Mixing hempcrete - The Hempcrete Topic: Designing and Building with Hemp-lime - page 337

course, the mixing speed has to match the speed that the placing team can work at, which
can vary around different parts of the frame (placing slows down around corners and open-
ings, and also relies on the shuttering being moved on ahead), as you don't want tubs of
mix sitting around drying out or getting rained on. In any case, you need the tubs back to
keep emptying the mixer, unless you want to invest in more than 25 tubs.
We return to this subject in Chapter 19 , but for now, the point to remember is that finding
the balance between the speed of mixing, ferrying and placing hempcrete is important. The
balance needs to be constantly monitored and readjusted as necessary, in order that the op-
eration is run efficiently and maximum productivity is achieved.
Mixing in a bell mixer
For applications where placement of the hempcrete will be slower (e.g. fiddly historic
building work, or work with complicated or narrow shuttering), or where the total amount
placed is smaller (e.g. a small building or extension), it is possible to mix hempcrete in
a standard bell (or 'drum') concrete mixer. This is not recommended for large new-build
applications, as you will not be able to produce enough to keep up with the speed of place-
ment work.
A bell mixer is more difficult to use than a pan mixer, and requires even more attention to
technique in order to produce a working hempcrete mix. This is another good reason to use
a large pan mixer whenever possible.
If you do decide to use a bell mixer, get the larger type, designed for mixing concrete.
These usually have a wheel at the side to alter and set the tilt of the bell, so you can run it
closer to horizontal (bell mouth at the front rather than pointing up at 45 degrees). This is
much easier on your back than the type that just has handles at the back to lift and tip the
bell: to use these with the bell close to horizontal you have to stand there and hold it in the
right position while it mixes.
Bear in mind that to make the job as easy as possible you also need to get the largest bell
size available, and you will probably want to hire two, as with a bit of practice it's possible
to have two mixers running at the same time.
As well as the mixer, you need the essential equipment outlined for use with a pan mixer
(see page 196 ) . In addition, you need:
Buckets (half a dozen or so at least).