a wrote in message ...
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....



There are two major types of polymer mixes for use in/with concrete
patches.

One type is mixed into the concrete and:

a. Increases the strength of the concrete
b. Increases the chemical resistance of the concrete
c. Increases the bonding strength to other concrete et al.
(the very best internal additives will will improve the bond
of concrete to your tools so well that you will regret not cleaning them
immediately after use)

The other type is painted onto the surface to be "bonded to" It
improves the bonding ability of the patch.

You have to read the label. The types available in my local building
supply store cannot be mixed; you use one or the other.

Regards
Old Al