Wrapping fiber roving
FLEXSTREN Technology consists in wrapping an impregnated fiber roving around the product to be reinforced.
- The fiber roving is wrapped in tension along with a thermo setting resin and this generate a compression in the concrete.
- This tensioned wrapping is applied in multiple layers taking advantage of a very uniform stress distribution and a very low resin requirement.
- The number of layers determines the amount of compression given to the concrete.
The generated compression is bi-axial. The process is applicable to many concrete products, even from immediate stripping process where is it very difficult to apply prestressing and where traditional post tensioning is difficult due to geometry, cost, and the intrinsic limited productivity.
While this is a quite revolutionary method, there are ASTM, ACI and ISO specs for appropriate calculations. These basically follow the FRP prestressing and post tensioned reinforcement method.
ABOUT EXISTING USAGE OF CONCRETE AND FRP
Most of the fibers and FRP rebars currently in use as reinforcement for concrete, have a much lower Young’s Modulus vs. steel and in many cases just slighter higher than concrete.
Because of this the concrete cracks with very modest reinforcement stress making FRP very expensive vs. traditional steel reinforcing if the crack size is what is driving the structure sizing. This is typically the norm worldwide.
FRP rebars are produced by pultrusion which is a method that is not very effective on the medium and large rebar sizes, the sizes the market is normally requiring. This low efficiency is not related to production volume but is actually related to the pultruted product specific stress capacity. Basically, the large rebar sections are experiencing up to a 60% drop in the stress capacity.
In case of dispersed fibers, the situation is even worse since most of the fibers are not oriented to the concrete product tensile stress and when the dosage exceeds a relatively small percentage, the concrete becomes difficult to be placed and handled.
As we know, high strength fibers have a cost per Kg that is much higher than steel and magnitude of times higher of any concrete component and admixture.
is basically to use the least amount of fiber as possible. To achieve this we use it in tension, transforming the fiber’s low Young’s Modulus from a disadvantage to an advantage.
Our fiber is 100% oriented in the tensile stress direction and the specific stress capacity of our formed FRP is significantly higher than what is possible to achieve with pultrusion or any other method for produce FRP rebars.