Mechanical properties and interface microscopic characterisation of fibre-reinforced slag-fly ash geopolymer agglutinated iron tailings filling materials

In order to study the deformation resistance of fibre-reinforced alkali activated slag-fly ash geopolymer agglutinated iron tailings filling materials, the mechanical properties test, scanning electron microscope (SEM) and Xray diffraction (XRD) microscopic test are performed using the macro-micro cross-scale method. Then, the evolution law of mechanical behaviour and microstructure of samples are studied, revealing the internal relationship between macro-mechanical properties and fibre parameters. The results show that based on experimental results, as the fibre content increases, the compressive strength of the sample first increases and then decreases. When 6%0 9-mm fibre is added to the sample, the compressive strength and flexural strength of the sample reach the maximum. Through SEM and XRD, it was found that fly ash and slag in an alkaline environment to generate polymerization products hydrated calcium silicate and hydrated calcium aluminosilicate filled in the basic skeleton formed by iron tailings sand particles, making the filling material more dense. When the fibre content is 4-5%0, the fibre exists as a single embedded fibre. When the fibre content is 6%0, the occurrence form shows a three-dimensional (3D) network structure, and when the fibre content exceeds 6%0, the fibre appears to be entangled in the sample. The mechanical properties of the filling material are improved by the single embedded fibre and the 3D reticular knot distribution fibre through the wrapping effect and the reticular inhibition effect, respectively. The results obtained can provide a reference for theoretical research and practical applications of polypropylene fibre-reinforced geopolymer materials.