Help! i screwed up my concrete mix - Do i have a problem?

[splashgordon]

Now this sounds stupid in hindsight but I need some advice.

I have just laid strip foundations for a retaining wall for a patio project. I used an electric mixer, ballast mix (from Wickes) and cement. Problem is that I got my calculations wrong. I had intended to use a 5:1 ballast:cement mix but ended up using 80Kg of cement with 900Kg of ballast. Schoolboy error I know! It seems to be setting OK but rather slowly.

Am I going to have any problems? Is there anything I should do. I don't really fancy digging it all out to start again.

Any advice/reassurance welcomed!

Regards,
Gordon Anderson

[splashgordon]

Having done some more research, I think what I have done is to effectively create a weak concrete mix (roughly equivalent to C7.5). It has now set hard.

As the retaining wall standing on this foundation will be double skin and typically only be 30cm high (except in one 1m run where it will be 50cm high), it is not exactly a heavy load.

So, in summary, I think I will be OK. Some expert external verification though would be welcomed!

Regards,
Gordon.

[Tony McC]

Is there any chance of casting a 100mm thick layer of a stronger concrete over the existing foundation?

[splashgordon]

Is there any chance of casting a 100mm thick layer of a stronger concrete over the existing foundation?

Not anymore! In one stretch (for the risers for 3 flights of terrassed steps) I did lay another foundation of C20 mix about 120mm thick. The foundations for the retaining walls remain ay C7.5 and the walls are now built on top of them.

I hope it is all OK. I have pretty much finished the patio this bank holiday weekend. Everything has held in place despite being pummeled repeatedly with a wacker so I guess it is all OK.

Cheers,
Gordon.