Effect of silica fume addition on reinforcing steel bar corrosion

EFFECT OF SILICA FUME ADDITION ONREINFORCING STEEL BAR CORROSION(M. Sc. Thesis)Aykut DEĞ RMENCGAZI UNIVERSITYINSTITUTE OF SCIENCE AND TECHNOLOGYSeptember 2006ABSTRACTThis study was carried out to investigate the effects of silica fume (SF) additionon the reinforcing steel bar corrosion.For this purpose, SF was applied to PC 42,5 cement by replacement for 5%,10% and 15% in weight. To determine the compressive strength of concrete atthe 7, 28 and 90 days, standard cube samples of 100 mm were prepared, whilespecial cylindrical reinforced concrete samples of 50x100 mm were used inmeasurements of electrochemical corrosion.A three-electrode system was used to measure the corrosion in reinforcing steelbars. The current/potential noise measuring methods were adapted to thereinforcing steel bar corrosion, and the reinforcing steel bar corrosion wasdetermined by means of aging through the damaged and undamaged measuringmethods.The compressive strength test reveals that the compressive strength of concretesusually increases with the increasing SF amount. SF addition has twocontroversial effects on the reinforcing steel bar corrosion. Though it limits thediffusion rate of various corrosive substances on to the steel surface as a resultof the decreased concrete porosity, it reduces the corrosion strength at itscontact areas on the steel surface, so that particularly the localized corrosion isaccelerated. This could be attributed both to the corrosive effects of the highvalue ferric compounds in SF and locally pH drop, and also to the increase incomposite characteristics of the concrete.Scientific Code : 714.1.143Keywords : Pozzolan, silica fume, corrosion, reinforcing steelbar, three-electrode system, polarizationNumber of Pages : 89Thesis Supervisors : Assoc. Prof. Dr. H. Yılmaz ARUNTAŞAssoc. Prof. Dr. Tülin KIYAK