Improve performance of a Fact Table
Lots of stuff wrong here, thankfully lots that can be fixed.

Problems:


You have a heap. Good odds this is heavily fragmented and pages are spread throughout the 82GB data file. See sys.dm_db_index_physical_stats for guidance on checking fragmentation.
You only have 6GB of memory, if you're lucky maybe 4GB is available to the buffer pool.
Reading between the lines, you are using dog slow SATA spinner drives.
A scan of the table will require 11GB of random IO across that dog slow drive and churn the buffer pool completely 3 times over.


Fixes:


Create a clustered index on the table. CardTransactionId looks like the only sensible choice currently.
You desperately need memory. 128GB would be reasonable for an 82GB data warehouse.
You have woefully inadequate IO. SSDs would the cheapest fastest fix.


11GB does not fit into 6GB, it really is that simple. A very rough estimate suggests the table will occupy ~1.5million 8KB pages which given 100 IOPS would take approximately 4 hours to read from disk (assuming worst case, 100% random read, no read-ahead etc).