This course is part of the Concrete Academy

Future of LC3

One of the key discussions around LC3 compared to other SCM mixes, is that its two main components—limestone and calcined clay—are widely available for the foreseeable future. Calcined clay can be obtained through a variety of natural clay sources, some of which is in current stockpiles of waste. Limestone is, likewise, a naturally abundant material. Fly ash and slag is available now, but the shutdown of coal fired electric power plants and steel blast furnaces respectively, means that the supply of those materials is dwindling.

Another area where LC3 has an advantage is in testing. It has been widely tested and demonstrated compared to some other SCMs and technologies, and has seen favorable results in demonstration projects. Its use is being encouraged by organizations such as the United Nations Development Programme (UNDP) and the International Energy Agency (IEA).

BIOCHAR CONCRETE

Biochar is a type of charcoal produced from organic matter. It’s created by heating organic material, such as wood chips or agricultural waste, in an oxygen-deprived environment through a process called pyrolysis. Biochar is often used in agriculture as a soil additive to improve its quality and fertility because the porous structure of biochar can increase soil water retention and nutrient availability, leading to better plant growth. It can also be made from agricultural and forestry waste materials that would otherwise be burned or left to decompose, contributing to greenhouse gas emissions and air pollution. Converting waste into biochar makes that waste useful while also reducing their environmental impact. In addition, the process of pyrolysis used to make biochar produces bio-oil and syngas, and those can be used as renewable sources of energy.

Photo courtesy of John Mead, Solid Carbon

Biochar is a type of charcoal produced from organic matter that can improve concrete’s mechanical and thermal properties while also reducing the carbon footpring of building projects.

When added to concrete, biochar can improve concrete’s mechanical and thermal properties. It can increase the strength and durability of concrete by reducing cracking and enhancing its resistance to freeze-thaw cycles. The porous nature of biochar allows it to absorb moisture, which can reduce the weight of the concrete and improve its insulating properties.

Incorporating biochar into concrete has strong environmental benefits. It is a carbon-negative material, meaning that it removes carbon dioxide from the atmosphere when it is produced. By using biochar in concrete, it is possible to greatly reduce the carbon footprint of construction projects and contribute to climate change mitigation efforts.

Biochar concrete represents an innovative approach to sustainable construction that combines the benefits of traditional concrete with the advantages of biochar.

CASE STUDY: REMY WINES

Photo courtesy of John Mead, Solid Carbon

The carbon-neutral concrete floor at Remy Wines Winery, which utilized biochar, sequestered over 5 tons of CO₂ emissions and was only 10% more expensive than a conventional concrete slab would have been.

Project: Remy Wines Winery
Location: Dayton, Oregon
Date: June 1, 2022
Project Adaptive Reuse Conversion of Ag Barn into Production Winery
Concrete: 5,000-square-foot slab dosed at 100 lbs biochar per yard
Sequestration: 10,230 lbs of CO₂ equivalent locked into concrete

Remy Wines is a peek into the potential future of biochar concrete. When Remy Wines Owner and Winemaker Remy Drabkin decided to open a new facility in the Willamette Valley, she wanted it to be a demonstration project for sustainability with the highest of standards. The adaptive-reuse project used reclaimed wood and metal, as well as salvaged fixtures and doors.

But when Remy realized that commercial concrete is responsible for 7-9% of the world’s CO₂ emissions, she challenged her building partners to explore alternatives. The result was a completely new concrete, dubbed the Drabkin-Mead Formulation, that not only decreased carbon emissions to zero but sequestered carbon during production. The formula achieves its carbon-neutral state with biochar made from pyrolyzed organic municipal waste.

The floor was poured in July 2022 and became the first commercial application for the Drabkin-Mead Formulation. The concrete slab sequestered over 5 tons of CO₂ emissions and was only 10% more expensive than a conventional concrete slab would have been. It is the world’s first carbon-neutral concrete floor, but hopefully not the last. The concrete remains open-sourced so it can be replicated around the world, playing a part in decreasing the global carbon footprint.

The Remy Wines Project is an example of a concrete building that used an advanced admixture (a novel carbon sequestration technology) to dramatically improve the sustainability of the project while maintaining the performance characteristics of the concrete. The commercial use of the net-zero concrete allowed for testing and validation of dozens of mix designs. Once the mix was identified, the manufacturing company was able to take a technical deep dive and test the concrete for ASTM C39, C944, C157, and C666 for strength, shrinkage, freeze-thaw, and abrasion. The concrete went through testing for air, slump, and fresh quality assessment, as well as finisher assessment.

The case study shows that there is promise for sequestering carbon that has been captured by nature. Normally at the end of life all biogenic carbon will be re-released into the atmosphere. Biochar products provide the opportunity to change that trajectory. In addition, the concrete slab at Remy Wines establishes the time for carbon neutrality is possible much sooner than the industry goals of reducing greenhouse gases to net-zero by 2050.

History of Biochar Innovations

Several pioneering milestones have helped support biochar’s use in concrete. From 2012 to 2016, research and experiments were able to showcase its effects as a filler and improve on its mechanical properties. A 2012 study found that a dosage of 5% by weight of cement of hardwood biochar improved the compressive strength of concrete by between 10% and 12%.

In 2014, the Ithaka Institute in Sion, Switzerland, where biochar is studied, was host to several onsite demonstration projects utilizing a wall plaster containing biochar. In 2015, bamboo biochar produced at 850 degrees Celsius and a heating rate of 60 degrees C per minute for an hour was able to improve the compressive strength of biochar-cement pastes by 40-50%, toughness by 103%, and flexural strength by 66%. In 2016, research found that adding biochar up to 1 wt% increased the fracture energy of cement-based composites by 61%.