Wettability of earthen sites protected by PVA solution with a high degree of alcoholysis

Abstract

Earthen sites in northwest China represent a precious cultural heritage; however, these sites have been seriously damaged by weathering. Chemical consolidation treatment is a widely accepted conservation method, and PVA solution with a high degree of alcoholysis has exhibited potential for improving the strength of soil. However, research on the influence of the PVA solution on the wettability of these earthen sites is rarely reported. Therefore, the aim of this study is to investigate the change in wettability of earthen sites protected with the PVA by laboratory experiments. First, the compressive strength and wettability of soil specimens are analysed with varying PVA content, water content, and drying temperature. The results indicate that the soil strength and hydrophobicity are highest when the PVA content in the soil is 1.0 wt%. The relationship between the soil hydrophobicity and water content follows a one-peak distribution, whereas the hydrophobicity decreases with increasing in drying temperature and is lost when the drying temperature is 80 °C or more. Second, factors influencing the wettability of the composite soil are discussed, and water vapour permeability of 1 cm thick composite soil is investigated in conjunction with exfoliation of surface crust. Finally, the feasibility of protecting different parts (i.e. the upper, middle, and lower parts) of earthen sites with PVA is briefly discussed, and it is emphasised that the wettability should be considered as crucial evaluation criterion for the protection of earthen sites.