Project start: 01.08.2021
Project duration: 2 years
Funding: Internal Research Funding (IFF)
Contact person: Daniel Lahmann
A combination of desirable properties such as a high compressive strength, a broad availability of its raw materials and a superior cost efficiency make concrete the most widely used construction material in the world. However, due to its low tensile strength the formation of cracks from micro to macro scale due to load and load independent deformation caused by e.g., shrinkage, is unavoidable. Cracks can serve as pathways for aggressive chemical substances that can lead to a progressive deterioration of the cement stone as well as of the reinforcement, affecting the load capacity, service life and usability of concrete structures.
Concrete and reinforced concrete exhibit an intrinsic ability to heal cracks, defined as “autogenous self-healing”. This effect can be subdivided in (1) chemical causes: precipitation of calcium carbonate in the presence of water and CO2 and the ongoing hydration of unhydrated cement particles, (2) physical causes: swelling of the cement stone and (3) mechanical causes: blocking of the crack pathway with particles.
Experiments led to the consideration of crack healing by autogenous self-healing in DIN EN 1992-3 for water retaining concrete structures as well as in the German standard for waterproof concrete (“WU-Richtlinie” DAfStb). The standard regulates the boundary conditions, crack widths and hydraulic gradients under which autogenous self-healing is likely to occur. However, despite code restrictions, autogenous self-healing of concrete shows limited effectiveness in practice.
Therefore, our research aims for identification of the boundary conditions of autogenous self-healing, optimizing the understanding of the relevant healing processes and the transfer of laboratory results to real concrete structures. In our laboratory, we have developed a special experimental cell that can simulate realistic conditions of crack formation, initiation of autogenous self-healing and assessment of the healing efficiency through water permeation. In combination with chemical-mineralogical investigations, the self-healing effect is to be quantified as a function of time, concrete composition and water chemistry.
Letzte Änderung: 11. April 2022