The impact of coal gasification slag powder on fluidity, rheology and viscoelasticity properties of fresh cement paste

Coal gasification slag (GS) is a potential pozzolanic industrial waste discharged during coal gasification. The study aimed to investigate the effect of finely ground GS powder on the fluidity, rheology and viscoelasticity properties of cement paste, which is essential for utilizing GS as a supplementary cementitious material for building materials. The research revealed that the morphology, physical filling effect, and particle size distribution of GS powder played a vital role in the workability of cement. The particle size distribution of the GS-cement system followed the Rosin-Rammler distribution model, and the width of the particle size distribution negatively correlated with paste fluidity. The rheological characteristics of blended paste transitioned from Bingham to modified Bingham fluid with increased GS powder content, showing shear thinning. Plastic viscosity can predict the fluidity and thixotropy of the paste. GS powder at 10% content broadened the particle size distribution, improved fluidity and rheological properties, with minimal effect on viscoelastic characteristics. With increased GS powder content, plastic viscosity, yield stress, and thixotropy of blended paste increased continuously, resulting in a slow transition from viscosity to elastic solid. Extending mechanical grinding time improved the fineness and activity of GS powder, optimized the particle size distribution, and reduced water demand, minimizing negative effects. •The morphology and particle size distribution of GS powder mainly affect the workability of cement.•The fluidity and thixotropy can be predicted by the plastic viscosity.•The paste containing 10% GS powder has the best fluidity and rheological properties.•Mechanical grinding can reduce the crystallinity of GS crystalline phase, improve its activity and viscoelasticity.