Concrete Mix for Stumps

[OBBob]

Hi Guy's

I am putting in stumps for a timber extension and have holes bored 750mm, which is about 250mm into the clay in my area. Anyway I had to put a 200mm concrete layer at the bottom of the hole, insert the stump and back fill. However I was told to use the mix ratio of the back of the GP concrete bag listed as 'foundations'. I'm a bit worried now after some more reading that this is too weak. The mix is 1 concrete, 3 sand, 5 stone.

About a quarter of the stumps have been done like this. Is this of major concrne given that it is well into the clay and that the actual amount of cement in the base of the hole is in reality about 350mm dia. by 300 - 400mm deeep?

Any advice would be appreciated.

[some_one]

Mate when restumping was done at my place they got a premix truck and a concrete pump. But there were a few about 4 stumps that they guys did the next day and used some kind of cement and just put some water in the hole first and then emptied the cement bag and then mixed them in the hole itself, that was it. So if it can work for a stump on a house you have got nothing to worry about i would say? But you may have to look into the fact that how deep you have to go to get stability and that some one more experienced could tell you better. Cheers.

[OBBob]

Thanks ... it's definately in solid ground, there is no problem there. I think you guys probably used some rapid set or the like. From a technical viewpoint I tend to think is should be OK because of the quantity but these things always worry you in the back of your head until you some experienced clarification.

I mean when these old places were originally built they unly used a plate of redgum under the redgum stump ... and it laste 80 years!