New mortar course powdery between thermalites.

[Draughtsman]

I have had to repair some thermalite blockwork that had masonry joint hangers put in at the wrong height, plus a few cracks. The repair work mortar comes out easily with an old 10mm wood chisel an mallet, it's rubbish. I'll have to hook it all out and replace.

Fresh bag of cement, using 4:1.

Has it dried too quickly? I did give the joints a spray of water before repointing but it all dried out very quickly anyway.

Maybe I should have given the freshly exposed block sides a dose of 5:1 pva mix and let it dry, to seal and prevent the blocks leeching away the moisture too quickly?

 

[garyo]

How long did you give it before testing it with the chisel?

 

[Draughtsman]

About 40hrs.

I tried spraying a fine mist of water in the general vicinity periodically, just to get some moisture back into the equation. It seems to have worked. I started spraying a weak pva mix on new joints and letting it dry before adding mortar, to try and stop the dry block from ripping the moisture out of the mortar.

The roof and doors have been on for quite a while, now. The thermalites are dry as a bone.

 

[John D v2.0]

40 hours it hadn't had enough time to become properly hard really. First time I used mortar I thought I did it wrong as it crumbled easily at the end of the weekend, I was thinking I'd need to pull it out and try again next weekend, but by then it was solid as a rock!

 

[^woody^]

Did you compact the mortar well and iron the face to compress it?

Anyway the mix is too strong and despite you thinking it will dry hard, it will dry too quick because of the cement, no matter how much you wet it.

6 or 7:1. Wet the block, press the mortar in well, iron the face will the towel. No PVA nonsense.

 

[Draughtsman]

It does seem to have gone off now. It was pushed in from a float using the handle of of a spoon that was a handy size, it compacted nicely as it went in and the surface was ironed off with the trowel.

I did notice that my mix is stronger than that used when the wall went up, it may have been wiser to have used a similar mix to the original.