Performance Evaluation and Mechanical Characteristics of Calcinated Red Mud-Based Cement for Eco-Friendly Surface Casing

The Bayer process for alumina production generates substantial quantities of red mud (RM), a highly alkaline industrial byproduct enriched with metal ions, presenting significant environmental management challenges. Approximately 1.5 tons of RM are produced per ton of alumina, contributing to global stockpiles estimated at nearly 4 billion tons. Conventional disposal methods, such as landfilling or aquatic dumping, are both economically burdensome and environmentally detrimental. This study explores the feasibility of incorporating calcinated red mud (CRM) as a partial cement replacement in lightweight cement slurries (LWS) for surface casing applications at depths of 3000 ft. Two cement systems were formulated: a reference neat cement slurry (base slurry, BS) and a CRM-enhanced slurry. CRM was produced by calcining raw RM at 750 °C for 6 hours. Cement slurries were prepared in accordance with API standards and cured at 125 °F for 24 hours prior to testing. Mechanical and physical performance-including compressive strength, tensile strength, and porosity-was evaluated after 1 and 3 days of curing. Initial results indicated a lower 1-day compressive strength for CRM (11.4 MPa) compared to BS (28.9 MPa). However, CRM exhibited a significant strength gain of 80% by day 3, reaching 20.5 MPa, whereas BS showed a decline to 24 MPa. Tensile strength results demonstrated consistent superiority of CRM over BS, with 20% and 3% higher values on days 1 and 3, respectively. Porosity measurements revealed slightly elevated porosity in CRM samples; however, a decrease from day 1 to day 3 suggests continued hydration and matrix densification. These findings highlight the potential of CRM as a sustainable alternative material in LWS formulations for well cementing. To the best of our knowledge, this is the first study to systematically investigate the application of thermally treated RM in cementing operations, underscoring its promising role in advancing environmentally responsible cement technologies.