I just found a product that basically takes the place of pouring concrete to secure fence posts.
This is the first time that I'm hearing of this product.
I know from their website that one of the pros is convenience. You don't have to lug around heavy bags of concrete mix. All you have are two bottles...part A and part B. You mix them when you're ready to pour into the hole.
How durable is this method? Supposedly you don't have to worry about moisture damage to the 'foundation' of the posts because the foam insulates it from moisture.