Resurfacing portions of a concrete slab ...?

[voyager]

Another un-permitted, owner built, less than satisfactory condition:

I had noticed the roughness of this area of the back lanai's slab, just outside the french doors that lead out to it, when we were looking before buying.
I did not see it as a problem at the time.
Now, after it being exposed to not being covered by a roof during my re-roof of the back lanai, it has proven to be a low area where water has pooled.
Green and black algae had begun to grow and discolor the surface.

I'm now considering bringing this low area up to where it is the same as the smooth areas that surround it and smoothing it out to match.
It will be a fairly large thin addition to the surface of the slab.
That strikes me as having many potential problems to be dealt with to obtain long term satisfactory results.

The extent of my experience of this type of thing is as a kid watching documentaries that described the concrete pours done to build the Grand Coulee.
If memory serves me, that entailed cleaning, etching and grinding of the surface prior to the next pour.
That seems to be a bit extreme for this situation.
But, the thinness of what needs to be done here does seem to complicate the job.

What would need to be done to get a long term satisfactory fix for this situation?

 

[nealtw]

From the little we can see of the door frame and siding it already too high. Outside it should be 6" lower than the floor inside and under a cover you would like 2" It's all about water sitting next to wood work and holding moisture there.

 

[voyager]

The lanai slab butts up to the house slab.
The low area is 6" lower than the house's floor surface.
The siding is 2-1/2" above the lanai slab.
The door frame is 3" to 4" above the lanai slab depending on where you measure it.
The low area runs from about 5' to the L of the screen wall to about 8' +/- to the R of the screen wall running in front of the door.

The area has always been dry because of the old roof being in place.
It was wet only for the few weeks while there was no roof over it.
The new roof is now in place and the area is dry again.
I expect it to stay that way baring eruptions, earthquakes and hurricanes.

What ever problems with the lanai slab that exist, other than the unevenness of its surface, are there to stay.
I am not going to remove and replace a 12' x 60' slab.
I won't even hire someone to do it.

I may even decide to not do anything more than cleaning the surface of the algae, rust and other stains it acquired while it was open to the rains.

The rest of the slab is nice and smooth and level.
Why they left this low area right in front of this high usage door leaves me dumbfound.
My only thought is that they ran out of concrete and said "Good Enough".
I have run into several "Good Enough" spots in the structure over the slab.
Been able to correct them so far.

Any problems from water damage to the screen wall's bottom plate will be dealt with at a later date when it becomes obvious.

So, back to how to deal with the low area and/or the stains?

 

[nealtw]

Those are better pictures. Perhaps they were thinking of tile or stone in this area.
I think there are products for re surfacing but I am not the guy to talk about that. I have not read the book.

 

[voyager]

After checking around about this, I've decided that I will not do more than clean the stains and discolorations from the slab's surface, all 12' x 60' of it, after I finish the re-roof.
Once the area is covered and dry, pooling should no longer be a problem.

Thanks Neal.

 

[nealtw]

After checking around about this, I've decided that I will not do more than clean the stains and discolorations from the slab's surface, all 12' x 60' of it, after I finish the re-roof.
Once the area is covered and dry, pooling should no longer be a problem.

Thanks Neal.

It's worked like that for years, save it for a make work project when you have everything else done.