Sika fence post mix is a very good alternative for installing a fence post without using concrete.
One 2.5 pound bag of Sika Postfix Fence Post mix replaces TWO 50 lb. bags of concrete mix.
It's available to purchase on Amazon with FREE delivery if you're a PRIME member.
The video below is from Sika USA. It does a good job of showing how to install a fence post using their foam post mix product.
These are the basic coverage rates for each pouch:
TYPE OF POST
2 inch round
4" x 4" square
4" x 4" square
6" x 6" square
DIAMETER OF HOLE
DEPTH OF HOLE
# OF POUCHES
One 33 fluid oz. pouch (976 ml) makes 0.7 cubic feet of foam (20 L)
Cure Time: Initial set is 3 - 5 minutes
Final Set: 2 hours
SIKA'S product data sheet explains it like this;
It's an easy to prepare, mix in the bag, expanding polyurethane foam.
Consisting of a 2-Part, pre-measured, polyurethane resin. When the 2 parts are mixed together they make an expanding foam. It's been designed to be lightweight, fast-setting, and diy friendly.
No water or special tools are needed to use this, you mix it right next to the post your installing.
The post mix can be used for setting wooden, PVC, and steel posts like:
Here's the instructions for how to use Sika PostFix Fence Post Mix.
Materials you need:
STEP 1. Dig the hole to the diameter and depth required to support your post. Set your post inside the hole then level & brace it in place or hold it in place. (there cannot be any standing water in the hole)
STEP 2. Wearing your safety goggles and gloves, roll the pouch in the direction of the arrows (towards the central burst seal) until it ruptures and the two pouches combine.
STEP 3. Mix the combined ingredients by rubbing the pouch over a 90 degree angle, (like your leg) for 15 seconds. Make the material in the pouch move from one end to the other. Don't puncture the bag!
Step 4. Quickly after mixing, cut the bags corner marked with a dotted line. Pour the mixture into the bottom of the hole, evenly around the post before it begins to expand.
STEP 5. You now want to level and adjust your post to exactly where you want it. You'll have about 10 - 15 seconds to do this before the foam begins to swell and rise in the hole.
Support the post for up to 3 minutes as the polyurethane foam hardens around the post. After 3 minutes the foam will be able to support the post on its own.
STEP 6. Wait 2 hours for it to fully harden before installing any sections of fence. Use a hand saw to saw away any excess foam above grade.
PRO TIP: Remove any splatters from the post with a solvent like paint thinner before they dry. Once dry, you'll have to use a putty knife to remove any excess foam.
Out of 221 reviews on Amazon.com, 85% of them were 4 - 5 stars. 8% were 3 stars and 8% were either 1 or 2 stars.
Most people found it was easy to use and performed as advertised.
You can check out the reviews here.