Frequently Asked Questions


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The Where to Buy page lists many distributors of Fast 2K™ If you wish to purchase bulk quantities, please contact and H.B. Fuller representative.
Fast 2K™ is a more convenient and faster alternative than concrete for setting posts, poles, signs and much more. Fast 2K™ is a two-part proprietary polymer that expands to fill the peripheral void between the post and the hole, using the same technology applied by H.B. Fuller to set utility poles for over 20 years. Because of its expanding nature, one bag of Fast 2K™ Expanding Backfill Composite For Fence Posts replaces up to two bags of 50 lbs (25 kg) concrete. Fast 2K™ Expanding Backfill Composite For Fence Posts expands immediately after mixing and holds the posts in 3-5 minutes. Fences can be built in 15-30 minutes after l finishes expanding. Fast 2K™ does not require water and becomes waterproof after fully cured 

A single 32.8 fl. oz (970 mL) bag of Fast 2K™ Expanding Backfill Composite For Fence Posts replaces two 50lbs (25 kg) bags of concrete. Check the calculator chart on the packaging label or below: 

Fast 2K usage chart

Fast 2K™ Expanding Backfill Composite For Fence Posts is available in 32.8 fl. oz (970mL) bags packaged in either individual packages in retail stores or sold by cases through contractor specialty stores.

Package Type graphic

Yes. Fast 2K™ Expanding Backfill Composite For Fence Posts will bond to itself.
When using concrete, a hole for a 4” x 4” (10 x 10 cm) post has to have a diameter of at least 8” (20 cm). This is because concrete is very thick and cannot be placed in a smaller hole. There would be large air pockets in smaller holes, which would make the concrete very weak. With Fast 2K™ Expanding Backfill Composite For Fence Posts, you have the option to use a smaller diameter hole without impacting performance. 
In addition to setting all types of fence posts, here are some other examples where Fast 2K™ Expanding Backfill Composite For Fence Posts can be used: 
  • Bollards
  • Pergolas
  • Mailboxes 
  • Signs
  • Flagpoles
  • Gate Posts
  • Garden Light Posts
  • Clotheslines
  • Posts for sport/athletic applications such as Basketball, Soccer, Volleyball and Tennis
  • Other light weight pillar foundation applications  
There are endless potential applications, please contact us if you would like guidance regarding your application inspiration
No, however we do offer other products for those applications. Fast 2K™ Expanding Backfill Composite For Fence Posts is specifically engineered for post and pole setting and where the post/pole is placed at bottom of hole and Fast 2K™ Expanding Backfill Composite For Fence Posts acts to prevent lateral movement and uplift. H.B. Fuller offers other formulation grades that are specifically designed for various load bearing structures. Please consult your H.B. Fuller representative for more guidance on our portfolio of foundation solutions.
It is important to consider all installation costs. Fast 2K™ labor costs are lower because for example (A) installers do not need to load/unload heavy bags of concrete; (B) mixing Fast 2K™ Expanding Backfill Composite For Fence Posts bags only takes 30 seconds; mixing concrete takes much longer; (C) Fast 2K™ Expanding Backfill Composite For Fence Posts cures in as little as 15 minutes; regular concrete takes 24 hours to cure.  
There is no need to move crews and equipment in and out of a job site waiting for concrete to cure. Fast 2K™ is also much cheaper to transport and saves warehouse/store space as a pallet of Fast 2K™ Expanding Backfill Composite For Fence Posts replaces approximately a truck load of concrete bags. There is also no waste with Fast 2K™ due to torn bags compared to what often happens with concrete bags. 
Testing shows better performance results with Fast 2K™ than with concrete in terms of resistance to lateral force. The post does not break as easily with Fast 2K™ compared to concrete. Concrete is very rigid and has zero flexibility, so the total lateral force is directly on the wood post. Fast 2K™ absorbs some of the force and has a little flexibility so the post does not break as easily. Wood posts set with concrete typically break when 500-550 lbs (225-250 kg) of lateral force is applied. On the other hand, wood posts set with Fast 2K™ will not break until 600-750 lbs (270-340 kg) of lateral force is applied. In other words, the higher lateral force supported by Fast 2K™ will allow a fence to withstand higher wind force than concrete. The figure below shows how tests were performed. 
The compressive strength of Fast 2K™ is slightly higher than tamped soil. The soil and the post are the “weaker links” in the fence post installation. In other words, if a strong wind or a car hits a fence post, the ground will give or the post will crack before any damage happens to the footing, no matter if the footing is made of a 100 psi or 1,000 psi material.   
In addition, Fast 2K™ has a much higher adhesive strength to the post than concrete, making it much harder for the post to move laterally inside the Fast 2K™ footing compared to a concrete footing. Finally, Fast 2K™ is waterproof after it sets, so it helps prevent the wood post from rotting. 

