Mixing Fiber Reinforced Concrete (FRC) is different from traditional concrete in how it lacks large aggregate or pebbles and is blended with paddle mixers instead of the large drum mixers associated with a traditional concrete mix. Fiber reinforced concrete contains only fine sands, portland cement, fibers, and chemistry to accelerate its cure time.
You may have heard of GFRC which is an abbreviation for glass fiber reinforced concrete and perhaps the most common of all the FRC’s, but with new developments in fiber technology, many mixes are utilizing fibers made from basalt, polypropylene, poly vinyl acetate (PVA) , and even hemp. Mixing fiber reinforced concrete from scratch can be an overwhelming endeavor involving hours of weighing and measuring up to eight individual components for each batch.Which is why we recommend sticking with pre-blended mixes to assure consistency in performance and quality.
Perhaps the biggest advantage of FRC is how thin it can be made without compromising the concrete’s strength. While we won’t get into it here, FRC can be cast using a wide range of techniques. It can be poured, like traditional concrete, or hand pressed into a mold to create a veined technique, or sprayed into a form.
Scrape the sides of the bucket with a trowel and continue blending until the pigment is completely mixed.
Step 3 – Add GFRC Mix
Add 1/2 of your dry concrete mix and thoroughly blend.
Slowly add the remaining dry mix to your bucket, while periodically scraping the sides and bottom with a trowel to make sure all of the fiber reinforced concrete mix is blended.
Step 4 – Add Additional Water if Necessary
You can safely add up to 16 ounces of additional water for each 50 pound bag of fiber reinforced concrete mix you use. This rule applies to CHENG D-FRC and Surecrete Xtreme Series Concrete Mixes.
Keep in mind when mixing fiber reinforced concrete that grey cement based concrete mixes will have lower water requirements than white cement based products.
Both the CHENG D-FRC and Surecrete Xtreme Series mixes will experience a false set between 5 and 10 minutes after the initial mix. When this occurs, simply blend it again with the paddle mixer and it should return to its original state. Repeat this often as necessary to keep the mix workable while you are casting.
Total working time when re-mixing is up to 1 hour.
Video – Mixing Fiber Reinforced Concrete for Spray Applications
This video clip is from a series that we co-produced with ConcreteNetwork to demonstrate mixing fiber reinforced concrete to spray through a hopper gun.