We use M50 Grade concrete in heavily reinforced structures which have to bear dynamic loading .Presently in my project which is a 2.9 Km RCC High level Bridge , we have been using M50 Grade concrete for casting of segments .
Here you can see how heavily reinforced a segment is . It requires heavy shuttering material as well to make sure that each and every segment is similar in dimension. Most of segments are match casted so they fix together after launching with adjacent segments .
Once segments are casted , they are cured for 30 days , only after which they are fit for transportation to site where they are to be launched and become part of main structure .
You can see in the back ground , where segments are lifted and finally launched on top of Piers . Once they are launched , they are stressed and grouted which completes the task.