What should be happening in the scenario where i've concatenated 6 scans together?

They were scanned back to back during the same scanning session, with the same 15 direction + 2 b0 protocol.  I concatenated them all together into a long 4D nii.gz ( including the bvalues and bvectors ).

I was expecting DTIPrep to average all the B0 and treat the all the gradient directions individually, but what actually happened is that they were averaged into a single 17 direction scan, then processed.  Also, my b0s were never averaged.