Application of Blast Furnace Granulated Slag for Self-Healing Bio-Concretes

Abstract

The properties of fine-grained concrete containing 20–80% granulated blast furnace slag and bacteria species Bacillus Subtilis have been studied. An assessment was made of changes in strength, self-healing of cracks using optical and electron microscopy and measuring the speed of ultrasound propagation perpendicular to the crack plane; composition and characteristics of the healing agent in cracks using X-ray analysis methods. Self-healing of cracks in concrete without bacteria occurred due to calcite deposition as a result of carbonation of portlandite during 50–65 cycles of humidification-drying, and in the presence of Bacillus Subtilis bacteria due to calcite deposition during their vital activity in 10–15 cycles. It is shown that the addition of granulated blast furnace slag slows down the crystallization of calcite, which forms a healing substance in the crack. It is assumed that the combined use of granulated blast furnace slag in dosages of 40–80% and Bacillus Subtilis bacteria in concrete structures operating under conditions of variable humidification can ensure the process of self-healing cracks and maintaining the strength of concrete in the long term due to simultaneous processes of strengthening the structure due to prolonged hydration of slag minerals and calcite deposition in cracks due to the vital activity of Bacillus Subtilis bacteria.