If you hit a ladder in the middle of the freeway that caused extensive damage to your vehicle will it be considered an at fault accident?

Depends on the circumstances in which you hit it. If it's dark and raining when you hit it, chances are you were simply unable to see it until you were right on top of it and therefore it would have most likely been unavoidable and non-fault. It it's daylight and traffic is congested and you can't see the ladder because of other vehicles ahead of you and it seems your only option is to hit the ladder or hit another car, it may be non-fault. It simply depends on the claims adjuster handling your file and the circumstances in which you were driving.