Manhole Cover (Cement Cracking Just 2 Yrs)

BathDIY · 25 Jun 2020

About 2 yrs. ago In repaired an inspection chamber in my garden, I noticed these cracks appearing.

I also had to replace 2 brick courses below this point, I went down to a solid base to build from.

I replaced like for like and (retained the rather steep drop in level away from the path).

I want to ensure that when I repair it doesn't reoccur so quickly. Any ideas what could be causing this?

Not a particularly high traffic area (and those dumpy bags are a recent addition in place way after cracking occurred).

JohnD · 25 Jun 2020

might be shrinkage, which is worse when there is too much water in the mix. Is worse if it is laid in hot summer sun (best to lay it in the afternoon when the sun has passed, and cover it). It is a shape that will always be prone to cracking as the steel rectangle prevents it from shinking in one piece.

Might have dried out too fast (concrete reaches good strength after staying wet, continually, for about two weeks). You can spray it with water from day 2 onwards to keep it wet.

You can improve resistance to cracking by mixing in fibres, or adding simple steel reinforcement.

Alastairreid · 25 Jun 2020

Why not drop the cover level with the grass and do away with the cement around the cover.

BathDIY · 25 Jun 2020

Thanks JohnD will give that a go.

Alastairreid said:
Why not drop the cover level with the grass and do away with the cement around the cover.

Good idea I would love to but the trouble is the manhole (which I inherited) isn't remotely level, which I'm guessing would make this difficult to do.

Alastairreid · 25 Jun 2020

Set the frame level with the top course of bricks, it wont matter if the grass is slightly higher on one side.

noseall · 26 Jun 2020

Alastairreid said:
do away with the cement around the cover.

The mortar haunching around the frame is what's holding it there.

Remove two courses of brick. Replace one of those courses with some solid blues. Mix some concrete sand and cement with a splash of building sand and re-haunch around the frame.

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Manhole Cover (Cement Cracking Just 2 Yrs)

BathDIY

JohnD

Alastairreid

BathDIY

Alastairreid

noseall

DIYnot Local

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