Control joints

[3Dsigns]

After they poured my slab they came back and cut some control joints with a diamond saw. I noticed places that have some black stuff filling the joints. What would you recommend?.

 

[PopcornSutton]

What is the black stuff? Dust, hard material, or? Try to vacuum it out, or dig into the cut with a screw driver to see what it is.

 

[Lorydr]

Did they fill the cracks with some sort of joint compund/crack filler?

 

[Rusted Nut]

If they used a wet diamind saw, the black stuff is dark grey slurry. Let everything cure, then dig it out and seal joint.