Effect of Microbiological Growth Components for Bacteria-Based Self-Healing on the Properties of Cement Mortar

Abstract

Previous studies of bacteria-based self-healing concrete have shown that it is necessary to encapsulate and separate the self-healing ingredients (bacteria, nutrients, and precursors) in the concrete so that when a crack forms, capsules rupture, which allows the self-healing ingredients to come together and precipitate calcite into the crack. Because of the shearing action in the concrete mixer, there is a chance that these capsules, or other carriers, may rupture and release the self-healing ingredients. This would affect the efficiency of self-healing, but may detrimentally affect the concrete’s properties. This work investigated the effects of multi-component growth media, containing germination and sporulation aids for the bacterial aerobic oxidation pathway, on the basic properties of fresh and hardened concrete instead of the potential self-healing efficiency in a structural service. Tests were carried out to measure the effects of growth media on air content, fluidity, capillary absorption, strength development of cement mortar following corresponding standards, hydration kinetics, setting properties, and the microstructure of cement paste, according to certain specifications or using specific machines. The research has demonstrated that a multi-constituent growth media will not have a significant effect on the properties of concrete in the proportions likely to be released during mixing. This important conclusion will allow further development of these novel materials by removing one of the key technical barriers to increased adoption.

Understanding the Impacts of Healing Agents on the Properties of Fresh and Hardened Self-Healing Concrete: A Review

“…On the contrary, a drastic drop of the mortar compressive strength was observed when the yeast extract was added into the mix, which is in agreement with the result reported by Jonkers et al [6]. Chen et al [70] proved that the addition of yeast extract (0.06% by weight of cement) into the mortar mixes lowered the compressive strength, approximately from 38 to 32 MPa. This may be explained due to the fact that the air content of mortar containing yeast extract was almost doubled in relation to the reference mortar without nutrients; increasing from 2.1 to 3.8%.…”

Review of the Effects of Supplementary Cementitious Materials and Chemical Additives on the Physical, Mechanical and Durability Properties of Hydraulic Concrete

“…However, the use of bacteria is very challenging in the alkaline environment of concrete [ 241 ]. As a result, autogenous, autonomous and bacteria-based self-healing concrete technology is a double-edged sword [ 242 ]. There is a need for more extensive investigation in future real concrete structure application by considering such various aspects as the particle size of microcapsules and the enhancement of bacterial growth by providing required nutrients [ 230 , 242 ].…”

Investigation of Self-Healing Mortars with and without Bagasse Ash at Pre- and Post-Crack Times

“…However, only a few bacteria types can withstand extreme concrete settings since it shortens their life span. Bacteria S. pasteurii or Bacillus pasteurii are often-utilized bacteria for self-healing concrete due to their endospores’ ability to withstand the harsh environment of concrete [ 21 ]. Furthermore, the inclusion of Bacillus pasteurii into concretes increased the compressive strength, durability, and resistance to freeze–thaw of samples due to calcite precipitation.…”