Concrete Slab Curing Time

LynnLegend

Hi All,

We are having a conservatory built, and have had a 100mm concrete slab laid. I understand that it apparently takes 1 day per 1mm of concrete to allow the slab to cure properly. I have two questions based on this:

1. Will the slab have been curing despite the fact it has been exposed to the elements since it was laid (frame etc is going in next week). Or will it only start curing once in the dry?

2. Do I really need to wait the 100 days before tiling, or is the 'day per mm' advice a bit OTT?

Thanks in advance,

LL.

Cisco001

Don't need 100 days.

28 days

LynnLegend

Thank you very much for the reply.

Just to clarify, 28 days from the slab being laid, or 28 days of dry under-roof conditions.

FreeBear

LynnLegend wrote: »

Just to clarify, 28 days from the slab being laid, or 28 days of dry under-roof conditions.

Ordinary Portland Cement (OPC) sets by way of a chemical reaction with water - General advice is to allow 28 days for cement/concrete to reach full strength from the time it was poured.

In reality, OPC will continue to gain strength well beyond 28 days, but as long as the slab is dry, you can start laying your tiles after four weeks. Although if you can leave it longer, the dryer the slab will be at the core.

Just remember, tile adhesive is also usually a cement based product, so once you've laid the tiles, the longer you can leave them before walking on the floor, the better - Although they say 24 hours, seven days is better.

Kiran

1mm per day is standard sand cement screed not a concrete slab.a concrete slab requires moisture to cure and properly as part of he exothermic reaction in th cement. As for tiling, you need to read the specification of the adhesive, that will tell you what moisture level is acceptable. 28 days under cover will be fine, you can in all likeliness do it before that but if you want to be certain then you can use a dpm on the slab. The epoxy ones are best I've used on previous projects.

southcoastrgi

I have always allowed 1 month per inch before laying flooring

Heedtheadvice

As has been said it is a chemical reaction so will even cure under water. Two critical things are to keep it damp initially to slow initial curing process (preventing hairline cracks that ultimately may lead to failure with high loading or temperature variations) so do not try to dry it out over the first week and indeed keep it damp with light spraying and then let it dry before laying tiles (though those cement based adhesives may also benefit from a bit of surface dampness for similar reasons - see instructions!).

Strength continues to increase over time (even from Roman times!!)unless other influences cause it to deteriorate. Critical strength, such as for 40Newton concrete, that is laid must be left (OPC is assumed here) the full 28 days but you will not need that spec for a conservatory or tiles but given that a few weeks will be fine. Uncritical foundations are often left a lot less time but those requiring structural integrity usually are left at least two to three weeks before any loading.

Collectively with all these responses you should now have a plan!

LynnLegend

Thank You's have been distributed. Thank you all for your knowledgable answers.