What is Self-Healing Concrete ?

Self-healing concrete is a type of concrete that can heal itself from the micro-cracks formed in it and regain its original state. The self-healing property in concrete gives the ability to heal itself during cracks and protects the interior matrix and reinforcement bars within concrete. This help to increase the durability of concrete structures. 

What is Self-Healing Concrete?

Self-healing concrete is made by introducing healing agents like bacteria, fungus or sodium silicate, or polymers to concrete. These healing agents are used and studied over years by scientists and engineers around the world.

Fig.1. Self-Healing Concrete

The concept of self-healing in concrete is evolved from biological life forms like plants and animals that exhibit a self-healing process naturally when any damage occurs to them.

This article explains different processes or systems by which self-healing in concrete happens, different healing agents, and important features of self-healing concrete.

Self-Healing Concrete System

The self-healing system present in self-healing concrete is mainly divided into two parts:

1. Autogenous Self-Healing in Concrete
2. Autonomic Self-Healing in Concrete

1. Autogenous Self-Healing in Concrete

The autogenous self-healing process is an intrinsic property of concrete, where it initiates healing with the already present generic materials in the concrete. To be more precise, we know that concrete attains strength due to hydration reactions and hydration products. 

During the process, there are chances for some amount of unhydrated cement present in the concrete. There are chances for rehydration of these unhydrated cement present over the cracked surface and exhibit the repairing ability to heal by themselves. 

Hence, a self-healing process in concrete using material components that are not traditionally added to the concrete is termed an autogenous self-healing process or autogenous self-healing of concrete.

Autogenous self-healing can be improved by the presence of fiber, shrinkable polymers, or minerals. Each material has its own style of improving the autogenous healing of concrete. 

As autogenous self-healing follows the process of hydration of unhydrated cement that is remaining in the matrix, it is best suitable for filling the crack width up to  50 to 150 µm.

In the figure-2, the use of traditional concrete materials for the autogenous self-healing process is depicted for different materials.

Fig.2. Autogenous Self-Healing in Concrete

Read More on: What is Autogenous Self-Healing of Concrete? Self-Healing Concrete

2. Autonomous Self-Healing in Concrete

An autonomous self-healing system requires the help of a healing agent to facilitate self-healing in concrete. The healing agent is released through the process of reverse encapsulation or continuous vascular network.

The common healing agents used for autonomic self-healing in concrete are epoxy resins, expansive minerals, hydrogel, and bacteria-based micro-organisms as shown in figure-3 below.

Fig.3. Autonomic Self-Healing in Concrete

Features of Self-Healing Concrete

Self-Healing Concrete is an innovative technology that is useful in bringing up more smart and resilient infrastructure development. The technology used for self-healing is decided based on the application.

Self-healing concrete technology helps to develop concrete structures without the worry of damage or intensive maintenance. 

However, self-healing concrete is still in its proving stage to flourish for greater applications in the construction industry.

Also Read: Rheology of Concrete - Bingham Model Representation