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

Abstract

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 distribution 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.