I believe the construction was added in October 2008 but CERM 11 was not available.
Construction was added as a seperate section to the NCEES exam in April 2008 for the first time (because that's what I took). CERM #11 was released within the first few weeks after the April 2008 exam had been given.
CERM 10 has MOST of the same info as 11 does concerning construction, it's just rearranged. Things like:
1) "Temporary Excavations" is in the Geotech section
2) "Earthwork & construction staking" is in the Transportation
3) "Economic Analysis" and "Construction Jobsite Safety" are in the Systems, Management, & Professional section.
These are just the obvious ones, but all of the above (plus a few of the sub-chapter sections related to construction) are now found within the new Construction section of #11, but are unchanged from their wording/layout from #10. I don't believe #11 added any info specific to the construction section that wasn't already found within #10. There are even a few items that could be classified as both "construction" and their previously denoted chapter, but are left in their original place because the context of the subject makes it easier to explain where it was than if it had been relocated.
Here is a link on the PPI website discussing some of the "upgraded" portions of 11 vs 10 (it's old, from April 2008):
http://ppi2pass.com/forums/posts/list/1155083865.page
From a construction standpoint, see above. However, it appears as if the transportation and structural portions have been updated to reflect updated industry codes and standards. Unless you are very familiar with the updated codes and know how to properly update your 10th edition, I would upgrade.
Get the 11th edition.