Bio Concrete: An Emerging Construction Technology With Great Promise for Concrete Life Extension & CO2 Reduction
By Myat Cyn, Assistant Project Manager, Beacon Consulting Group, Inc.
Bio concrete is a self-healing concrete designed to repair its own cracks. It was invented by a Dutch researcher, Hendrik Jonkers, at Delft University of Technology in the Netherlands. Bio concrete is concrete with the addition of limestone producing bacteria utilizing a biochemical process called Microbially Induced Calcium Carbonate Precipitation (MICP). MICP is a biochemical process found in nature in soils, caves, freshwater, marine sediments, and hypersaline habitats. The process is brought on by the metabolic interactions between diverse microbial factions with organic and/or inorganic compounds present in the environment.
Bio concrete consists of three main components: microorganisms capable of MICP, nutrients, and calcium ions. Jonkers created biodegradable capsules and clay pellets that contain bacillus bacteria spores and calcium lactate. Bio concrete is created by mixing in these capsules or pellets into regular wet concrete mix. This approach is used to ensure the bacteria will stay dormant in its encapsulated state within the concrete for up to 200 years. The bacteria will become active when cracks eventually begin to form in concrete, water enters and open the capsules.
The bacteria spores inside the capsule germinate in contact with water and they multiply and feed on the calcium lactate. In this process, the bacillus bacteria converts the calcium ions into a form of calcium carbonate (also known as calcite, a principal component of limestone). The newly formed calcite closes the cracks as they form in the concrete. According to the inventor, the bacteria used in bio concrete are harmless to humans because they can only survive in concrete under alkaline conditions.
In today’s industry, more than 10 billion tons of conventional concrete are used annually at a global level. The process of producing conventional concrete accounts to 8% to 10% of global emissions of CO2 resulting from human activities. This is about 4 times the carbon emissions of the global aviation industry. Bio concrete can reduce the environmental impact by eliminating the additional use of concrete need in repair process. The average cost of cost repair involved in the maintenance and repair of concrete structures is estimated to be $138/m3 ($106 per cubic yard). Bio concrete can reduce and eliminate the cost involved in the repair and maintenance of bridges, tunnel, and infrastructures. Bio concrete can also extend the lifetime of future concrete structure as well.
Commercial use of bio concrete products is already happening. One U.S.-based company, Biomason, is producing bio concrete tiles that have already been used in real-world applications by large companies such as H&M and Martin Marietta. The company's bio-concrete material was also used in a demonstration project funded by the U.S. government (a biocement-based helicopter landing pad located in Guam). Unlike traditional concrete production, which requires a tremendous amount of heat (and the burning of fossil fuels), Biomason "grows" its products without the use of heat. Instead, carbon and calcium are combined to produce a biologically formed limestone material.
Unlike traditional concrete, which can take up to 28-days reach final strength after pouring, Biomason's Biocement® reportedly reaches its full strength in less than 72 hours of "growth" (a process which reportedly takes around 24 hours and occurs at ambient temperature). The company's "Biolith tile" consists of approximately 85% granite from recycled sources and 15% biologically grown limestone. The company is reportedly in the process of scaling up its U.S. production of biolith tiles. In 2021, it opened a 20,000-square foot plant in North Carolina and is working to ramp up production from 100,000 square feet of product per year to its goal of 1 million square feet. It also recently entered into a partnership with Amsterdam-based StoneCycling to sell and distribute its products in Europe.
In conclusion, bio concrete can have positive impacts for cost, structural integrity, and the environment. It's definitely a technology to watch in the years ahead.