3:1:12 mortar mix for chimney

[MortarThePoint]

The Architect's specified 3:1:12 mortar for the chimney above eave level. So that's 3 parts white cement, 1 part hydraulic lime and 12 parts sharp sand. For the rest of the exterior walls we have used a lime mortar (so no cement) and we'll therefore be transitioning, so fingers crossed the changeover won't be too noticeable. Any tips welcome on that.

 

One question I have is around admixtures (aka feb). Brickies love the feb, but I presume that's not a good idea with a 3:1:12 mix as the lime should be the plasticiser or is it fine to add feb?

[nod]

26 minutes ago, MortarThePoint said:

The Architect's specified 3:1:12 mortar for the chimney above eave level. So that's 3 parts white cement, 1 part hydraulic lime and 12 parts sharp sand. For the rest of the exterior walls we have used a lime mortar (so no cement) and we'll therefore be transitioning, so fingers crossed the changeover won't be too noticeable. Any tips welcome on that.

 

One question I have is around admixtures (aka feb). Brickies love the feb, but I presume that's not a good idea with a 3:1:12 mix as the lime should be the plasticiser or is it fine to add feb?

Your correct The lime will plaster-size the mortar 

[tonyshouse]

No plasticiser additives when using lime, lime dose it for you. 

[MortarThePoint]

Just now, tonyshouse said:

No plasticiser additives when using lime, lime dose it for you. 

 

I know I'll have to talk them out of it though ?