Study of lime hemp composite precasting by compaction of fresh mix — An instrumented die to measure friction and stress state

• An original instrumented die able to strongly compact hempcrete was developed.
• Water and lime paste do not always act as a lubricant at wall level.
• Water and lime paste make packing more cohesive and reduce radial stress transmission.
• A parameter to evaluate stress uniformity into the mould is proposed.
• The heterogeneity parameter shows a maximum at 15% moisture and Paste Shiv Ratio of 1.

This paper deals with the processing of lime hemp composite blocks by compaction. A rigid compression die has been developed to reach relatively high compression pressure. This has been fitted with force and strain transducers to measure the stress state during compaction. It provides some means of understanding the effect of mix design and stress level on the compressibility and homogeneity of hardened composites. It is shown that moisture globally increases both friction and packing compressibility. Proper moisture content and paste-to-shiv mass ratio (P/S) can be chosen to reduce the heterogeneity. The combination of friction at wall level and stress transmission is the most detrimental for a moisture content of 20% and a P/S = 1.

A rigid compression die has been developed to reach high pressure during LHC moulding. The die is fitted with force and strain transducers to measure the stress state during compaction. It allows understanding the influence of mix design and stress level on the compressibility and homogeneity of produced composites.Figure optionsDownload as PowerPoint slide