Could this be used to fill a plaster of Paris mold?

Not that I'm aware of, it doesn't really say on the package but it does sit up very fast and is very durable. Sorry but that's the best I can answer your question.

Could this be used to hold an 8x8 supporting a substantial weight?

I had to replace a 4x4 post for my mailbox and used this 2K Post Back Fill. I already had a deep hole in the cement, so this stuff fills up the gaps beautifully all around and keep the post solidly planted. I'm not sure about 8x8, weight is not the issue here but you would need a "solid" hole like in my case to hold to post, then this foam would then fill up any gaps. Good luck.

Can this be used to form the deck list foundation where the 8x8 post then sits on top held by a bracket anchored in the foundation?

No, Fast 2K can only be used for installing posts that are sunk into the ground. It cannot be used as a foundation material nor can any brackets be anchored into it.

Would this be good to use for posts for a horse fence strong and sturdy?

Yes, also sets up quick and should be good for a horse fence.

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Fast 2K Post Anchor Mix | Expanding Composite Footing Compound (Fence, 1)

Product ID: 17019209

Details

Brand
H.B. Fuller
Color
Yellow
Item Form
Foam
Item Package Quantity
1
Material
Adhesive

⚡2.5lb replaces 80lbs concrete

⏱️Sets in 5 minutes, build in 30

🌡️-5°F to 105°F use range

₩86455

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Description

🚀 Build Fast, Build Smart—No Heavy Lifting Required!

ALL WEATHER READY - Works flawlessly from freezing -5°F to scorching 105°F, so your project never waits for perfect weather.
RAPID SET BUILD - Mix in 30 seconds, set in 5 minutes, and build on your post in just 30 minutes—perfect for fast-paced projects.
LIGHTWEIGHT POWERHOUSE - Ditch the heavy concrete—just 2.5lbs for the strength of 80lbs, saving your back and your time.
ROT CORROSION DEFENSE - Hydrophobic formula adheres tightly to posts, preventing rot and corrosion for long-lasting durability.
UNIVERSAL COMPATIBILITY - Bonds seamlessly with wood, metal, and vinyl—ideal for fences, decks, mailboxes, and more.

H.B. Fuller Fast 2K Post Anchor Mix is a lightweight, expanding composite footing compound designed to replace traditional concrete. It sets rapidly within 5 minutes and supports post installation in just 30 minutes. Compatible with wood, metal, and vinyl posts, it operates effectively in temperatures from -5°F to 105°F. Its hydrophobic technology prevents rot and corrosion, meeting building code standards for load-bearing applications.

Specifications

ASIN	B00LAFUC34
Best Sellers Rank	#34,439 in Tools & Home Improvement ( See Top 100 in Tools & Home Improvement ) #64 in Decking & Fencing Materials
Brand Name	H.B. Fuller
Color	Yellow
Compatible Material	Metal, Vinyl, Wood
Container Type	Bag
Customer Reviews	4.3 4.3 out of 5 stars (1,764)
Global Trade Identification Number	00669602000322
Included Components	Multitool Accessory
Item Form	Foam
Item Package Quantity	1
Item Type Name	Fast 2K 26OZ Back Fill
Item Weight	2.2 pounds
Manufacturer	H.B. Fuller
Material Type	Adhesive, Sealant
Model	250
Number of Pieces	1
Part Number	254-20-S
UPC	713976908484 669602000322
Unit Count	33.8 Ounce
Volume	32.8 fluid ounces
Warranty Description	Warranty

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₩86455

Duties & taxes included

In stock

Sold byAmazon South KoreaDelivered byDesertcartCustomer service byDesertcartReturns14 days · 30 with PRO

Buyer Protection · Full refund if your order doesn't arrive as described.

Desertcart purchases this item on your behalf and handles shipping, customs, and support to South Korea.

Secure transaction

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TrustScore 4.5 | 7,300+ reviews

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