Glass encapsulated minerals for self-healing in cement based composites

This study presents the encapsulation of mineral compounds as healing materials for cement-based composites. Three liquid (sodium silicate, colloidal silica and tetraethyl orthosilicate) and one powdered (magnesium oxide) minerals were encapsulated in thin walled soda glass capsules. Load regain was obtained for samples healed under three different curing regimes; ambient conditions, high humidity exposure or immersed in water. Water immersion resulted in crack area closure that ranged from 85% to 100% for all mineral treated samples. The measured reduction in both sorptivity and intrinsic gas permeability varied from 18% to 69% depending on the measured parameter and mineral type. Sodium silicate and colloidal silica presented with the best and more consistent response in all applied measurements, both in terms of load and durability recovery. These results demonstrate how self-healing can be achieved by utilising cost effective mineral compounds which are also compatible with the host cementitious matrix.