Functional engineered cementitious composite preparation via partial substitution of cementing material by reconstructed red mud: Physicochemical and electromagnetic wave absorption properties

Abstract

Electromagnetic pollution has emerged as a critical concern in contemporary environmental protection. The development of cost-effective and high-performance electromagnetic wave-absorbing building materials is a critical technology for addressing the electromagnetic pollution in architectural space. The utilization of metallurgical solid waste to produce electromagnetic wave absorbers, which serve as functional ingredients in concrete, represents a promising approach. In this study, a functional engineered cementitious composite (ECC) with superior electromagnetic wave absorption property was developed through the partial substitution of cementing materials with reconstructed red mud (RM). RM was initially reconstructed to wave-absorbing ferrite by solid-phase reaction with ferruginous manganese ore in an oxidative roasting process. The solidification behaviors and wave-absorbing properties of ECC samples with 30 % substitution of cementing material by original RM or reconstructed RM were compared. The physicochemical properties including the phase composition, microstructure, hydration degree, and electromagnetic parameters were characterized by XRD, XPS, SEM-EDS, FTIR, and VNA analyses. It’s demonstrated that the addition of RM after ferrite transformation can considerably improve the electromagnetic wave absorption property of ECC. The average reflection loss (RL) was reduced from −7.6 dB to −9.68 dB, and the minimum RL decreased from −12.83 dB to −26.49 dB as well as the effective absorption bandwidth (-10 dB) was extended from 0.53 GHz to 3.99 GHz with the addition of reconstructed RM. Moreover, its mechanical strength can satisfy the requirements of most construction applications, and the sodium in RM can be solidified after phase reconstruction, thereby posing an extremely weak risk of environmental migration. The possible wave absorption mechanisms of functional ECC, including the magnetic loss, the porous resonance, and the dielectric loss, were discussed. This study offers an alternative application pathway for hazardous RM in the development of high-value functional engineered cementitious composites.