incorrect concrete ratio - what now?

[julianthegypsy]

I had the misfortune to supervise the construction of our company's new offices in Sumatra many years ago, so I've seen more slump tests than I'd care to! Utter chaos, concrete lifts breaking down, ready mix trucks queuing up with concrete going off, contractor trying to add cement and water to the mix to keep it going, utter nightmare! And that was just one day, out of many. The best story was a colleague who was consulting for a factory being built in the middle of nowhere. When they poured the foundations he was called away so couldn't be present. He told them to do the test and keep the cones for him to see on his next visit. They'd never heard of a slump test and didn't understand the instructions properly...When he eventually got down to site and asked, they presented him with a row of perfect 30cm cones......

 

[premmington]

Years and years ago, I used to work for contractor who fitted Fichet-Bauche vault doors to secure enclosures (bank vaults and blast areas). I used to weld the steelwork together, fit the mesh and help with the shuttering! The firm used to mix all the concrete on site with two huge benford mixers. Mostly due to access reasons and also because they could not ever get a dry enough mix off a lorry to get the impact strength!


The problem with concrete is cost! Wet mixes are easier to pour and water is cheap per ton!

 

[captain-destructo]

i would say dont worry about it
give it extra time to harden....stay off it!!

i know someone that once it had gone off enough to walk on it he covered it with visquine and once a day for a month lifted the plastic and watered the concrete

 

[jenki]

Since it was only laid yesterday you could try a 4 or 5 to 1 mix of dust to cement and lay a 1inch topping over the new concrete ASAP, bonding with PVA may help and allow to dry as slowly as possible covering with damp sacks or carpet. The principle is similar to slip formed concrete.

 

[julianf]

The level on the job cant go any higher.

Basically, its either paint some 'stuff' on the top, or do nothing.



It wont be a terrible job. It just wont be as good as it could have been due to me listening to someone who made out they knew better.
Id be more irritated if id let them put the fairly liquid into the mix also, that's for sure....

 

[ukracer]

Just not runny.... cement mixes require very little water to cure, the majority of the water is for workability

A minimum water mix requires hydraulic/ heavy mechanical compaction. .... a 4 lb hammer on a 150mm test cube can't achieve complete compaction

You will probably see some surface wear, but if it is over 100mm and was compacted and worked to bring sufficient cement to the surface and troweled properly you may be ok

When you say worked what does that mean. I am only laying a shed floor and the substrate is concrete and slabs been down for years but laid on a slop and too low for the shed...

 

[ukracer]

The level on the job cant go any higher.

Basically, its either paint some 'stuff' on the top, or do nothing.



It wont be a terrible job. It just wont be as good as it could have been due to me listening to someone who made out they knew better.
Id be more irritated if id let them put the fairly liquid into the mix also, that's for sure....

What's wrong with fairy liquid. I seem to remember they put it in mortar years ago?

 

[Westfield-builder]

And sugar? We often added sugar to slow down the rate concreter set, especially on large pours on hot days.

 

[Pete.]

They have plasticisers and inhibitors to do this nowadays.

 

[brightspark]

What's wrong with fairy liquid. I seem to remember they put it in mortar years ago?

yes cowboys using it instead of plasticiser which makes a fattier mix

 

[Bobtail4x4]

the salt in washing up liquid destroys cement

 

[S-Rail]

Julian , give it 28 to 30 days before you worry to much , it will take that to reach full strength , In that time it will already have reached something like 80% at 7 days . It may be hard the next day but no doubt will dust up . Just give it a chance before making any rash decisions .

Cheers

 

[mike os]

It will be fine... or good enough for what you want is my guess, if not, worry about it in a month or so

 

[lincoln2013]

As Sam said Give it as long as possible before driving on it. I would be tempted to try painting something on it to seal it I personally haven't had any experience with these products but they aren't expensive so worth a try.
I have just laid 23cubic metres of concrete & power floated it I plan to seal it before using it.

 

[julianthegypsy]

The best hardener has to be floated on as the concrete is setting. It's only about 5mm thick but sets it like rock.

 

[daleyd]

Any hardener that's sprayed on will only affect the top few mm of the base though, it's not going to make the the whole base harder or more able to withstand loads. It's more for making the surface layer able to withstand knocks and dings, if the base mix is weak no
Matter what you spray on after will change that.

From the sounds of it though it doesn't sound too bad, hopefully it should be fine the way it is.

 

[lincoln2013]

I was thinking to seal the top and stop it dusting which you typically get with mixes laid wet

 

[mike os]

sealing can be done when it has cured.. just wait

 

[daleyd]

I was thinking to seal the top and stop it dusting which you typically get with mixes laid wet

Yeah, that was just bad timing - my post wasn't a dig at what you suggested, more a reply to Julian's original post. Whatever you paint on may improve the hardness of the surface but the general strength of the slab can't be improved significantly by anything sprayed or painted AFAIK.