In typical fashion, I used some Concrete Bonding Agent (a white liquid) ....
before I read the directions.

My intent was to apply some concrete patch onto the cracks in an existing
concrete driveway. I had cleaned the cracks out & pressure washed it to
both remove dirt / loose material and to saturate the concrete with water.

I then brushed on the Concrete Bonding Agent straight from the bottle and
mixed the proper amount of it (for that I read the mixing directions) into
the concrete patching material then applied it onto the old concrete.

After setting for a day - I brushed more of the Concrete Bonding Agent on
top of the newly placed patch.

Then I read the directions.....

They said - "Do not apply Concrete Bonding agent straight onto existing
concrete - but instead blend it into the concrete mixture". ACK!!

Any idea why they say not to apply it directly onto the existing concrete?

I could see they want it mixed in the new concrete mixture to give it more
strength or to bond better to the old concrete (and I did do that).

My (theory) was that by brushing it directly onto the existing concrete it
might help 'bond' the new concrete onto the older concrete better.

As to why I brushed it on top of the new concrete - well I thought maybe it
would form a seal of sorts....