Iron ore tailings, phosphate slags, and lithium slags as ternary supplementary cementitious materials for concrete: Study on compression strength and microstructure

Abstract

The high carbon emissions in the construction industry and the large-scale storage of high silicon iron ore tailings (IOTs, SiO2 > 60% wt., Fe2O3 > 10% wt.) associated with mining pose a serious challenge to sustainable development. Therefore, using IOTs as a replacement for cement to produce supplementary cementitious materials (SCMs) for concrete is a sustainable solution. However, the progress of this solution has been hindered by the low pozzolanic activity of IOTs. In this study, an IPL system SCMs was prepared using phosphorus slag (PS), lithium slag (LS), and high silicon IOTs, and applied to concrete. The feasibility of this approach was evaluated through the compressive strength tests, matrix pore structure analysis, and interface transition zone (ITZ) performance evaluation. The results showed that the compressive strength of concrete with IPL system SCMs reached 52 MPa at a dosage of 20%, which was higher than that of the control group at 48.7 MPa after 28 days. In addition, the IPL system SCMs optimized the pore structure of the concrete matrix, reducing the pore rate and unhydrated rate in the ITZ. This study not only provides a sustainable solution for the large-scale application of IOTs in the construction industry but also further alleviates the pressure of mining.