Self-healing of concrete incorporating seashells as partial cement replacement

The current experimental study aims to evaluate the effectiveness of a bacteria-based self-healing admixture in low-carbon concrete to minimise maintenance demands on concrete structures. The implementation of such innovative technologies has the potential to enhance structural durability, reduce the frequency and extent of repairs, lower the consumption of additional repair materials, and consequently decrease the embodied carbon associated with maintenance activities. This research investigates the enhancement of concrete’s self-healing capability through the incorporation of a bacterial healing agent, and the use of scallop seashells as a partial cement replacement at a substitution rate of 30 % to reduce carbon emissions. Furthermore, the study explores the synergistic effect of combining both the self-healing agent with an anti-corrosion inhibitor (NitCal) to improve the overall durability and performance of concrete. The experimental program comprises concrete specimens categorised into three sets. The first set includes control samples with 30 % scallop seashell replacement, serving as reference specimens. The second set consists of samples containing 30 % seashells and the self-healing agent, while the third set comprises samples incorporating 30 % seashells, the self-healing agent and NitCal. After 28 days of curing, controlled cracks of 0.4 mm width were introduced into all specimens. The second and third sets were then placed in an incubation chamber to facilitate and evaluate the biological self-healing process, in comparison to the control group. In addition to self-healing assessment, the study investigates fresh and hardened concrete properties, including compressive strength, modulus of elasticity and carbon emission, for mixtures containing 30 % scallop seashells with varying dosages of NitCal. The findings aim to support the development of more sustainable and resilient concrete materials.