Corrosion Mechanism of Cemented Soil in MgCl₂ Solution

• Main Authors: P.-J. Han, W.-B. Zhang, X.-H. Bai, T. Tong
• Format: Article
• Language: English
• Published: Croatian Society of Chemical Engineers 2014-09-01
• Series: Kemija u Industriji
• Subjects: Cemented soil; compressive strength; modified coefficient; corrosion
• Online Access: http://pierre.fkit.hr/hdki/kui/vol63/broj9-10/311.pdf

Mechanical properties of the cemented soil will be reduced when cemented soils are applied in the MgCl₂ corrosive environment to conduct seepage control in hydraulic engineering. The corrosive conditions will inevitably cause serious damage to the cement-soil composite, and further reduce stablity of the whole structure. Therefore, this cementation technique could be commonly used to stabilize infrastructures. More engineering practices regarding the reduction in mechanical properties of cemented soil in the MgCl₂ environment are required. To simulate and study the corrosion process, a series of tests including photographing, unconfined compression tests, and measuring Mg²⁺ and Cl⁻ concentrations of solution were conducted on cured cemented soil blocks with different concentrations of MgCl₂ solutions. Results show that the surface corrosion of the sample increases while the compression strength decreases with the increase in solution concentration given the same curing time of the concrete block. Chemical analysis of the corrosive environment indicates that the volumes of new products such as CaCl₂ ∙ 6 H₂O and Mg₂(OH)₃Cl ⋅ 4 H₂O amount to seven times that of Ca(OH)₂ after reaction. The corrosion of cemented soil is a sort of crystallizing corrosion. The Mg(OH)₂ takes chemical reactions with 3 CaO ∙ 2 SiO₂ ∙ 3 H₂O and forms new products such as MgO ∙ SiO₂ ∙ H₂O, which is a sort of dissolving corrosion. In addition, the authors analysed the relationships between the unconfined compressive strength of cemented soils cured for 28 days and the initial concentrations of Mg²⁺ and C^l−. Finally, the regression equations of the strength were established.