using lime in cement mix

[karlosmaximos]

The worst bit used to be cleaning all the bricks for re-use.
The mixer used to be like a big cake mixer,and it stayed useable for ages!

 

[lostinfens]

That cake mixer was called a mill

 

[Highgate Handyman]

Lemme make this easy to understand. In Britain, lime is hydrated lime. It doesn't set. It's added to cement to soften it up and make it less hard and aggressive to soft bricks and stone.

In France, lime is hydraulic. It does set and no cement is added. Again the mortar is softer than rock hard cement which cracks stones and soft bricks as the can't breathe.


In restoration. In the U.K., add a little lime to the cement. This will set lovely and the mortar will be easy to shape and tool. It will be nice and hard but less brittle than cement mix and allow bricks to breathe a little and not pop.

Get a bowl or bucket and use it to gauge parts. 1 part cement, 1/2 part hydrated lime, 4.5 part sand.

Or in whole numbers. 9 scoops of sand, 2 scoops of cement, 1 scoop of lime. ( hydrated lime)

If you can find it. Use hydraulic lime. Just add water and sand. No cement. Especially for stone. Most english. Builders only know about cement, sand and plasticiser. That's because we use bricks not stone mainly. The old French masons use lime for stone buildings as the need to allow moisture to flow through , wick up and away from the ground.

Hydrated lime added to cement improves the workability yes but also the chemical properties of the mortar. By reducing hardness. Hard = brittle. It draws water and damp out of the stone/ bricks. Like putting a dry sponge on a spillage it wicks the damp and this is evaporated by the wind. It's basically more porous. Bricks expand and contract too. Lime moves and rolls with the punches. Cement doesnt and will form cracks over time. Lime mortar and cement mortar with lime in it won't spall the bricks. Especially old , softer stocks. Use pure cement when laying foundations and floors. For everything else ( mortar to stick around brickwork) put lime in it to help the bricks.

Imagine being wrapped in cling film. Sweating and building up damp. That's what a pure cement render does. Over stone and soft brick without damp courses this is what happens. The Render will blow/ crack and pull the faces of the bricks off.
Now imagine being wrapped in a cotton towel and being sweaty. The towel wicks the juice off the work.

Cement is super hard and water proof. It's too hard and too water proof for some building materials. As buildings shift, softer mortars will roll with punches. If cracking occurs, the mortar will crack. If the mortar is too hard, the bricks will crack when the mortar cracks. Mortar should be softer than the bricks. Soft bricks want soft mortar.
It's counter intuitive but 'strong' mortar (pure cement) will detrimental over time to the brickwork. Basic restoration is to repoint a house with cement:lime mortar. Easy peezy, job done.

 

[mointainwalker]

"Lemme make this easy to understand........"

This thread is seven years old, so it is doubtful that the OP will still need advice.

You are also wrong when talking about lime in France. Hydrated lime is the only lime I see in the merchants I visit and I don't recall seeing any hydraulic, although it does exist - see link below of the main producer. I have used a fair bit rebuilding my barn.

http://www.c-e-s-a.fr/wp-content/uploads/2011/09/fiche-CHAUX-PURE-BLANCHE-LC-DN-Janv2015.pdf

 

[John D v2.0]

It's not too hard to get NHL (hydraulic) from builders merchants. Just the sheds don't have it.
I had to use it for repointing our front wall bay below window level as the bricks were like sponges, most of the original lime had dissolved due to damp penetrating and there was cement pointing or possibly very hard line on top. The bricks were spalling badly in places.
NHL was a pleasure to work with and looked really good. Hopefully it'll be the last time I'll need to do that pointing!

 

[Highgate Handyman]

Ok my thread wasn't easy to understand. It's hard to digest.

Anyway it's all I saw in France. Yes, 'caux'. Or NHL naturally hydraulic lime.
Chaux Blanche is the white one. But normal chaux is still light in colour

It's the business. It's even better when left in a tub over night with a sheet over it. And knocked up again. It sticks the trowel, it sticks to the work. It can stand on a peak, you can flick it, fling it. And it looks beautiful when it's dry.

It's also what you use for stone and soft brick. And even any brick.

The frogs know what they're doing

 

[Highgate Handyman]

Hydraulic lime is everywhere. Try bricomarche. Or Leroy merlin

Check the small print on the back. Some are cut with 10% cement
You want the pure chaux