I'm not sure these are the best options but they'll definitely get the job done:
declare @durations table
(
Duration int
)
Insert into @durations(Duration)
values(60),(80),(90),(150),(180),(1000)
--Option 1 - Manually concatenate the values together
select right('0' + convert(varchar,Duration / 60),2) + ':' + right('0' + convert(varchar,Duration % 60),2)
from @Durations
--Option 2 - Make use of the time variable available since SQL Server 2008
select left(convert(time,DATEADD(minute,Duration,0)),5)
from @durations
GO