Performance of hempcrete in a building - The Hempcrete Topic: Designing and Building with Hemp-lime - page 133

Hempcrete on its own
There is an issue regarding the suitability of assessing hempcrete using current methods
for testing the structural performance of masonry and mortars, since hempcrete does not
fail in the same way as these materials do. Instead of cracking or fracturing under compres-
sion, hempcrete fails by deforming - bending out of shape, with some recovery towards its
original shape when the load is removed. Further investigation into the positive implica-
tions of hempcrete's ability to deform without breaking, in the context of the movement of
buildings, would be worthwhile.
The main focus of research into hempcrete as a structural material has been in relation
to pre-cast blocks, which are sometimes described as either 'thermal' (lower density) or
'structural' (higher density). In order to achieve blocks with the degree of compressive
strength needed for load-bearing applications, a significant increase in hempcrete density
is required. Since this is achieved by increasing the proportion of binder in the mix, some-
times with the addition of some cement and/or sand, increased structural performance can
only be gained at the cost of some insulative value (which is the primary reason for the use
of hempcrete) as well as an increase in the material's embodied energy. Therefore the nor-
mal use of hempcrete in blocks is as thermal blocks - used, as with cast-in-situ hempcrete,
to infill around a structural frame.