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

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.

Cross validation of hygrothermal properties of historical Chinese blue bricks with isothermal sorption experiments

The historical,cultural,and social value of heritage buildings mandates special protection of these structures.Blue brick is one kind of the main construction materials of heritage buildings,which is porous material and easily subject to deterioration due to environmental factors such as humidity.Therefore,determining the dynamic moisture content rule of materials under fluctuant ambient humidity is necessary for preventative conservation.This study measured the equilibrium moisture content of eight types of Chinese blue bricks under isothermal conditions with varying humidity levels.The results show that when ambient humidity increased from 10%to 90%,the moisture sorption of historical Chinese blue bricks tripled,which is 3 times greater than that of modern Chinese blue bricks and 10(at low humidity)to 20 times(at high humidity)greater than that of clay bricks in the international handbook.The results contribute to the improvement of the international building material database and research related to hygrothermal performance of heritage buildings in East Asia.©2021 Higher Education Press Limited Company.Publishing services by Elsevier B.V.on behalf of KeAi Communications Co.Ltd.This is an open access article under the CC BY-NC-ND license(http://creativecommons.Org/licenses/by-nc-nd/4.0/).