Critical chloride concentrations in reinforced concrete specimens with ordinary Portland and blast furnace slag cement
article
Chloride induced reinforcement corrosion is the predominant degradation mechanism
affecting reinforced concrete structures. Chlorides (Cl¯) contained in sea water or de-icing
salts penetrate through concrete pores by diffusion and/or convection. Reinforcement
corrosion initiates when the Cl concentration at the reinforcing steel surface equals or exceeds
a specific concentration. This concentration is known as the critical chloride content (Ccrit ).
This study presents an experimental method proposed by the RILEM Committee 235-CTC
“corrosion initiating chloride threshold concentrations”. Two series of reinforced concrete
specimens were fabricated: one with ordinary Portland cement (CEM I) and another with
ground granulated blast furnace slag –GGBS- (CEM III/B) cement, both commercially
available in The Netherlands. Subsequently, the specimens were partially submerged in a
chloride-rich solution (3.3 wt. % NaCl) for 6 months. During this period, continuous
monitoring of the open-circuit potential (OCP) of the steel reinforcement was used to
determine the initiation of reinforcement corrosion. The concentration of Cl could be
determined by acid digestion and subsequent titration of powder samples collected from
individual layers in the concrete cover. Results show that after the exposure period,
theCcrit could be determined in PC specimens whereas in GGBS concrete specimens the
higher resistance to chloride ingress prevented from obtaining corrosion initiation.
affecting reinforced concrete structures. Chlorides (Cl¯) contained in sea water or de-icing
salts penetrate through concrete pores by diffusion and/or convection. Reinforcement
corrosion initiates when the Cl concentration at the reinforcing steel surface equals or exceeds
a specific concentration. This concentration is known as the critical chloride content (Ccrit ).
This study presents an experimental method proposed by the RILEM Committee 235-CTC
“corrosion initiating chloride threshold concentrations”. Two series of reinforced concrete
specimens were fabricated: one with ordinary Portland cement (CEM I) and another with
ground granulated blast furnace slag –GGBS- (CEM III/B) cement, both commercially
available in The Netherlands. Subsequently, the specimens were partially submerged in a
chloride-rich solution (3.3 wt. % NaCl) for 6 months. During this period, continuous
monitoring of the open-circuit potential (OCP) of the steel reinforcement was used to
determine the initiation of reinforcement corrosion. The concentration of Cl could be
determined by acid digestion and subsequent titration of powder samples collected from
individual layers in the concrete cover. Results show that after the exposure period,
theCcrit could be determined in PC specimens whereas in GGBS concrete specimens the
higher resistance to chloride ingress prevented from obtaining corrosion initiation.
TNO Identifier
573191
Source
Heron, 61(2), pp. 99-120.
Pages
99-120