Hysteretic Behaviour and Moisture Buffering of Hemp Concrete

Abstract

Moisture transfer in hygroscopic building materials affects the indoor air quality by exchanging moisture and buffering the ambient relative humidity variations. The paper deals with experimental and numerical study on hysteretic sorption behaviour of the hemp concrete sorption process. Experimental intermediate scanning curves of hemp concrete are measured and used to compare two hysteresis models, Huang’s model and Carmeliet’s model. An original method is achieved to fit the numerical results on the experimental ones leading to the identification of the main desorption curve. The most relevant model, Huang’s model, is implemented in a heat and moisture transfer model based on Kunzel formalism. The transient hydric response of hemp concrete submitted to cyclic hydric loadings is investigated and compared to experimental results issued from the literature. These investigations show the relevance to consider the hysteresis phenomenon into the model. Then, the influence of initial conditions is discussed. The results point out that transient response of hemp concrete strongly depends on the initial hydric state (initial moisture content as well as initial relative humidity).