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

Abstract

Fly ash and lime by-products are the two main waste streams generated by the pulp and paper industry. Traditionally, these wastes are disposed of either in surface impoundment or landfills. Greater environmental concerns and limited land availability have made these disposal practices increasingly unacceptable and costly. Thus, the objective of this study was to determine the feasibility of beneficial utilization alternatives with emphasis on their use as road construction amendment materials based on technical, economical, and environmental considerations. The experiments were conducted to comprehensively characterize the chemical, physical, engineering, and environmental properties for both waste samples and their mixtures prepared with local soils at different curing conditions. Field road tests were then conducted to verify and assess the performance of the mixtures in terms of load bearing capacity, serviceability, and compaction. The results showed that pulp mill wastes would have little adverse environmental impact and could be used as road construction amendments to improve soil strength and reduce deformation. This improvement was significantly affected by soil types, moisture contents, and waste addition rates. During waste-soil amendment, the metal leachability would be further reduced by the occurrence of solidification processes.Key words: wood ash, fly ash, lime by-products, solid waste management, pulp mill waste, waste utilization, leaching tests.