Non availment of abatement in construction service?

In case of a Construction service if we "do not" avail abatement of 70% (In order to claim CENVAT credit on input) On what amount do we pay service tax?

1) The entire sale proceeds or,

2) Only amount related to service portion (i.e. Ignoring value of materials included)  

Is there any Circular etc to verify the matter?

Thank you.