INSTRUMENTED COLUMN TESTING OF SALT UPTAKE FROM UNDERNEATH COMPACTED RED MUD TO OVERLYING SOIL COVER

A cover of inert material overlain by topsoil is required over compacted, seawater-neutralised red mud, a waste product from the refining of bauxite to produce alumina. The cover is to be re-vegetated, and it is necessary to demonstrate that the potential evaporation-driven uptake of salts from the seawater neutralised red mud will not impact the re-vegetation. An instrumented column was constructed to test the evaporation-driven uptake of salts from compacted red mud into an overlying cover material. The column is instrumented with 10 of each of moisture, suction, salinity and temperature sensors, installed through the wall of the column at regular depth intervals, with each set of sensors located at quarter points around the circumference of the column. Two pressure transducers were installed in the column to monitor the change of water level due to rainfall and evaporation. The column was filled with compacted red mud and cover material and was installed on a building roof at UQ, alongside weather stations, and will be subjected to the prevailing weather conditions for up to one year in the first instance, during which time the weather conditions and sensor responses will be continuously monitored. This paper will report on the instrumented column set-up and the early results obtained from the test.