Sustainable structural engineering, ie reducing the energy and resources consumption as well as CO2 emissions due to the construction and operation of a structure, is one of the main goals of nowadays engineers and scientists. Concrete is, next to steel, one of the most popular structural materials. Over the years, various modifications of concrete composition have been proposed in order to improve its properties. Lately, ways to decrease the negative environmental impact of concrete has been extensively studied. Lowering carbon footprint of concrete can be done by, ie replacing cement with Supplementary Cementitious Materials and lowering maintenance and repair costs. The forms can be done by developing concrete using industrial waste, eg fly ash, or blast furnace stroke, while the laughter can be achieved by designing a material with self-healing properties. Self-repair of tissue and bones in biological materials has always been an interesting concept. Mimicking natural phenomena and mechanisms give a possibility to develop new materials with smart behavior.
The self-healing characteristic, ie the ability of material to sense and repair inner damage without human intervention, is one of the most desirable properties in material science. Recently, attention has been paid to the self-healing phenomena in cementitious materials. Concrete is a brittle material with low tensile strength. In order to increase tensile strength of concrete additional reinforcement has to be implemented, usually made of steel. Concrete provides alkaline environment for the reinforcement, protecting it from corrosion. Due to its brittleness, concrete is prone to cracking not only due to external mechanical loading but also forming as a result of thermal drying or autogenous shrinkage. The cracks provide a way for acidic ions to reach the reinforcement leading to its corrosion and deterioration of concrete microstructure. As a consequence, material's strength decreases which is a serious issue.
Concrete composite with the ability to heal the cracks and, as a result, regain the transport and mechanical properties is a scientific goal for many researchers, as it is not only a fundamental physicochemical riddle but also a solution to many industrial issues such as reduction of necessary repair works. This could lead to more sustainable construction and lower maintenance costs. The potential of self-healing or concrete was already noticed over 100 years ago. Nowadays, various techniques are being investigated in order to accelerate and increase the benefits of this process.