Ready mixed mortar + SBR. ok?

[mattrgee]

Hi all,

I've got some rendering to do and have a couple of bags of Tarmac multipurpose mortar to use up. The SBR calls for 25kg OPC and 75Kg of sharp sand, however I don't know the ratio used in the multipurpose mortar.

Anyone used this combination before?

Thanks.

 

[theprinceofdarkness]

So SBR calls for 5l per 100Kg of mix. How heavy are your bags? - do it pro rata. Pre-mixed mortar will contain plasticiser which leaves air bubbles in the finished mortar, the SBR will have a problem filling these voids so don't use it for sealing a dam. Adding SBR to a mix sort of lubricates it and it will slump easily - be VERY careful with your added water (might not be required).
Frank