Self-healing Compounds Best for Cracks up to 150m

Brief 

Self-healing compounds can help seal concrete cracks up to 150 meters, according to a recent study. Concrete cracks can be healed through autogenous recovery or autonomous recovery.

Insight

Crack self-healing in concrete is analyzed thoroughly in the journal Cement and Concrete Composites using water permeability testing. It was found that self-healing can improve the durability of concrete, using additional healing agents into cement materials.

Concrete: the Popular Material and Its Problem

Concrete is an extensively used construction material, and it is frequently regarded as a material with high strength and high durability. Cracks caused by natural or external load conditions, on the other hand, provide quick entry points for advanced species into cementitious materials, resulting in deterioration and even breakdown of concrete structures.

Conventional concrete can be defined as having no or poor self-healing ability, requiring external fixing to extend its life span. Self-healing concrete can seal cracks or defects on its own, potentially restoring mechanical and physical properties. The methods of self-healing, as known in the literature, can be divided into two categories: autogenous recovery and autonomous recovery.

Healing Cracks in Concretes

The response of dehydrated cement particles (UHCs) and carbonation is primarily responsible for autogenous healing. It is a very slow process that always requires water as an essential component. The recovery effect is proportional to the crack width, as well as the number of UHCs.

It has been discovered that if the crack width is less than 150 m, a significant self-healing influence can be accomplished. This effect can be amplified further if the crack width is lowered to 60 m.

However, predicting the accurate figure of crack width where the crack can be considered healed remains difficult. A significant recovery effect has been observed due to the large number of UHCs throughout ultra-high performance concrete (UHPC).