Exploring the potential of bayer red mud: Toward self-sensing cementitious composites

Bayer Red mud, a byproduct of the Bayer process for alumina production, poses both environmental threats and resource wastage. This study aims to develop new applications for red mud and carbon fibers as functional fillers in self-sensing cementitious composites, enhancing material performance and promoting sustainable utilization. By preparing ternary cement paste specimens with varying contents of red mud and carbon fibers, the effects of red mud and carbon fiber content on the mechanical properties, pore structure, microstructure, and conductivity were investigated. Research results indicates that red mud concentration can significantly enhance the ionic conductivity of pore solutions in cement-based materials. After 28 days of curing, the compressive strength of the binary slurry containing 40 % red mud reached 38.61 MPa, the pore solution conductivity reached 0.8 s/m, and the resistivity was 3369.6 Ω*cm. Compared to the control group, the resistivity decreased by 36.82 %, and the pore solution conductivity increased by 16.25 %. The resistivity of the sample containing 40 % red mud and 0.4 % carbon fibers decreased to 230.1 Ω*cm, a reduction of 93.17 % compared to the sample with only 40 % red mud. The combination of ionic and electronic conductivity demonstrates excellent electrical performance and strain sensitivity, with a strain sensitivity of 649.9, an 8.8-fold increase compared to the sample with only 40 % red mud. The stability coefficient reached 0.94, indicating stable piezoelectric performance under cyclic testing. Moreover, NMR results indicate that red mud can effectively reduce the porosity of self-sensing cementitious composites. For the sample with 40 % red mud, the porosity decreased by 35 %. The proportion of pores with a diameter greater than 50 nm reduced from 42.22 % in the reference group to 27.44 % in the 40 % red mud group. The study not only provides a new solution for the self-sensing performance of cement-based materials but also highlights the significant potential of red mud-based self-sensing cementitious composites in sustainable building applications, reducing the negative environmental impact of red mud and enhancing the intelligence of building materials. • The BRM-CF-cement composite has the characteristics of environmental friendliness and high sensitivity. • BRM enhances the pore structure of cement-based materials. • R40C0.4 exhibits excellent electrical conductivity, high strain sensitivity, and good stability.