I would look into preferential etching agents.

Thanks Jovan. What kind of etching agents would be preferable which will not affect the strength of concrete? Solution containing 1 part muriatic acid to 10 parts water? Will it be possible to etch hardened concrete?

Syed, may I ask what exactly are you trying to accomplish after you reveal the aggregate? Any etching will damage the concrete, it just depends what level of damage is acceptable to you. Muratic acid should work well. 1:10 ratio of muratic acid-water solution would be good to start with, but I am almost fully certain that you will have to go up to 1:5 or 1:4. Also, don't forget to pressure wash the concrete and let it fully dry before treating it with acid solution.

Thanks Aria. These sites are about decorative concrete. I wanted to remove the top cement paste layer on the sides of my beam.

Thanks Jovan. I tried muratic acid-water solution and it worked to some extent. I can see thin aggregate particles near surface. But I dropped the idea of revealing the aggregate as it might damage the concrete.

A search with "exposed aggregate concrete" may be helpful. The grading and the mineral composition of the aggregate should be taken into account accordingly. Light surface macining maybe of help for existing structures.