Open Access

ARTICLE

The Influence of Two Natural Reinforcement Fibers on the Hygrothermal Properties of Earthen Plasters in Mogao Grottoes of China

by Wenbei Bi, Zengfeng Yan, Huan Zhao, Lixin Sun, Xudong Wang, Zhengmo Zhang

1 School of Architecture, Xi’an University of Architecture and Technology, Xi’an, 710055, China
2 China Academy of Building Research, Beijing, 100044, China
3 Conservation Institute, Dunhuang Academy, Dunhuang, 736200, China
4 School of Engineering and Mechanics, Lanzhou University, Lanzhou, 730000, China

* Corresponding Author: Zengfeng Yan. Email:

Journal of Renewable Materials 2020, 8(12), 1691-1710. https://doi.org/10.32604/jrm.2020.012808

Received 13 July 2020; Accepted 26 August 2020; Issue published 12 November 2020

Abstract

Murals in Mogao Grottoes consist of three parts: support layer, earthen plasters and paint layer. The earthen plasters play a key role in the preservation of murals. It is a mixture of Dengban soil, sand, and plant fiber. Two different natural fibers, hemp fiber and cotton fiber, were reinforced to earthen plasters in the same percentage to evaluate the influence on hygrothermal performance. The two types of earthen plasters were studied: one containing hemp fiber in the fine plaster (HFP) and the other containing cotton fiber in the fine plaster (CFP). Specific heat capacity, dry thermal conductivity, water vapor permeability, and sorption isotherms were investigated. The results showed that the difference between two natural fibers has much more impact on the hygric properties (water vapor permeability and sorption isotherms) of earthen plasters than on their thermal performance (specific heat capacity and dry thermal conductivity). The CFP with higher density has higher thermal conductivity than the HFP with lower density. But no significant differences of specific heat capacity were observed. Compared with HFP, CFP used in murals can reduce the rate of water transfer and prevent salt from transferring water to the mural surface. The overall findings highlight that all these features of CFP are beneficial to the long-term preservation of murals. The study of the earthen plasters in Mogao Grottoes is of general significance, and the measured properties can be used to obtain coupled heat and moisture analysis of the earthen plasters and to dissect the degradation mechanism of murals.

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