by Jim Schneider
Many designers instinctively resist the use of concrete in sustainable design, noting obvious reservations regarding the amount of carbon dioxide (CO2) generated by the concrete industry. That is not an incorrect observation: the concrete industry does contribute roughly 10% of global CO2 emissions each year (slightly less than the impact made by other building materials).
Concrete, the most abundant manmade material in the world, provides durability, resilience, and quality. It has a relatively low impact on the environment when viewed from a lifecycle perspective, but the concrete industry is stepping up to decrease its initial impact on the climate and reduce greenhouse gas emissions through new approaches to minimize concrete production carbon emissions, reduce Portland cement use, and boost strength with less material.
Reclaiming carbon involves injecting captured industrial carbon into concrete, effectively entombing it there and keeping it out of the atmosphere. Proprietary technologies are available to help projects meet embodied carbon goals by helping to offset the CO2 emitted in the production of concrete. This strategy can reduce the overall net footprint of the material.
Supplementary cementitious materials (SCMs) are another area of focus, as they can reduce the use of Portland cement, which is the primary emitter of greenhouse gases in the production of concrete. Materials like fly ash, slag cement, and silica fume are common examples of SCMs that can bring down cement content in many concretes. Research is pushing the envelope regarding how much can be used, and many SCMs carry great promise for decreasing the impact of concrete.
Recycled glass can replace about 20% to 30% of cement in most concretes when ground up. Missoula Credit Union, which was the first LEED platinum building in the state of Montana, used recycled aggregate with a mixture of fly ash and ground glass to achieve a low-impact concrete that eliminated the use of Portland cement.
Doing more with less is another innovative approach to sustainability. Ultra High Performance Concrete has a minimum strength of 14,000 to 17,000 psi and a flexural strength of at least 1400 psi, enabling building and bridge projects to achieve carbon reduction by reducing material and weight while still delivering a durable, long-lasting end product.
Precast concrete is a long-lasting, durable, efficient, and resilient material that can deliver a high level of performance for many decades. Read the full article in Ascent magazine to learn how the industry is working tirelessly with new innovations to make concrete even better, stronger, and less environmentally impactful.
Jim Schneider, LEED AP is executive director at PCI Mountain States.