Mesoscopic damage characteristics of hydrophobicity-modified geopolymer composites under freezing-thawing cycles based on CT scanning

The mesoscopic damage characteristics of geopolymer under freezing-thawing (F-T) cycles affect its macroscopic physical and mechanical properties, which further influence the safety of geopolymer buildings. This paper presents a study on the mesoscopic damage characteristics of hydrophobicity-modified geopolymer composites (HM-GC) based on the CT scanning technique. The damage degree and damage distribution characteristics of geopolymer composites (GC) before and after hydrophobic modification were compared. The gradient distri-bution characteristics of damage caused by F-T cycles in HM-GC were further analyzed. The results show that the volumetric porosity of the GC is always larger than that of HM-GC under the same F-T cycle number, indicating the hydrophobic treatment can reduce the F-T cycle damage rate and damage degree. The results also show that the damage induced by F-T cycles in GC and HM-GC shows obvious spatial gradient characteristics. As the F-T cycle number increases, the average gradient coefficient of GC increases first and then decreases, while the average gradient coefficient of HM-GC increases first and then stabilizes. The hydrophobic treatment can reduce the gradient characteristics of the F-T cycle damage and improve the F-T durability of geopolymer composites.