Durability of Galvanized Soil Reinforcement: More Than 30 Years of Experience with Mechanically Stabilized Earth

Metal Loss for Metallic Reinforcements and Implications for LRFD Design of MSE Walls

“…Many of these data represent metal loss that is less than half of what is computed with the AASHTO model. This is consistent with the analysis of metal loss and corrosion rate measurements reported by Gladstone et al (2006).…”

State of the Practice of MSE Wall Design for Highway Structures

“…Research on buried galvanized steel, conducted by the National Bureau of Standards, Terre Armee Internationale (TAI), FHWA, and several state DOTs, confirms that the metal loss rates used in the design of MSE structures (Table 3) are conservative for steel soil reinforcements galvanized with 86 ȝm of zinc and buried in backfill meeting the electrochemical requirements shown in Table 4 (AMSE, 2006;Gladstone, et al, 2006). These loss rates and backfill electrochemical requirements have been codified in the AASHTO specifications (AASHTO, 2002;AASHTO, 2010).…”

Corrosion resistance of hot-dip galvanized steel in simulated soil solution: A factorial design and pit chemistry study

“…According to the American Association of State Highway and Transportation Officials (AASHTO), an aggressive soil is defined as having either: an chloride concentration greater than 29 100 ppm, an sulfate concentration greater than 200 ppm, soil resistivity lower than 3,000 Ω.cm, a pH outside the range of 5 to 10, or organic content more than 1% [75]. A survey of up to 20 years of service life for galvanized steel structures buried in different soils has shown that structures buried in soils out of AASHTO limits experience considerably higher corrosion rates, which are related to either higher chloride or sulfate concentrations, a low pH or high soil organic content [76]. For soil with the resistivity of more than 3,000 Ω.cm, the AASHTO model predicts that the corrosion rate of a Zn coating would be 1.0 µA/cm² (or a corrosion rate of 15 µm/year) [76].…”

“…A survey of up to 20 years of service life for galvanized steel structures buried in different soils has shown that structures buried in soils out of AASHTO limits experience considerably higher corrosion rates, which are related to either higher chloride or sulfate concentrations, a low pH or high soil organic content [76]. For soil with the resistivity of more than 3,000 Ω.cm, the AASHTO model predicts that the corrosion rate of a Zn coating would be 1.0 µA/cm² (or a corrosion rate of 15 µm/year) [76]. Although this model was found to be conservative, it predicts cumulative metal loss less than 2,000 µm after 75 years of service life for a galvanized steel [74].…”