Effect of Iron Powder on Inhibition of Carbonation Process in Cementitious Materials

Addition of a pore blocker to cementitious materials is one of the known measures for protection from carbonation. However, the connected pore network inherent to cementitious materials can make conventional pore blockers ineffective, but these connected pores can be advantageous when iron powder is used. This study found that ionised iron powders can diffuse along the connected pores and fill the neighbouring pores that mostly range in diameter from 0.075 to 7.500 µm, which is equivalent to the range that harmful ionic species can penetrate. Under the severe condition of accelerating carbonation and corrosion-accelerating curing, the replacement of sand with 2% iron powder is found to reduce the total porosity by up to 50% compared to that of the control specimen without iron powder. An electron probe micro-analyser was used to visually confirm the corrosion, ionisation, and diffusion of the iron powder that filled the pores in the cementitious materials.