I always wondered why ArcGIS doesn't have an option to concatenate text fields when using dissolve tool. This image is taken from another discussion:
The solution given at this discussion was a Spatial Join Tool and using field mapping. But the result was not as anticipated. It repeats every field value over and over, eventually fails because of field size.
It would be logical to have option in the Dissolve tool and using field mapping. Currently there is field mapping option but that is only for numbers.