Characterization of Bulyanhulu gold mine tailings for utilization in infrastructural development works

Mining activities in Tanzania produce millions of tons of waste rock and tailings yearly. Improper disposal of these mine wastes may cause pollution and degradation of the environment. Stabilization and utilization of stabilized mine waste is idealized to offer an alternative method of mitigating the environmental effects and to provide alternative construction materials. This will also preserve other natural materials and land degradation resulting from borrowing materials for construction activities. However, characterization of the tailings should be done prior to further studies. This research has dealt with characterization of Bulyanhulu Gold Mine tailings for utilization in infrastructure development projects. Two sampling criteria were adopted; sampling due to age and sampling due to depth. Laboratory tests done include mineralogical and chemical analyses, determination of heavy metal contents, Atterberg limits, linear shrinkage, sieve analysis, electric conductivity, pH, compaction, CBR, free swell, UCS, consolidation and triaxial tests. Mineralogical composition test revealed that the tailings comprises of quartz and muscovite subordinated with clinochlore and biotite. The XRF test shows that the major oxide constituent of tailings includes SiO2 (51.5%), SO3 (19.7%), Al2O3 (14.6), Fe2O3 (10.4%), CaO (5.3%), K2O (3.5%) and MgO (2.5%). The tailings was classified as SILT of low plasticity (ML) with the density of solids ranging from 2.89 g/cm3 to 2.93 g/cm3. The MDD (standard compaction) ranges from 1.850 g/cm3 to 2.24 g/cm3 and OMC ranges from 13.5% to 16.5%. The internal angle of friction ranges from 29˚ to 38˚ and cohesion ranges from 12 kN/m2 to 117 kN/m2. The stiffness modulus ranges from 5.6 MN/m2 to 15.2 MN/m2. Compressibility index ranges from 0.04 to 0.11. The heavy metal analysis shows that, with the exception of copper, the heavy metal contents were within the limits of acceptance by the WHO/UNEPA regulatory limits for land application. Based on the results, there is possibility for utilizing Bulyanhulu gold tailings for infrastructure works. However, there is a need of intensive research on stabilization of tailings, and also research on environmental acceptability of the stabilized tailings. Moreover, assessment on applicability of tailings as filler materials for asphalt and cement concretes and in the production of bricks for low cost house scheme need to be done.