Sustainable eco-friendly bricks from slate tailings through geopolymerization: synthesis and characterization analysis

With the objective of decreasing the adverse impact on the environment and recycling the waste of tailings, the possibility of producing eco-friendly building materials by utilizing the slate tailings (ST) was investigated. Besides ST, the fly ash (FA) and metakaolin (MK) mixtures were added to the raw materials through geopolymerization to improve the brick quality. The mechanical performance of the geopolymer brick was characterized by unconfined compression tests, and the physical properties, microstructure and geopolymerization processes were evaluated using X-ray diffraction (XRD), Scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). The results show that at different ST contents, the variations of the compressive strength are attributed to the coupling effects of pore filling and geopolymer gelation. Higher alkaline activator/solid ratio and extended curing time generally lead to higher strength and bulk density while reduce the water absorption rate. Atomic force microscopy (AFM) was utilized to offer detailed information of geopolymer gels at higher resolutions for obtaining both surface morphology and nano-mechanical properties. The optimum conditions are found to be that the ST is 50%, alkali content and forming days are respectively 14% and 28 days. Under these conditions, the compressive strength and water absorption of the brick samples are 20.47 MPa and 13.4%, respectively, and the other physical properties meet the Chinese Non-sintered Waste Tailing Brick Standard (JC/T 422-2007). (C) 2021 Elsevier Ltd. All rights reserved.