Developments in the Built Environment (Mar 2024)
Effect of bacteria on uncracked concrete mechanical properties correlated with damage self-healing efficiency – A critical review
Abstract
Self-healing concrete has established its effectiveness in repairing cracks, ultimately leading to improved durability. Additionally, there is a need to ensure that other crucial mechanical properties, particularly the strength of the intact (uncracked) material, remain uncompromised. Despite CaCO3 precipitation being the primary component of the bacterial reaction product responsible for healing cracks and enhancing concrete strength, leveraging the effect of bacteria on concrete's mechanical properties could be subjective, given that several factors could influence the mechanical properties in either a positive or an adverse manner. Existing reviews on the topic predominantly focus on self-healing performance (post-damage recovery), with none of the published reviews dedicated, purely, to the mechanical properties of intact self-healing cementitious/concrete material. This paper reviews the impact of bacteria on mechanical properties, with a focus on the control (intact) strength of concrete and mortar under various conditions, with or without the incorporation of other materials such as fibers, bacteria carriers, aggregate replacement, and cementitious material replacement. Since concretes with strong self-healing attributes but poor mechanical properties would be unsuitable for structural applications, a detailed correlation between the effect of bacteria on mechanical properties before and after self-healing activation is discussed. Research gaps are identified, and an outlook for future research is presented, along with the perspective of self-healing concrete/cementitious material production for robust mechanical properties. The study also contributes to addressing one of the identified research gaps – the need for a generalized self-healing performance index that incorporates both mechanical and self-healing efficiency of the material. This paper proposes a typical model for such an index and illustrates its application using numerous existing experimental results of bacterial self-healing concrete performance. This sheds light on the overall performance – both mechanical and healing – of the material.
