Inspection chamber benching

[Pepsiandshirlee]

What is the mix for benching an inspection chamber ? As in sand cement etc ? Any other liquids ? Needs to stop tissues sticking on benching . Also is it trial and error ?

 

[noseall]

What is the mix for benching an inspection chamber ? As in sand cement etc ? Any other liquids ? Needs to stop tissues sticking on benching . Also is it trial and error ?

Concrete and hard work.

We add some screed sand to the conc and make sure its generous with the cement. No need for plasticiser. It needs to be quite firm, so that when you work it, it takes a bit of effort to shape it and bring the fat to the top. You need to bench in the morning then refine your finishing later on in the day.
It helps to have a small bladed pointing trowel handy. Well worn ones are the best. They need to be clean.

 

[^woody^]

No building sand in the mix, normal strong concrete. Granno gives a lovely finish.

It's all in the wrist to get that smooth surface like glass.

And curved too, none of that straight sides and top nonsense.

 

[Pepsiandshirlee]

Concrete and hard work.

We add some screed sand to the conc and make sure its generous with the cement. No need for plasticiser. It needs to be quite firm, so that when you work it, it takes a bit of effort to shape it and bring the fat to the top. You need to bench in the morning then refine your finishing later on in the day.
It helps to have a small bladed pointing trowel handy. Well worn ones are the best. They need to be clean.

Sharp sand and extra rapid cement ?

 

[noseall]

Sharp sand and extra rapid cement ?

Sharp sand and normal cement.

 

[Pepsiandshirlee]

Sharp sand and normal cement.

Extra rapid would be okay tho ?

 

[stuart45]

Extra rapid would be okay tho ?

You can if you want, but it goes off really quick, so you need to work it into shape really quick. Probably best to mix up just enough for one side at a time.
Normally when a drain is in use you block the inlets long enough for the final set.
The benching normally doesn't get much over it in normal use. It's worse when you need to repair the channels. Ciment Fondu was good for this.

 

[Pepsiandshirlee]

Hard to get the right shape / angle as can’t flush tissue till cement dries so don’t know

 

[noseall]

Extra rapid would be okay tho ?

yeah. I'm of the opinion you forsake a bit of strength for speed of setting.