Benching in a manhole - What mix?

[Ted]

If you were doing some benching in a manhole, what mix would you use?

I would use a fairly strong mix of either sharp sand/cement or concrete probably with 10mm aggregate. I would also include a waterproofer.

Is building sand acceptable?

What should be the cement:aggregate ratio?

Would you advocate a waterproofer too?

If so, do you need to use a fancy one like Sika, do you think?

[flowjoe]

Ted

I usually use building sand and granno down to dust 3-2-1, a little more expensive for the bagged granno but it sets like iron and is as smooth as glass.

Never bothered with any additional agents, the importan bit is keeping the slope/wall adjacent to the channels fairly steep.

[seanandruby]

grano dust, cement and building sand. 6 2 1 ratio. i have used sharp sand and cement when grano unavailable. i use 1 to 1 ratio.