$50 for what? So you have paid nothing for the work? Where is the original part ? I am totally confused about what they were matching and of course this is a mess but you paid nothing so not sure what the recourse is other than getting another contractor. Where I love no one woudl do this work in January. What was the weather like where you are in January, seems like the winter has been weird everywhere.

Needs to be ripped out and re-poured nothing will fix that. If there was a step up into the enclosed area you could do a 2" cap over it, but you are out of luck in this case. Call someone who knows what they doing.

Good luck.

I would expect that an accelerator was used in the mix, not a retarder, for a cold-weather pour. That would then vibe with what looks like the pea gravel was tossed on an already set slab, so when they washed the cream off some of the stones just washed away.

If they come back, expect that they will combine demo with another job nearby, so you might have to wait for that. The expense of bringing a bobcat and dump truck to site and then disposing the concrete isn't worth doing just a small slab.

It's a simple case of SCALING

Scaling is a form of disintegration. A common cause of scaling could be freezing and thawing

conditions. Flaking or peeling is normally a form of scaling. Scaling, which can also be referred to as spalling, is rated based on the depth of the defect.

The rating usually goes is as follows:

1. Light spalling is when the loss of surface mortar does not expose any coarse

aggregate.

2. Medium spalling occurs when the damage has a depth of up to 0.4"

3. Severe spalling is determined when the depth of the damage ranges from 0.2

to 0.4". There is also some loss of mortar surrounding aggregate particles

with a depth range of 0.4 to 0.8".

4. Very severe spalling is the loss of coarse aggregate particles, as well as surface

mortar and surrounding aggregate, generally to a depth greater than 0.8".

Other reasons for scaling could be:

• Improper concrete mix.
• The use of air-entrained agents.
• Improper concrete finishing.
• Water shouldn't be added to the concrete surface during finishing works.(you see this issue when they pour too much of an area and it starts to set faster before finishing work so they add water to the surface)
• If it's poured during freezing weather concrete must be protected from freezing and thawing cycles so if there is a need to pour during the winter we use blankets.
• Another cause is the usage of corrosive materials like salts, etc.

Good luck.