Influence of chloride salt type on critical chloride content of reinforcement corrosion in concrete

Abstract

The objective of this study is to examine the influence of chloride salt type on the critical chloride content for the corrosion of steel reinforcement in concrete. The experiment was carried out in Portland cement concrete and concrete incorporating fly ash and ground granulated blast-furnace slag. Sodium chloride (NaCl), potassium chloride (KCl), calcium chloride (CaCl 2 ) and magnesium chloride (MgCl 2 ) were chosen to corrode the steel reinforcement. The initiation of pitting corrosion was detected by half-cell potential, linear polarisation and electrochemical impedance spectra methods. The critical chloride content was expressed as free chloride or total chloride by mass of binder, as well as [Cl 2 ]/[OH 2 ]. In addition, X-ray diffraction and differential scanning calorimetry-thermogravimetry analyses were employed to study the products in concrete. Test results show that the chloride salt type has a marked influence on the critical chloride content. The critical chloride contents expressed as free Cl 2 for the specimens contaminated by external magnesium chloride and calcium chloride are lower than those for the specimens contaminated by external sodium chloride and potassium chloride. Contrary to the trend for free Cl 2 , the critical chloride contents expressed as total Cl 2 and [Cl 2 ]/[OH 2 ] for the specimens contaminated by external magnesium chloride and calcium chloride are higher than those for the specimens contaminated by external sodium chloride and potassium chloride.The concrete specimens contaminated by external sodium chloride have the same critical chloride content as those contaminated by external potassium chloride, regardless of the water-binder ratio, mineral admixtures, or the form of critical chloride content.

Chloride Induced Reinforcement Corrosion in Mortars Containing Coal Bottom Ash and Coal Fly Ash

“…The higher the coal ash content in the mortar, the lower the critical chloride content, C critical (Figure 3). Chloride threshold level is affected by several factors [10,29], such as the chloride salt type [30], supplementary cementitious materials in the cement-based materials [11,31], origin of the chloride ions [32] and so on. Therefore, a wide range of threshold values has been reported.…”

Size Distribution Model and Development Characteristics of Corrosion Pits in Concrete under Two Curing Methods

“…Many coastal cities have begun to utilize sea sand as a construction material [1]. Chloride ions contained in marine aggregates pose a great threat to steel bars within concrete by destroying integrality of the steel bars’ passive film, resulting in corrosion of the steel bars and a significant reduction of service life of the structure [2,3,4,5,6].…”