avast doesn't block or delete, but scans for infection and alerts, the 'user' chooses what action to take. If avast feel a file is infected, even if you choose no action avast won't allow you to run what it considers an infected file, so may appear to be blocking. The only way to have avast allow it to run is by exclusion, but that shouldn't be carried out until you confirm the detection is a false positive.
Deletion isn't really a good first option (you have none left), 'first do no harm' don't delete, send virus to the chest and investigate. The investigation takes the form suggested by onlysomeone confirm the detection at virustotal.
You can't do this with the file securely in the chest, you need to extract it to a temporary (not original) location first, see below.
Create a folder called Suspect in the C:\ drive, e.g. C:\Suspect. Now exclude that folder in the Standard Shield, Customize, Advanced, Add, type (or copy and paste) C:\Suspect\* That will stop the standard shield scanning any file you put in that folder. You should now be able to export any file in the chest to this folder and upload it to VirusTotal without avast alerting.
