It’s been a while. Apparently life happens! I’m happy to be back.
Maggie and I enjoyed visiting a modern rammed earth (RE) home last weekend. The photo is a representation of the same style used by the Winnipeg family (I & L) we visited. The final look of any RE wall is totally 
dependent on what materials are used. I&L didn’t have appropriate soil to use on site so had to import all their material from outside of the city. They used differing materials – sand, shale, clay – to create layers of colour. They used both white and grey cement as binders which offered even a greater range of colours. They also used oxides (that react with the clay) to create bold seams between colours. The wall is painted with a non-reactive sealant and voila, a beautiful, strong wall that absorbs heat during the day and releases it at night.
Our plan is to use only soils dug out of the footprint we’ve already created on our site. Early testing shows that we have the right ratio of sand to clay (70% to 30%) – but – the sand we have is quite fine so we may need to add some courser material. This next week I’ll collect samples of the soil mix we want to use so I can make blocks and text walls in our shop during the winter. Once we get a good look at the results we’ll decide (with the help of Tim our engineer) what if anything we want to add to the mix – both for look and stability.
Is Cement absolutely necessary? A reader of this blog asked me – after seeing the video in https://www.roomtogrowinfo.ca/surely-on-the-level/ – why we chose to use cement in creating the foundation for our otherwise sustainable home. The up sides to using cement are that we now have a reliably level surface to work on – and – we’re fortunate to have a local supplier who uses local crushed rock and sand in their concrete mix. The down side to cement is that it has a high embedded energy – meaning – it takes a lot of petroleum fueled power to dig, powder, bag and transport. For green builders it’s one of those ‘hold my nose’ decisions we make.
Are there alternatives to using cement? The one we considered was Rubble Trench foundation. The Rubble Trench (http://www.buildnaturally.com/EDucate/Articles/RubbleTrench.htm) is inexpensive and is based on the use of local materials. It’s the uncertainty that discouraged us. We trust concrete to hold up the very heavy walls we’re building. We have no experience with a zero cement rubble foundation. If we were building a workshop first, I’d be more inclined to experiment. We often wish we had friends around with experience to add to all the various decisions we need to make – in real time.
Can we avoid using cement in our walls? I hope so. My tests this winter will tell.
Blessings on your day.