Changes in the rate of ion penetration of alternative cementitious materials with time

Abstract

A major concern with concrete durability is the penetration of ions that cause deterioration. One concern about alternative cementitious materials (ACMs) is the lack of information regarding their long-term resistance to ion penetration. This study compares the changes for the permeable porosity, apparent diffusion coefficient, surface concentration, and depth of penetration for three different ACMs and Portland cement, over one year. The work shows that the decrease in the apparent diffusion coefficient for the mixtures with calcium sulfoaluminate cement, alkali-activated, and ordinary Portland cement after one year was equal to 66%, 93%, and 48%, respectively. The diffusion coefficient for the calcium sulfoaluminate sample deteriorated over time. This is likely caused by the conversion of the hydration products. The work also shows that the permeable porosity is not a good indicator of the apparent diffusion coefficient for these materials. Finally, the binding capacity (the ratio of free ions to total ions) is similar for the Portland cement, calcium aluminate cement, and calcium sulfoaluminate cement and the alkali-activated material showed no binding capacity.