The Brew Cabin

Posted: **Tue Aug 02, 2005 5:02 pm**

Hello folks - been lurking for a while, on and off, and thought I'd register and ask a question........

I am going to lay some Bradstone Old Town stone circles (just waiting on delivery of a round tuit apparently!) and have a question on using plasticiser.
I checked the mortar pages on here a while ago and got similar advice from my local building supplies yard on using a 3-4:1 mix of building/grit sand to cement so that is what I have.
I also have a ton of scalpings (40mm-dust?) for a sub-base (not that that matters I don't think).

I see on the mortar page (and elsewhere) that there is talk of perhaps using plasticiser - but there seems to be no hard and fast rule?
I recall labouring for my grandad who was a brickie (specialising in mixing muck and demolition!) and don't recall ever using plasticiser (but lime maybe?). This was over 25 years ago mind - but can anybody give me a definitive answer on when to use the stuff - and sepcifically for my current 'project'?

Thanks in Advance

Posted: **Wed Aug 03, 2005 1:09 pm**

Adding plasticiser to a mortar mix reduces the amount of water needed to reach a certain workability. This can increase the strength of the mortar and means it remains workable for longer.

Some people say that a squirt of fairy liquid is just as good, but I've read that although fairy liquid improves workability of the mortar, it impaires the finaly strengh and durability.

I used a liquid plasticiser in both my edge spots and any haunching and it definitely made the mix easier to handle, more workable and for longer.

In terms of where you use it in your current project, it depends on how you intend to lay and point your flags. If using the standard 10:1 sharp to cement bedding mix, then no plasticiser should be used. If you've chosen to lay on a full mortar bed, then you could add plasticiser if desired. However, for a bed I don't think the workability of the mortar is that important. Like I said above, you can use it in any mortar for edge restraints and if you choose to point with a wet mortar it can also be used.

Good Luck

Posted: **Fri Aug 19, 2005 4:23 pm**

Fairy Liquid, or any other detergent/wash-up liquid, is better than nowt for non-critical mortars and concretes, but shouldn't be used with brickwork as it can, and does, weaken the mortars end strength.

Liquid plasticisers usually come in 5 litre containers, which would be enough for a bus load of DIYers for a year, and so it may be unreasonable to expect your avergae DIYer to splash out on a full container. In such cases, a splash of the owld wash-up is a handy fall back, as trying to work with an unplasticised mortar is an experience never to be repeated! However, if there are any builders in your area, you might be able to scrounge a yoghurt pot of plasticiser, which would be enough for around 3-4 barrows of mortar.

Another alternative is to buy one of the cements with an in-built plasticiser - Matercretre is the one that springs to mind. The cement contains a powder form plasticiser that comes to life when the mix is wetted.

The Brew Cabin

Platiciser = when to use it.........? - Mixing mortar and using plasticiser