Mechanical properties and durability enhancement of MgO-doped engineered cementitious composites (ECC) under long-term chloride exposure

Abstract

Chloride-induced corrosion severely undermines the longevity of coastal concrete structures and demands durable, high-performance cementitious materials. This study aims to evaluate the influence of MgO doses (0–8 %) and long-term (periods up to ∼270 days) sodium chloride exposure on the chloride aggregation resistance of Engineered Cementitious Composites (MgO-ECC). Mechanical properties and durability of MgO-ECC were evaluated using accelerated chloride penetration, compressive, and tensile tests. Meanwhile, the microstructural evolution was characterized using scanning electron microscopy, X-ray diffraction and thermogravimetric analysis. The environmental and economic impacts were assessed to clarify how MgO dosage influences durability and mechanical behavior in aggressive environments. The mixture containing 8 % MgO-doped ECC achieved a compressive strength of 60.7 MPa after 270 days of chloride exposure, while simultaneously exhibiting the highest tensile ductility with an ultimate strain capacity of 1.6 %, developing multiple fine cracks, and showing superior durability by passing the lowest charge passed (1722 C) in the chloride permeability test. These enhancements are attributed to pore refinement driven by brucite and magnesium silicate hydrate formation. Furthermore, sustainability normalization demonstrated that, after chloride exposure, the 8 % MgO-doped ECC achieved the most favorable energy consumption and CO₂ footprint. These outcomes guide the use of MgO–ECC in chloride-rich environments-such as marine structures, underground pipelines, and rehabilitation overlays-supporting durability design and life-cycle benefits.