Durability of high performance self-healing concrete produced with a crystalline admixture

Abstract

Cracks present in mortars make the material more susceptible to deterioration, especially when exposed to marine environments, high in chloride ion content, as those commonly present here in Malta. The effect of chloride penetration in different mortars is investigated in this dissertation. Apart from the control mix, other mixes containing Pulverised Fuel Ash, Silica Fume and Crystalline Admixture were manufactured and exposed to different conditions - air, water and different concentrations of chloride solutions. The conditions were also varied to that being fully immersed in the solutions or else in a wet/dry cycle fashion. The samples were pre-cracked and the effect of the presence of the chloride solution was recorded so as to establish the effect it had on the self healing process. The cracks were monitored by means of microscopic measurements. On the uncracked samples, chloride penetration was recorded using different colorimetric techniques and chloride profiles. This study showed that those samples containing Silica Fume gave better results overall but when compared to cost, the Crystalline Admixture is a more feasible solution as a self-healing additive agent. The Pulverised Fuel Ash gave remarkable results and it can be a sustainable solution since it is technically considered as a waste product. By limiting the crack widths to 0.100 mm, almost all the samples experienced a high degree of crack closure when considering the limited time frame of this project. Crack closure is potentially the result of delayed hydration of the cementitious content in the mortars that precipitate insoluble Calcium Carbonate in the cracks, and hence crack closure occurs. The variables present in this study were the content and type of additive, exposure conditions and the initial crack width.