Preparation and characterization of the greener alkali-activated grouting materials based on multi-index optimization

•A green road grouting material AASFGM was prepared at ambient temperature.•A multi-index optimization design based grey correlation and objective weighting is applied systematically.•The physical properties of AASFGM were tested and compared with those of cement grouting materials.•The microstructure and strength development mechanism of AASFGM was further characterized. As a green and carbon-friendly material, alkali-activated grouting material (AAGM) has great application potential in reinforcement engineering. In this study, the alkali-activated slag/fly ash grouting material (AASFGM) was prepared with industrial-waste ground granulated blast-furnace slag (GGBS) and fly ash (FA) as raw materials. In order to meet the multi-performance requirements, a multi-index optimization design based on grey correlation and objective weight was adopted to prepare AASFGM pastes. And its physical performances including fresh and harden properties were tested and compared with those of cement grouting materials (CGM), more than that, the microstructure and strength development mechanism of AASFGM was further characterized by means of X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Energy-dispersive Spectrum (EDS) and Fourier transform infrared spectroscopy (FT-IR). It is found that the AASFGM paste possesses clean production, high mechanical strength, high fluidity, low bleeding rate and low porosity, providing appealing properties as grouting materials for reinforcement. The new multi-index optimization method, based on grey correlation and objective weights determined, is much more scientific and objective to obtain a balanced performance for AASFGM preparation. The optimized AASFGM paste has a uniform and compact microstructure, and it also has remarkable advantages in mechanical strength, bleeding rate and porosity compared with CGM. As a carbon-friendly grouting material, it may become a greener substitute of CGM for the cleaner reinforcement engineering.