Jonathan wrote:
On 10 Sep, 23:08, Dundonald wrote:
On Sep 10, 8:03 am, Lobster wrote:



On 09/09/2010 19:36, Dave Osborne wrote:
Dundonald wrote:
Hi,
I've concreted for the first time, mixing my own in a proper mixer, to
lay a new slab alongside a slab that already existed. I used 1 part
cement to 5 parts balast. The new slab has now been curing for 6 days
(with a couple days of intermittent heavy rain and my having to cover
the cement with plastic sheeting) but the new slab is a darker shade,
may be a browny shade, where as the existing slab is lighter and is a
shade of grey.
My questions are - Does all concrete wind up roughly the same shade of
grey? Will my new slab eventually look the same (ish) as the existing
one after curing is complete? How long does it take to fully cure?
The final colour of concrete depends on the colour of the aggregate it's
made from. If the new batch is made from the same ingredients in the
same proportion as the old batch, then the two batches will end up the
same colour.
Yes I've experienced the same thing myself with aggregate obtained from
different suppliers - the colours were still quite noticeably different
when fully cured. Didn't matter to me as mine was going to be hidden
uder floor covering, but assuming yours isn't, maybe you could use floor
paint (ie grey, concrete-coloured?)
David
Thanks both posts.

My mix will definitely be of a different aggregate so I'm sure the
colours will noticeably remain different. Oh well it's a utility area
anyway for sheds so no huge deal. I'm just a perfectionist and like to
have consistency. Paint might be the answer.

It would be nice if it stopped raining enough to allow it to cure
properly too.

The rain shouldn't affect it. Curing is not drying, it's a chemical
process. Concrete sets under water as the Romans discoverd.

Jonathan

Rain *will* affect concrete curing in the first 24 hours or so as it
will weaken the mix at the surface and will increase the amount of laitence.