Keeping cement mix fresh

chabsey

Going to be laying a patio this weekend and will need a fairly large amount (at least a wheelbarrow full or two) of cement mix at hand. I remember from the last time mixing cement that it dried out damn quick and I will be leaving this cement for maybe 20 - 30 mins at a time before needing it again.

Obvious solution is to hire a mixer but that's not an option so I was thinking of maybe mixing up a barrow-full (maybe being a little generous with water in the mix, but not sure) and then soaking a canvas cloth and covering the barrow with that.

Will this work or is a mixer the only option?

Thanks!

northdublin

you could add some plasticiser to the mix and it should make it last a day or so......depending on how much you put in.......im sure there are instructions on the bottle of what quantities to use.

squire1

Mix a half barrowful.

Are all your slabs the same thickness? If yes and you are feeling confident you could lay the slabs on a dry mix 10:1 screeded out.(it will take a couple of days to go off) but wet mix is probably easier to work with if you are not used to it.

godtabh

squire1 wrote:

Mix a half barrowful.

Are all your slabs the same thickness? If yes and you are feeling confident you could lay the slabs on a dry mix 10:1 screeded out.(it will take a couple of days to go off) but wet mix is probably easier to work with if you are not used to it.

Maybe I'm reading this wrong but you seem to be refering to concrete rather than cement?

Does adding water help? That keeps it running (not a good idea for concrete)

chabsey

kearnsr wrote:

Maybe I'm reading this wrong but you seem to be refering to concrete rather than cement?

Does adding water help? That keeps it running (not a good idea for concrete)

Sorry, quite possible I'm phrasing it badly. I won't be using it for bedding, I'll be using my 10:1 sharp sand mix for that. I will be using this for buttering the edges of the slabs as I lay them.

As for it being conrete versus cement...I'm talking about the result of mixing builders sand with cement dust (roughly 4:1 ratio) and adding water. That's the stuff i'm trying to keep moist so I can use it for buttering a bunch of the slabs instead of mixing on a per slab basis.

Unfortunatley it's indian sandstone so not uniform size.

ircoha

in this case the plasticiser will work very well: keep it covered in barrow with a damp towel or something and u will be grand.

the plasticiser will be v good because it will make it tacky and will stick to edges v well

northdublin

plasticiser will also make it easier to work with, has something to do with trapping air bubbles in the mix. as i said in my first post plasticiser is the way to go but only for a mortar mix, dont think its used for a concrete mix

chabsey

northdublin wrote:

plasticiser will also make it easier to work with, has something to do with trapping air bubbles in the mix. as i said in my first post plasticiser is the way to go but only for a mortar mix, dont think its used for a concrete mix

Just out of interest, and seeing as I'm a very amateur DIYer, what's the difference between cement, concrete and mortar?

oleras

chabsey wrote:

Just out of interest, and seeing as I'm a very amateur DIYer, what's the difference between cement, concrete and mortar?

Concrete has stones in it, like reinforcement eg. a footpath, foundation.
mortar is sand and cement mixed smooth eg. what you want.
cement is the stuff that comes in the brown bags.......

Keeks

Ordinary Washing up liquid does the same job as plasticiser. Stops it from setting quickly

ircoha

Keeks wrote:

Ordinary Washing up liquid does the same job as plasticiser. Stops it from setting quickly

Keeks, as a moderator [ albeit on Green issues ] I am surprised to see you post a comment which might lead to others following such bad practice.

Washing up liquid, by no stretch of the imagination, does the same job.

Soap and all soap related products interfere with the chemical process that takes place while concrete or mortar sets and result in substandard material.

I would respectfully refer you to page 87 of the 4th edition of the Home Builders Manual

Sonnenblumen

oleras wrote:

Concrete has stones in it, like reinforcement eg. a footpath, foundation.
mortar is sand and cement mixed smooth eg. what you want.
cement is the stuff that comes in the brown bags.......

Concrete is a mix of cement, sand and gravel different ratios depending on usage. Mortar is a blend of sand and lime but can also be a sand/cement+ lime (or nowadays plasticiser) that is used for block/bricklaying. Lime/plasticiser makes mix more pliable or workable especially for trowelling and setting purposes.

Cement (generally Portland cement is the main adhesive ingredient) but there are many different types of cement but even the common Portland is available in a range of colour bags, the brown one being one particular brand supplier.

Mix for sandstone should be approx 6:1 (Coarse ie Builders or plastering Sand : Cement), little water is required as slab laying is best done on a semi -wet mix not a mortar bed which would be too wet and too soft and make level setting too cumbersome.

Semi dry can be left in barrow/mixer for 30 mins no prob only you need to do is give it a quick turn before continuing. In extreme situations no harm to sprinkle over a little water with handbrush.

Mellor

Careful careful, some of the advice here is very border line.
I think Sonnenblumen wrapped it up nicely, in terms of cement, mortar and concrete. Although mortar doesn't need lime in the mix to quailify.
Cement is the agent,
mortar is sand and cement plus additives, ( various)
Concrete is sand & cement & aggretive(sp), which can be various compounds depounds depending on the situation

be wary with advice, boards with bite you