Effects of different mineral admixtures on the self-healing ability of engineered cementitious composites

The presence of deleterious substances, such as chloride ion, and their transport are among the most important factors controlling the durability of cementitious composites, and the presence of mechanical loads on those causes cracks, which increases the permeability. The increase in permeability as a result of the cracks allows more chloride ions to penetrate into the cementitious composites, facilitating or speeding the deterioration. The present thesis studies the relationship among the applied mechanical deterioration in terms of splitting tensile deformation, curing conditions and chloride ion permeability of the Engineered Cementitious Composites (ECC) that contain different supplementary cementitious materials (SCMs). The splitting tensile deformations are introduced to generate microcracks in ECC specimens. After that, mechanically pre-cracked and pristine ECC specimens exposed to three different curing conditions (continuous wet, continuous air, and freeze-thaw cycle) up to two months. Rapid chloride permeability test (RCPT), microscopic observation and microstructural analysis were used to assess the rate and extent of self-healing. Test results indicate that the SCM type is very effective on the self-healing capacity of cementitious composites as measured by chloride ion permeability. Although ECC samples with fly ash have more unhydrated cementitious materials, and therefore, expectedly, a higher capacity for self-healing, more evident self-healing product was observed from ECC mixture incorporating slag indicating that the chemical productions stemming from SCM have great impacts on the self-healing capability of cementitious composites.Keywords: Self-healing; Engineered Cementitious Composites (ECC); Supplementary cementitious material (SCM); Exposure conditions.