Utilisation of activated recycled micro-powder from waste concrete in cement-stabilised base courses: preparation, activation and mechanical properties

The low recycling rate and lack of extensive utilisation methods for waste concrete have led to resource waste and environmental problems. The high-value utilisation of recycled micro-powder (RMP) obtained from waste concrete may help alleviate these issues. In this study, the preparation process of RMP was optimised by adjusting the crushing parameters. Using sodium silicate solution (SSS) as the activator, the optimal activation scheme was determined through orthogonal tests with different moduli and concentrations. Scanning electron microscopy was used to observe the surface morphology of RMP activated at different concentrations of SSS. Response surface tests were employed to analyse the effects of cement dosage, RMP replacement rate and water consumption on the mechanical properties of cement-stabilised composite concrete. The results showed that the correlation curves between the output rate of RMP and each crushing parameter followed a parabolic pattern; SSS with a modulus of 2.6 and a concentration of 5–6% showed a relatively better activation result. RMP had a clear impact on mechanical properties and the optimal replacement range was found to be 12–18%. A parameter range associated with optimal mechanical properties was identified, providing an experimental reference for the utilisation of RMP from waste concrete.