Drying shrinkage and carbonation of steel slag-metakaolin alkali-activated composites: Effect of vegetable oil addition and slag aggregates

The influence of vegetable oil and steel slag aggregates on the drying shrinkage and carbonation performance of steel slag-based alkali activated materials was investigated. Decrease in carbonation rates by up to 19% attributed to the formation of metal soap phases which strongly reduced the gel and small capillary porosity as well as the specific surface area of the materials. When combined with steel slag aggregates, an additional reduction in carbonation rate of up to 50% could be achieved. Furthermore, the strain induced by shrinkage and rewetting was highly influenced by the type of aggregate used, with a reduction of 40 to 50% observed due to presence of soap phases resulting from the hydrolysis of oil in the metal-alkaline conditions. The observed improvement in durability properties may enable new application possibilities for alkali activated materials, overcoming well-known technical limitations such as high drying shrinkage and high carbonation rates.