Concrete curing isnt the problem, concrete itself is. With no yield point or elastic limit, its ultimate limit is the failure point. Hence, other than injecting concrete and waiting for it to cure, you would need to think about adding in steel casings for reinforcement. Then we are talking about the same timeframe as building constructions. To be able of achieveing 26m of tunnelling/day and ending up completing the project one year ahead of schedule they are doing much more than just 26m/d. Hence when time is an issue alternatives are considered.