Remembering that the aim is to obtain an aerated mix resembling sticky crumble in which the hemp particles are well covered by the binder materials without the building material being too wet.
STEP 1: In a pan mixer add the hemp, then add the water.
Wear a dust mask. The hemp, AHMC Binder and sand are all fine particulates.
Allow the ingredients to mix for a few minutes – just until all of the hemp has been coated with the water. It is important that all surfaces are wetted so that the binder can adhere to the hemp. It’s equally important that this wetting is done quickly because hemp is extremely absorbent and you don’t want the water absorbed, you want enough moisture on the surface of the hemp for the binder to evenly adhere to all of it.
Lime based masonry needs thorough mixing so that a light fluffy mix is achieved. This is quite a fast process.
STEP 2: Add the binder next and mix until all the hemp is evenly coated 5 mins.
Have a piece of damp hessian handy to cover the top of mixer for a minute or two after emptying in the Binder. A fine water mister can also be useful to settle any dust.
All of the hemp needs to be coated in binder. Stop the mixer after 2 mins and check that the material is mixed evenly.
STEP 3: The sand is added
This is the last ingredient in the mix.. Once all of the hemp in the mixer is evenly coated with Binder, add the sand, mixing just until the sand has been evenly dispersed.
Empty into tubs and install in formwork that has been misted with water.
Mixed AHMC building materials can be used for up to 6 hours. After that, old mix material can be added into new mixes at a rate of 10% per mix. So there should be no waste onsite.
Your mixer should be selected to suit the task and site organisation. Using a pan mixer is highly recommended. 120L mixers are suitable for smaller jobs using AHMC 9Kg Binder. Builders often prefer to mix in larger batches using a 350 litre pan mixer and we supply AHMC Binder in 18Kg bags for this purpose.
While it is possible to mix Hemp Masonry in a normal 60 litre or 3 cubic foot rotary drum mixer, this is much slower than using a pan mixer mainly because the minimal Lime Binder tends to coat the walls of the drum resulting in the frequent need for stopping the mix.
We send out further detailed mixing instructions with our materials.