Big Mistake

[txDIYer]

Hello all,

First I want to say thank you for this forum. It has been extremely helpful in our build (though we are not quite done yet). I have posted a few pics for reference.

My 9 year old son and I have been building this together and it has been going fairly well. However, today I realized that I may have given a little bit too much empowerment to him, he has been the "Mortar Man". The mortar mix that we have been using since we started turns out to be a 2-1-1-1 homebrew (silica sand, Portland cement, Hawthorns Bond, and Lime). I am keenly aware that the recommended mix is 3-1-1-1 and I own not double checking our work.

I'm hoping its not the end of the world, but he and I could use some reassurance if anyone is willing to offer it?!?

Thanks again for any help!

[MarkJerling]

2-1-1-1 really just means that you'll have a stronger mortar than you need. I can't really see a problem.

[david s]

You might be ok, but as lime is also considered a cementious ingredient you have a cement to aggregate ratio that’s 1:1.5 which is really rich. The clay is not cementious so should be considered a really fine aggregate. The problem with a really rich brew is that it can be too brittle and produces shrinkage problems. The high clay content also contributes to higher shrinkage rates. Sorry , I’m not really providing reassurance, I hope it works ok for you. Only one way to find out.

[txDIYer]

Thank you for the response, would I be better served to keep the temps a bit lower so as to slow down the shrinking? Also, when would I notice the shrinking, would it be right away or over time?

[david s]

Any shrinkage cracks should be apparent on drying as most of the shrinkage takes early.
If it looks ok now then you’re probably good to go.

[Gulf]

All good advice. Looks like you've done your other homework. The arch looks great! The pompeii style oven can't fall in on itself. It would be too late to turn back now anyway. Who knows, it may not last for 2000 years for a future Indiana Jones to uncover. Oh Well, I guess a few generations is good enough