Use of a Design of Experiments (DOE) for Studying the Substitution of Natural River Sand (NRS) by Gold Mine Tailings (GMT) in Concrete Manufacturing

The extraction of precious minerals leaves behind an important amount of tailings. When stored in nature, these tailings contribute to environmental degradation. To reduce this degradation, tailings are incorporated in construction as substitute to natural materials. The objective of this study was to use a design of experiments (DOE) to reveal how the substitution of natural river sand (NRS) by gold mine tailings (GMT) in concrete manufacturing can be optimally achieved. This DOE considered three constituents: the amounts of NRS/GMT, that of gravel and of cement. The experimental domain was defined within the concrete standards dosage of 350 kg/m3 and 400 kg/m3 as the lower and upper levels, respectively. The smallest compressive strength on standard cubic specimens on the 28th day varied between 11 N/mm2 and 37 N/mm2 following to the experimental domain. The values of the compressive strength of the experiments carried out allowed to acquire the model of the strength with the coefficients of each factor: Strength=23.25−5.86*A+4.56*B−1.96*C−0.56*A*B+1.41*A*C+1.08*B*C+0.71*A*B*C (with A: GMT+NRS; B: cement; C: gravel). The values of the cumulative weight of the coefficients of each factor were 36.7% (A), 64.5% (B) and 76.6% (C). The study also found that a larger dosage of gravel (40 kg) improves the concrete compressive strength when GMT substitutes NRS between 70% and 100% and when 15 kg of cement is used. For a sustainable and better reuse of GMT as construction materials, an economic and environmental study (the leaching of metals) of the concrete based on GMT would be ideal to consider a large scale production.