Bracing is supposed to act in tension and insures the stability in the plane frame where it is placed; usually we talk about steel braces for steel structures. But if it is compressed, it may be done in concrete in particular situations. Consider only that the resistance of the steel is the same in tension and in compression in the absence of buckling, while the resistance of reinforced concrete to tension is much, much lower than the resistance to compression. In any cross section the bending moments induce tension and shear and reinforced concrete has small resistances for both these stresses; some geometries of the concrete cross sections may behave more favorable to bending and shear (depending on the neutral axis position and shape of the section)

Not at all in structures prone to seismic loading as they will be loaded in tension. To provide structural stability, maybe. 

I think reinforced concrete braces would reveal suitable behaviors against different loads, as far as they were confined with FRP sheet (not closely spaced steel spirals). As FRP confined concretes have hardening behaviors in compression with significant crushing strain capacity (above 1% in most cases). In tension they would also perform good thanks to their embedded rebars. I think the main drawback of concrete braces roots in their constructional difficulties rather than structural performance. They need inclined formworks.

Thank you very much, Teleman Carmen, Saeed Mahjoubi, Seyed Amin Mouusavi. For your valuable answers.

You can try for RC braces that too for strengthening or for stability purposes. You can never use it when is prone to seismic effects. Strengthening that too at risk as it is difficult to construct......

Yes, if properly designed for tension or compression to which it is being subjected to.

It would not be advisable to use RC braces.

I agree with previous replies - not for tension members -  but commonly used for shear panels to provide lateral stability to the structure as a whole.