The Influence of the Type of Lime on the Hygric Behaviour and Bio-Receptivity of Hemp Lime Composites Used for Rendering Applications in Sustainable New Construction and Repair Works

The benefits of using sustainable building materials are linked not only to the adoption of manufacturing processes that entail reduced pollution, CO2 emissions and energy consumption, but also to the onset of improved performance in the building. In particular, hemp-lime composite shows low shrinkage and high thermal and acoustic insulating properties. However, this material also shows a great ability to absorb water, an aspect that can turn out to be negative for the long-term durability of the building. For this reason, the hygric properties of hemp-based composites need to be studied to ensure the correct use of this material in construction and repair works. The water absorption, drying and transpirability of hemp composites made with aerial (in the form of dry powder and putty) and hydraulic limes were investigated here and related to the microbial growth induced by the water movements within the material. Results show that hemp-natural hydraulic lime mixes exhibit the highest transpirability and drying rate, the lowest water absorption by immersion and capillary uptake and the least intense microbial attack and chromatic change. A microscopical study of the hemp shives also related their great ability to absorb water to the near-irreversible swelling of their structure under dry-wet conditions.The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 326983 (NaturALiMe), and the Spanish project MAT-2012-34473 of the Ministerio de Ciencia y Competitividad. Author MB, owner of the CANNABRIC company, had some role in the design and preparation of mortar samples and in the preparation of this manuscript, but did not have any additional role in data collection and analysis

Temperature dependence of sorption isotherm of hygroscopic building materials. Part 1: Experimental evidence and modeling

International audienceThe knowledge of sorption isotherm is of high importance when evaluating the performance and the durability of building envelope. Whereas the influence of hysteresis was often investigated, less attention has been paid to the influence of temperature. In the present paper, a specific experimental protocol is defined to investigate the influence of temperature on relative humidity variations within three building materials (Autoclaved Aerated Concrete, wood fiber insulation and hemp concrete). The measurements are analyzed in terms of a hygrometric coefficient K [%r.h./degrees C], defined as the maximal relative humidity amplitude against the maximal temperature amplitude, and are compared to three modeling approaches: temperature dependent sorption model, Kelvin equation and Clausius-Clapeyrbn equation. Discussions show that the third approach is relevant and that it can be used to evaluate effortless the isosteric heat of sorption and the temperature dependence of the sorption isotherm. (C)2017 Elsevier B.V. All rights reserved

Influence of the setting process and the formulation on the drying of hemp concrete

International audienceHempconcrete is a sustainable material that becomes successful in the field of building construction. It is made out of hemp shivs mixed with a lime based binder and water and manufactured through three processes: spraying, moulding or mechanical mixing and tamping. Experiments were performed under natural and forced convection on several instrumented blocks during the curing time. The instrumentation (thermocouples, humidity sensors, weight-scales) allows investigating the drying kinetics and the moisture diffusivity and apprehending the hygrothermal behaviour of the material. It is observed that manufacturing processinfluences the initial water content and the final density whereas the hygrothermal behaviour depends on the material formulation

Temperature dependence of sorption isotherm of hygroscopic building materials. Part 2: Influence on hygrothermal behavior of hemp concrete

International audienceIn the part I of the paper, a temperature effect was experimentally observed for the relative humidity measurement. This effect was correlated to the temperature dependence of the sorption isotherm. In this part II of the paper, the influence of this temperature dependence is investigated on the simulated hygrothermal behavior of hemp concrete. Sorption isotherm was modeled through three approaches: a unique curve (like in WUFI), a temperature-dependent GAB model or the Clapeyron equation associated to the isosteric heat of sorption evaluated in the part I of the paper. Comparison between simulation and experiment is performed for the sample presented the part I of the paper and for a wall subjected either to a slow temperature decrease toward 0 degrees C or to a fast temperature increase due to solar radiation. Whatever the investigated case, results underline that accounting for the temperature dependence improve the relative humidity prediction. Nevertheless, a great sensitivity to the modeling approach and to the input parameter was observed. (C) 2017 Elsevier B.V. All rights reserved

Etude expérimentale et numérique de la phase de séchage d'une paroi en béton de chanvre projeté

Séminaire International du Génie Climatique et de l'Energétique, Constantine, Algérie, décembre 201

Experimental and numerical studies of the drying of hemp concrete

International audienc

Etude et modélisation du comportement thermo-hydrique d'une paroi en béton de chanvre

Conférence Francophone, IBPSA France, Novembre 2010, communication oral