Investigating the hydration characteristics of iron tailings powder cement mortar produced by the mortar substitution method

Abstract

Due to excessive iron tailings production and low recycling rates, large quantities of iron tailings powder (ITP) have accumulated, leading to severe environmental concerns. To solve this problem, this paper incorporated ITP into building materials by employing the mortar substitution method (replacing cement, water and river sand with ITP) to prepare ITP cement mortar, subsequently evaluating its mechanical properties. The findings showed that the compressive strength of ITP cement mortar (with 20 % replacement of ITP) significantly increased by 34.9 % compared with pure cement mortar at 28 days. To investigate the underlying mechanism, various experiments including XRD, TGA, hydration kinetic analysis, BSE-EDS and MIP were performed to analyze the hydration characteristics of the ITP cement paste. The studies revealed that the ITP provides more nucleation sites for C3S hydration, which promotes a higher hydration reaction rate and generates plentiful hydration yields (C–S–H), during early stage of curing. Furthermore, SEM and BSE-EDS observed that calcium-rich and silicon-poor C–S–H effectively filled the interfacial region between ITP and cement matrix. This dense pore structure and excellent interfacial bonding contributed to the strength improvement of ITP cement mortar. In conclusion, this study proposes an effective method for preparing higher-strength ITP cement mortar and further investigates the underlying mechanism, providing a theoretical foundation for the application of ITP in building materials.