Bacteria-based self-healing concrete

A typical durability-related phenomenon in many concrete constructions is crack formation. While larger cracks hamper structural integrity, also smaller sub-millimeter sized cracks may result in durability problems as particularly connected cracks increase matrix permeability. Ingress water and chemicals can cause premature matrix degradation and corrosion of embedded steel reinforcement. As regular manual maintenance and repair of concrete constructions is costly and in some cases not at all possible, inclusion of an autonomous self-healing repair mechanism would be highly beneficial as it could both reduce maintenance and increase material durability. Therefore, within the Delft Centre for Materials at the Delft University of Technology, the functionality of various self-healing additives is investigated in order to develop a new generation of self-healing concretes. In the present study the crack healing capacity of a specific bio-chemical additive, consisting of a mixture of viable but dormant bacteria and organic compounds packed in porous expanded clay particles, was investigated. Microscopic techniques in combination with permeability tests revealed that complete healing of cracks occurred in bacterial concrete and only partly in control concrete. The mechanism of crack healing in bacterial concrete presumably occurs through metabolic conversion of calcium lactate to calcium carbonate what results in crack-sealing. This biochemically mediated process resulted in efficient sealing of sub-millimeter sized (0.15 mm width) cracks. It is expected that further development of this new type of self-healing concrete will result in a more durable and moreover sustainable concrete which will be particularly suited for applications in wet environments where reinforcement corrosion tends to impede durability of traditional concrete constructions

Healing agent for self-healing cementious material

The invention provides a process for the production of a cementious material. The process comprises mixing cement starting materials and a particulate healing agent to provide the cementious material. The healing agent comprises coated particles, wherein the coated particles comprise bacterial material and additive. The bacterial material is selected from the group consisting of a bacterium, a lyophilized bacterium and a bacterial spore of a bacterium. The present invention solves these problems, as (substantially leakage-proof) tablets containing the actual healing agent may neither interfere with either the workability of the liquid mixture ("cementious material") nor negatively affect properties of either mixture or final material (hardened concrete), even when applied in large quantities. During crack formation in cementious based constructions, the particles also crack, and healing agent is released.BT/BiotechnologyApplied Science

Development and application of bacteria-based self-healing materials

In 2006 a research program was launched at Delft University of Technology aiming for the development of a new class of materials, i.e. materials with an inbuilt healing mechanism. The idea is that these novel materials can self repair damage resulting in substantially decreased maintenance and repair costs and increased service life. Several research projects focus on cement-based materials such as concrete and asphalt. One project that will be discussed here concerns bacterial-based concrete. The bacteria which are added to the concrete mixture are able to produce calcium carbonate-based minerals, a process that can result in sealing and water tightening of cracks. These and more examples show that novel materials and constructions which are designed to control damage rather than prevent damage by featuring an inbuilt healing mechanism could be more economical than traditional ones.Structural EngineeringCivil Engineering and Geoscience

Toward Bio-based geo- & Civil Engineering for a Sustainable Society

The since 2010 running research program 'Bio-Based Geo & Civil Engineering for a Sustainable Society (BioGeoCivil)', funded by the Dutch technology foundation STW, aims to develop novel bio-based construction materials that can be used in Civil- and Geo-engineering constructions to enhance the sustainability performance of the sector. Rationale is that the sector produces still today excess amounts of waste in all life cycle phases of a construction, from building to use phase as well as end-of-life phase. Aim of the program is to mimic nature as 'building' processes in nature do not produce any waste as all elements, also residual material. is considered a high grade resource. In order to substantially improve the sustainability profile of the sector, upgrading of secondary- or byproducts must be achieved to allow functional performance similar to primary materials and resources. The challenge of the six currently running projects within the BioGeoCivil program is therefore not only to mimic nature but also to include bio-based materials or processes in civil- or geo-engineering applications which result, in comparison to traditional building products, in drastically improved performance both on sustainability and durability level. The six projects comprise: 1. Fungal biofilms (coating) for wood protection, 2. Bacteria-based repair and performance improvements of aged concrete structures, 3. Bacteria-based ground stabilization to mitigate liquefaction and piping of granular sediments, 4. Engineering of bacterial biofilms on buildings and infrastructure as a basis for natural protection, 5. Lift up Lowlands: upgrading of natural materials (bio-remediation of sludge) for sustainable lift up of low lying polder areas, and 6. Towards the development of carbon dioxide neutral renewable cement.Materials and Environmen

Healing agent in cement-based materials and structures, and process for its preparation

The present invention relates to healing agent in cement-based materials and structures, wherein said healing agent comprises organic compounds and/or bacteria-loaded porous particles, which porous particles comprise expanded clay- or sintered fly ash. Furthermore, said porous particles are intact spheres, broken or crushed particles derived from said intact spheres, having a specific density between 0.4 and 2 g cm-3. Finally, the present invention relates to a process for the preparation of the healing agentCivil Engineering and Geoscience