In our fifth article about the companies short-listed within the Global Cement & Concrete Association's Innovandi Open Challenge, Global Cement speaks to Charles Maddox, CEO of self-healing concrete developer Enzymatic...
Global Cement (GC): Please could you introduce Enzymatic to our readers?
Charles Maddox (CM): Enzymatic was founded in early 2023 to develop a form of self-healing concrete that had been developed by Prof Nima Rahbar and Prof Suzanne Scarlata at the Worcester Polytechnic Institute (WPI), a top engineering university in the north east of the US. Having worked in the US Air Force, I was extremely interested to work in this area, as damage to concrete runways costs the USAF dearly in lost time for repairs. There is also the very real risk of concrete being drawn into the engines, which is very dangerous and also a multi-million dollar repair bill.
Today Enzymatic is growing rapidly. It operates a laboratory in Worcester, Massachusetts, and employs PhD graduates, experienced entrepreneurs and advisors. Over the past 12 months we have developed our technology to make it commercially feasible, thanks in large part to our Chief Technology Officer Dr Isaac Nardi.
GC: How does the technology work?
CM: Our technology relies on carbonic anhydrase. In nature, this enzyme converts carbon dioxide to bicarbonate in cells so that it can dissolve in the blood. It also converts it back to carbon dioxide when it reaches the lungs. It is the most efficient enzyme found in nature, speeding up the reaction by a factor of 10 million.
In Enzymatic's solutions, we harness this enzyme's ability to combine unbound calcium ions in the concrete mix with atmospheric carbon dioxide, which converts it into calcium carbonate during setting. This helps to plug voids in the concrete, which leads to a range of benefits.
Initially we used naturally-derived carbonic anhydrase from cows, which cost about US$1000 for 250mg from commercial suppliers! However, we have since evolved a proprietary strain of carbonic anhydrase that can be synthesised at a cost of single digit dollars per 250mg. Crucially, it is stable at temperatures of up to 60°C for up to 45 days, with no reduction in activity. This is ideal for applications in which the concrete reaches high internal temperatures as it cures. We are developing this commercially as one of our two solutions - the Enzymatic Corrosion Inhibitor (ECI), for conventional concrete blends.
GC: What dosage of ECI is required?
CM: The dose of ECI needed is very small, with a typical loading of 130 - 260mg/m3, but it has a big effect. It's just a drop of water in each m3, unlike some other porosity reducers which might need hundreds of grams. We need so little, because the enzyme is not consumed in the reaction. One enzyme molecule, just 4 - 5nm wide, can convert 10,000 calcium ions into calcium carbonate using ambient CO2 by the time the matrix is immobilised. Multiply that by the 10 trillion molecules in a typical dose and you have an extremely potent solution.
To illustrate, we took MRI scans of a control concrete sample with no ECI and an identical concrete sample containing ECI. In the control, there were 55,000 pores, many of them closely bunched together. In the sample containing ECI, the number of pores was just 143 - a huge difference. The pore volume fell massively and there were no connected pores, unlike in the control. There are far fewer opportunities for the sample to develop cracks and no pathway for corrosive ions to penetrate the matrix. This considerably reduces the chance of damage to the concrete and any supporting steel. Additionally, this opens up some fantastic possibilities. We no longer need to worry about the 'dangers' of smooth marine sand and can be more accommodating when it comes to aggregate selection too.
GC: How long does the enzyme survive?
CM: It survives for about 12 months, whether in solution or in concrete. However, in concrete it is immobile and cannot access the free calcium ions or ambient CO2. However, it remains active for the full 12 months, perhaps even longer. Indeed, we took a seven month old concrete sample, cut a notch into it, and sprayed a calcium silicate solution on the exposed surface. The material re-grew extra calcium carbonate in the notch, all with no CO2 emissions.
GC: What are the CO2 benefits of ECI?
CM: The selling point of ECI is not the reduction of CO2 emissions per se, but there is a marginal reduction. However, ECI is just one of the two ways that we can harness the power of enzymes in the building materials sector.
Our Enzymatic Construction Material (ECM) is a supplementary product to regular cement. We envisage capturing CO2 from cement plants and using it as a feedstock for ECM.
To make ECM, we use a two-step process that starts with a bulk phase of mostly sand and then incorporates a secondary liquid phase. This secondary phase uses the enzyme and calcium solution to absorb CO2 and form calcium carbonate that becomes part of the final structure and binds the sand together. The curing phase lasts just two hours, making this a powerful process to make pre-cast elements. This would provide another stream of revenue for the cement plant operators, as well as a way to remove up to 90% of the CO2 emissions from a cement plant stack.
We have now reached compressive strengths of 30MPa with ECM, strong enough for low-rise construction, blocks, pavements, roof tiles and many other applications. We can't consider high-rises or bridges at this stage, although we are working on it. ECM structures can be repaired by adding calcium and enzyme solutions, even for cracks of up to 3-4mm. The benefit is that the repaired area is just as strong as the rest of the material, reducing the risk of the crack reforming.
GC: What are the CO2 credentials of ECM?
CM: By removing the CO2 from the cement plant stack and using it as a construction material, ECM can entirely eliminate the CO2 associated with the heating and decarbonisation of limestone and additionally sequester an additional 66kg/m3 of CO2.
GC: What scale have you reached and what's next?
CM: At its core, Enzymatic is an enzyme development company. Right now, we are proving that the concepts behind ECI and ECM work. Once this has been achieved, this will demonstrate to participants in the sector how they can use our enzymes to their advantage. We are already well into our scale up plans to produce enough ECI for 30Mm3/yr of concrete. This will be the easier technology to implement at first, as it is - literally - a 'drop-in' solution. The next step for ECM is to build a pilot plant that can generate 1t in batches. We are keen to develop links to industry, and so are appreciative to have been short-listed by the Global Cement & Concrete Association in its ongoing second Innovandi Open Challenge, which seeks to identify novel, low-CO2 additives for cement and concrete. We are now in ongoing discussions with six GCCA members to form a consortium focusing on ECI.
GC: What are the biggest barriers to roll out?
CM: The biggest issue is regulatory hurdles. We are currently sending out ECI samples to our consortium partners to make sure that it can meet regulations in different markets. Then we need to start getting approval for their use. However, this can be a long drawn-out process. We hope to leverage their expertise and work with GCCA to help us roll this out globally.
GC: How much impact do you think ECM and ECI will have by 2030?
CM: If implemented worldwide, ECM will reduce emissions by 3.7Bnt/yr, over 18% of all emissions reduction targets. I know this is a 'bit' on the high side, but we have to aim high to be in with a shot of meeting our collective CO2 targets.
GC: Thank you for your time today Charles. We look forward to Enzymatic's next steps.
CM: You are very welcome Peter!
About Charles Maddox
Charles Maddox is the CEO and one of the co-founders of Enzymatic, based in Las Vegas, Nevada, and Worcester, Massachusetts. An ex-US Air Force pilot with an MBA
from the Worcester Polytechnic Institute, Charles has launched and sold several start-ups since leaving the airforce and is also a partner in a construction company.
