Combined load and leachant pH effects on contaminant release from fly ash
Several studies have been performed recently on the suitability of particulate waste materials as substitute aggregate in load bearing and geoenvironmental structures. To investigate the long-term performance and durability of these recycled materials, the coupled effects of the interacting fluid chemistry and applied load are herein analysed experimentally. The leachability of heavy metals (copper, selenium and arsenic) from coal combustion fly ash as a function of load (under uni-axial stress of about 570 kPa, 1425 kPa, 2850 kPa and 5707 kPa) was assessed in a specially designed leaching device at leachant pH levels of 4, 6 and 8. The rate of release of Cu from fly ash is decreased by applied uni-axial load when compared to that of column leaching for the low L/S ratio of about 1. Release of Se and As is accelerated by uni-axial stress greater than 1425 kPa compared to leaching in a column.
Keywords: leaching, fly ash, contaminant release, uni-axial loads, pressure dissolution, particulate waste materials, aggregate, load bearing structures, geoenvironmental structures, performance, durability, heavy metals, copper, selenium, arsenic, coal combustion, uni-axial stress, waste management, environmental management, recycling, reuse