In case you couldn't tell, I'm seldom impulsive. I view pouring concrete as a fairly permanent action that one undertakes only after one is sure he won't want to reverse that action. Since I've got several conduits under this section of sidewalk that was removed three years ago, I've been hesitant to bury them "permanently" until I was sure everything was installed in this area that we intend to install. The inconvenience of not having this section of sidewalk finally outweighed my reluctance to commit to concrete.
Unfortunately, I don't have photos of the removal of the top layer. After waiting a couple hours, I used a light spray of water and a plastic brush to gingerly remove the concrete while trying not to disturb the gravel underneath. It didn't take long before I brushed too hard in one spot and removed more gravel than I desired. Having learned that lesson, I tried to be more careful on the remaining areas and felt pretty good about the result. Twenty four hours later, I used a light spray of water to rinse off the gravel that was no longer attached to the concrete and gradually increased the intensity of the spray to do a more vigorous cleaning. Mistake. The retardant was evidently still effective on some of the later concrete, so the water jet created a few more pock marks where the exposed aggregate had been curing nicely. Even after reading several warnings not to be too aggressive in removing the concrete, I had to learn the hard way how aggressive was too aggressive.
Krud Kutter Concrete Clean & Etch which is supposed to be a safer cleaning alternative. I found the product cleaned the new concrete well after I learned to rinse the concrete quickly after cleaning. The photo above shows the sealing process in progress using a lacquer-based semi-gloss sealant.