Whether production of RMC a business auxiliary service

Dear All

Production or processing of goods for or on behalf of a client falls uder Business Auxiliary Service provided such activity doesnot amounts to 'manufacuture of excisable goods'.
Ready-Mix Concrete attracts excise duty and as such falls under excisable goods (i believe).
A company produces RMC for outside parties. Here my query is whether the company is liable to pay service tax in the following situations:
1) if the raw materials are supplied by the client
2) if the raw materials are used in-house.

If service tax is not applicable then whether Excise registration is required?.

Regards

CS Saju Philip
sajuphilipcs @ yahoo.com