Affiliation:
1. Guilin University of Technology
Abstract
Abstract
The Bayer red mud and phosphogypsum accumulation has caused significant environmental contamination. However, practical and effective resource utilization technologies are still lacking currently. This study aims to develop ferric sulfoaluminate cement (FSAC) using low-cost materials including Bayer red mud, phosphogypsum, and limestone while investigating the influence of different red mud dosages on cement mineral formation, workability, and mechanical properties. The impact of phosphogypsum on FSAC properties, including the hydration process, workability, mechanical properties, hydration products, and morphology, is investigated. It discovers that the C4AF formation in clinker increases as the dosage of Bayer red mud rises. During the calcination process, the maximum replacement of Al3+ in C4A3\(\stackrel{\text{-}}{\text{S}}\) by Fe3+ generates a crystal transformation, leading to more highly reactive cubic C4A3\(\stackrel{\text{-}}{\text{S}}\) minerals (C4A3\(\stackrel{\text{-}}{\text{S}}\)-C) formation, thereby accelerating FSAC hydration kinetics with enhanced early strength and shorter setting time. When phosphogypsum replaces natural gypsum as a retarder agent, P2O5 forms a Ca3(PO4)2 protective film on cement particle surfaces during hydration, and PO43- readily generates AlPO4 with Al3+, reducing the concentration of Al3+ in the system, slowing down hydration, and decreasing the driving force for AFt generation, which increases structure densification. When the Bayer red mud and phosphogypsum contents are 17.64% and 9.21%, respectively, and the dosage of retarder phosphogypsum is set at 20%, the prepared FSAC exhibits satisfactory performance conforming to engineering requirements, showing a significant curing effect on heavy metal ions. It demonstrates compressive / flexural strengths of 34.6 MPa / 4.6 MPa at 3 days and 52.3 MPa / 6.2 MPa at 28 days.
Publisher
Research Square Platform LLC