Study on crack-healing effect of cement mortar with fiber under dynamic water environment

Microbial self-healing concrete is a new sustainable construction material based on microbially induced calcite precipitation (MICP) technology. However, most research on self-healing con-struction materials has been carried out in static water environments. The actual working envi-ronment of concrete is complex, with water in both flowing and stationary states. In this study, the self-healing effect of self-healing concrete with MICP functionality in dynamic water envi-ronments is investigated for the first time. Fiber, as a common additive in concrete, can improve its toughness, flexural tensile strength, and compressive strength. In this study, the four most common fibers (basalt fiber, glass fiber, polypropylene fiber, polyvinyl alcohol fiber) used in the Chinese building materials market were selected as additives for microbial concrete, and their effects on the crack-healing effect were studied. The chloride ion (Cl ) permeability and crack -healing rate were used to reflect the crack-healing effect. It was found that the mortar speci-mens containing basalt fibers had the best crack-healing effect compared to the other three fibers. It was also found that at the fiber content (volume fraction) of 0.1%-0.15%, the chloride ion penetration resistance of mortar specimens with a healing time of 28 d was closest to that of specimens without cracking. The chloride ion penetration depth increased merely by 1 mm. Further, the chloride ion binding value decreased only by 0.0103. The effect of crack-healing under static and dynamic water environments was further studied based on the above research. The research shows that the height of the specimen from the water surface is negatively related to the crack-healing effect in the static water environment. When the water flow rate is & GE; 30 ml/h, the crack cannot be healed under the dynamic water environment. This study provides a theoretical basis and support for the engineering application of microbial self-healing concrete.