Evaluation of Self-Healing Mechanisms in Concrete with Double-Walled Sodium Silicate Microcapsules

A Review of Self‐Healing Concrete for Damage Management of Structures

“…For better control of cargo release, recent advances on performance‐related microcapsule shells have aimed to enhance durability. The use of double‐walled shells combining polyurea–urea–formaldehyde has been demonstrated . Similarly, the investigation of more thermally stable materials like polyurea has led to the development of capsules ( Figure b) for survivability in elevated temperature environments .…”

“…These systems are still favorable as they allow faster reaction time and higher degree of mechanical restoration; however, the long‐term stability of reacted organic healing agents in the highly alkaline cementitious matrix is questionable as well as their long‐term functionality . Nonetheless emerging research favors compatibility and bonding with the mineral substrate of the cementitious matrix, shifting toward cargos that can deliver healing products of such nature; these include encapsulated bacterial spores (see Section ) and mineral cargos such as colloidal silica and sodium silicate . The former can enhance the precipitation of carbonates, while the latter can convert calcium hydroxide to more favorable CSH gel.…”

Validation of Self‐Healing Properties of Construction Materials through Nondestructive and Minimal Invasive Testing

“…Mostavi et al used SEM analysis to perform a parametric study and select the most ideal preparation parameters for the production of their double‐walled polyurethane /urea‐formaldehyde microcapsules containing sodium silicate for healing cracks in concrete. The influence of the agitation rate, pH and temperature on the shell thickness, and size and morphology of the prepared capsules were characterized using SEM to determine the optimum production process.…”

A review study on encapsulation‐based self‐healing for cementitious materials

“…Gilford III et al reported that an improvement of 11% in elasticity modulus wad achieved for the concrete after being healed by sodium silicate filled in the microcapsules. Mostavi et al developed a double‐walled microcapsule filled with sodium silicate, and put additional focus on the performance of the capsules. As the self‐healing efficiency is affected by concentration of sodium silicate solution, the exhaustion of healing agents and low mechanical strength may restrict the engineering application of sodium silicate solution …”

“…Moreover, the PMMA tube shows promising results in terms of the compatibility with various self‐healing agents. Mostavi et al developed a double‐walled PU/urea‐formaldehyde (PU/UF) microcapsule filled with sodium silicate, and revealed that low pH value, high agitation rate, and high curing temperature can improve the formation of capsule shells. Optical microscope results confirmed that the self‐healing microcapsule contains phenol‐formaldehyde resin as shell and dicyclopentadiene as healing agent, respectively …”