Lateral Force Test Graphic

Fast 2K™ is a closed celled polymeric material that nearly eliminates all water vapour transmission through the product. Therefore, preventing wooden posts from rotting and metal posts from corrosion. To improve protection, installers should wet the sides of the post with Fast 2K™ Expanding Backfill Composite For Fence Posts at least 6" (15 cm) above ground level. 
Ensure there is no more than 1”-2” (2.5-5 cm) of standing water in the hole before pouring Fast 2K™ Expanding Backfill Composite For Fence Posts into the hole. If there is water in the hole, wait until the water is absorbed by the surrounding soil. Alternatively, users can throw some dirt or gravel into the hole. Remove water with a pump if time is a concern. Fast 2K™ will perform well in muddy soil as it is hydrophobic and repels water. 
Fast 2K™ is closed cell, so water transmission into the foam is very low; on the contrary, concrete allows water to penetrate resulting in the opportunity for expansion and contraction stress, which may lead to cracks. Furthermore, the slightly elastic nature of Fast 2K™ allows for expansion and contraction of posts caused by thermal cycling, without impacting adhesion or cracking. 
When used as per the instructions, Fast 2K™ has no negative environmental consequences on the surrounding soil. Once Fast 2K™ cures, the composite becomes a solid, inert plastic and will not leach into the soil. 
Also, by limiting the water transmission to posts, Fast 2K™ will also prevent the leaching of dangerous chemical used to treat wood posts. 
Fences posts do not require building code approval in almost all municipalities and counties. The same is true for posts used for deck footings when the finished deck level is not more than 2’ (60 cm) above the adjacent finished grade. 
We also offer products that are approved for various other applications including decks, barns, utility poles, etc. Please speak with your sales representative for alternative products. 
Safety is our priority, so we have two built-in safety features on the mixing bag: 
  • Tear notch to assist with opening the bag IMMEDIATELY AFTER MIXING however we always suggest you have scissors or a knife next to you ready to cut the corner of the bag as soon as mixing is complete. Failure to cut the bag immediately after mixing will result in the composite expanding inside the bag which may cause the bag to rupture. Mixing must be complete, and the bag cut within 45 seconds of removing outer black clip.
  • Frangible Safety Seal which is designed to control the release of mixed material and reduces the possibility of the bag rupturing and subsequent personal injury and property damage if not opened in time. 
No, the material should be poured directly into the ground without using such tubes. It is structurally better without a tube as the backfill material is very liquid and will penetrate soil crevices thus providing more of an anchoring effect. 
While Fast 2K™ can be used when ambient temperatures range from -5°F to 105°F (-20°C to 40°C), it is ideal to condition the bags between 65°F to 80°F (18°C to 27°C) for 1-2 hours prior to use, to provide optimal mixing and cure rate performance. Product from bags used at lower temperatures will take longer to react, expand and set, and will produce less volume. Product from bags used at higher temperatures will react, expand and set faster, lowering the working time and producing a higher volume, weaker composite. 
After Fast 2K™ cures it is hard to remove it from clothing. You can try to remove it by carefully scrubbing it off with a pumice stone. Please keep in mind that this technique may damage the clothing. 
Fast 2K™ is a structural composite that is much stronger than the typical spray foam used around window and door frames.  The 2-component chemistry of Fast 2K™ provides a consistent closed-cell structure that is waterproof with a much higher compressive strength.  The “blow chemistry” of spray foams create large voids in the cell structure which makes the final product unsuitable for structural projects. 
Fast Fast 2K™ Expanding Backfill Composite For Fence Posts sets in just a few minutes and reaches full strength in 30 minutes, whereas spray foams need the humidity in the air to cure which may take several hours. 
Yes, however the bags must be conditioned between 65°F to 80°F (18°C to 27°C) for 1-2 hours prior to use, to provide optimal mixing and cure rate performance. 
The low absorption rate of water into Fast 2K™ will allow water to drain around the outside of Fast 2K™, in contrast to concrete which adsorbs water quickly.
No, the soil pH will not affect the resilience of the composite. The composite will protect posts from decay if soil happens to be acidic. 
Yes. Fast 2K™ is hydrophobic so it will repel water and once cured it is waterproof. Ensure that there is no more than 1-2” (2.5-5 cm) of standing water in the hole before application. If the posts are installed with Fast 2K™ Expanding Backfill Composite For Fence Posts and it rains before the fence can be built, there will be no issues at all. 
It is not uncommon that the actual hole created by an auger will be larger than the bit size. As such, it is possible to utilize a 6" (15 cm) auger to reduce the amount of composite needed. However, larger sizes will work as well. The diameter of the hole will depend on the quality of the soil and how straight the auger goes into the hole.
Removing excessive material can be easily done using a knife or shovel. Disposing material is like concrete and is generally classified as general construction material.  Please contact your local municipality for specific regulations regarding disposal. 

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