Combined effects of ceramic polishing powder and GGBS on microstructure and freeze–thaw performance of concrete

The concrete industry faces dual challenges of high carbon emissions and large-scale accumulation of industrial solid wastes, particularly in cold regions where freeze–thaw damage significantly reduces structural durability. This study investigates the combined use of ceramic polishing powder (CP) and ground granulated blast-furnace slag (GGBS) as composite admixtures in C30 concrete. A systematic multi-scale experimental program—including compressive strength testing, rapid freeze–thaw cycling, NMR-based pore structure analysis, and SEM morphological observation—was conducted on seven mix proportions with fixed 20% GGBS and variable CP dosages (5–15%). The optimized mixture S20CP10 (20% GGBS + 10% CP) achieved a 28-day compressive strength of 46.5 MPa, representing a 36.8% increase over the reference concrete. At the termination of freeze–thaw testing (200 cycles), this mixture maintained a relative dynamic elastic modulus of 74.0% and exhibited the lowest mass loss (0.53%), outperforming all other groups. Microstructural analysis reveals that the performance enhancement arises from pore refinement: the CP-GGBS combination reducing the proportion of pores larger than 100 nm. The findings demonstrate that the CP-GGBS composite approach offers a promising pathway for producing durable, resource-efficient concrete for cold-region applications.