Innovations in Concrete: The Use of Self-Healing Concrete in Modern Construction Projects

Concrete is one of the most commonly used construction materials due to its durability and versatility. Approximately 8 billion cubic meters of concrete are produced worldwide each year: one cubic meter for every citizen of the world. A large portion of this concrete must withstand (salt) water and damage such as cracks, which can significantly reduce its longevity and stability. In recent decades, the development of self-healing concrete represents a significant advancement in construction. This article explores innovations in the use of self-healing concrete, focusing on new materials and technologies that improve the longevity and sustainability of concrete structures.

History and Development of Self-Healing Concrete

Self-healing concrete represents a revolutionary technology with the potential to significantly enhance the longevity and sustainability of concrete structures. The idea of concrete that can repair itself has developed over several decades, with an increasing emphasis on reducing the need for maintenance and repairs, as well as improving the ecological sustainability of construction materials.

The concept of self-healing materials is not new and can be traced back several decades. Initial concepts were inspired by natural healing processes, where researchers aimed to replicate these processes in construction materials. The first serious research papers on this topic appeared in the late 20th century, when researchers began experimenting with various additives and technologies that would enable concrete to repair itself.

Early experiments involved the use of microcapsules containing adhesives or chemical agents. When cracks occurred in the concrete, these capsules would break open and release their contents, which would then fill the crack and harden. Although these approaches showed potential, they had limitations in terms of durability and effectiveness.

Biological Self-Healing Concrete

One of the most significant advancements in the development of self-healing concrete occurred in the early 21st century with the introduction of biological methods. Dutch researchers Henk Jonkers and Erik Schlangen from TU Delft’s Faculty of Civil Engineering and Geosciences developed the concept of using bacteria to repair concrete. These bacteria, most commonly from the genus Bacillus, can survive in harsh conditions and produce calcite when they come into contact with water and nutrients. Calcite, the mineral produced by the bacteria, effectively seals cracks in the concrete.

Biological self-healing concrete works by encapsulating bacteria (e.g., Bacillus pasteurii) in the concrete along with nutrients (calcium lactate). When cracks occur and water enters the concrete, the bacteria become active, consume the nutrients, and produce calcite, which fills the cracks.

Chemical Self-Healing Concrete

In addition to biological methods, chemical self-healing concrete has been developed as an alternative that uses microcapsules containing chemical agents. These capsules, made from materials sensitive to mechanical changes, the presence of water, or other reagents, release their contents when cracks occur. These agents react with calcium hydroxide in the concrete to form a solid gel that fills and seals the cracks.

Polymeric Materials and Fibers

Further advancements have been made with the introduction of polymeric materials and fibers that can expand and fill cracks when they occur. Polymeric resins, activated by moisture or temperature changes, expand and fill the cracks, providing additional strength and stability while reducing the likelihood of new cracks forming. Fibers are added to the concrete mixture and become activated when cracks occur, filling the gaps.

Advantages of Using Self-Healing Concrete

Using self-healing concrete offers numerous benefits that significantly enhance the longevity and sustainability of concrete structures:

Longevity: Self-healing concrete extends the lifespan of concrete structures by reducing the need for frequent repairs and maintenance. This is particularly beneficial for infrastructure projects such as bridges, roads, and buildings.

Cost-Effectiveness: Reduced maintenance and repair costs directly impact the overall project costs. Although the initial cost of self-healing concrete is higher, long-term savings make it a more economical option.

Flexibility: Self-Healing Concrete can be used for production of monolithic and precast concrete elements.

Improved Protection in New Construction: It provides better water protection and requires less reinforcement, saving money and reducing CO2 emissions.

Environmental Sustainability: Fewer repairs mean less resource consumption and reduced carbon dioxide emissions, contributing to a more sustainable construction sector.

Safety: Self-healing structures are less prone to sudden and unexpected failures, increasing the overall safety of buildings, especially in critical infrastructure projects.

Examples of Self-Healing Concrete Applications

Case Study 1: Bridge in the Netherlands

The bridge in Delft represents a pioneering example of the application of self-healing concrete in construction, demonstrating the potential of this technology to increase the longevity and reduce maintenance costs of infrastructure. The use of biological concrete with Bacillus bacteria has proven to be an effective method for the autonomous repair of cracks and the preservation of the structural integrity of concrete structures. This project showcases the practical application of biological self-healing concrete developed by researcher Henk Jonkers at Delft University of Technology.

Case Study 2: Residential Building in South Korea

In South Korea, a residential building was constructed using chemically self-healing concrete. Microcapsules containing sodium silicate were added to the concrete mix. When cracks occurred, the capsules opened, and the chemicals reacted with moisture, filling the cracks. This technology significantly reduced the need for repairs in the initial years of the building’s use.