Can I use steel fibers as the primary reinforcement?

The answer is no, No, NO, H—NO.

Concrete is a fantastic construction material. However, the real strength of concrete is in compression. In tension, concrete has little reliable strength. We make up for lack of tension strength by using reinforcement. We have learned that steel reinforcement bar (rebar) adds the best tension strength for the lowest cost of any reinforcement material. Many other reinforcements are available. They range from bamboo to carbon strands to fiberglass rebar, etc. In addition many fibers (glass, polypropylene, carbon, nylon and steel) have been used primarily for secondary reinforcements. We now have Basalt Rebar. It is new to us and far better than what we have had in the past. It is twice as strong as steel and weights 1/5 as much. And most importantly it will not rust. It is the new reinforcing for the EcoShells.

Fibers are used in hundreds of concrete applications for both primary and supplementary reinforcements. But we are concerned with its use in thin-shell domes. Rebar is the only reinforcement recognized by the codes for primary reinforcements. Small domes can be fiber-reinforced but they will not meet codes and are not as tough as rebar-reinforced buildings. So far, we have had serious failures on several projects where we used steel fibers as the primary reinforcements. There is no way I will ever be convinced to try it again. As recent as 1998, we tried steel fibers one more time on a small dome (20 feet in diameter). It was a failure as well. Even though it did not fall in, it did develop cracks, and the cracks are getting larger each year. Cracks are not a problem with rebar, but they are a disaster with fiber reinforcements. See Some Lessons are Learned the Way

Even if steel fibers worked (and they do not) as the primary reinforcement, you would have to overcome the lack of code acceptance. Concrete and rebar are well known, accepted and available worldwide. Even more important is the fact that steel fibers are expensive and difficult to handle. It has been our experience that the extra cost of the fibers will pay for hanging the rebar. Lastly, the rebar acts as a depth gauge. If it is properly embedded the concrete is generally thick enough. With fiber concrete you cannot tell, by looking, exactly how thick it is. It can vary from ¼ inch to 12 inches.