Why does SQL Server 2012 Express use 9.5GB of RAM on my server?
SQL Express is limited to 1GB for the Buffer Pool, but there are many other memory pools in SQL Server. What I find surprising is the excessive use of non-buffer memory pools.
To find out memory usage per memory clerk, run this:

SELECT type, SUM(pages_kb)/1024 AS MemoryMB
FROM sys.dm_os_memory_clerks
GROUP BY type
ORDER BY 2 DESC


Hope this helps