The effect of polyvinyl alcohol solution with a high degree of alcoholysis on the expansion and cracking behaviour of quicklime-treated soil in earthen sites

Abstract

Earthen sites with historical, scientific, social, cultural, and artistic values can be destroyed by weathering. Chemical consolidation is an effective method to protect earthen sites, and organic–inorganic composites are often considered ideal. The primary aim of this study was to investigate the effect of polyvinyl alcohol (PVA) with a high degree of alcoholysis on the expansion and cracking behaviour of quicklime-treated soil. The expansion and surface cracking behaviour of the composite soil were investigated with a Crack Image Analysis System. Changes inside the soil samples were observed and analysed by X-ray computed tomography and ImageJ. The results indicated that the expansion of quicklime-treated soil decreased with increasing PVA content, and the cracking behaviour on the surface was different from the inside of the samples. Surface cracks were significantly weakened when PVA was added to soil with a quicklime content ≤ 5%. As the quicklime content increased to 10% or more, the PVA transformed long and wide surface cracks into short and narrow cracks. The development of internal cracks was not as evident as those developing at the surface. Soil samples with 1.0% PVA had no obvious internal cracks at 0–25% lime content. Samples with 0.5% PVA content had internal cracks only when the quicklime content was ≥ 20%. A mechanism for the cracking phenomenon was proposed considering the results obtained from X-ray diffractometry. Soil particles were cemented together through physicochemical reactions with PVA, and these soil particles shared the expansion resulting from the hydration reaction of quicklime instead of through local expansion.