Patching boiler room trench

[branimal]

I had to cut the slab (1.5 - 2" thick) to make a couple of plumbing repairs. Rough estimate is 22 sq ft. Do I need to chip the edges of the existing slab to create a rough surface for the new concrete to bond to?

 

[Leaflessshadetree]

2" isn't very thick. Normal procedure would be to drill into the existing slab and insert rebar pegs. Clean the existing edges and coat with bonding agent. Then pour the new.

 

[mm08822]

You'll do yourself a big favor by saw cutting clean lines to form a simple square or rectangle. Also easier to add remesh.

Otherwise, the finished floor will look terrible and crack easier.

 

[tncatadjuster]

Bonding agent and let it rip, smooth cut needs rebar, any profile will help mechanical bond.

 

[ConCretin]

People tend to overthink this sometimes. I wouldn't mess with mesh, dowels or bonding agent. Square it up if the aesthetics matter to you. Otherwise compact the soils well and scrape a little soil from under the existing concrete edge so the new concrete will run under the lip and key things together. Keep the slump of the new concrete reasonable so you don't get excessive shrinkage. Done and done.

 

[branimal]

I patched the floor Tuesday and covered it with a plastic sheet. It's been 72 hours and the concrete is hard to the touch but still wet. The room is 58*F and humidity varies from 40% to 60%. Sackrete Crack resistant concrete.

Should I remove the sheet at this point? I've read keeping it covered doesn't hurt. I don't need access to that area for a few days.

 

[tncatadjuster]

I would keep it wet and covered.