Corrosion Protection Of Micropiles-Paper

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The paper examines corrosion protection for Type E micropiles, which use continuously threaded hollow bars as drilling rods, grout-injection tubes, and reinforcement. Because buried steel is difficult to inspect and soil conditions vary, corrosion risk depends on factors such as pH, resistivity, moisture, and chemical content. European and U.S. standards provide guidance on assessing soil aggressiveness and on protective measures, including grout cover, coatings, and sacrificial steel.<br /><br />The authors question the use of sacrificial corrosion loss for permanent micropiles. Unlike sheet piles or other steel sections, micropiles rely on threaded couplers to transfer loads. Corrosion can damage the threads and compromise a connection, potentially reducing the pile’s structural capacity even if the bar retains sufficient cross-section.<br /><br />As an alternative, the paper presents grout encapsulation as a corrosion barrier, drawing on principles used in reinforced concrete. Tests on TITAN-thread micropiles reportedly found narrow cracks in the grout—below 0.1 mm in tensile tests and up to 0.01 mm in a separate examination. The authors argue that suitable grout cover and the grout’s alkalinity can protect the steel; galvanizing or other coatings may provide additional protection in aggressive soils.<br /><br />The paper concludes that sacrificial corrosion should not be treated as the default protection method for permanent Type E micropiles. Properly designed grout encapsulation, potentially combined with coatings, is presented as a more appropriate approach. However, the authors note that long-term evidence on sacrificial corrosion and its effects on coupled connections remains limited, underscoring the need for careful project-specific design.

Keywords

Type E micropiles

corrosion protection

grout encapsulation

sacrificial corrosion

threaded couplers

buried steel

soil aggressiveness

galvanizing

grout cover

structural capacity