There has been much discussion about which polymer is best for GFRC (glass-fiber reinforced concrete), Smooth-On's Forton VF-774 or Blue Concrete's PRA1210 Dry Polymer. We have used both, extensively, in a working studio creating client work. Before we discuss our preference, let's review each, per the manufacturer's websites:
Forton VF-774 is an all acrylic, co-polymer dispersion (51% solids) specifically formulated for the GFRC production process. It is UV stable in the high pH matrix associated with Portland cements.The primary benefits of VF-774 are:
- The elimination of the seven day wet cure required to achieve the maximum strengths of concrete
- Significant improvements in the long-term durability of the GFRC composite, especially the maintenance of the long-term flexural strain to failure property
Additional Benefits of VF-774 include:
- Reduces crazing and drying shrinkage cracks
- Improved workability of the mix at low water/cement ratios
- Reduces moisture absorption
- UV stable
- Uniform distribution of pigments for batch to batch color consistency
- Flame Rated
*VF-774 cannot freeze
PRA1210 can be used as a replacement of your traditional curing polymers. Internal testing has shown increases in strength, durability and density over traditional liquid polymers.
Dosage of PRA is simple. PRA is 100% solids, so if you are dosing your polymer at 3% solids to your cement content, then you would have 3 lb PRA per 100 lb of cement.
If you are replacing a liquid polymer that is 50% solids, here is how that would look-
Assume your batch calls for 1.5 lb liquid polymer and 7.5 lb of water.
50% of your liquid polymer is water, so your batch with PRA at the same solids rate-
0.75 lb PRA1210 and 8.25 lb water
The dry goes twice as far, which means you are shipping half of the weight. Plus you don't have to worry about spoilage or freezing.
For us, PRA1210 is the clear winner, for the following reasons:
- Foaming: We used Forton VF-774 for many, many years as it was the only option. It is a liquid polymer, and as is the case with most liquid polymers, it foams the mix. In the olden days of GFRC concrete countertops and sinks, we sealed using topical sealers. The foamed mix was actually a benefit, as the surface was more porous which helped create a better bond for the sealer. The problem with topical sealers (EAP, E32K, etc.) is that on a long enough timeline they scratch, yellow, peel and/or delaminate. When we moved away from topical sealers to reactive technologies a porous surface was no longer a benefit but rather a detriment.
- Strength/Density: The PRA1210 has yielded far superior concrete in our experience versus the Forton VF-774. The concrete is stronger and denser. When every project counts and you have to create the best concrete possible, PRA1210 has delivered for us.
- Shelf-life: Another issue we experienced with Forton VF-774 was shelf-life, or lack thereof. Because it is a liquid, the manufacturer has to add a bactericide and a defoamer. The bactericide helps reduce bacteria growth in the polymer, for a period of time, and the defoamer helps reduce foaming, again, for a while. Both additives only last for 6-12 months, at which point the VF-774 polymer will begin to turn rancid and foaming will become much worse.
- Shipping: Forton VF-774 is half water. Water is heavy (8.34 lbs per gallon). Shipping water is a waste of money. To compound this, Forton VF-774 can't freeze, so in winter months if freezing is a possibility the shipment must be sent HazMat because the trucks are heated. This increases the already high cost of shipping.
- Cost: Forton VF-774 and PRA1210 are roughly the same cost when you remove the water from the VF-774, but the shipping for the Forton is higher, so the scale tips in PRA1210's favor.
In summary, we use what works best for our client projects. We have used both products for several years each. For us, PRA1210 is hands-down the best polymer for GFRC concrete countertops and sinks.