Investigating the use of iron ore tailings as subbase material for pavements.
Abstract
Mining of Iron ore results in large quantities of iron ore tailings (waste) and disposing of such large quantities
of waste poses tremendous challenges for the mining industry and significantly impact the environment. On
their Website, The World Counts estimates that every year, approximately 55 billion tons of fossil energy,
minerals, metals, and biomass are extracted from the earth. Mineral extraction from the earth is coming at a
steep environmental cost.
Due to a ban on the exportation of unprocessed iron ore, the iron mining sector in Uganda has been rather
slow. While meeting NRM youth leaders from the Kigezi region on 13th December 2020, the president
promised that the government was going to implement its plan of constructing a steel factory in Rubanda
district very soon to exploit the approximately 580 million tones of the country’s iron ore resources. This
large scale operation of mining will result in the generation of huge amounts of iron tailings and the so many
problems associated with these tailings will require sustainable and economically viable options.
Therefore this study is about assessing the suitability of Iron ore Tailings for use in Sub bases of Flexible
Pavements. Assessing the suitability of iron ore tailings as a sub-base material will help to determine
whether or not these tailings can be put to profitable use. In case they are found to be suitable, then the
study will not only have cut down on the negative impacts meted on to the environment as a result of iron
ore tailings (i.e. sedimentation, acid mine drainage, destruction of bio-diversity) but will also provide an
alternative material (which will most likely be cheaper since it’s waste) to the commonly used gravel
material for sub-bases.
To assess the Engineering properties of the Iron Ore Tailings, Unconfined Compressive Strength,
California Bearing Ratio, Particle size distribution (Sieve Analysis), Liquid limit, Plastic limit, Plasticity
index, USCS, Specific Gravity, Grading Modulus, Compaction tests were conducted in the Highways lab
at Makerere University. Electron microscope analysis was also carried out to characterize the sample. We
also stabilized the sample using cement to improve its strength properties.
The results of our study are presented in chapters 4 and 5 whereby the California Bearing Ratio of the neat
sample (30.5%) qualifies it to be used as G30 material. The Unconfined Compressive Strength of the
sample increases with the increase of the stabilizer content (Cement) and any cement content > 1.2% gives
a UCS greater than 0.75MPa which qualifies it to be used as a G45 material