What's the difference between healing and self healing concrete?

Self-healing is recognized as concrete containing something native in the concrete composite that was mixed into the concrete before the crack occurred. This additive activates its own set of mechanics or kinetics to form bridges over the cracks that form within the concrete surface and throughout the body of the composite. The material that bridges over the cracks does not necessarily have to have a strength equal to or greater than the parent concrete material. That being said, the material forming the bridges within the concrete cracks should provide some resistance to moisture and impurities migration / capillary movement.

Healing of concrete assumes that the structure is retrofit, where the concrete has been put in place for some time, and that you’re either integrating or spraying on a product to the concrete and relying on the crack to allow for the migration or permeability pathways of that added material. It is imperative that the product is added after the concrete is already in its cracked state rather than natively present in the concrete like self-healing concrete.

Healing and Self-Healing product types have three things in common. First, the material that repairs the crack must have a greater than or equal to strength in the native concrete.Secondly, the products must have the same or better durability of the native concrete hydrated cement matrix.Finally, the material has to have the ability to create its own zone. It is important that the product created is not going to create its own deleterious or nasty and environment. For example, a nalkali silica reaction gel that’s expansive and can give great result in stresses in those cracks where the gel that is being developed is not really bridging the cracks but actually making the crack wider and ensuring more localized stresses that can cause additional cracking.