Wall Ties

[MdB]

Big thanks to Ushy for sending through a copy of the grouting spec they used. I would be interested on peoples comments on the mix they used:

One part lime putty
Two parts soft pozzolanic material
Eight parts fine sand

Solids to water ratio 1:3 to 1:4

This sounds like an awful lot of water to me. I can understand that a liquid mix is required to get the grout to flow everywhere but that amount of water is going to make my wall very wet. As it is held together with mud, this can't be a good thing.

 

[Ushy M]

To be honest, we weren't as scientific as suggested in the written method statement and went by the verbal advice from buildings chappie, that we were after a consistency "thicker than cream and thinner than porridge". I quite understand your concern about whether that is appropriate for your building though - sensible to get advice from someone who's used a hydraulic grouting approach on mud rather than risk it.

 

[Flyfisher]

Can't really help with the amount of water in the mix (although I would also be concerned about the amount of water when used on walls with a mud component) but I'm interested in the term "soft pozzolanic material" - what on earth does this mean?

I've heard and read about brick dust and even soil being used as a pozzolan to promote a chemical set when using lime but it all seems a bit vague. I can't envisage brick dust and soil having the same chemical effect - heck, even soil composition can vary enormously. Or am I misunderstanding something here?

Also, ignoring all the environmental and purist issues, does the addition of cement have basically the same effect as these 'more traditional' pozzolans?

 

[MdB]

I'm not sure I understand it myself. This has more info: http://en.wikipedia.org/wiki/Pozzolan

My reading is that it doesn't work the same way as cement but has basically the same properties when combined with lime.

 

[Flyfisher]

Good link - I should have thought of that before posting!

Interesting that pozzolans are also used with portland cement mixtures.

 

[Penners]

I'm interested in the term "soft pozzolanic material" - what on earth does this mean?

I've heard and read about brick dust and even soil being used as a pozzolan to promote a chemical set when using lime but it all seems a bit vague. I can't envisage brick dust and soil having the same chemical effect

But isn't brick dust simply a form of soil?

 

[Moo]

Well, it is in a way, if you're thinking of the fact that bricks are made from clay.
But in order to become a brick the clay has to be fired to a very high temperature, and I understand that in the process some complicated chemical changes take place. And if you were to grind up a brick and mix it with water you wouldn't have something with the same properties as the original clay.