Self-Healing Concrete in Aggressive Environments

The aim to develop mechanisms and technologies that increase the durability of concrete structures and hence the service life has gained great focus in the last years, due to the fact that cementitious materials are susceptible to cracking and thus cause damage related to degradation, being aggravated in highly aggressive environments. Satisfactory results of cracks healed autonomously and/or triggered by some external stimuli are described in the literature. However, much of this evidence was acquired in environments considered to be ideal conditions. The ideal conditions can vary depending on the healing agent. In this way, if there is a discretion to know how to choose the healing agent for each environmental condition to which it will be exposed, efficiency can be guaranteed by increasing the durability of the structure. Some research studies were also employed in real situations in order to show that the self-healing techniques developed in laboratory scale could be extended to real site applications. However, further research should focus on long-term durability of the healed structures, considering more realistic environmental conditions, e.g., resistance to corrosion, freeze/thaw, salt crystallization, and steady vs. non-steady cracks. Assessing the durability of materials after damage and consequent healing is essential to validate full-scale use. There are rare large-scale self-healing concrete applications that generally show insufficient or even unproven efficiency. The research project aims to describe in a clear and reliable way how the self-healing concrete behaves in different aggressive conditions. The topic forecasts the production of a selection matrix for self-healing methodologies that can be tailored to specific real environments such as temperatures from -10 to 60 °C (incl. freeze-thaw effects), high salt or acid concentrations, low or high moisture content, a certain level of water pressure, etc. The various (extreme) conditions will be applied during and/or after healing and the latter will provide information on the durability of the healed material. Thus, through reliable results based on experimental tests and knowledge extracted from the literature, it is expected that self-healing mechanisms, if selected well, can be used in practical situations and that they obtain good performance. By discovering the best healing agents for each extreme condition, the market may have a reliable guideline for developing the mixtures considering the most suitable self-healing mechanism.