Electrochemical investigations of carbon steel reinforcement and galvanized steel reinforcement in fresh geopolymer mortars

摘要

Concrete is the most produced material in the world. Every year approx. 6.000.000.000 m are produced worldwide and it is expected that the production volume will continue to increase because of the economic growth of many countries around the world. This development will also result in an increase of manufacturing CO_2 emissions if nothing changes. The cement production is already responsible for 5-10 % of the worldwide anthropogenic CO_2 emissions. An immense decrease of the CO_2 emissions (approx. 45-65 %) can be achieved by the use of geopolymers as binder instead of ordinary Portland cement. However, so far only limited data exists regarding the corrosion behavior of reinforcements in geopolymer concretes. The poster shows by means of different electrochemical investigations the formation of a protective layer on the surface of carbon steel reinforcement and galvanized steel reinforcement in fresh geopolymer mortars and in a fresh mortar with Portland cement as reference. The free corrosion potential in combination with current density potential curves as well as polarization resistances show the development of a protective layer on the reinforcement. The monitoring of the free corrosion potential starts with the first contact of the rebar with fresh mortar and ends after a passive condition was reached. The further electrochemical investigations are done during the potential monitoring under active conditions, semi active conditions and passive conditions. The results show that the formation of the protective layer in geopolymer mortars is significant slower than in mortar with Portland cement. The two investigated geopolymer mortars also show a significant difference in formation of the protective layer. This can depend on the different solidification time of the geopolymer mortar.