Feasibility of protecting earthen sites with sticky rice and lime composite

Abstract

Earthen sites have important historical, artistic, social, cultural, and scientific values. However, due to the extreme natural environment, they have suffered serious damage. The sticky rice and lime composite is one of the most important technological inventions in Chinese architectural history, which is an alternative material for the protection of earthen sites. In the past, the mechanical and microscopic properties of sticky rice and lime composite as binding material have been discussed. However, these properties are not sufficient to evaluate the feasibility of protecting earthen sites with sticky rice and lime composite. In this study, 25 groups of soil samples were prepared at five different lime contents (i.e. 0%, 3%, 6%, 9% and 12% by dry weight of sample) and five different sticky rice contents (i.e. 0.0%, 0.5%, 1.0%, 1.5% and 2.0% by dry weight of sample), and several important characteristics of the samples such as drying shrinkage, colour difference, surface hardness, unconfined compressive strength (UCS), and water vapour permeability are investigated comprehensively. Scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) were used to study the microstructure of samples. Then, the feasibility of protecting earthen sites with sticky rice and lime composite was systematically evaluated. The results indicate that the effectiveness of sticky rice and lime composite is better than that of their individual application. The optimal formula is 6% lime and 0.5% sticky rice for the protection of earthen sites when above indicators are compared. The surface fractal dimension builds bridges between microstructure and macroscopic properties of the soil with sticky rice and lime. Surface hardness and UCS are positively related to the surface fractal dimension, while water vapour permeability is negative related to the surface fractal dimension. This research further provides insights into the potential application of traditional Chinese inorganic–organic composite for protecting earthen sites in arid and semi-arid regions of northwest China.