Original Paper(Vol.61 No.8 pp.736-741)

Influence of the Ions in Pore Solution and around the Steel Bar on Corrosion of Steel in BFS and FA Mortars

Nobuaki OTSUKI, Anita II ODCHIMAR and Tsuyoshi SAITO

Abstract:This research investigated the corrosion behavior of steel in mortars with 40% blast furnace slag cement replacement and 20% fly ash cement replacement to ordinary Portland cement, considering the concentrations of chloride and other ions present in the mortarsf saturated pores and around the steel bar. Three methods were used to extract solutions from mortars wherefrom ions were measured. Results showed that reinforcing bar corrosion activity was lower for FA mortars than BFS mortars; and both having better corrosion resistances than mortars with only OPC as binder. Correspondingly, Cl- contents in pore solutions followed the trend OPC>BFS>FA mortars. The Cl-/OH- contents in the solutions obtained from around the steel bar correspond to the mortarsf corrosion behavior, signifying the influence of Cl- and OH- on corrosion and the greater importance of investigating the ions around the bar than that in the pore solutions of the bulk mortar. Moreover, significant differences in Cl- contents were measured using the 3 methods of solution extraction, which validate that the variations in the method of solution extraction account for the inconclusive Cl- threshold values for reinforcing bar corrosion published in literatures.

Key Words:Reinforcing bar corrosion, Chloride threshold value, Fly ash cement, Blast furnace slag cement