Self-healing capability of conventional, high-performance, and Ultra High-Performance Concrete with commercial bacteria characterized by means of water and chloride penetration

This study analyzes the self-healing capability of conventional, High-Performance, and Ultra High-Performance Concrete specimens, incorporating commercial bacteria products that are easily accessible, marketed, and affordable from different sectors. Bacteria were incorporated into different mediums: immobilized in diatomaceous earth and liquid. Specimens were pre-cracked to a range of 50-450 & mu;m cracks and were left to heal for 28 days in 3 different conditions (1) water immersion, 2) one week of water immersion followed by three weeks in a humidity chamber, and 3) humidity chamber. To evaluate the self-healing enhancements of specimens using a bacteria-based healing agent, self-healing efficiency was quantified by optical assessment of crack closure, recovery of water tightness via water permeability testing, and chloride permeability via cracks and matrix. The results show that bacterial agents increased the protection against chloride penetration in cracked and healed specimens of conventional concrete, especially when the specimens were healed in water immersion. Owing to the dense matrix of HPC and UHPC, the chloride penetration in the presence of cracks up to 400 & mu;m can be kept below 10 mm. Crack closure greater than 50% is required in UHPC samples to get a significant healing ratio. The penetration through the cracks is approximately twice that of the matrix penetration in conditions when healing is not enhanced.