maaf kijiye, but the logic i thought was as follows :
for wooden sleepers, u simply need to chop down tree , process at timber mill and lay the sleeper
for concrete sleeper, u need to set up concrete plants, huge cement factories, stone chips, sand and gravel as raw material, huge area and space required for storage...
so what i felt was wooden...
more... sleepers are economical than concrete ones...correct me if i am wrong...
i had read somewhere that every concrete sleeper costs 3.5 times that of wooden sleeper but to promote bio environment railways switched to concrete sleepers...