Initial tests on helically reinforced columns
In March 1904, Wayss & Freytag AG acquired the French patent for helically reinforced concrete (spiralumschnürter Beton) (Béton fretté) from Armand Considère, „Inspecteur Général des Ponts et Chaussées en retraite“ in Paris. Considère had placed an additional helical reinforcement with a narrow winding on the outside of the concrete core of reinforced concrete columns which were exposed to a high axial pressure.
After W&F had acquired the sole right to execution for Germany, they approached the material test institute of the Technical University in Stuttgart to carry out extensive tests on helically reinforced columns in 1905. Emil Mörsch described the load increasing effect of such helical reinforcement in the 4th edition of his book „Der Eisenbetonbau“(“Concrete-Steel Construction”). W&F granted the execution right to their competitors for individual projects and supplied prefabricated spirals.