Characterization and use of pulp mill fly ash and lime by-products as roadconstruction amendments

Fly ash and lime by-products are the two main waste streams generated by th e pulp and paper industry. Traditionally, these wastes are disposed of eith er in surface impoundment or landfills. Greater environmental concerns and limited land availability have made these disposal practices increasingly u nacceptable and costly. Thus, the objective of this study was to determine the feasibility of beneficial utilization alternatives with emphasis on the ir use as road construction amendment materials based on technical, economi cal, and environmental considerations. The experiments were conducted to co mprehensively characterize the chemical, physical, engineering, and environ mental properties for both waste samples and their mixtures prepared with l ocal soils at different curing conditions. Field road tests were then condu cted to verify and assess the performance of the mixtures in terms of load bearing capacity, serviceability, and compaction. The results showed that p ulp mill wastes would have little adverse environmental impact and could be used as road construction amendments to improve soil strength and reduce d eformation. This improvement was significantly affected by soil types, mois ture contents, and waste addition rates. During waste-soil amendment, the m etal leachability would be further reduced by the occurrence of solidificat ion processes.