PVA increases efficiency of bacterially-induced self-healing in cement mortars

Abstract

Different strains of bacteria capable of calcite precipitation can be incorporated into fresh concrete or cement mortars to efficiently promote self-healing of microcracks after hardening. To date, all bacterial strains investigated have required protection against the highly alkaline environments and high pressures in cementitious matrices. The core objective of this study was to eliminate the inconveniences related to protecting (typically encapsulating) bacteria. Poly(vinyl alcohol) (PVA) doped with spores of Bacillus pseudofirmus and nutrients were added to mixing water when cementitious mortars were prepared. The hardened mortar specimens were cracked and studied using microscopy, resonance measurements, X-ray microtomography (μ-CT), and destructive mechanical tests to assess the rate and efficiency of the healing processes. PVA was efficient in promoting remediation in all mortar specimens, both with and without bacteria. Specimens containing PVA plus bacteria showed the most efficient self-repair processes, while autogenous remediation in reference samples lacking PVA or bacteria were least efficient in healing microcracks.