Shotcrete has been used to successfully rehabilitate sewers for over 50 years.
The thickness to be used is an engineering issue and beyond the scope of our association. We would recommend a 2 in. (50 mm) minimum thickness reinforced with either polypropylene fibers or a light-gauge welded wire reinforcement. The surfaces must be cleaned thoroughly to remove grease, oils, and other substances deleterious to good bond. Bonding to brick is not a problem.
Finish is another consideration. The added liner thickness will reduce the size of the culvert. If capacity is not an issue, it is recommended to leave the new shotcrete lining with a nozzle finish. If capacity might be a problem, then a float or trowel-smooth finish may be necessary.