Encapsulation of expansive powder minerals within a concentric glass capsule system for self-healing concrete

This study presents the application of encapsulated expansive powder minerals (magnesium oxide, bentonite and quicklime) for self-healing of cement-based mortars. A system of concentric glass macrocapsules was used to envelope the expansive minerals (outer capsule) and water (inner capsule). Mortar samples containing concentric macrocapsules with different mineral combinations were cracked and healed under three different curing regimes; ambient conditions, high humidity exposure and immersed in water. Self-healing was assessed based on visual crack sealing, mechanical strength recovery and improvement in durability investigated by means of capillary sorption tests. Micro-structural analysis of the healing materials was investigated using FT-IR, XRD and SEM-EDX for exploring self-healing kinetics. Immersed in water have yielded the optimum healing efficiency with ∼95% crack sealing and ∼25% strength recovery in 28 days. Data showed an increasing trend in 56 days for both crack sealing and load recovery. The improvement in terms of capillary absorption of healed samples was also significant after 28 days of healing. Self-healing kinetics revealed that the expansive minerals were hydrated in the initial healing period and slowly carbonated over time until the peripheral crack zone became adequately water tight.The support of Islamic Development Bank (IDB) scholarship collaborating with Cambridge Overseas Trust for the first author’s PhD research is greatly appreciated. Moreover, financial support from the Engineering and Physical Sciences Research Council (EPSRC) for this study (Project Ref. EP/K026631/1 – “Materials for Life”) is also gratefully acknowledged.This is the final version of the article. It first appeared from Elsevier at http://dx.doi.org/10.1016/j.conbuildmat.2016.06.030