Electric Prestressing of Reinforcing Steel
Karl P. Billner and Roy W. Carlson
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In the electric method of prestressing, smooth re- inforcing rods are stressed by being temporarily expanded by an electric current after the concrete has hardened. The rods are coated with a thermo- plastic material such as sulfur which melts and re- lieves the bond only while the rods are temporarily heated by the electric current. While the rods are expanded, nuts are taken up at the ends a predeter- mined amount to provide the desired prestress. Two notable features of the method are (I) that bond is restored with cooling and resolidification of the sulfur coating and (2) that the quick heating of the rods does not warm the concrete appreciably. Interesting results of tests and trials are reported.