Mechanism of regulating the mechanical properties and paste structure of supersulfated cement through ultrafine iron tailings powder

Abstract

To improve the defects of supersulfate cement (SSC), such as slow hydration rate and low strength, this research investigated the influence of ultra-fine iron tailings powder (UITP) on the strength of SSC. The mechanism of UITP's influence on the mechanical properties of SSC was studied by scanning electron microscope (SEM), X-ray diffraction (XRD), thermogravimetric–differential scanning calorimetry analysis (TG–DSC), and chemical titration analysis of ettringite (AFt). Results show that the compressive strength of SSC paste can be significantly improved when the UITP content was 30%–60%. When the UITP content was 40%, the compressive strength of the SSC paste was increased by 20.4% for 3 d and 44.1% for 28 d compared with that of the control sample. The hydration products of UITP and slag powder were consistent, which were calcium silicate aluminate hydrate (C-A-S-H) and ettringite (AFt); The addition of UITP can increase the amount of hydration products in SSC paste and regulate the ratio of AFt to C-A-S-H, thereby affecting the density of paste microstructure. Moreover, the pore structure of the SSC hardened paste can be improved by adding UITP, and the pore size distribution was optimal when the content of UITP was 40%. This study confirms that UITP and slag powder exhibit a synergistic hydration effect in the SSC system. This synergistic effect significantly improves mechanical properties and volume stability of the SSC hardened paste.