STABILIZATION OF RECYCLED BASE MATERIALS WITH HIGH CARBON FLY ASH

Abstract

<bold> ABSTRACT</bold>

Fly ashes produced by several power plants in United States occasionally contain significant amounts of unburned carbon due to common use of low nitrogen-oxide and sulphur-oxide burners in recent years. This ash cannot be reused in concrete production due to its reactivity with air entrainment admixtures and is being landfilled at large percentages. 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, 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. Most of the factor considered on the thickness of the base layer and cost calculations.