Extra Sticky Concrete

aidanki

I have a gap in a concrete cover which I need to fill.

See my drawing attached, the slot I want to fill is ~1m long.

I would like to make my concrete extra sticky so it gets a really good grip on the sloping sides.

Is there anything I can mix with the concrete to make it stick better to the sides ?

I can mix the gravel and cement at 3:1 which will give me a plenty strong mix and I can vibrate the mix with electric drill and hammer action engaged, however I have no bright ideas on how to make the concrete adhese better to the old surfaces.

223vmax

Is it possible to make a new cover as I wouldn't try to fix that. What type of traffic do you expect on top of the cover?

listermint

Any pictures of what we are talking about here, As it all sounds like an accident waiting to happen.

If there is any people traffic beneath this it could be fatal

aidanki

223vmax wrote: »

Is it possible to make a new cover as I wouldn't try to fix that. What type of traffic do you expect on top of the cover?

traffic is humans walking on top

nothing underneath, its covering a water well, but its a fair lump of concrete 2m X 2m

Nekarsulm

Make a new cover, incorporate weld-mesh in the concrete. 30 newton at least.
The way the hole is shaped, any plug you make will be liable to come loose and fall down.

Calahonda52

flip it over, fix a strip of alu chequer plate with stainless steel screws, flip over and fill

GreeBo

Calahonda52 wrote: »

flip it over, fix a strip of alu chequer plate with stainless steel screws, flip over and fill

Just fit the chequer plate on top and be done?

PhoenixParker

Calahonda52 wrote: »

flip it over, fix a strip of alu chequer plate with stainless steel screws, flip over and fill

Or fix a strip of alu chequer plate, flip it over and fill.
That way your new wedge is supported by the existing concrete.

listermint

All valid ideas. But I think a swing rope is the obvious path to go down

aidanki

listermint wrote: »

All valid ideas. But I think a swing rope is the obvious path to go down

apologies i dont get it swing rope ?

listermint

aidanki wrote: »

apologies i dont get it swing rope ?

Draw a swing rope over your diagram... It will all come clear

Lumen

Is this an invitation to invent a manhole cover?

Grind or cut a V into the top part, creating what will look like a bowtie on its side when you look at the gap from the end.

On mobile, so no picture except this:
._____......______
...........\..../
._____/....\______

Diamond grinding disk on a 9” grinder or a bolster should do the job.

You could straddle the upper V from side to side with wedged threaded rod cut to length, if you want belt and braces measures.
.______......______
.............\==/
.______/....\______

If you fold mesh or weave a piece of rebar to ‘tie’ the top and bottom together, that should help prevent the bottom part from falling off over time, even if it cracks. I’m not even going to try to draw that though!

Ignore the dots...

aidanki

anything I can add to the concrete to make the cement extra sticky so it really bonds to the sides?

something like this ?

https://www.topline.ie/building-supplies/building-chemicals/adhesives-glue-tapes/pva/cementone/rendabond-pva-5-litre

aidanki

listermint wrote: »

Draw a swing rope over your diagram... It will all come clear

I get it, this is how you think I should position my timber underneath when filling with concrete, this is what I had intended

listermint

aidanki wrote: »

I get it, this is how you think I should position my timber underneath when filling with concrete, this is what I had intended

No I was making a joke about swinging over the gap. I apologize. But now it sounds like good engineering.

Calahonda52

aidanki wrote: »

anything I can add to the concrete to make the cement extra sticky so it really bonds to the sides?

something like this ?

https://www.topline.ie/building-supplies/building-chemicals/adhesives-glue-tapes/pva/cementone/rendabond-pva-5-litre

PVA is not used in exposed positions

BrokenArrows

There is nothing you can do here to make concrete stick to the sides so that its secure enough not to fall eventually.

The easiest option would be to just get a thick sheet of steel and fix it over the top. You could grind out the sides of the hole so that it sits flush with the surface and isnt a trip hazard.

The more complex option is to drill holes in both sides and fit lengths of rebar throughtout the hole so that it connects the new concrete with metal to the sides.

CJhaughey

Personally I would get a fabricator to make a length or two of chequer plate that will overlap the hole and screw it into the existing slabs with concrete screws.
The idea of pouring concrete into that upside down channel is only asking for it to fall down and some one will break an ankle.
Alloy is light and strong and needs no maintenance.

Safehands

BrokenArrows wrote: »

There is nothing you can do here to make concrete stick to the sides so that its secure enough not to fall eventually.

The easiest option would be to just get a thick sheet of steel and fix it over the top. You could grind out the sides of the hole so that it sits flush with the surface and isnt a trip hazard.

The more complex option is to drill holes in both sides and fit lengths of rebar throughtout the hole so that it connects the new concrete with metal to the sides.

First of all I would fit a couple of starter bars to the side of that hole if you can. Resin anchor them. That will give you a mechanical fixing. Then, just before placing the concrete, apply an epoxy bonding agent to the sides of the ope (Bondcoat UF by Parex will do it). That will give you a monolithic bond to the existing concrete. Either use a pre-bagged concrete or get ready mix with a low water content. I wouldn't use hand mixed concrete.