Repair around manhole cover....

[dishman]

I was clearing a neglected part of my driveway, in which is situated a manhole cover.

Unfortunately the driveway surrounding it has eroded away leaving a hole around one side.

I removed all the earth and plant-growth, made a suitable base with sand and fine aggregate. I then had some left over high strength concrete and filled it as much as possible.

There was not enough to fully fill the hole however. There is still a void from the top of the drive to the drain surround. So I need to get some more....

However, from what I understand, concrete likes to self level and prefers to be poured into a mould. The concrete I used certainly did not like to be shaped. At the moment it has formed a solid base.

In this case, the drive is higher than the manhole cover. So I wanted to slope the repair to meet the edge of the drain surround.

Is there a type of ready-mix concrete that will hold it's shape a bit like mortar, but with more strength? Or will a mortar mix be OK?

My alternative is to make a mould, but have a sharp drop to the drain surround rather than a slope.

Many Thanks!

 

[Ian H]

As long as your mix isn’t too wet you can trowel the top of your mortar/concrete to the shape you want.

It will only want to self level if it’s too wet.

 

[dishman]

Perhaps it was because the spare mix I had contained a lot of aggregate, it made doing that more difficult. The window of not enough water/ too much seemed very small.

I'll get a bag of general mix to finish it off then. Something like this maybe:

https://www.wickes.co.uk/Hanson-Multi-Purpose-Ready-Mixed-Concrete-Maxi-Bag---20kg/p/137252

 

[23vc]

You should still be able to trowel it even tho it’s got aggregate in, the stones tend to go below the surface leaving a smooth top surface that you’re trowelling.. kinda

 

[Ian H]

When it seems dry sometimes more mixing will create the perfect mix. I’ve done it myself many times, thought it was too dry, added a little water and ended up with a barrow of soup like mix.

 

[dishman]

Yeh, that seems to be where I was going wrong....I'm not doing barrow loads...and adding gradually....but there was so much aggregate it seemed too dry....then I suddenly reached a tipping point where it seemed there was too much water....and it just wanted to self level no matter what I did.

 

[John D v2.0]

Cement needs hardly any water to actually set, most water in a mix is for workability and actually hinders the strength and causes shrinkage. So always err on the side of too little water and see how it goes.

 

[dishman]

Thanks all....

Bought another bag, decided on another brand with slightly less aggregate would probably make it easier. I also added the water more slowly and mixed for longer. It worked! I got a nice stable mix which I could shape.

I also used a more general pre-mix. The first lot I used was 40n stuff. Probably over-kill for what I used it for and it certainly seemed to turn into a runnier mix faster than this general pre-mix.

So whether it was to do with the type of pre-mix or my refined mixing technique....it worked!