Influence of the type of binder on the properties of lime-hemp concrete

Abstract

This paper compares the properties of hemp concrete made with hydrated lime and pozzolan with those of composites made with commercial binders containing hydraulic additions, in an effort to make hemp concrete more sustainable. The binder type affects the properties and microstructure of hemp concrete. The results indicate that increasing the binder's hydraulicity enhances compressive strength and lowers capillary action. As in lime and cement-lime mortars, this is probably due to the presence of hydrates.Despite the high hydraulic content of the commercial binder evidenced with Scanning Electron Microscopy, the ultimate strength of the commercial concrete is similar to that of the lime-pozzolan concrete. The commercial composite did not reach its full potential strength due to the strong hydraulic nature of its binder and the competition for water with the hemp. The paper also concludes that, initially, composites including highly hydraulic binders dry faster however, at later ages, composites with hydrated lime binders dry faster. The slow early drying of the lime is likely due to its high water retention while drying becomes faster at later ages due to its higher permeability.