Bacteria-based self-healing concrete: evaluation of full scale demonstrator projects

Abstract

Bacteria-based self-healing concrete is an innovative concrete that contains a self-healing agent that provides the material with enhanced autonomous crack-sealing performance. A specific type of this concrete, based on a healing agent composed of bacterial spores and lactate as carbon source, has been developed and applied by the Delft University of Technology for over ten years. Under laboratory conditions it was proven that, depending on the dosage of healing agent, self-healing of cracks up to 0.8 mm widths occurs. As such the material potentially allows reduction of steel reinforcement used for crack width limitation in watertight constructions. Application of self-healing concrete would therefore not only result in a reduction of costs but also in improvement of environmental performance (lower CO2 footprint) and ease of in situ casting due to reduction of use of steel in waterproof applications. However, according to the EN 1990 Eurocode (Basis of structural design), customary application of a novel type of concrete must be preceded by full scale demonstrators proving evidence for safe and functional performance. In this contribution we portray full scale application of bacteria-based self-healing agent as developed by the Delft research group in two repair mortar-and in two concrete construction demonstrator projects. These demonstrator projects show that addition of the bacteria-based self-healing agent to the concrete mix is safe as no negative side effects on construction performance was observed. However, it also proved difficult to find evidence for increased crack-healing performance as cracking in the demonstrator constructions hardly occurred. In further full scale demonstrators we therefore plan to drastically reduce amount of crack width-restraining reinforcement to show crackhealing capacity and potential to save on use of reinforcement steel in watertight concrete constructions.

Contribution of bacterial cells as nucleation centers in microbiologically induced CaCO3 precipitation—A mathematical modeling approach

“…The obtained results suggested that all tested bacteria are part of the most commonly used type of bacteria in the MICP [11,30,31]. In recent scientific literature, Bacillus and similar genus (e.g., Lysinibacillus) present a good choice of Grampositive bacteria for alkaline matrix during MICP application [32][33][34][35]. It can be observed that the average size of wild-type Bacillus strains is different from the referent strain.…”

Self-healing concrete-What Is it Good For?

“…Five months after casting, no signs of cracking were detected. In 2016 bacterial self-healing concrete was used in two projects (124): the construction of prefabricated parts of a wastewater purification tank and in two walls of a water reservoir. Monitoring in the following two years suggested that the repairs were effective.…”

“…Improving self-healing is still in a lower TRL level, currently validated in relevant environments (16)(17)(18). • Bacteria concept has been validated in laboratory and field pilots (123,124), but the products are not generally produced at large scales (96,97). Currently, bacteria production is limited, which complicates its application in concrete structures, but its production may improve in the next years.…”

Bio-Engineered Concrete: A Critical Review on The Next Generation of Durable Concrete

“…Although most of these studies were laboratorybased, a few conducted in the last five years were still related to the application of bio-cultures as healers and strength increasers in practical structural elements. Mors and Jonkers (2019), conducted several practical implementations on bio-engineered mortar and concrete. This was the largest practical study that mainly focused on the ability of bio-cultures, towards crack healing within a realistic environment.…”

“…Figure 8. Application of bacteria-based self-healing repair mortar on actively leaking cracked concrete basement walls (Mors & Jonkers, 2019).…”