Title: ACCELERATED MORTAR TEST METHOD TO DETERMINE CHLORIDE THRESHOLD VALUES

Author(s): Neal S. Berke, Matthew A. Miltenberger, Lianfang Li, Brian Miller and Ralf Carvajal

Publication: Symposium Paper

Volume: 308

Issue:

Appears on pages(s): 1-14

Keywords: Chloride; Chloride threshold; Concrete; Corrosion; Corrosion inhibitors; Reinforcement; Service life

DOI: 10.14359/51689180

Date: 6/1/2016

Abstract:
Chloride-induced corrosion of steel in concrete adversely affects the service life of concrete in marine or deicing salt environments. Service life models determine failure based upon the time to reach a critical chloride concentration at the reinforcing bar known as the chloride threshold. Unfortunately, there is no universally accepted value or test method for determining this critical chloride threshold value. In this paper a new test method developed in ASTM subcommittee G1.14, Corrosion of Metals in Cement, Mortar or Concrete is discussed. This paper presents the preliminary screening research conducted in several laboratories that was used to develop the method. The proposed test method uses reinforcing steel embedded in a standard mortar. Macrocell current and polarization resistance measurements are used to detect corrosion initiation. The data show that the mean critical chloride threshold value is close to what is commonly accepted, but is quite variable. The data suggests that the chloride threshold values follow a normal probability distribution. The time to reach the threshold value is a function of curing time and w/cm. Addition of corrosion inhibitors significantly increases time to corrosion initiation, due to increasing the critical chloride threshold value, reducing chloride ingress, or both.