the ash. CBR increased with increasing CaO content as well as with CaO/SiO₂ and CaO/(SiO₂ + Al₂O₃) ratio of the mixtures; however, these parameters could not be correlated with the SMR. The unpaved road materials stabilized with LKD and fly ash is expected to lose 31 to 67% of their initial moduli after twelve cycles of freezing and thawing. Finally, required base thicknesses were calculated using the laboratory-based strength parameters.