Investigation of the mechanical performance and drying shrinkage of hemp concrete

Abstract

The aim of this paper is to investigate the influence of the binder (lime) on the mechanical performance and drying shrinkage of hemp concrete. In order to study the mechanical behaviour, four mixes were made for: external rendering, roof insulation, floor insulation and shuttered walls. The variation of the lime was between 22 and 41 % of the global mass of the hemp concrete. Firstly, the intrinsic characteristics of the hemp shiv were measured through various tests, such as : the particle size which was determinate by scanning the particles and analysing with ImageJ, the water absorption. Secondly, the compressive strengths were determinate for all mixes at 7 and 28 days. The results show that higher compressive strengths were obtained when higher proportion of lime used. Finally the drying shrinkage of these mixes was measured in three curing conditions: the first type curing was in air with relative humidity 50% and temperature 20°C. The second type of curing was covering samples with aluminum foil with relative humidity 50% and temperature 20°C and the last type of curing was covering samples with plastic bags and to place outside with variable relative humidity and temperature. The results of drying shrinkage of hemp concrete increased when the proportion of lime reduced, and the drying shrinkage was higher for the samples kept without any cover.