ASP.NET - session time out against ajax timer auto refresh

I want to session time out in asp.net application which is windows based authentication. I implemented timer for auto refresh for 1 minute.  Due to this session did not time out which is 10 min.

All subsequent ajax service calls to your asp.net app act just like the visitor viewing another page.  So, your session timeout is getting refreshed with each call.  You'd have to write your own code to keep track of a different timer and Session.Abandon(); on your own if you want to force expiration in this scenario.