Experimenting with lime mortar – August 2010

Yesterday I built a lime mortar based garden retaining wall.  Here are my notes;

Last weekend I mixed lime with water.  I’m having difficulty with this, because all of the references I read say that you have to use hydraulic lime, not hydrated lime.  But somewhere, I’ve read that you can make hydraulic lime by soaking hydrated lime in water to make lime putty/hydraulic lime.

OTOH the wikipedia article suggests that using hydrated lime to make lime putty results in a mix that’s not as strong as lime putty that’s never been hydrated lime and gets hard with a different chemical process. (further reading suggests that hydrated lime that’s been sitting in water for a while doesn’t have this problem)

I used hydrated lime (Calcium hydroxide) + water (H2O) = Lime Putty (Calcium Oxide)

I mixed 2 buckets of sand from Rose’s sandpit with 2/3 of a bucket of lime.  I was going to make a 2:1 mix but changed my mind and made a 3:1 mix.  I need to find a way to exclude more of the water, because it made a very runny mix.

Then I started laying my wall.  This article says that you need to keep the mortar wet, including wetting all the surfaces, covering with wet burlap and wetting 3-7 times per day.  I wet my first two layers of bricks, but the mortar mix was so sloppy that I gave up and let the bricks absorb some of the moisture from the mortar.

Most of the mortar appeared dry and hard within a couple of hours.  Today the wall seems to be strong enough to stand on.  The first mortar I laid is grey and the later mortar (that perhaps dried faster) is white.  It wasn’t very strong against a sideways kick, but it might be better next week.

Today’s  reading suggests that a ratio of 6:1 has also been used.  Maybe I’ll have a play with that later today.  When it’s stopped raining and I feel better.

Hooray!  The best and most definitive and trustworthy for Australian building products article is here.  I am now comfortable with my process.  Also, really glad that the lime we have in Ballarat has been sitting in water for nearly 12 months. 

Notes for next week;
bring eye protection (others should too)
bring waterproof gloves.  (others should too)
bring a course brush for wetting bricks with water.
bring stuff for a string line
order clean “sharp” sand
Wear warm clothes

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