Passivation of galvanized and carbon steels in phosphate mortars manufactured with alternative MgO sources Articles uri icon

publication date

  • June 2025

start page

  • 113303-1

end page

  • 113303-20

volume

  • 111

International Standard Serial Number (ISSN)

  • 2352-7102

abstract

  • Magnesium potassium phosphate cements (MKPCs) are cementitious materials that harden simply with water and are very useful for repairing damaged concrete structures. However, obtaining MgO implies high CO2 emissions. In the present study, the MgO is obtained from two different industrial by-products (cyclone dust during the industrial calcination of magnesite and tundish deskulling waste generated in the steel manufacturing), as they can be an ecological alternative to manufacture mortars. The properties of these innovative mortars still deserve further research. Moreover, if the MKPCs need to be used for repairs of reinforced building structures or for applications that could involve embedded metal bars, the ability of these mortars to passivate the metal is another key point that is investigated in the present research. The characteristics of the alternative MKPC mortars, such as curing shrinkages, mechanical properties, porosities and pHs, are compared with those of conventional ordinary Portland cement mortar. Ribbed carbon steel and galvanized steel bars were used as reinforcements. Six different types of reinforced mortar samples were exposed to high relative humidity (RH) for four months and their electrochemical performances were monitored. Both carbon and galvanized steels embedded in the highly ecological MKPC mortars manufactured with MgO from tundish wastes are able to be passive in environments with high RH. However, galvanized and carbon steel bars are not able to reach a stable passivity in mortars made with cyclone dust MgO. Analysis of the pore solutions obtained after pore pressing enable these results to be understood.

subjects

  • Chemistry

keywords

  • magnesium phosphate cement; refractory waste; passivation; carbon steel; galvanized steel; electrochemical impedance spectroscopy