Advice regading correction to concrete slab

[keystrokes]

Hi all,

Using the wealth of info on here I took on the project of laying a 6.8mtr x 4.4 mtr contrete slab, 100ml thick.

I split it into sections and layed the first section, but ran out of materials at the very end so a corner of it (about 1mtr x 0.5 mtr sqr) is about 1inch below the top level.

The following weekend I completed the rest of the project and I am extremely pleased with the result, of course getting better with every section.

Now the problem, I have not been succesful in filling in the corner of the first section I did (mentioned above), when the concrete sets, it seems to not to take to the layer below and seems to dry crumbly and breaks up and can be swept away when I go over it with a broom.

Any ideas, would it be okay to fill in this area with a cement/sand mix? if so, what sort of ratio/mix would I need?

Many thanks in advance,

Lloyd

 

[noseall]

leaving the unfinished concrete only 1" down was a crime.

you are best using sharp sand (screed sand, grit sand) and cement and thoroughly damp the area first.

 

[keystrokes]

Thank you noseall, that was a quick response.

Yes it was a crime, but it was 3.50pm on a Sunday when I releasied I was going to be short of materials.

Can you perhaps give me more detail. I was thinking of making a load (I have a cement mixer) and pouring it in and using a trowel/float to get a smooth level finish, I just was not sure of the ration mix to use.

Would it be 6 sand to 1 cement?

 

[WabbitPoo]

Sounds OK to me, but I would brush a cement slurry on first to help adhesion. Just a gut feeling that'd be a good plan. Your problem will have been that it is drying (curing) too quickly, so be prepared to do it on a cool, damp day or to cover it with sacking or sheeting to keep it moist.

 

[Thermo]

i would be inclined to cut some lines into it with an angle grinder as well if you have one just to give a bit more of a key

 

[noseall]

Would it be 6 sand to 1 cement?

6:1 is ok for concrete, but you will need to beef it up to 4:1 for sharp sand as there is a lot less aggregate.

 

[keystrokes]

Thank you all, some very good advice.

I have an angle grinder so I will cut some lines in to give grip.

4:1 sounds good, I will do that

WabbitPoo, was is the ratio for a slurry mix, is this just a very thick mix that i put on first and then the 4:1 mix for proper?

Many thanks guys

Lloyd